UNIVERSITY OF GHANA 
COLLEGE OF BASIC AND APPLIED SCIENCES 
 
PROCESS DEVELOPMENT AND PRODUCT CHARACTERISTICS OF 
EXTRUDED RICE-SOYBEAN SNACK 
 
 
 
BY 
HANNAH FOSUA AKOTO 
(10396902) 
 
 
 
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN 
PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF 
MPHIL FOOD SCIENCE DEGREE. 
 
 
 
 
 
MAY, 2015.
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DECLARATION 
This is to certify that this thesis is the result of research work undertaken by Hannah Fosua 
Akoto towards the award of Master of Philosophy in Food Science in the Department of 
Nutrition and Food Science, University of Ghana. 
 
 
 
…………………………………………   ……………………… 
HANNAH FOSUA AKOTO  
(Student)  
 
 
…………………………………………   ……………………… 
PROF. ESTHER SAKYI-DAWSON 
 (Supervisor)  
 
 
…………………………………………   ……………………… 
PROF. FIRIBU K. SAALIA 
 (Supervisor) 
 
 
…………………………………………                                   ……………………… 
PROF. PAA NII TORGBOR JOHNSON 
 (Supervisor) 
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ABSTRACT 
The eating patterns of Ghanaians are changing due to urbanization, globalization, economic 
trends, as well as changes in social structure as a result of the increasing number of women 
working outside the home. These changes in eating patterns include higher consumption of 
snack foods by all age groups. A snack food is often smaller than a regular meal and 
normally consumed between meal times. Among cereal-based snacks, wheat and corn are 
the most popularly used cereals as compared to rice.  
Locally grown and milled rice tends to be poorly patronized by consumers in Ghana due to 
quality defects, so incorporating this low grade rice into a ready to eat snack would provide 
an avenue for using the commodity which may otherwise be underutilized. This study 
therefore sought to develop a rice-soybean snack from low grade rice (parboiled or raw 
form) using extrusion-cooking technology. Rice and partially defatted soy flour blends of 
composition (75:25-90:10) were obtained based on ratios that were determined using 
constrained mixture designs for two components. In all twenty formulations were obtained 
and extruded using an intermeshing co-rotating twin screw extruder at constant screw 
speed of 1000rpm, barrel temperature of 200oC and a circular die diameter of 4mm.  
Evaluation of consumer sensory preference was carried out using a 9 point hedonic scale to 
obtain five most preferred extrudates with high percentage of rice (TMF3 (90% raw Togo 
Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 (75% raw TM, 25% PDS); 
TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled TM, 10% PDS); PTMF4 
(75% parboiled TM, 25% PDS)) for further analysis. Physicochemical analysis on the five 
extrudates showed that increasing amount of partially defatted soybean (PDS) and rice 
parboiling treatment generally decreased expansion ratio, lightness and increased hardness. 
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For characterization of proteins, amount of PDS and rice parboiling treatment had a 
substantial effect on accessible thiols, protein solubility and electrophoretic patterns. 
Extrudate made using 75% raw rice and 25% PDS (TMF4) showed the least protein 
digestibility suggesting the presence of antinutritional factor such as trypsin inhibitors. 
Principal Component Analysis (PCA) was used to discriminate extruded snacks based on 
odour and taste from data obtained from electronic nose and tongue analysis. Taste 
characteristics were discriminated based on umami, saltiness, bitterness, sourness and 
astringency.  It was concluded that amount of PDS and rice treatment has a significant 
effect on the physicochemical properties of the extrudates.  
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DEDICATION 
This academic piece is dedicated to my parents Mr. and Mrs. Akoto, my siblings and Mr. 
Victor Essel. Thank you all for the love, support and encouragement throughout my stay in 
school. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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ACKNOWLEDGEMENT 
I am sincerely grateful to the almighty God for his favour and blessings throughout these 
years and for bringing me this far in life. Glory and honour be unto his holy name. 
I am most grateful to my guides; Prof. Esther Sakyi-Dawson, Prof. Paa Nii Torgbor 
Johnson, and Prof. F. Saalia for their time and guidance that has enabled the successful 
completion of this thesis. Prof. Esther Sakyi-Dawson and Prof. Paa Nii Torgbor Johnson, 
thank you for your encouragement and patience. Thank you, Prof. F. Saalia for your 
patience, advice, encouragement and support that has made me a better person. 
My appreciation also goes to the Global Rice Science Partnership (GRiSP) project partners 
and management especially Dr. John Manful for the opportunity granted me to take up this 
investigation. I sincerely thank Professor Francesco Bonomi, Professor Stefania Iametti, 
Professor Maria Ambrogina Pagani, Dr. Marengo, Mr. Carpen, Dr. Miriani, Dr. Buratti, 
Dr. Benedetti, Miriam and Laura all in the Department of Food, Environmental, and 
Nutrition Sciences, University of Milan, Italy for their guidance and assistance extended to 
me during the course of the work and also allowing me use their labs. 
My heartfelt thanks go to Mr. Seth Graham-Acquaah (AfricaRice) and his team in Benin 
for assisting me in their lab as well. To Mr. Nana Kwame Owusu-Brafi, God richly bless 
you for your prompt support and co-operation. Now to all my course mate, thank you for 
the love and encouragement.  
I sincerely thank my parents Mr. and Mrs. Akoto as well as Mr. Victor Essel for their love, 
constant encouragement, understanding, and moral supports. God richly bless you all. 
 
 
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TABLE OF CONTENTS 
DECLARATION ............................................................................................................................. i 
ABSTRACT .................................................................................................................................... ii 
DEDICATION ............................................................................................................................... iv 
ACKNOWLEDGEMENT .............................................................................................................. v 
TABLE OF CONTENTS ............................................................................................................... vi 
LIST OF TABLES ....................................................................................................................... xiii 
LIST OF FIGURES ...................................................................................................................... xv 
LIST OF PLATES ...................................................................................................................... xvii 
1.0 INTRODUCTION .................................................................................................................... 1 
1.1 Background ........................................................................................................................... 1 
1.1 Rationale................................................................................................................................ 3 
1.2 Main objective ....................................................................................................................... 4 
1.3 Specific objectives................................................................................................................. 4 
2.0 LITERATURE REVIEW ......................................................................................................... 5 
2.1 Rice Agronomy ..................................................................................................................... 5 
2.1.1 Origin and Distribution of Rice ...................................................................................... 7 
2.1.2 Differences Between O. glaberrima and O. sativa ........................................................ 7 
2.1.3 Rice production and varietal distribution in Ghana ........................................................ 9 
2.2 Rice preference and its utilization ......................................................................................... 9 
2.2.1 Rice as a staple food and as a source of employment .................................................. 11 
2.2.2 Nutrition composition of rice ....................................................................................... 12 
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2.3 Rice Processing ................................................................................................................... 15 
2.3.1 Parboiled rice ................................................................................................................ 15 
2.4 Rice Quality......................................................................................................................... 17 
2.4.1 Quality characteristics of Paddy Rice ........................................................................... 17 
2.4.2 Grain Quality ................................................................................................................ 19 
2.4.2.1 Physical quality characteristics of rice grain ............................................................. 19 
2.4.2.2 Chemical quality characteristics of rice grains .......................................................... 20 
2.5 Soybean ............................................................................................................................... 23 
2.5.1 General information on soybean................................................................................... 23 
2.5.2 Uses of Soybean ........................................................................................................... 24 
2.5.3 Anti-nutritional factors ................................................................................................. 24 
2.5.4 Soybean quality ............................................................................................................ 25 
2.5.5 Soybean and its application as a fortificant .................................................................. 25 
2.6 Snack intake ........................................................................................................................ 26 
2.6.1 Types of snacks ............................................................................................................ 26 
2.7 Extrusion processing ........................................................................................................... 27 
2.7.1 Characteristics of extruded products and their quality indices ..................................... 28 
2.7.2 Physicochemical Characteristics of extruded products ................................................ 30 
2.7.2.1 Colour ........................................................................................................................ 30 
2.7.2.2 Water absorption index (WAI) .................................................................................. 30 
2.7.2.3 Water solubility index (WSI) .................................................................................... 31 
2.7.2.4 Expansion ratio .......................................................................................................... 32 
2.7.2.5 Bulk density (BD) ...................................................................................................... 33 
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2.7.2.6 Texture ....................................................................................................................... 33 
2.7.2.7 Microstructure ........................................................................................................... 34 
2.7.2.8 Protein digestibility.................................................................................................... 35 
2.7.2.9 Odour and taste characteristics .................................................................................. 36 
2.8 Conclusion ........................................................................................................................... 40 
3.0 MATERIALS AND METHODS ............................................................................................ 41 
3.1 Raw materials ...................................................................................................................... 41 
3.2 Methods ............................................................................................................................... 41 
3.2.1 Determination of physicochemical properties of rice grains ........................................ 41 
3.2.1.1 Chalkiness and grain dimension determination. ........................................................ 41 
3.2.1.2 Raw grain hardness .................................................................................................... 42 
3.2.1.3 Alkaline spreading value (ASV) ................................................................................ 43 
3.2.1.4 Milling recovery ........................................................................................................ 43 
3.2.1.5 Cooking time ............................................................................................................. 44 
3.2.2 Parboiling of Rice ......................................................................................................... 45 
3.2.3 Flour Preparation from milled and parboiled rice ........................................................ 46 
3.2.4 Determination of physicochemical properties of rice flour .......................................... 46 
3.2.4.1 Colour of rice flour .................................................................................................... 46 
3.2.4.2 Apparent Amylose content ........................................................................................ 47 
3.2.4.3 Protein solubility of rice ............................................................................................ 48 
3.2.4.4 Electrophoretic pattern of extracted proteins in rice ................................................. 48 
3.2.5 Partially Defatted Soybean (PDS) flour Preparation .................................................... 49 
3.2.5.1 Determination of physicochemical properties of soybean flour ................................ 49 
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3.2.5.1.1 Fat content determination on raw and partially defatted soybean .......................... 49 
3.2.5.1.2 Colour determination of partially defatted soybean (PDS) .................................... 50 
3.2.5.1.3 Protein solubility of PDS ........................................................................................ 50 
3.2.5.1.4 Electrophoretic pattern of the extracted proteins .................................................... 51 
3.2.6 Product Formulations ................................................................................................... 51 
3.2.7 Physicochemical analysis on formulations ................................................................... 52 
3.2.7.1 Moisture determination.............................................................................................. 52 
3.2.7.2 Apparent Amylose content ........................................................................................ 53 
3.2.7.3 Pasting properties ...................................................................................................... 53 
3.2.8 Extrusion process .......................................................................................................... 54 
3.2.9 Visual inspection of the twenty extrudates ................................................................... 54 
3.2.10 Sensory Evaluation of extruded snacks ...................................................................... 55 
3.2.11 Physicochemical analysis on the five selected extrudates .......................................... 55 
3.2.11.1 Moisture determination............................................................................................ 55 
3.2.11.2 Colour ...................................................................................................................... 55 
3.2.11.3 Aroma determination using electronic nose ............................................................ 56 
3.2.11.3.1 Operation Procedure ............................................................................................. 58 
3.2.11.4 Taste determination using electronic tongue ........................................................... 59 
3.2.11.5 Bulk density ............................................................................................................. 63 
3.2.11.6 Water Absorption Index (WAI) and Water Solubility Index (WSI) ....................... 64 
3.2.11.7 Expansion ratio ........................................................................................................ 64 
3.2.11.8 Hardness analysis .................................................................................................... 65 
3.2.11.9 Protein solubility...................................................................................................... 65 
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3.2.11.10 Electrophoretic pattern of the extracted proteins ................................................... 66 
3.2.11.11 Accessible thiols .................................................................................................... 66 
3.2.11.12 In vitro protein digestibility ................................................................................... 67 
4.0 RESULTS AND DISCUSSION ............................................................................................. 68 
4.1 Selection of local rice varieties for the preparation of extruded snack. .............................. 68 
4.2 Physicochemical characterization of two selected local rice varieties. ............................... 69 
4.2.1 Grain hardness .............................................................................................................. 69 
4.2.2 Milling recovery (%) .................................................................................................... 70 
4.2.3 Grain Dimension........................................................................................................... 70 
4.2.4 Grain Chalkiness........................................................................................................... 71 
4.2.5 Cooking time ................................................................................................................ 72 
4.2.6 Alkaline spreading value (ASV) ................................................................................... 73 
4.2.7 Apparent amylose content (AAC) ................................................................................ 74 
4.3 Physical and chemical analysis of the raw materials used for extruded products ............... 75 
4.3.1 Colour analysis ............................................................................................................. 75 
4.3.2 Protein solubility........................................................................................................... 77 
4.3.3 Protein electrophoretic patterns .................................................................................... 79 
4.4 Chemical analysis of soybean ............................................................................................. 83 
4.4.1 Changes in fat content due to defatting ........................................................................ 83 
4.5 Evaluation of extrudate quality through visual examination .............................................. 83 
4.6 Consumer acceptability of twenty extruded snacks ............................................................ 87 
4.7 Chemical analysis of the formulations of the selected extrudates ...................................... 91 
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4.7.1 Apparent amylose content (AAC) ................................................................................ 91 
4.8 Functional properties of the formulations of the selected extrudates.................................. 92 
4.8.1 Pasting properties of the five formulations ................................................................... 92 
4.8.1.1 Beginning of gelatinization/Initial viscosity.............................................................. 93 
4.8.1.2 Maximum/peak viscosity ........................................................................................... 94 
4.8.1.3 Hot paste viscosity ..................................................................................................... 95 
4.8.1.4 Breakdown ................................................................................................................. 95 
4.8.1.5 Setback....................................................................................................................... 96 
4.8.1.6 Pasting temperature ................................................................................................... 96 
4.9 Chemical analysis of the five formulation and their extrudates .......................................... 99 
4.9.1 Changes in moisture content for formulation and their extrudates .............................. 99 
4.10 Physical properties of the selected Rice extrudates ........................................................ 100 
4.10.1 Expansion ratio (ER) ................................................................................................ 100 
4.10.2 Bulk density (BD) ..................................................................................................... 100 
4.10.3 Colour ....................................................................................................................... 101 
4.10.4 Hardness of five extrudates ...................................................................................... 103 
4.11 Functional properties of selected extrudates ................................................................... 104 
4.11.1 Water absorption index (WAI) ................................................................................. 105 
4.11.2 Water solubility index (WSI) ................................................................................... 105 
4.12 Molecular characterization of protein from five extrudates ............................................ 106 
4.12.1 Protein solubility....................................................................................................... 106 
4.12.2 Electrophoretic patterns of extracted proteins from the selected extrudates ............ 109 
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4.12.3 Accessible protein thiols from extrudates ................................................................ 111 
4.12.4 In vitro protein digestibility ...................................................................................... 113 
4.13 Aroma and taste determination using electronic nose and tongue .................................. 115 
4.13.1 Aroma analysis of the five extrudates ...................................................................... 115 
4.9.4.2 Taste analysis of the five extrudates ........................................................................ 119 
5.0 CONCLUSION AND RECOMMENDATION .................................................................... 123 
5.1 Conclusion ......................................................................................................................... 123 
5.2 Recommendation ............................................................................................................... 124 
6.0 REFERENCES ..................................................................................................................... 125 
APPENDICES ............................................................................................................................ 150 
APPENDIX I: SENSORY SCORE SHEET ........................................................................... 150 
APPENDIX II: BALLOT SHEET FOR CONSUMER ACCEPTANCE OF EXTRUDED 
RICE-SOYBEAN SNACK ..................................................................................................... 154 
APPENDIX III: ANOVA TABLES ....................................................................................... 156 
APPENDIX IV: MULTIPLE RANGE TESTS ...................................................................... 158 
 
 
 
 
 
 
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LIST OF TABLES 
Table 2.1: Top 10 Rice Producing and Consuming Countries. ........................................ 12 
Table 2.2: Proximate Composition of some rice varieties ................................................ 13 
Table 2.3: Effect of milling on vitamin and mineral content of rice ................................ 14 
Table 2.4: Physical and chemical properties of ten local rice varieties in Ghana. ........... 22 
Table 2.5: Amylose content and colour of four rice varieties grown in Ghana. ............... 22 
Table 3.1: Mixture design formulations from different treatments of rice and 
partiallydefatted soybean flour ....................................................................... 52 
Table 3.2: List and characteristics of 10 Metal Oxide Semiconductors (MOS) of sensor      
array in electronic nose PEN2. ........................................................................ 58 
Table 3.3: Five selected extrudates and their coding for electronic nose analysis. .......... 59 
Table 3.4: List and characteristics of electronic tongue detecting sensors. ...................... 60 
Table 4.1: Physical properties of Togo marshall and Viwonor rice varieties. .................. 73 
Table 4.2: Chemical properties of Togo marshall and Viwonor rice varieties ................. 75 
Table 4.3: Colour measurement of raw materials ............................................................. 77 
Table 4.4: Mean scores of sensory attributes of twenty extruded snacks from different 
rice varieties and partially defatted soybean. .................................................. 90 
Table 4.5: Pasting parameters of five formulations (Rice and Partially Defatted Soybean 
(PDS)). ............................................................................................................ 98 
Table 4.6: Changes in moisture content ............................................................................ 99 
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Table 4.7: Expansion ratio, bulk density and colour characteristics of five extrudates .. 102 
Table 4.8: Water Absorption (WAI) and water solubility indexes (WSI) of five 
extrudates. ..................................................................................................... 106 
 
 
 
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LIST OF FIGURES 
Figure 2.1: A Paddy Kernel, Showing the Major Parts ...................................................... 6 
Figure 3.1: Process flow for parboiling rice ..................................................................... 45 
Figure 3.2: Process flow chart for rice flour preparation .................................................. 46 
Figure 3.3: Electronic Tongue measuring process. ........................................................... 61 
Figure 4.1: Amount of solubilized protein from raw materials. ....................................... 79 
Figure 4.2: Electrophoretic patterns of proteins in the raw materials ............................... 82 
Figure 4.3: Changes in fat content. RS: Raw soybean (full fat soybean); PDS: Partially 
defatted Soybean. ............................................................................................. 83 
Figure 4.4: Apparent Amylose Content (AAC) for five formulations from Togo marshall 
rice variety and Partially Defatted Soybean. .................................................... 92 
Figure 4.5: Hardness (N) of five extrudates.................................................................... 104 
Figure 4.6: Amount of solubilized protein in different buffers systems. ........................ 109 
Figure 4.7: Electrophoretic patterns of proteins in five extrudates ................................. 111 
Figure 4.8: Accessible thiols of five extrudates from rice and partially defatted soybean.
 ........................................................................................................................ 113 
Figure 4.9: In-vitro protein digestibility of five extrudates from rice and partially defatted 
soybean. .......................................................................................................... 115 
Figure 4. 10a: PCA score plot of five extrudates. ........................................................... 118 
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Figure 4.10b: PCA loading plot of five extrudates.........................................................119 
Figure 4.11a: Score plot of samples (A-E) in the plane defined by the first two principal 
component.................................................................................................121  
Figure 4.11b: Loading plot of samples (A-E) in the plane defined by the first two 
principal component.................................................................................122 
 
 
 
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LIST OF PLATES 
Plate 3.1: Electronic nose PEN2 ................................................................................................... 56 
Plate 3.2: Basic elements of an electronic nose ............................................................................ 57 
Plate 3.3: Taste sensing system. .................................................................................................... 60 
Plate 4.1: Two locally cultivated (low grade) rice varieties (Togo marshall and Viwonor). ....... 69 
Plate 4.2: Extrudates from Raw ‘Viwonor’ rice variety. (Rice: Soybean) ................................... 85 
Plate 4.3: Extrudates from Parboiled ‘Viwonor’ rice variety. (Rice: Soybean) ........................... 85 
Plate 4.4: Extrudates from Raw ‘Togo marshall’ rice variety. (Rice: Soybean) .......................... 86 
Plate 4.5: Extrudates from Parboiled ‘Togo marshall’ rice variety. (Rice: Soybean) .................. 86 
 
 
 
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1.0 INTRODUCTION 
1.1 Background 
Changes in eating patterns are occurring at an increasing rate due to urbanization, 
globalization, economic trends, and changing demographics. This is further fuelled by 
changes in our social structure as a result of increase in the number of mothers working 
outside the home. These changes in eating patterns include an increase in the consumption 
of snack foods in all age groups (Noor Aziah, 2012; Piernas and Popkin, 2010). The 
increase in the consumption rate of snacks is also ascribed to changes in life styles and 
trends in consumer demands for attractive appearance and convenience foods (Harris et al., 
2007; Omwamba et al.  2014). A snack food is often smaller than a regular meal and 
normally consumed between meal times (Savige et al., 2007).  Snack foods comprise a 
very large variety of items including biscuit, popcorn, crackers, nuts and extruded snacks 
among others. Presently, high snack consumption in Ghana is manifested by their 
widespread presence in open markets, supermarkets, petty trading, and restaurants, in both 
urban and rural areas.  
 
Techniques for manufacturing snack foods include drying, frying, roasting, baking, 
extrusion and many others (Okafor, 2014). Among several processing techniques, 
extrusion cooking has gained widespread application in the cereal based snack food 
industry, because it is considered an efficient manufacturing process (White, 1994; Raiz, 
2001; Mezreb et al., 2003, Ibanoglu et al., 2006). Furthermore, extrusion processing 
completely eliminates the trypsin inhibitor activity of the extrudates thereby improving 
protein digestibility (Otegbayo et al. 2002). 
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. 
Cereal-based snack products provide an important part of the daily nutrient and calorie 
intake for many consumers (Bhattacharyya, 1997; Rhee et al. 2004). Among the cereals, 
wheat and corn are most popularly used. Rice (Oryza sativa) based snacks including 
extruded rice products are less common as compared to snack products from wheat and 
corn. However, rice has become an attractive ingredient in the extrusion industry as a result 
of its bland taste, hypoallergenicity and high digestibility (Kadan et al., 2003). Rice (Oryza 
sativa) is a staple food for approximately half of the world’s population (Zhou et al., 
2002). According to Itani et al. (2002), rice is ranked as the world’s number one food crop. 
Tomlins et al. (2005) observed that rice has become a staple in Ghana and much of West 
Africa where it serves as an important convenience food for urban dwellers. Rice has 
become the second most important food staple after maize in Ghana (Ministry of Food and 
Agriculture, 2011a) and its intake continues to increase as a result of urbanization, 
population growth and change in consumer habits.  
 
Even though rice forms a major part of the Ghanaian diet, preference is for imported rice 
over locally produced rice. Estimates by Amanor‐Boadu (2012) showed that imported rice 
comprises about 70% of the quantity consumed in Ghana. This is because locally grown 
rice is low in quality and inconsistent in terms of taste, cooking quality, cooking time and 
aroma (Tetteh Anang et al., 2011). Moreover, the excessive chalkiness and high breakage 
percentage of local milled rice lowers the quality and reduces milling recovery.  According 
to Gayin et al. (2009), these quality defects are influenced by inappropriate post-harvest 
handling, poor quality planting materials and poor agronomic practices.  
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1.1 Rationale 
Even though locally grown and milled rice is poorly patronized by consumers in Ghana 
due to quality defects, incorporating this low grade rice into a ready to eat snack would 
provide an avenue for using commodity which may otherwise be underutilized. The 
growing consumer demand for convenience foods including snacks can be exploited by 
developing a nutritious and healthy snack using locally milled low grade rice.  
Increasing the protein content of snack foods may further improve their consumer appeal 
and acceptance. Soybean (Glycine max) is an excellent source of protein (Liu, 1999) but it 
is underutilized in Ghana. Like most legumes, soybean protein is limiting in methionine, 
tryptophan and cysteine (Wang et al., 2006, Shewery, 2007). On the other hand, rice which 
is a typical cereal has high amounts of the limiting amino acids of soybeans (Tsai et al., 
1975, Iqbal et al., 2006, Shewery, 2007). Furthermore rice is also deficient in the essential 
amino acids lysine and threonine (Tsai et al., 1975, Shewery, 2007) which are high in soy 
proteins. Therefore blending rice and soybeans in the right ratios provides a good protein 
source, since they mutually complement each other.  According to Nkama et al. (1995), 
protein-energy malnutrition has been identified as one of the most important problems in 
Africa including Ghana. This is generally because some people can hardly afford high 
protein foods such as animal foods. There is therefore the need for developing nutritious 
snacks of high protein and energy using cereal-legume combinations. This work seeks to 
use High temperature, short time (HTST) extrusion cooking technology to produce ready 
to eat and consumer acceptable snack from locally milled rice and decorticated and 
partially defatted soybean. The development of a ready to eat snack will diversify the usage 
of locally grown rice and also maximize its utilization. This could lead to the provision of 
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ready market for locally grown rice. It could also lead to the strengthening of food security 
and sustainable livelihoods among rice processors and consumers in Ghana.    
 
1.2 Main objective 
The objective of this work was to develop a rice-soybean snack using extrusion-cooking 
technology.  
1.3 Specific objectives 
 To characterize two low grade rice varieties in Ghana. 
 To evaluate the physicochemical properties of the raw materials and rice-soybean 
flour formulations. 
 To determine an acceptable formulation for the production of extruded rice-
soybean snack. 
 To determine the physicochemical, functional, aroma and taste characteristics of 
the extrudates. 
 
 
 
 
 
 
 
 
 
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2.0 LITERATURE REVIEW 
2.1 Rice Agronomy 
Rice (genus Oryza) is a semi-aquatic grass crop that grows more easily in the tropics (Hof, 
2007). However, it is tolerant to hot, humid, flooded, dry, and cool conditions and grows in 
saline, alkaline, and acidic soils. It also grows faster and most vigorously in wet and warm 
conditions (Hof, 2007). It is a member of the grass family (Gramineae) and belongs to the 
genus Oryza under tribe Oryzeae (Chang, 1985).The genus Oryza includes 20 wild species 
and 2 cultivated or domesticated species or cultigens (Chang, 1985). The wild species are 
widely distributed in the humid tropics and subtropics of Africa, Asia, Central and South 
America, and Australia (Chang 1985). The domesticated rice comprises two species of 
food crop in the Poaceae (“true grass”) family: Oryza sativa (Asian rice) and Oryza 
glaberrima (African rice) (Owens, 2001, Linscombe, 2006 as stated in Tokpah, 2010). 
These plants are native to Tropical and Subtropical Southern Asia and South eastern 
Africa, respectively (Linares, 2002).  
Among the several Oryza species, Oryza sativa is the one most commonly cultivated in the 
humid tropics of Asia, where it originated. Asian cultivated rice has evolved into three eco-
geographic subgroups: Japonica (broad thick grains; round-grain), Javanica (roundish 
grains; medium-grain) and Indica (slender, somewhat flat grains; long-grain). Indica 
varieties account for 80% of cultivated rice and feed about 3 billion people, mainly in 
developing countries (UNCTAD, 2005). Even though, Oryza sativa was originally known 
as Asian rice, it is now commercially grown in 112 countries, covering six continents 
except Antarctica, extending from 50° north latitude to 40° south latitude and from sea 
level to an altitude of 3000 m (Chang 1985). At the present time, O. glaberrima is being 
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replaced everywhere in West Africa by the higher yielding O. sativa varieties, introduced 
into the continent by the Portuguese as early as the middle of the 16th century (Linares, 
2002). The long history of cultivation and selection under diverse environments has caused 
O. sativa to acquire a broad range of adaptability and tolerance enabling it to be grown in a 
wide range of water/soil regimens from deeply flooded land to dry hilly slopes (Lu and 
Chang, 1980). 
The rice plant develops a main stem and many tillers, which arch into many clusters of 
flowers bearing the grains. It is normally grown as an annual plant, although in tropical 
areas it can survive as a perennial plant. The rice plant develops grain clusters called 
panicles; the plants are cut and threshed to release the grains. The edible seed is a grain 
(caryopsis) 5–12 mm (0.20–0.47 in) long and 2–3 mm (0.079–0.12 in) thick (Boumas, 
1985). The intact grain has an abrasive, silicaceous seed coat or husk and known as paddy 
or rough rice as shown in Figure 2.1. 
 
Figure 2.1: A Paddy Kernel, Showing the Major Parts  
(Source: Bond, 2004)  
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The common forms of rice are referred to as rough rice, brown rice, and milled rice. 
Rough rice (paddy rice) is composed of 20% hull (the outermost layer), 10% bran and 
germ, and 70% starchy endosperm (Figure 2.1).  
 
2.1.1 Origin and Distribution of Rice 
The geographical site of the origin of rice domestication is not yet definitely known. 
According to Juliano (1993), the general consensus is that O. sativa rice domestication 
occurred independently in China, India and Indonesia, thereby giving rise to three races of 
rice: Sinica also known as Japonica (round-grain), Indica (long-grain) and Javanica 
(medium-grain). There are indications that rice was cultivated in India between 1500 and 
2000 B.C. and in Indonesia around 1648 B.C (Chang, 1983 as stated in Juliano, 1993). 
Archaeological findings have shown that tropical or Indica rice was being cultivated in Ho-
mu-tu, Chekiang Province, China at least 7000 years ago (Chang, 1983 as stated in Juliano, 
1993). 
Oryza glaberrima, commonly known as African rice, is a domesticated rice species. 
African rice is believed to have been domesticated 2,000-3,000 years ago in the inland 
delta of the Upper Niger River, in what is now Mali (Linares, 2002). Its wild ancestor, 
which still grows wild in Africa, is Oryza barthii (Linares, 2002). 
 
2.1.2 Differences Between O. glaberrima and O. sativa  
According to Richards (1996), minor morphological differences separate the two species of 
rice, making it difficult to differentiate them in the field. O. glaberrima has small grains 
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that are pear-shaped and have red bran and an olive-to-black seed coat, straight panicles 
that are simply branched, and short, rounded ligules. However, some O. sativa types also 
have pear-shaped grains with red bran. Other ecological differences are that African O. 
glaberrima varieties have certain negative features with respect to the Asian O. sativa: the 
seed scatters easily, the grain is brittle and difficult to mill, and most importantly its yields 
are lower. Nevertheless the O. glaberrima varieties also offer distinct advantages: the 
plants have luxurious wide leaves that shade out weeds and the species is more resistant 
than O. sativa to diseases and pests.  African rice is more tolerant of fluctuations in water 
depth, iron toxicity, infertile soils, severe climates, and human neglect. However, despite 
the popularity of Asian rice (as a result of their higher yields), they are poorly adapted to 
many of the African environments where rice is grown (Somado et al., 2008). According to 
Linares (2002), these characteristics have made it worthwhile to attempt to cross both 
species. The new varieties, named ‘‘New Rice for Africa’’ (hence NERICA) developed in 
2004 by Africa Rice Centre (WARDA, 2005), are a cross between O. glaberrima and O. 
sativa. They combine the hardiness of the African species with the productivity of the 
Asian species. Scientists at the West African Rice Development Association (WARDA) 
succeeded in crossing the two species by employing embryo rescue techniques that ensure 
the crosses are fertile and mature successfully due to high levels of hybrid vigour. 
Examples of NERICA rice varieties in Ghana are NERICA 1 (SAR-RICE 5) and NERICA 
2 (SAR-RICE 6) (Ragasa et al., 2013). 
 
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2.1.3 Rice production and varietal distribution in Ghana 
Rice is important to Ghana’s economy and agriculture, accounting for nearly 15% of the 
Gross Domestic Product (GDP) and it is the second most important cereal after maize in 
Ghana (MiDA, 2010; Osei-Asare, 2010). The rice producing area totals about 45% of the 
total area planted to cereals (Kranjac-Berisavljevic, 2000). Ghana’s rice production 
estimates range from 200,000 to 300,000 MT of paddy or roughly and 120,000 to 180,000 
MT of milled rice (JICA, 2007). Rainfall remains the greatest driver of production 
variance. According to Kranjac-Berisavljevic (2000), and JICA (2007), rice production in 
Ghana can be categorized into three primary cropping types or undertaken in three 
different ecologies: lowland rain-fed ecology, which includes rice planted in the receding 
waters of the Volta and other rivers accounts for 78% of total harvested area; upland rain-
fed ecology (6%), and irrigated ecology (16%).  
Mechanization levels in rice production are low throughout Ghana, although most farmers 
hire tractor services for ploughing and harrowing. In the Northern Regions, bullock-drawn 
ploughs are also common. All other production and post-harvest activities are done 
manually, especially by the smallholders. Other constraints to production include low land-
levelling of paddy fields and lack of bunds to retain rain water; inadequate supply of 
certified seed, fertilizers and other agro-chemicals; and inadequate credit facilities to 
ensure investment in productivity-enhancing technologies. 
 
2.2 Rice preference and its utilization 
Rice has become the second most important food staple after maize in Ghana and its 
consumption keeps increasing as a result of population growth, urbanization and change in 
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consumer habits. According to a report by JICA (2007), rice is cultivated in Ghana both as 
a food crop and a cash crop. Rice cultivation serves to meet the financial needs of the 
household. It also serves to sustain the food security during the lean season. There is a 
wide variation in rice consumer preference in Ghana on the basis of grain characteristics.  
Various studies show that Ghanaian consumers have a higher preference for imported rice 
because of its perceived higher cooking and sensory characteristics and quality (Diako et 
al., 2011; Tomlins et al., 2005). Diako et al. (2010) stated that while the appearance of raw 
rice is critical to consumers’ choice, taste and aroma determine consumer preference for 
cooked rice. The study by Tomlins and his colleagues found that 86% of consumers prefer 
imported rice which was influenced by the consumer’s gender and location, while local 
rice was only appealing to a “niche segment” comprising 14% (Tomlins et al., 2005).  The 
reasons given for not purchasing locally cultivated rice were poor postharvest handling and 
the generally perceived poor quality (Diako et al. 2010). Consumers therefore prefer rice 
imported mainly from Thailand, Vietnam, Taiwan and USA (Kula et al., 2009). Even 
though, a study by Diako et al. (2011) confirms that local varieties have a higher mineral 
content than imported varieties only a certain niche segments of health-conscious 
consumers purchase local brown rice. Parboiled local rice is commonly patronized in the 
Northern regions of the country.   
In Ghana, a very small fraction of the rice crop is used as an ingredient in processed foods 
but the bulk is consumed as cooked rice. Rice is used in a wide range of  traditional staples 
dishes the most common include fried rice, jollof rice, rice balls, rice porridge and plain-
cooked rice. The various rice products are fundamentally different in their appearance and 
characteristics: plain rice is boiled rice with each rice grain still whole and independent of 
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the other, while ‘rice balls’ and ‘rice porridge’ may have the rice grains completely or 
partially broken in the product. 
 
2.2.1 Rice as a staple food and as a source of employment 
The importance of rice lies in many spheres – as food, as a source of income and 
employment (economy), as well as in social development and culture (Maclean et al. 
2002). According to IRRI (2009a) as stated in Appiah et al. (2011), rice is second of the 
world’s most consumed cereals after wheat and before maize. The world average annual 
per-capita consumption of milled rice was 57.8 kg per person (1997-1999 average). This 
average is second to wheat, which averaged 70.8 kg per person from 1997 - 1999 for the 
world average. Maize averaged 19.0 kg per person as the third most consumed cereal per-
capita worldwide from 1997 - 1999 (Childs, 2004). 
It is estimated that rice sustains the livelihood for 100 million people and its production has 
employed more than 20 million farmers in Africa (WARDA, 2005 as stated in Appiah et 
al., 2011). Mohanty et al. (2010) estimated that 2.3 billion farmers and their households 
depend on rice as their main source of livelihood. It has also been stated by Hui (2007) that 
rice grains sustain two-thirds of the world’s population, although the contribution of rice is 
different in the developing and developed countries, and also the types of processing are 
quite different. It is primarily consumed in the milled form, but there are also a number of 
products where rice is added as an ingredient, conferring creaminess, crunchiness, firmness 
and more (Rosell, et al., 2006). According to Hui (2007), rice-based products have often 
been a solution for consumers with allergenic problems due to its hypoallergenicity.  
 
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Table 2.1: Top 10 Rice Producing and Consuming Countries. 
Countries Production  
(metric tonnes) 
Countries  Human consumption 
 (kg per capita per year)  
World 575,105,490 World 85.9 
China 176,342,195 Myanmar 306.9 
India 113,580,000 Vietnam 253.3 
Indonesia 51,579,100 Bangladesh 245.4 
Vietnam 34,447,200 Indonesia 222.6 
Thailand 25,610,900 Philippines 156.8 
Myanmar 22,780,000 Thailand 153.8 
Philippines 13,270,650 Nepal 152.8 
Japan 11,111,000 India 125.0 
Brazil 10,457,100 China 124.1 
(Source: Hui, 2007). 
 
2.2.2 Nutrition composition of rice 
Several factors affect the nutritional value of rice, such as genotype, environmental 
conditions during growth, crop management, storage and post-harvest processes; especially 
the degree of milling is paramount in contributing to the nutritional value of rice (Malik et 
al., 2002). Mbatchou and Dawda (2013) reported on proximate composition of four rice 
varieties cultivated in Ghana. Other studies have also reported the proximate composition 
of other rice varieties grown in different parts of the world. These are presented in Table 
2.2. 
 
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Table 2.2: Proximate Composition of some rice varieties  
(Source: Mbatchou and Dawda, 2013; Oko and Ugwu, 2010; Sompong et al. 2011). 
 
Work reported by Abbas et al. (2011) showed the effect of milling on vitamin and mineral 
content of rice (Table 2.3). 
Sample Country %Moisture %Fat %Crude 
protein 
%Crude 
fibre 
%Ash %Carbo- 
hydrate 
IR12979-24-1 Ghana 8.50 1.20 6.01 0.16 0.86 83.27 
JASMINE-85 Ghana 13.50 1.10 6.82 0.76 0.93 76.89 
WITA-9 Ghana 22.00 0.80 7.08 0.53 2.48 67.11 
ANDY-11 Ghana 13.00 1.20 7.42 0.11 1.37 76.04 
 SIPI Nigeria 18.00 0.50 1.58 2.00 1.00 76.92 
 FARO 14 Nigeria 7.33 0.50  6.22  1.50 1.00  83.45 
BAHNG 
GAWK (BG) 
Thailand 11.55 2.86 9.21 3.63 1.33 75.04 
HAEK YAH 
(HY) 
Thailand 12.38 2.91 7.40 4.18 1.40 75.92 
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Table 2.3: Effect of milling on vitamin and mineral content of rice 
Extraction Rate% 100 Rough 82 Brown rice 72 Milling rice 
 
Mineral content 
 
   
Calcium (mg/g) 0.3 0.1 0.1 
 
Phosphorus (mg/g) 3.1 3.2 1.5 
 
Zinc (ppm) 2.4 3.3 18.0 
 
Iron (ppm) 38.0 8.8 4.1 
 
Copper (ppm) 2.8 2.7 2.2 
 
Vitamin Content 
 
   
Thiamine (μg/g) 2.8 
 
2.4 1.6 
Riboflavin (μg/g) 0.5 0.3 0.2 
 
Pyridoxine (μg/g) 5.1 5.1 1.9 
 
Biotin (μg/g) 91.0 48.0 43.0 
 
Source: Abbas et al. (2011). 
 
Cereal such as rice is deficient in lysine and threonine but have sufficient sulphur 
containing amino acids which are limited in legumes (Wang and Daun, 2006; Iqbal et al., 
2006; Shewry, 2007) whereas legumes are rich in lysine and threonine. Therefore 
combining them in product development is highly beneficial, since there is an increase in 
both the quantity and quality of the protein mix and also in some minerals such as iron 
(Pastor Cavada et al., 2011). 
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2.3 Rice Processing 
Rice harvested from the field is threshed to produce paddy rice or rough rice, where the 
kernel is still within the hull or husk. The paddy rice is dried, either mechanically or by 
open-air. It is then cleaned to eliminate all straw, stones and other foreign objects that are 
larger or smaller than the rice kernels. The cleaned paddy rice may be milled thus 
removing the husk or hull to obtain brown rice which may be consumed as it is.  The 
brown colour of the rice is caused by the presence of the bran layers, which are rich in 
minerals and vitamins especially the B-complex (Hui, 2008). This brown rice can be 
further milled into white grain rice by stripping off the bran of the endosperm and 
separating out broken kernels and other altered kernels such as portions of damaged and 
chalky kernels (Wood, 2002). The milled rice economic value is dependent on the 
proportion of broken rice kernels in the bulk (Monsoor et al., 2004) leading to rice grading. 
The milled rice can then be processed into several products such as table rice, expanded 
rice, snacks and more. The bran obtained can be used for protein concentrate, rice oil and 
biodiesel (Ju et al., 2005).  According to Shaikh et al., (2013), the husks or hull is normally 
used for silica ash or as a source of energy. The broken kernels separated from the whole 
grain can further be milled into rice flour (Hui, 2007) which is normally used for rice 
porridge, bread, biscuit and more.  
 
2.3.1 Parboiled rice 
Parboiling of rice is a process that involves the hydrothermal treatment of paddy before 
milling. It is obtained by soaking paddy rice at a temperature below the gelatinization 
temperature of the starch, steaming with or without pressure for several minutes, and 
cooling and slowly drying to minimize the formation of cracks (Hui, 2007). The resulting 
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rice is slightly yellowish, although its colour intensity decreases after cooking. It has been 
established that parboiled rice presents a superior nutritional value in relation to milled 
rice, mainly due to the retention of minerals and water-soluble vitamins (Juliano, 1985, 
Pedersenet et al., 1989). Parboiling has been found by Wolever et al., (1986) to reduce the 
glycaemic index of rice, particularly that of high and intermediate amylose rice. Work 
carried out by Sareepuang et al., (2008), showed that the parboiling process significantly 
(p<0.05) increased protein and ash contents. At least theoretically, the higher retention of 
micronutrients in parboiled rice has been attributed to their solubilization and migration to 
the centre of the grain during the starch gelatinization process (Juliano, 1985). According 
to Barbiroli et al. (2013), parboiling stiffens the protein network in rice and makes starch 
more accessible to hydrolysis. 
Drying of the gelatinized grain leads to a clear and harder endosperm, more resistant to 
breaking during milling (Hoseney, 1994). Parboiled rice requires longer cooking time 
because the gelatinized starch is more resistant to water absorption and the cooked rice is 
firmer and less sticky (Sinha, 2007). It is also used as a raw material for the subsequent 
production of canned rice, and other processed rice products. Puffed-rice products are also 
obtained from parboiled rice subject to pressure steaming, leading to its higher volume 
expansion (Sinha, 2007). 
According to Bhattacharya et al. (1985) and Larsen et al. (2000), the advantages of the 
parboiling process stems from the gelatinization of rice starch which leads to hardening of 
rice kernel. The preservation of parboiled paddy and milled rice is longer and better than in 
the raw state. Germination is no longer possible and the endosperm has a compact texture 
making it resistant to attack by insects and microorganism (Matz, 1991). 
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Tomlins et al., (2005) stated that parboiling rice is a very common practice in the northern 
part of Ghana. It also causes the rice starch to become gelatinized resulting in harder, 
glassier rice which reduces breakages during milling. Most urban consumers in Ghana do 
not prefer parboiled rice especially due to change in rice colour and so it is difficult for the 
product to penetrate the southern markets and compete effectively with imported rice. 
 
2.4 Rice Quality 
Although rice forms a major part of the Ghanaian diet, locally grown rice is not much 
patronized because it has variable quality characteristics. Several factors account for the 
variability in rice quality (Tomlins et al., 2005).  Rice quality can be considered in terms of 
paddy or milled form and it is mainly graded based upon several criteria, among which are 
starch (amylose/amylopectin) content, flavour, degree of milling, kernel size, percentage of 
broken kernels in milled rice (United States Standards for Rice, 2005). Although broken 
and whole rice kernels have similar starch yields and protein contents, broken kernels have 
been reported to be more susceptible to lipid hydrolysis than whole kernels (Monsoor and 
Proctor, 2003; Wang et al., 2002). 
 
2.4.1 Quality characteristics of Paddy Rice 
The quality characteristics of paddy rice are determined by factors such as the 
environmental weather conditions during production, crop production practices, soil 
conditions, harvesting and postharvest practices (Brooker, 1992). Some characteristic 
which determine the quality of paddy rice are; Moisture content of paddy. Paddy is at its 
optimum milling potential at moisture content of approximately 12-14% wet weight basis. 
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Grains with high moisture content are too soft to withstand hulling pressure which results 
in grain breakage and possibly pulverization of the grain (Badi, 2013). Grain that is too dry 
becomes brittle and has greater breakage. Therefore the optimal stage to harvest grain is at 
about 20-24% grain moisture or about 30 days after flowering (Farid et al., 2014). Purity 
degree refers to the presence of foreign materials such as chaff, stones, weed seeds, soil, 
rice straw, and stalks in the paddy (Badi, 2013). Unclean paddy increases the time taken to 
clean and process the grain. Foreign matter in the grain reduces milling recoveries and the 
quality of rice and increases the wear and tear on milling machinery. According to Sun and 
Siebenmorgen (1993), varietal impurity arising from a mixture of varieties results in 
different sizes and shape making it difficult to adjust hullers, whiteners and polisher to 
produce whole grains. These result in low initial husking efficiencies, a higher percentage 
of re-circulated paddy, non-uniform whitening, and lower grade of milled rice. 
Overexposure of mature paddy to fluctuating temperature and moisture conditions leads to 
development of cracks in individual kernel (Ram, 2009). Ram (2009) again stated that 
cracks in the kernel are the most important factor contributing to rice breakage during 
milling since it reduces head rice recovery.  Another common defect is the presence of 
immature grains. The amount of immature paddy grains in a sample has a major effect on 
head rice yield and quality (Ram, 2009). According to Badi (2013), the immature rice 
kernels are very slender and chalky and this results in excessive production of bran, broken 
grains and brewer’s rice.  
 
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2.4.2 Grain Quality 
Rice is the only cereal crop cooked and consumed mainly as whole grains, and therefore 
quality considerations are very important (Hossain et al., 2009). According to Horna et al. 
(2005), grain quality is one of the important selection criteria by farmers and consumers of 
rice. Grain quality is not just dependent on the variety of rice, but also depends on the crop 
production environment, harvesting, processing and milling systems (Gayin et al., 2009). 
Consequently, the quality of rice grain is a complex character composed of many 
components such as physical, chemical and nutritional. Quality also depends on the 
consumer and the intended end use for the grain.   
 
2.4.2.1 Physical quality characteristics of rice grain 
The physical quality of milled rice is characterized by a combination of desirable and 
measurable characteristics. In line with the market requirements, the characteristics used to 
classify rice into grades are:  
Chalkiness: Rice is referred to be chalky when the milled rice kernel is opaque instead of 
being translucent. Chalkiness disappears upon cooking and has no effect on taste or aroma; 
however it downgrades the quality and reduces milling recovery of rice grain (Gummert, 
2010). 
Milling degree is the measure of percentage bran removed from the brown rice kernel 
(Tokpah, 2010). Milling degree influences the colour and also the cooking behaviour of 
rice as under milled rice absorbs water slowly and does not cook well (Mandal, 2012).  
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Head rice is the weight of head grain or whole kernels in the rice lot. It normally includes 
broken kernels that are 75-80% of the whole kernel. High head rice yield is one of the most 
important criteria for measuring milled rice quality.  
Damaged grains are whole or broken grains showing damage due to moisture, pests and 
diseases. Grain whiteness is a combination of varietal and physical characteristics as well 
as the degree of milling (Mutters et al., 2009). Grain whiteness is measured by a 
colourimeter or as an index number from a whiteness meter. It is often used to determine 
milling degree. According to Gummert (2010), brown rice gives a reading of 
approximately 20 on the whiteness meter, whereas well-milled rice is close to 40. 
Rice is marketed according to three grain sizes and shapes. Thus long grain (3 to 4 times as 
long as it is wide), medium grain (2 to 3 times as long as it is wide) and short grain (short 
and almost round) are recognized. Kernel dimensions are primary quality factors in most 
phases of processing, drying, handling equipment, breeding and grading (Owen, 2001). 
The marketing values of rice as an agricultural product depend on its physical qualities 
after processing. The percentage of whole grain is the most important parameter for the 
rice processing industry. 
 
2.4.2.2 Chemical quality characteristics of rice grains 
Gelatinization temperature can be used to determine the time required for cooking milled 
rice. It is affected by the temperature during ripening  (Mujumdar, 2014). According to  
Mutters et al. (2009), a high ambient temperature during development results in starch with 
a higher gelatinization temperature. Gelatinization temperature of milled rice is determined 
by its alkali spreading value (Mutters et al., 2009). In many rice-growing countries, there is 
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a distinct preference for rice with intermediate gelatinization temperature. Based on 
gelatinization temperature, rice can be classified as low when the temperature range is 
between 55-69oC with alkaline spreading value having a range of 6-7 (Anonymous 1, 
Quality; Ram, 2009). Intermediate has a temperature range of 70-74oC and alkaline 
spreading value of 4-5 (Ram, 2009). Rice has a high gelatinization temperature when it has 
a temperature above 74oC with an alkaline spreading value of 2-3 (Anonymous 1, Rice 
Quality). 
Starch is a polymer of glucose and the starch granules in rice are very small 2-8µm and 
polygonal in shape (Wang et al., 2002). Ram in 2009 stated that the amylose content of 
rice starches usually ranges from 15 to 35%. High amylose content rice shows high volume 
expansion and high degree of flakiness (Mutters et al., 2009). High amylose grains cook 
dry, are less tender, and become hard upon cooling (Ram, 2009). In contrast, low-amylose 
rice cooks moist and sticky (Anonymous 1, Rice Quality). Intermediate amylose rice is 
preferred in most rice-growing areas of the world, except where low-amylose japonicas are 
grown (Mutters et al., 2009). Based on amylose content, milled rice is classified as waxy 
(1-2% amylose), very low amylose content (2-9% amylose), low amylose content (10-20% 
amylose), intermediate amylose content (20-25% amylose) and high amylose content (25-
35% amylose) (Lawal et al., 2011). Mutter et al. (2009) stated that amylose content of 
milled rice can be determined by using the colorimetric iodine assay index method. 
Gel consistency measures the tendency of the cooked rice to harden after cooling (Shinde 
et al., 2014). Within the same amylose group, varieties with a softer gel consistency are 
preferred, and the cooked rice has a higher degree of tenderness. Harder gel consistency is 
associated with harder cooked rice and this is evident in high-amylose rice. Hard cooked 
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rice also tends to be less sticky (Mandal, 2012). Gel consistency is determined by heating a 
small quantity of rice in a diluted alkali (Mutters et al., 2009). In terms of gel consistency, 
measurement ranges and category are as follows: soft rice has a consistency of 61-100mm, 
medium rice has a gel consistency of 41-60mm and hard rice has a gel consistency of 26-
40mm (Mandal, 2012). 
  
Table 2.4: Physical and chemical properties of ten local rice varieties in Ghana. 
Variety Chemical properties (%) Physical properties 
Amylose Protein  Moisture Ash Fat Grain classification Colour  
     Size   Shape   
Ex-Hohoe 22.70 5.60    11.60 0.70 0.70 Long Slender White 
Marshall 19.30 5.93    12.20 0.60 0.70 Medium Slender White 
Jasmine 85 20.20 5.81    11.60 0.60 0.50 Long Slender White 
Viwonor  30.50 7.32    11.39 0.44 1.56 - - Red 
Bouake 189 31.60 8.08    10.41 0.58 0.11 - - - 
Wita 9 28.39 7.53    13.78 0.52 1.23 - - - 
TOX 3107 27.75 7.98    10.75 0.46 1.25 - - - 
Jet 3 - -     - - - - - - 
Perfumed  25.60 8.55    12.91 0.47 0.36 - - - 
Emo korkor - -     - - - - - Red 
Source: Awudi, (2013) (MPhil thesis). 
 
Table 2.5: Amylose content and colour of four rice varieties grown in Ghana. 
Variety      L*      a*     b* Amylose (%) 
Ex-Baika 73.98±0.03c 1.46±0.04c 8.36±0.15a 17.5±0.91b 
Ex-hohoe 69.04±0.19a 6.43±0.05e 10.54±0.06c 22.7±0.06d 
Jasmine 85 72.50±0.38b 1.91±0.10d 9.00±0.06b 20.2±0.02c 
Togo marshall 74.22±0.42c 1.16±0.10b 9.08±0.10b 19.3±0.01c 
Source: Diako et al. (2011). 
 
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2.5 Soybean 
2.5.1 General information on soybean 
Legumes such as beans, peas, nuts, and soybeans play an important role in the traditional 
diets of many regions throughout the world. Soybeans (Glycine max) belonging to the 
family leguminosae is  one of the oldest cultivated crops of the tropics and sub-tropical 
regions, and one of the world’s most important sources of protein and oil (Arogundade et 
al., 2009).  In general, soybeans comprise approximately 8% hull, 90% cotyledon, 2% 
hypocotyl axis (Cheftel et al., 1985 as stated in Eshun, 2009). The soy cotyledons contain 
the highest percentage of both protein and oil, whereas the hull has the lowest values of 
these components (Oomah et al., 1996). The seeds vary in shape and colour depending on 
the cultivar. In shape, they can be spherical to flatten while the colour varies from white, 
yellow and brown to black. It is the richest sources of protein among the plant foods.  Soy 
protein provides several functionalities such as water-holding, binding, and emulsifying 
properties (Arrese et al., 1991; Liu, 1997). Soy protein lowers blood serum cholesterol in 
high cholesterol individuals and decreases the risk of coronary heart disease (Anderson et 
al., 1995; Messina, 1999, 2001). Work reported  by Kennedy (1995); Gallagher et al., 
(2000) and Trock et al., (2000) show that soy protein can also decrease the incidences of 
breast and prostate cancer and inhibit bone resorption, partially because of the presence of 
isoflavones. Soy oils contain a significant amount of unsaturated acids: α -linolenic acid, 
known as omega-3 acid, linoleic, γ-linolenic and arachidonic acid, known as omega-6, 
oleic acid known as omega-9 acid, are important in the human nutrition (Nikolic et al., 
2009; Olguin et al., 2003). Such health benefits have increased the interest in incorporating 
soy into food products. 
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2.5.2 Uses of Soybean 
Soybeans in the form of full fat flour, partially defatted, concentrate, isolate and texturized 
have been used in a wide range of food products. According to Tunde-Akintunde (2000), 
soybean can be processed into soy milk, a valuable protein supplement in infant feeding, 
soy curds and cheese. It is also used in the production of soy sauce, tempeh, miso, natto, 
making of candies and ice cream and soybean flour which could be mixed with wheat flour 
to produce a wide variety of baked goods such as bread and biscuits (Onwueme et al., 
1999). In Ghana, soybean is becoming an important crop due to its high protein and oil 
content. It is used in the production of soy khebab, soy paste, cooking oil, weanimix, and 
non-dairy milk especially for lactose intolerant consumers and the more. 
 
2.5.3 Anti-nutritional factors 
According to Liener (1994) and Liu (1997), the anti-nutritional factors (ANFs) in soybean 
are often associated with the low acceptance of soybean products as they also inhibit 
protein digestibility. These mainly consist of heat labile trypsin inhibitors, lectins, 
goitrogens, and phytates. In order for the nutritional value of soybean meal to be 
maximised, the anti-nutritional factors need to be inactivated or minimised. Research by 
Akpapunan et al. (1979) also shows that low-molecular weight oligosaccharides, primarily 
raffinose, stachyose and verbascose present in most legume seeds of which soybean is not 
of exception are linked to flatulence. According to Ndubuaku et al. (1989), these can be 
reduced through fermentation, removal of seed coat (decorticating), soaking in water, 
germination and cooking with a mixture of sodium carbonate and bicarbonate. 
 
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2.5.4 Soybean quality 
Protein quality of soybean depends on two parameters: protein digestibility, and the 
amount of anti-nutritional factors (Parsons et al., 1991). Temperature is critical in the 
production of soybean in order to deactivate the anti-nutritional factors naturally occurring 
in the raw soybeans. Inadequate heating fails to completely destroy the anti-nutritional 
factors. An experiment carried out by Caprita et al., (2010) revealed that urease index (UI) 
is useful to determine whether soybean meal has been heated enough to reduce the anti-
nutritional factors.  
The routine determination of protein digestibility and anti-nutritional factors is difficult 
especially in the daily production of soybean product and can therefore be replaced with 
indirect tests such as urease index (UI), protein dispersibility index (PDI), nitrogen 
solubility index (NSI) and KOH protein solubility (PS). 
 
2.5.5 Soybean and its application as a fortificant 
One of the cheapest and less complicated way to curb the Protein Energy Malnutrition 
(PEM) in the developing world including Ghana is through food fortification of plant 
origin.  
Soybean has great potential as food because of its high levels of good quality protein and 
oil. It contains all the macro nutrients required for good nutrition, complete protein (40 
g/100 g), soluble carbohydrate (18 g/100 g), dietary fiber (15 g/100 g) and fat (18 g/100 g) 
as well as vitamins and minerals (Liu, 1997; Singh et al., 2009). Soybeans supply all nine 
essential amino acids and have cholesterol reducing and anti-carcinogenic properties (Riaz, 
1999). According to Caprita et al., (2010), soybean is the only vegetable food that contains 
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complete protein. Its high level of threonine and the high digestible lysine content 
complements the lysine deficiency of rice grains used in food products.  
 
2.6 Snack intake 
Snacks are small portions of food normally consumed in between meal times. Over the past 
few years in Ghana, there has been a shift in the food consumption patterns from 
traditional meal habits to processed foods like snacks (Steiner-Asiedu et al. 2012). The 
consumption of snacks has considerably increased because of changes in life styles and 
based on consumers demand for convenience foods (Harris et al., 2007, Omwamba et al.  
2014). 
 
 2.6.1 Types of snacks  
Snack processors use specific unit operations and different technologies to produce and 
classify snacks. According to Huber et al., (1990), snacks can be classified as follows: (i) 
first generation snacks: snacks in this category include all the natural products used for 
snacking, nuts, potato chips and popcorn. It is also obtained from whole grains combined 
with moisture content, cooking temperature and drying (Huber et al., 1990); (ii) second 
generation snack: majority of the snacks fall in this category. All the single ingredients 
snacks, simple shaped products like corn tortilla chips and puffed corn curls and all directly 
expanded snacks are included in this category; (iii) third generation snacks: these are not 
expanded through extrusion process and are therefore known as pellets or half cooked 
products (Serna-Saldivar, 2012). They normally expand through a process of deep-frying 
or hot air, or with the use of microwaves, just before consumption. Although they have an 
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additional process for expansion, these products present great advantages in transport and 
storage (Huber et al., 1990). 
Out of these extruded snacks are important part of many consumers’ daily nutrient and 
calories intake (Teltweiler, 1991). 
 
2.7 Extrusion processing 
Extrusion combines several unit operations such as mixing, kneading, cooking, shearing, 
shaping and forming (Akdogan, 1999). In extrusion cooking, the extruder transforms the 
starchy ingredients into a dough like melt under pressure (Serrano, 1997).  This allows the 
cooked mass to be forced through small die openings in order to form a shape and expands 
to its final shape. A cutting device reduces the continuous stretch into a biting size (Moore, 
1994). Extrusion cooking of starchy materials has become a very common technique to 
obtain a wide range of products, such as snacks, breakfast cereals, baby foods, 
confectionery, bakery products, pastas, pet food and meat analogues products (Bouzaza et 
al., 1996; Pansawat et al., 2008).  It is not only a high temperature short time process, but 
also a versatile one especially with respect to ingredient selection to obtain a wide range of 
snack products such as direct expanded snacks, co-extruded snacks and indirect expanded 
snack products. The production of snacks through extrusion represents a great achievement 
for the Food Technology area as it efficiently converts crude flours into products with 
different shapes, flavours and long shelf-life. The advantages of this cooking process are 
based mainly on the fact that it is a high temperature short time (HTST) process, which 
minimises the degradation of food nutrients by heat while improving digestibility by 
gelatinising starch, denaturing protein and deactivating undesirable compounds, such as 
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enzymes and non-nutritional factors (Alonso et al., 2000a; Shimelis et al., 2007). A high 
temperature, short time (HTST) procedure is one which uses short residence time, high 
temperature, high pressure, large shear forces and intensive mixing during the process 
(Zheng et al., 1994). Extrusion cooking has become one of the most popular technologies 
worldwide for processing a number of food products due to its versatility, high 
productivity, low operating costs, energy efficiency and shorter cooking times (Frame, 
1994; Harper, 1981; Smith et al., 1992). Cereals have excellent expansion properties 
because of their high starch content and are well suited to thermal extrusion (Singh et al., 
1994). According to Rosell and Marco (2008) and Bryant et al. (2001), the unique 
properties of rice such as its hypoallergenicity, ease of digestion and bland taste make it a 
very desirable grain for new extruded food product development.  
 
2.7.1 Characteristics of extruded products and their quality indices  
Despite increased use of extrusion processing due to its advantages especially low cost, it 
is still a complicated process that has yet to be mastered (Desrumaux et al., 1999). Small 
variations in processing conditions affect process variables as well as product quality such 
as crispness, hardness and more. Product quality can vary considerably depending on the 
extruder type, screw configuration, feed moisture content, residence time, screw speed, 
feed rate and temperature profile in the barrel session (Harper, 1981; Baike et al., 2004; 
Ding et al., 2005).    
The effect of extrusion variables on the properties of extruded cereals has been studied 
extensively (González et al., 2000; Kokini et al., 1992; Mason et al., 1986). The texture of 
expanded cereal based snacks is determined mainly by extrusion conditions such as 
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temperature profile in the barrel session, screw speed and feed moisture content (Ding et 
al., 2006). It is well known that the addition of legumes to cereals produces an increase in 
both the amount and quality of the protein mix (Young, 1991). This addition represents an 
economic way to improve the protein value of cereal-based foods (Messina, 1999). Starch 
is the main component of directly expanded products and the extent of starch 
transformation plays an important role in the functional properties of the final product. 
Extrusion conditions, characteristics of the starch granule and presence of other 
components such as protein, fibers and sugars directly affect the degree of transformation 
(Chanvrier et al., 2007). For example, molecules that readily hydrate (such as sugars and 
salts) may restrict water available to starch and reduce the degree of gelatinization (Tester 
et al., 2003). Variation in water addition is one processing parameter known to change the 
degree of transformation of the matrix, leading to differences in starch digestibility and in 
microstructure (Karkle et al., 2010; Yagci et al., 2010). Chanvrier et al. (2007) have 
suggested that extrudate microstructure may be used to control starch susceptibility to 
enzymatic action, however systematic studies on the relation between these two are 
lacking. Work carried out by Chaiyakul et al. (2008) showed that increasing of protein 
content significantly increased hardness and crispness intensity but less sticky mouth feel 
coating. Increasing feed moisture content resulted in increased final extrudate hardness, 
crispness and brittleness but reduced sticky mouth coating and colour.  
 
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2.7.2 Physicochemical Characteristics of extruded products 
2.7.2.1 Colour 
Colour is an important visual characteristic of food, and it also affects consumer preference 
and purchase decisions. According to Tiwari et al. (2008) and Esteve et al. (2005), colour 
correlates well with other physical, chemical and sensory quality indicators in food. Thus it 
plays a major role in the assessment of internal quality in the food industry and in food 
engineering (Alcicek et al., 2012; Mancini et al., 2005).  
According to a work carried out by Hagenimana et al. (2006), changes in colour in relation 
to extruded product are mostly dependent on temperature and moisture content. The higher 
the feed moisture content, the brighter was the colour of the extrudates which were 
characterized by a high L* value and low a* value. Decreasing moisture reduced the 
lightness due to different competing effects during the process. High temperatures in 
combination with low water content are known to favour the Maillard reaction between 
reducing sugars and free amino groups. Chaiyakul et al. (2008) showed  that  increasing 
protein content or barrel temperature, or decreasing feed moisture resulted in decreasing of 
L*, while a* and b* values were increased. 
  
2.7.2.2 Water absorption index (WAI) 
Anderson et al. (1969) stated that the WAI measures the amount of water absorbed by 
starch and can be used as an index of gelatinisation. Altan et al. (2008), observed that the 
WAI measures the volume occupied by the granule or starch polymer after swelling in 
excess water. Work carried out by Hagenimana, et al., (2006) showed that the highest 
values of WAI of an extruded snack was obtained at 19–22% moisture content. This was 
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because moisture, acting as a plasticizer during extrusion cooking, reduced the degradation 
of starch granules and this resulted in an increased capacity for water absorption. However, 
at lower moisture content (16%) and an increase in extrusion temperature of 160oC 
decreased WAI and this was probably due to an increase in starch degradation or starch 
decomposition as confirmed by Pelembe et al. (2002).  Ding et al. (2006) also stated that 
the WAI decreases with increasing temperature if starch melting or dextrinization prevails 
over the gelatinization phenomenon.  
 
2.7.2.3 Water solubility index (WSI) 
WSI measures the amount of soluble components released from the starch after extrusion 
cooking (Ding et al., 2006) and it is often used as an indicator of degradation of molecular 
components (Kirby et al., 1988). WSI is also reported to be related to the presence of 
soluble molecules that have sometimes been attributed to dextrinization (Colonna et al., 
1989). Work carried out by Hagenimana, et al. (2006) showed that low moisture content in 
extrusion cooking caused an increase in the amount of degraded starch granules resulting 
in an increased formation of water-soluble products. This phenomenon is caused by greater 
shear fragmentation of the starch during extrusion at low moisture contents. Nevertheless, 
extrusion of non-waxy, high amylose rice has been reported to result in low WSI (Pan et 
al., 1992). Furthermore, results from work carried out by Altan et al. (2008) showed that 
WSI increased significantly (P < 0.05) with increasing screw speed. A direct comparison of 
WSI values in the literature is difficult due to the difference in processing conditions and 
raw material used. 
 
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2.7.2.4 Expansion ratio  
According to Guy and Horne (1988) and Harper (1981), when starch is extrusion-cooked, 
expansion is dependent on the formation of a starch matrix that entraps the water vapour, 
resulting in formation of bubbles. Padmanabhan and Bhattacharya (1989) explained that 
there are two dominant forces that causes expansion of extrudates. One is the elastic force 
and the other is the bubble growth force due to water vapour pressure. The dough moisture 
flashes off as steam at the die exit and causes expansion of extrudates on rapid extrusion at 
high temperatures. Ding et al. (2006) in the work also stated that the feed moisture content 
was found to have the greatest effect on the expansion of the extrudate. Increased feed 
moisture content during extrusion may reduce the elasticity of the dough through 
plasticization of the melt, resulting in reduced specific mechanical energy (SME) and 
therefore reduced gelatinization, decreasing the expansion ratio of the extrudate (Ding et 
al., 2006). Furthermore, Liu et al. (2000) explained that the increased feed moisture 
content reduced friction between the feed material, screw and barrel and also had a 
negative impact on the starch gelatinisation and reduce the product expansion. Moreover, 
Suksomboon et al. (2011) in the work stated that increased barrel temperature led to a 
sharp increase in expansion ratio value at all moisture content and screw speed (p < 0.05). 
Screw speed was also observed to have a slight effect on the expansion ratio of snacks 
(Suksomboon et al. 2011). Thus increased screw speed caused a slight decrease in 
expansion ratio. Launay et al. in 1983 explained this to be that the higher shear resulting 
from the higher screw speed reduces the melt viscosity of the feed material resulting in 
decreased expansion ratio. 
 
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2.7.2.5 Bulk density (BD) 
The bulk density (BD) is an index of the extent of puffing. According to Ding et al. (2005), 
feed moisture and protein content have been found to be the main factor affecting the bulk 
density of extrudates. Previous work carried out by Hagenimana, et al., (2006) showed that 
the lowest BD value were obtained when rice flour was extruded at a lower moisture 
contents and higher temperatures, whereas the highest value was obtained at higher 
moisture contents and lower temperatures. On the contrary, Suksomboon et al. (2011) in 
the work stated that the bulk density of snacks increased directly with feed moisture at all 
barrel temperatures and screw speeds (P < 0.05). This is because feed moisture had an 
influence on the reduction of elasticity characteristics and gelatinisation of the starch-based 
materials (Fletcher et al., 1985). Suksomboon et al. (2011) again stated that high barrel 
temperature led to a decrease in bulk density of extrudates (P < 0.05). This is because an 
increase in barrel temperature would increase the degree of superheating of water 
promoting bubble formation and also a decrease in melt viscosity leading to increased 
expansion that caused a decrease in density of extrudates. Bulk density values were found 
to decrease with an increase with extrusion temperature and screw speed and this is 
probably due to starch gelatinization. According to Case et al. (1992), increase in 
gelatinization leads to an increment in the volume of an extruded products while 
decreasing the bulk density of the extruded products.   
 
2.7.2.6 Texture  
Mechanical properties of cereal (starch-based) extrudates are perceived by the final 
consumer as criteria of quality. Texture quality has an influence on taste sensory 
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evaluation, and thus on the acceptability of the product. Characteristics that have great 
influence on acceptability are crispness, elasticity, hardness and softness. Chaiyakul et al. 
(2008) found that an increase of protein content from 20 to 30%, resulted in significant 
(p≤0.05) increase in hardness, crispness and noise intensity. These results were similar to 
the instrumental measurement, for which breaking strength index increased as protein 
content increased. Similarly Ding et al in 2005 concluded that extrudates from wheat had a 
higher breaking strength as compared to extrudates from rice and this was due to the 
presences of the gluten protein in wheat (Harper, 1981).  
Increasing feed moisture content (>30%) led to an increment in breaking strength index 
(Ding et al., 2005). This was due to the collapsing of the expanded product as a result of 
high moisture content thereby becoming harder. According to work carried out by Faller 
and Heymann (1996), it was noted that low moisture (19%) potato extrudates were harder 
and crispier than high feed moisture (25%) samples. Murray (2001) also found that 
brittleness of maize based extrudates increased progressively with increased feed moisture 
content. Singh et al. (2007) noted that the hardness of rice-pea grits extrudates decreased 
with the increase in feed moisture content from 18 to 24 %. Furthermore, Chaiyakul et al. 
(2008) noted that decrease in barrel temperature resulted in an increase in breaking strength 
index. 
 
2.7.2.7 Microstructure 
Density, porosity and pore size distribution, are very useful properties for food process 
design, since they characterize the texture and quality of foods such as snacks. Moraru et 
al. (2003) stated that macro/microstructure formation in extrusion processes is the 
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consequence of several overlapping events including biopolymer structural transformations 
(starch gelatinization and/or protein denaturation), nucleation, die-swell, cell growth, and 
cell collapse. The microstructure and morphology of extruded foods and their quality, is 
significantly determined by extrusion variables such as screw configuration, feed moisture, 
temperature profile in the barrel session, residence time, screw speed and feed rate as well 
as the ingredient selection. According to Wang et al. (2005), water acts both as a 
plasticizer for melt formation and as a blowing agent for expansion during conventional 
steam-based extrusion cooking. When the melt passes through the extruder die to the 
outside, it undergoes a sudden pressure drop resulting in water vapour nuclei generation in 
the melt. These cells grow in size as additional water vapor flashes off. Research work by 
Winoto (2005) showed that supercritical CO2 (SC-CO2) and die diameter had effect on 
product morphology of the extrudates. The work showed that as the die diameter decreases 
from 5.9 to 2.9 mm, the cross sectional expansion and the number of cells increased 
whereas the average cell size of the extrudate decreased. 
 
2.7.2.8 Protein digestibility 
The utilization of legumes such as soybean is limited due to the presence of certain heat 
labile and heat-stable antinutritional factors (ANF) that exhibit undesirable physiological 
effects (Pusztai et al., 2004). Among these are phytates, polyphenols, enzyme inhibitors 
(trypsin, chymotrypsin, and α-amylase) and hemagglutinins. On the other hand, Shahidi 
(1997) reported that some antinutrients might exert beneficial health effects at low 
concentration. Therefore several attempts have been made using different food processing 
methods such as soaking, germination, decortication, fermentation, autoclaving, radiation, 
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roasting, supplementation with various chemicals and enzymes and extrusion cooking in 
order to improve upon their digestibility and nutritive value (Fernandez et al., 1997; 
Alonso et al., 1998; Alonso et al., 2000a, Ramakrishna et al., 2006). The presence of 
antinutritional factors in legumes is shown to be reduced at varying degrees based upon the 
food preparation method. Kalpanadevi et al., (2013) in their work noted that the 
combination of germination followed by autoclaving completely eliminated the total free 
phenolics, tannins, hydrogen cyanide, phytic acid, trypsin inhibitor, oligosaccharides and 
phytoheamagglutinating activity of Vigna unguiculata subsp. unguiculata thereby 
increasing its protein digestibility and improving its protein quality. Also, Abd El-Hady, et 
al., (2003) indicated that soaking and extrusion significantly decreased antinutrients such 
as phytic acid, tannins, phenols, α-amylase and trypsin inhibitors. Martín-Cabrejas et al. 
(2009) in their work showed that cooking after soaking of some legumes promoted higher 
protein digestibility (from 7% to 12% improvement). 
 
2.7.2.9 Odour and taste characteristics 
Flavour/odour and taste are mostly used as quality parameters by consumers. Traditionally, 
sensory evaluation has been used for taste analysis. Human sensory panels and 
chromatographic techniques such as gas chromatography–mass spectrometry (GC–MS), 
high performance liquid chromatography (HPLC) and ion chromatography (IC) have been 
the traditional methods used for odour analysis and regulation in the food industry.  
According to Franҫois et al., (2003), GC–MS, HPLC and IC provide very detailed 
information regarding the contents of the odourous compounds. Although chromatographic 
techniques such as GC–MS can separate, identify and quantify individual volatile 
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chemicals, it is very hard to correlate the data with those by human sensory evaluation. 
Since odours are usually composed of different volatiles, the chromatographic techniques 
are not practical and handy for persons’ daily use. Human sensory evaluation is a powerful 
method for odour and taste analysis since it provides immediate aroma and taste profile. 
However, it possesses some disadvantages in areas such as the standardization of 
measurements, correctness of training, reproducibility, high cost and taste saturation of the 
panelist (Beullens et al., 2008). Lau et al., (2000) noted that this method is highly 
subjective and illness or other factors can influence their performance and the final results 
of human sensory evaluation. 
In view of this, the electronic nose (e-nose) and electronic tongue (e-tongue), which works 
by mimicking the human olfactory system and taste buds, respectively, have proved to be  
good alternatives for traditional techniques in perceiving odour and taste of food (Escuder-
Gilabert et al, 2010). They can also be used in situations where human panelists could be 
exposed to potentially hazardous materials. E-noses and tongues are analytical systems that 
provide global information about the sample instead of information on particular 
components. However, if the data matrix obtained by such multisensory systems is 
analyzed with adequate chemometric processing tools, descriptive or predictive 
information of particular parameters could be extracted (Oliveri et al., 2010). Electronic 
nose and tongue can be considered as a qualitative and quantitative device for the analysis 
of complex samples. The objectives of qualitative analysis consists of discrimination, 
classification or identification of different samples (Vlasov et al., 2005). 
 In the area of foods, e-nose has been successful in studying flavour release relationships in 
low moisture bakery products (Piazza et al., 2008); monitoring the aroma of wines (García 
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38 
 
et al., 2006) and various fruit juices (Gobbi et al., 2010; Karlshøj et al., 2007; Reinhard et 
al., 2008). Also, Feng et al. (2011) analysed volatile compounds of Mesona Blumes 
gum/rice extrudates via GC–MS and electronic nose. The application of metal oxide 
microbalance array sensor for volatile and smell analysis has been reported in literature 
(Wyszynski et al., 2005; Strike et al., 1999). Electronic nose with the function of chemical 
imaging (Weimar et al., 1998; Gopel, 1998) and multiparameter sensor systems (Yu et al., 
2007) have been described. The sensing system can be an array of different sensing 
elements (chemical sensors), where each element measures a different property of the 
sensed chemical. Generally, result of an electronic nose is based on its evaluation of the 
sum of all the detected volatile compounds (Yu et al., 2008). The volatile compounds 
presenting in the headspace interact with the array of non-selective sensor and produce a 
chemical fingerprint or pattern characteristic to the odour or volatile compounds (Yu et al., 
2009) and the pattern recognition software system is able to distinguish and recognize the 
odours. 
Electronic tongue has also been used in evaluating the taste of food covering the area of 
freshness evaluation and shelf-life investigation (Gomez et al., 2008), process monitoring 
(Turner et al., 2003), authenticity assessment (Parra et al., 2006), foodstuff recognition 
(Legin et al., 1997), quantitative analysis and other quality control studies (Beullens et al., 
2006). The basic idea behind electronic tongue technology is the application of an array of 
non-specific chemical sensors with a high cross-sensitivity, thus a wide selectivity towards 
a range of inorganic and organic substances in solutions as possible (Vlasov et al., 2005). It 
can provide the corresponding food material with a digital fingerprint, and classify the 
samples according to their quality by combining various chemometric data-processing 
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tools. The measuring principle for the E-tongue is based on the measurement of potential 
changes of several working electrodes against a reference electrode in zero-current 
conditions. The potential of the working electrode is a function of activity of ionic species 
across an ion sensitive membrane by diffusion in a sample solution; the potentiometric 
response depends on the distribution of ions on the sensor membrane (Ciosek et al., 2007). 
It is evident that the e-nose and e-tongue sensor systems do not look at the same features 
when applied to the same sample. The e-nose sensors come into contact with its headspace 
while for the e-tongue, electrodes are immersed in the sample (Di Natale et al., 2000). The 
advantages of electronic nose and electronic tongue include rapid, real-time detection, 
lower operation costs, higher automation and easy-to-handle measurement set-up. 
 
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2.8 Conclusion 
From the preceding literature review it is clear that there have been research studies on rice 
in Ghana that have focused on the physicochemical characteristics and sensory quality of 
some local varieties. Several other studies have also been conducted to compare locally 
grown rice to imported rice as a basis for the improvement of local rice and enhancement 
of its market competitiveness (Gayin et al., 2009; Tomlins et al., 2007; Adu-Kwarteng et 
al., 2003; Amissah et al., 2003; Manful et al., 1996). Research work has also been reported 
on the quality and sensory characteristics of varieties that are on the verge of being 
released in Ghana (Adu-Kwarteng et al., 2003). However, very few works have been 
carried out on diversifying the use of the less preferred rice varieties. Such uses would 
include development of other food products such as snacks. There is, therefore the need to 
conduct research on other uses of local rice varieties which are not preferred for cooking. 
Different food products such as snacks can be obtained by combining the rice with local 
staples presently available in the country. Combination of cereals such as local rice 
varieties with inexpensive plant protein sources such as legumes can provide the ingredient 
base for development of new food products. Cereals are deficient in lysine but have 
sufficient sulphur containing amino acids which are limited in legumes (Tsai et al., 1975; 
Wang and Daun, 2006; Iqbal et al., 2006; Shewry, 2007) whereas legumes are rich in 
lysine. The effects of the supplementation are highly beneficial, since nutritive value of the 
product is also improved. This project studied the combination of local and readily 
available raw materials which are inexpensive to develop a ready to eat extruded snack 
with long keeping quality and overall consumer acceptability.  
 
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3.0 MATERIALS AND METHODS 
3.1 Raw materials 
The milled and paddy forms of two widely grown local rice varieties namely Viwonor 
(high amylose content) and Togo Marshall (low amylose content) were obtained from the 
agents of Ghana Rice Inter-Professional Body (GRIB) in Ghana. Soybean (Nangbaar 
variety) was obtained from the Crop Research Institute of the Council for Scientific and 
Industrial Research (CSIR) located in Kumasi.  
 
3.2 Methods 
3.2.1 Determination of physicochemical properties of rice grains  
The physicochemical properties of the rice grains, such as chalkiness, grain dimension, 
grain hardness and Alkaline spreading value (ASV) were determined using standard 
procedures. 
 
3.2.1.1 Chalkiness and grain dimension determination. 
Grain dimensions and chalkiness were estimated using the S21 Rice Statistics Analyzer, 
(LKL Technologia, Brazil). The equipment was run with a Classficador S21 version 4.05 
Software. The S21 was calibrated using a reference sample supplied by the manufacturer. 
Approximately 50g of whole grains were weighed and emptied into the sample receiver of 
the S21 Rice Statistics Analyzer. The ‘’long white’’ classification set up was opened in the 
capture mode software. The equipment was then switched on to vibrate and cause the 
release of individual grains from the receiver to slide on a blue tile background and pass 
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beneath the attached camera that captured images of the grains. When all the grains had 
exited the receiver; the image capturing mode was stopped.  
The grain dimensions were determined by processing the captured images and applying the 
‘’advanced filter length distribution’’ on the software. The grain length and width were 
then recorded and the length/width ratio calculated.  
To determine chalkiness, the ‘basic filter-chalky distribution’ was applied. The percentage 
total chalky area for the samples were recorded and reported as the percentage chalkiness 
of the samples.  
Chalkiness for ‘Togo Marshall’ and grain dimension for both rice varieties (‘Togo 
Marshall’ and ‘Viwonor’) were determined in triplicate and duplicate. Chalkiness was not 
determined on the Viwonor rice variety due to the natural reddish pericarp. 
 
3.2.1.2 Raw grain hardness 
Grain hardness was measured using a grain hardness tester (Fujihara Seisakusho LDT, 
Japan) as described by Fofana et al., (2011).  
Ten grains were used in the determination of hardness for each rice sample. The handle of 
the equipment was initially turned anti-clockwise to make room to place a grain on the 
sample table. The handle was then turned clockwise until a cracking sound was heard. At 
this time, the black pointer returned to the zero point and the “mother pointer” (red) 
remained. The reading of the “mother pointer” (kg) indicated the hardness of the grain. 
This measurement was carried out in duplicate. 
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3.2.1.3 Alkaline spreading value (ASV) 
Alkaline spreading value (ASV) was determined using the method developed by Little et 
al. (1958) which involved visual observation of the degree of dispersion of grains of the 
milled rice after their immersion in 1.7% potassium hydroxide solution (KOH).  
Approximately 10ml of 1.7% KOH solution was poured on 6 rice grains placed in a 
transparent petri dish and incubated at room temperature for 23 hours. ASV values were 
then evaluated by comparing it to a standard 7 point numerical scale chart (Jennings et al., 
1979). Grains that were unaffected were given ASV of 1 and grains that were dispersed 
and disappeared completely were given a score of 7. Based on the alkaline spreading value, 
the gelatinization temperature (GT) of the rice samples was directly determined. Analysis 
was carried out in duplicate. 
 
3.2.1.4 Milling recovery 
This was determined from an already milled rice. The brown rice was polished in a Ricepal 
32 (Yamamoto Co., Japan) rice polisher. The milled rice was separated into whole and 
broken grains using a Test rice grader.  The milling recoveries were then estimated using 
the following equations:  
 
Head rice yield (%) = weight of whole grains 
weight of brown rice 
 
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3.2.1.5 Cooking time 
This was carried out according to Fofana et al. (2011). Five grams of milled rice was 
poured into 135ml of vigorously boiling distilled water in a 400ml beaker and covered with 
a watch glass. After 10min of further boiling, 10 grains were taken out every minute with a 
perforated ladle. The 10grains were pressed between two petri dishes and the grains were 
considered cooked when at least 9 out of the 10 grains no longer had opaque centers. The 
time was then recorded. This analysis was carried out in duplicate. 
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3.2.2 Parboiling of Rice 
Parboiling of rice was carried out using a local process in a locally designed utensil in 
which both soaking and steaming is done. |The flow chart for the process is shown in 
Figure 3.1.  
 
 
 
 
 
 
 
 
      Drain water 
  
 
 
  
 
 
Figure 3.1: Process flow for parboiling rice   
(Anonymous 2). 
 
Steam paddy (120 oC for 20min) 
     Dry to a moisture content of 12-14% 
Paddy rice 
Winnow/Clean 
Wash with clean water 
Soak in water at a maximum 
temperature of 95oC for 24 hours 
       Mill rice 
     Package 
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3.2.3 Flour Preparation from milled and parboiled rice 
Rice flour was prepared according to the flow chart in Figure 3.2. 
 
 
 
 
 
                                                     
 
 
 
 
Figure 3.2: Process flow chart for rice flour preparation   
 
3.2.4 Determination of physicochemical properties of rice flour 
The parameters determined were colour, apparent amylose content, protein solubility and 
electrophoretic pattern of the extracted proteins 
 
3.2.4.1 Colour of rice flour 
The colour parameters of flour from raw and parboiled rice were placed in a plastic petri 
dish and was gently pressed to avoid space between them. L* (brightness/darkness index), 
a* (red/green index), b* (yellow/blue index) were determined using a Colorimeter (Minolta 
CR-300, Japan). The equipment was calibrated using the white calibration porcelain. The 
Mill Rice (raw and parboiled) 
    Clean and sort 
Cool 
Mill into flour (particle size 
500µm)  
Pack in sack lined with a 
polythene bag 
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protocol for calibration was adhered to. The positive and negative L* indicates 
brightness/darkness, positive and negative a* value indicates redness and greenness, 
respectively, and b* indicates yellowness for positive value and blueness for negative 
value. The Colorimeter was calibrated against a standard white calibration porcelain. For 
each sample, 5 measurements were taken at several points. 
 
3.2.4.2 Apparent Amylose content 
The cleaned milled grains (Raw Togo Marshall, Parboiled Togo Marshall, Raw Viwonor 
and Parboiled Viwonor) were ground in an Udy Cyclone Mill (UdyCorp., Fort Collins, 
USA) with a 1.0 mm mesh screen.  
Amylose content was measured using the standard iodine colourimetric method ISO 6647-
2-2011. Ethanol (1 ml, 95%) and 1M sodium hydroxide (9ml) were added to rice flour 
(100 mg) and heated in a boiling water bath for 10min to enable starch gelatinisation.  
After cooling, 1M acetic acid (1ml) and 2 ml iodine solution (prepared by dissolving 0.2g 
iodine and 2.0g potassium iodide in 100ml distilled water) were added and the volume 
made up to 100ml with distilled water. Absorbance of the mixture was measured using an 
Auto Analyzer 3 (Seal Analytical, Germany) at 600 nm. Amylose content was quantified 
from a standard curve generated from absorbance values of four well-known standard rice 
varieties (IR65, IR24, IR64 and IR8).  For each sample four replicate measurements were 
taken. 
 
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3.2.4.3 Protein solubility of rice 
Protein solubility of the two rice varieties; raw and parboiled (flour from ‘Togo Marshall’ 
and ‘Viwonor’) were determined using three different buffers. Thus buffer A: 50mM 
sodium phosphate monobasic dihydrate and 100mM NaCl at pH 7.0; buffer B: 50mM 
sodium phosphate monobasic dihydrate, 100mM NaCl and 6M urea at pH 7.0; buffer C: 
50mM sodium phosphate monobasic dihydrate, 100mM NaCl, 6M urea and 10mM DL-
Dithiothreitol (DTT) at pH 7.0. Protein solubility was carried out by suspending 0.5 g of 
finely ground sample in buffer A and 0.25g of finely ground samples in buffer B and also 
in buffer C. Suspensions were vortexed and agitated on a rotary shaker for 1 hour at 22oC. 
The samples were then centrifuged at 10,000 rpm, at a temperature of 20oC for 30min. The 
supernatant containing the total soluble proteins after centrifugation was used to prepare 
samples for Bradford Protein Assay and SDS-PAGE. The amount of protein in the 
supernatant was determined by the dye-binding method (Bradford, 1976) using bovine 
serum albumin as a standard. Results are expressed as mg proteins/g sample. 
 
3.2.4.4 Electrophoretic pattern of extracted proteins in rice 
Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the rice 
varieties; raw and parboiled was performed according to the method described by Iametti 
et al. (2006).  
A fixed volume of the supernatant obtained after treatment with the various solubilising 
buffers was diluted 1/1 (v/v) with SDS-PAGE denaturing buffer (0.125M Tris-HCl, pH 
6.8; 50% w/v glycerol, 1.7% w/v SDS; 0.01% w/v Bromophenol Blue). The protein 
samples were denatured by boiling at 100oC for 5 min. SDS-PAGE was carried out on a 
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fixed porosity gel at a constant 16mA (per gel). Gels were stained with Coomassie Brilliant 
Blue R250 (Simply Blue Safestain, Invitrogen, Carlsbad, CA, USA). Molecular mass 
markers (Lyophilized protein (LMW), 100µl of buffer pH 6.8 (Tris HCl; 1.5M + 0.4% 
SDS), 100 µl protein denaturing solution) covered 96, 65, 45, 30, 21 and 14 kDa. 
 
3.2.5 Partially Defatted Soybean (PDS) flour Preparation  
Soybean was cleaned and sorted. It was then dried in an oven at a temperature of 50oC for 
45min. It was then decorticated using a disc attrition mill (model 4E, Straub Co, 
Philadelphia, PA, USA) and winnowed in the open air. The decorticated soybean was 
partially defatted using the screw press to obtain partially defatted soybean cake. The cake 
was then milled into a particle size of 850µm. 
 
3.2.5.1 Determination of physicochemical properties of soybean flour 
3.2.5.1.1 Fat content determination on raw and partially defatted soybean 
Fat content was determined using the soxhlet procedure according to the AOAC Method 
no. 945.16 (AOAC, 2005) with some modifications. Determinations were in duplicates. 2g 
of pre-dried sample was weighed into an extraction thimble with porosity permitting a 
rapid flow of petroleum ether. Sample in the thimble was then covered with glass wool. 
Petroleum ether was then poured to fill two thirds of an already weighed pre-dried round 
bottom boiling flask. A condenser, soxhlet flask and extractor were then assembled. Fat 
was extracted into the soxhlet extractor at a rate of 5-6 drops per second condensation for 
three hours. Boiling flask with extracted fat was dried in an oven at 60oC overnight. It was 
then cooled in a desiccator and weighed. 
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% Fat  = g of fat in sample  x 100 
g of sample 
 
3.2.5.1.2 Colour determination of partially defatted soybean (PDS) 
Flour from PDS was placed in a plastic petri dish and was gently pressed to avoid space 
between them. A colorimeter (CR-300, Minolta, Japan) was used to determine colour value 
of the partially defatted soybean flour in terms of lightness, redness and yellowness (CIE 
L*, a* and b* values). The colorimeter was calibrated against a standard white calibration 
porcelain (L*= 97.15, a*= -0.01, b*= +2.08). For each sample 5 measurements were taken 
from several points. 
 
3.2.5.1.3 Protein solubility of PDS 
Protein solubility of partially defatted soybean was determined using three different 
buffers. Thus buffer A: 50mM sodium phosphate monobasic dihydrate and 100mM NaCl 
at pH 7.0; buffer B: 500mM sodium phosphate monobasic dihydrate, 100mM NaCl and 
6M urea at pH 7.0; buffer C: 500mM sodium phosphate monobasic dehydrate, 100mM 
NaCl, 6M urea and 10mM DL-Dithiothreitol (DTT) at pH 7.0. Protein solubility was 
carried out by suspending 0.5 g of finely ground sample in buffer A and 0.25g of finely 
ground samples in buffer B and also in buffer C. Suspensions were vortex and agitated on a 
rotary shaker for 1 hour at room temperature. The samples were then centrifuge at 10,000 
rpm, at a temperature of 20oC for 30min. The supernatant containing the total soluble 
proteins after centrifugation was used to prepare samples for Bradford Protein Assay and 
SDS-PAGE. The amount of protein in the supernatant was determined using the dye-
binding method (Bradford, 1976) with a calibration curve from bovine serum albumin. 
Results are expressed as mg proteins/g sample. 
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3.2.5.1.4 Electrophoretic pattern of the extracted proteins 
SDS-PAGE of the partially defatted soybean was performed according to the method 
described by Iametti et al. (2006). A fixed volume of the supernatant obtained after 
treatment with the various solubilising buffers was diluted 1/1 (v/v) with SDS-PAGE 
denaturing buffer (0.125M Tris-HCl, pH 6.8; 50% w/v glycerol, 1.7% w/v SDS; 0.01% 
w/v Bromophenol Blue). The protein samples were denatured by boiling at 100oC for 5 
min. SDS-PAGE was carried out on a fixed porosity gel at a constant 16mA (per gel). Gels 
were stained with Coomassie Brilliant Blue R250 (Simply Blue Safestain, Invitrogen, 
Carlsbad, CA, USA). Molecular mass markers (Lyophilized protein (LMW), 100µl of 
buffer pH 6.8 (Tris HCl; 1.5M + 0.4% SDS), 100 µl protein denaturing solution) covered 
96, 65, 45, 30, 21 and 14 kDa. 
 
3.2.6 Product Formulations  
To obtain rice soy extruded product, rice flour was mixed with partially defatted soy flour 
based on ratios that were determined using constrained mixture designs (Cornell, 1983) for 
two components. In all, five formulations for each rice treatment were obtained. For the 
four different rice treatments, twenty product formulations were obtained as shown in 
Table 3.1. 
 
 
 
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Table 3.1: Mixture design formulations from different treatments of rice and 
partiallydefatted soybean flour  
Sample           Composite (%) 
 Rice Partially 
defatted soybean 
Raw or milled Togo 
Marshall (TM) 
  
TMF1 67.5 32.5 
TMF2 60 40 
TMF3 90 10 
TMF4 75 25 
TMF5 82.5 17.5 
Parboiled  Togo 
Marshall (PTM) 
  
PTMF1 67.5 32.5 
PTMF2 60 40 
PTMF3 90 10 
PTMF4 75 25 
PTMF5 82.5 17.5 
(Raw) Viwonor (V)   
VF1 67.5 32.5 
VF2 60 40 
VF3 90 10 
VF4 75 25 
VF5 82.5 17.5 
Parboiled Viwonor 
(PV) 
  
PVF1 67.5 32.5 
PVF2 60 40 
PVF3 90 10 
PVF4 75 25 
PVF5 82.5 17.5 
 
3.2.7 Physicochemical analysis on formulations 
3.2.7.1 Moisture determination 
Moisture content was determined with reference to AOAC Official Method no 925.10 
(AOAC, 2000); air oven method. Determinations were in duplicates. 
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3.2.7.2 Apparent Amylose content 
The formulations were further ground in an Udy CycloneMill (UdyCorp., Fort Collins, 
USA) with a 1.0 mm mesh screen. Amylose content was measured using the standard 
iodine colourimetric method ISO 6647-2-2011 (ISO, 2011). Ethanol (1 ml, 95%) and 1M 
sodium hydroxide (9ml) were added to rice flour (100 mg) and heated in a boiling water 
bath for 10min to enable starch gelatinisation.  After cooling, 1M acetic acid (1ml) and 2 
ml iodine solution (prepared by dissolving 0.2g iodine and 2.0g potassium iodide in 100ml 
distilled water) were added and the volume made up to 100ml with distilled water. 
Absorbance of the mixture was measured using an Auto Analyzer 3 (Seal Analytical, 
Germany) at 600 nm. Amylose content was quantified from a standard curve generated 
from absorbance values of four well-known standard rice varieties (IR65, IR24, IR64 and 
IR8). For each sample four measurements were taken. 
 
3.2.7.3 Pasting properties 
Pasting properties of formulations were determined according to the method of Mariotti et 
al. (2005). Briefly, the formulation (15 g, db) dispersed in 100 ml of deionized water was 
directly placed into a stainless steel measuring bowl of Brabender Micro Visco Amylo-
Graph (MVAG) (Brabender OHG, Duisburg, Germany).  It was then heated from 30oC to 
95 oC, held for 20 min at 95oC and cooled to 30oC and finally held for 1 min. Heating and 
cooling rates were 3oC/min and -3oC/min. The rotation speed and measuring range were 
250 rpm and 300 cmg. The following indices were considered: beginning of gelatinization, 
pasting temperature (temperature at which an initial increase in viscosity occurs); 
maximum/peak viscosity achieved during the heating cycle; viscosity after holding time at 
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95 oC/hot paste viscosity; breakdown (decrease in viscosity during the holding period, 
corresponding to the peak viscosity minus the viscosity after the holding period at 95 oC); 
setback (viscosity increase during cooling). The viscosity was measured in arbitrary 
Brabender units (BU) and was determined in duplicate.  
  
3.2.8 Extrusion process 
The 20 formulations (Table 3.1) with moisture content ranging from 10%-13% were 
extruded into snack products using an intermeshing co-rotating twin screw extruder 
(CLEXTRAL BC 21, Germany).  
The extrusion conditions for all the 20 formulations were as follows: 
 Constant screw speed of 1000rpm,  
 Digi drive speed of 400 rpm,  
 Barrel temperature of 200oC  
 A circular die diameter of 4mm was used.  
 
3.2.9 Visual inspection of the twenty extrudates 
Extrudates from the twenty different formulations were visually inspected for expansion, 
colour and texture. This was to visually access the effect of rice treatment (raw milled rice 
or parboiled) and the increment of PDS on expansion and other quality characteristics of 
final extrudates.  
 
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3.2.10 Sensory Evaluation of extruded snacks   
Sensory panellists were recruited from the Kwame Nkrumah University of Science and 
Technology (KNUST), Kumasi, Ghana. Criteria for recruitment were that panellists were 
regular consumers of snacks. A balanced incomplete block design for 20 treatments (ie 
t=20), k = 5 (ie number of samples per panelists) as described by Cochran and Cox (1957) 
and Montgomery (2001) was used because an individual panelist would find it difficult to 
evaluate as many as 20 different products at one session. Extruded snacks prepared from 
raw of parboiled rice and partially defatted soybean were presented to consumers in 
disposable plates coded with three-digit random numbers. Water was provided for 
consumers to use during the test to minimize any residual effect between samples. 
Consumer preference test was carried out using the 9 point hedonic scale with 1 - dislike 
extremely, 5 – neither like nor dislike and 9 - like extremely (Peryam et al., 1957). Sensory 
attributes which were determined were aroma, colour, mouthfeel, aftertaste and overall 
acceptability.  
 
3.2.11 Physicochemical analysis on the five selected extrudates 
3.2.11.1 Moisture determination 
Moisture content was determined according to the air oven method described in the AOAC 
Official Method no. 925.10 (AOAC, 2000). Determinations were in duplicates. 
 
3.2.11.2 Colour 
Flour from the extrudates were placed in a plastic petri dish and was gently pressed to 
avoid space between them. A colorimeter (CR-300, Minolta, Japan) was used to determine 
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colour value of the extrudates in terms of lightness, redness and yellowness (CIE L*, a* 
and b* values). The colorimeter was calibrated against a standard white calibration 
porcelain. For each sample, 5 measurements were taken from several points. 
 
3.2.11.3 Aroma determination using electronic nose 
Analyses were performed with a Portable Electronic Nose (PEN2) from Win Muster 
Airsense (WMA) Analytics Inc. (Schwerin, Germany). It consists of a sampling apparatus, 
an array of chemical gas sensors producing an array of signals when confronted with a gas, 
vapour or odour and an appropriate pattern-recognition software (Win Muster v.1.6) for 
data recording and elaboration as shown in Plate 3.1.  
 
Plate 3.1: Electronic nose PEN2 
 
  
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The key principles involved in the electronic nose concept, is the transfer of the total 
headspace of a sample to a sensor array that detects the presence of volatile compounds in 
the headspace and a pattern of signals is provided that are dependent on the sensors 
selectivity and sensitivity and the characteristics of the volatile compounds in the 
headspace (Plate 3.1).  
 
Plate 3.2: Basic elements of an electronic nose 
 
By chemical interaction between odour compounds and the gas sensors the state of the 
sensors is altered giving rise to electrical signals which are registered by the instrument. In 
this way the signals from the individual sensors represent a pattern which is unique for the 
gas mixture measured and is interpreted by multivariate pattern recognition techniques. 
Samples with similar odourous generally give rise to similar sensor response patterns and 
samples with different odourous show differences in their patterns. 
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The sensor array of the electronic nose PEN2 is composed of 10 Metal Oxide 
Semiconductor (MOS) type chemical sensors as shown in Table 3.2. The sensor response 
is expressed as resistivity (Ω). 
 
Table 3.2: List and characteristics of 10 Metal Oxide Semiconductors (MOS) of sensor      
array in electronic nose PEN2. 
Number in 
array 
Sensor 
name 
General description 
1 W1C Aromatic compounds 
2 W5S Very sensitive, broad range sensitivity, react on nitrogen 
oxides, very sensitive with negative signal 
3 W3C Ammonia, used as sensor for aromatic compounds 
4 W6S Mainly hydrogen, selectively (breath gases) 
5 W5C Alkanes, aromatic compounds, less polar compounds 
6 W1S Sensitive to methane (environment) ca. 10 mg kg-1. Broad 
range 
7 W1W Reacts on sulphur compounds, H2S 0.1 mg kg-1. Otherwise 
sensitive to many terpenes and sulphur organic compounds, 
which are important for smell, limonene, pyrazine 
8 W2S Detect alcohols, partially aromatic compounds, broad range 
9 W2W Aromatic compounds, sulphur organic compounds 
10 W3S Reacts on high concentrations > 100 mg kg-1, sometime very 
selective (methane) 
 
3.2.11.3.1 Operation Procedure 
Lyophilized samples of 0.2g was placed in a 40 mL airtight glass vial fitted with a 
pierceable Silicon/Teflon disk in the cap. After an hour headspace equilibration at room 
temperature, the measurement sequence was started. Operating conditions were: flow rate 
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300mL/min, injection time 60 min, flush time 180 min, during which the surface of the 
sensors was cleaned with air filtered through active carbon. All samples were analysed 
twice and the average of the sensor responses was used for subsequent statistical analysis. 
The analysed samples are reported in Table 3.3.  
 
Table 3.3: Five selected extrudates and their coding for electronic nose analysis. 
Sample Code              Composition (%) 
 
Raw Togo 
Marshall Rice 
Variety (TM) 
 Rice Partially defatted soybean 
TMF3 B 90 10 
TMF4 C 75 25 
TMF5 A 82.5 17.5 
Parboiled Togo 
Marshall (PTM) 
   
PTMF3 D 90 10 
PTMF4 E 75 25 
 
 
3.2.11.4 Taste determination using electronic tongue 
Analyses were performed with the Taste-Sensing System SA 402B (Intelligent Sensor 
Technology Co. Ltd, Japan) namely Electronic Tongue (ET). The ET is a liquid analytical 
device that mimics the taste-sensing mechanism of the gustatory system; it comprises two 
sensor arrays that are specific for liquid and are able to evaluate tastes: sourness, saltiness, 
bitterness, umami and astringency as shown in Plate 3.3. 
 
 
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Plate 3.3: Taste sensing system.  
Source: Tahara and Toko, (2013) 
The detecting part of the system consists of 7 sensors whose surface is attached with 
artificial lipid membranes having different response properties to chemical substances on 
the basis of their taste as reported in Table 3.4. 
 
Table 3.4: List and characteristics of electronic tongue detecting sensors. 
 
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For this work a total of 5 detecting sensors and 2 reference electrodes were used, separated 
in two arrays according to membrane charge: hybrid (CT0; CA0; AAE) and positive (C00, 
AE1). The measurement principle of the electronic tongue (Plate 3.3) is based on the 
capability of taste substances to change the potential of detecting sensors through 
electrostatic or hydrophobic interaction with the hydrophilic and hydrophobic groups of the 
lipid membranes. The response of each sensor, recorded as the difference between the 
potential detected by the sensor and the potential of the reference electrode, is elaborated 
by a computer and processed via a pattern recognition system. 
   
                  
Figure 3.3: Electronic Tongue measuring process. 
 
A sample solution was first and foremost prepared by adding 3 g of flour obtained from the 
extrudates to 30 ml of distilled water to form suspensions. Suspensions were vortexed for 
about 2 min and centrifuged at 5000 rpm for 5 min at room temperature. After 
centrifuging, the supernatants were filtered and diluted 1: 4 (w/w) with distilled water. The 
Measuring Reference 
solution (Vr) 
Measuring Sample 
solution (Vs 
 
) 
Cleaning with Reference 
solution for 6 s 
Measuring Reference 
solution (Vr’) 
Cleaning with Washing 
and Reference solution 
for 270 s 
and Reference solution 
for 270 s 
Vs-Vr=relative value 
Vr’-Vr=CPA value 
 
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detecting sensors and reference electrodes were then dipped into the reference solution (30 
mM potassium chloride and 0.3mM tartaric acid) and the electric potential measured for 
each sensor was defined as Vr. Then the sensors were dipped for 30s into the sample 
solution. For each sensor the measured potential was defined as Vs. For each sensor the 
“relative value” (Rv) was represented by the difference (Vs-Vr) between the potential of 
the sample and the reference solution. Sensors were rinsed with fresh reference solution for 
6 s and then dipped into the reference solution again. The new potential of the reference 
solution was defined as Vr’. For each sensor, the difference (Vr’-Vr) between the potential 
of the reference solution before and after sample measurement is the CPA value (Change 
of Membrane Potential caused by Absorption) (CPAv) and corresponds to the ET 
“aftertastes”. Before a new measurement cycle started, electrodes were rinsed for 90 s with 
a washing solution and then for 180 s with the reference solution. Each sample was 
evaluated two times and the averages of the sensor outputs were converted to taste 
information. The “taste values” were calculated by multiplying sensor outputs for 
appropriate coefficients based on Weber–Fechner law, which gives the intensity of 
sensation considering the sensor properties for tastes. In particular, the “taste values” were 
estimated as: 
Sourness = 0.3316 × Rv(CA0) 
Saltiness = −0.252 × Rv(CT0) 
Bitterness = −0.140 × Rv(C00) + 0.084 × Rv(CT0) 
Aftertaste-bitterness = −0.210 × CPAv(C00) 
Astringency = 0.1575 × Rv(AE1) + 0.1575 × Rv(CT0) 
Aftertaste-astringency = −0.252 × CPAv(AE1) 
 
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Data Analysis for electronic nose and tongue. 
The data processing of the multivariate output data generated by the sensor array signals 
represents another essential part of the electronic nose and tongue concept. The statistical 
techniques used are based on commercial or specially designed software using pattern 
recognition routines like Principal Component Analysis (PCA). Principal Components 
Analysis (PCA) is a procedure that permits to extract useful information from the data, to 
explore the data structure, the relationship between objects, the relationship between 
objects and variables and the global correlation of the variables. It was used for explorative 
data analysis as it identifies orthogonal directions of maximum variance in the original 
data, in decreasing order, and projects the data into a lower-dimensionality space formed of 
a subset of the highest-variance components. The orthogonal directions are linear 
combinations (principal components PCs) of the original variables and each component 
explains in turns a part of the total variance of the data; in particular, the first significant 
component explains the largest percentage of the total variance, the second one, the second 
largest percentage, and so forth. 
 
3.2.11.5 Bulk density 
Bulk densities of the extrudates were determined using a seed displacement method by 
Bhatnagar et al., (1995) with some modifications.  The weight of each sample was weighed 
with an electronic balance. Sesame seeds were used as the displacement medium. A beaker 
was filled with sesame seeds to the brim and levelled with a straight edge. The seeds were 
poured out and the extrudate placed into the beaker; the sesame seeds were then poured 
back into the beaker and levelled with a straight edge. The displaced sesame seeds were 
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placed into a graduated cylinder (250 ml). The bulk density (g/cm3) was calculated by 
dividing the weight of the extrudates by the volume displaced. Nine measurements were 
taken for each extrudates. 
 
3.2.11.6 Water Absorption Index (WAI) and Water Solubility Index (WSI) 
The WAI and WSI indices were measured using a technique developed for cereals 
(Anderson et al., 1969). In particular, 2.5 g of ground extrudate was suspended in 25 ml of 
water at room temperature for 30 min., gently stirred using a stirring rod and then 
centrifuged at 3000 g for 10 min. The supernatant was decanted into an evaporating dish of 
known weight. The WSI is the weight of dissolved solids in the supernatant expressed as a 
percentage of the original dry weight of sample. The WAI is the weight of gel obtained 
after removal of the supernatant per unit weight of original dry solids. Determinations were 
made in duplicate. 
 
 
 
3.2.11.7 Expansion ratio 
Expansion ratio was determined according to the method of Bisharat et al., (2013).Thus the 
ratio of the diameter of the extrudates to the diameter of the die: 
Exp. = d  
do 
 
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where d (cm) is the diameter of the extrudates and do (cm) is the diameter of the die. Ten 
replicates were used for the determination of expansion ratio. 
 
3.2.11.8 Hardness analysis 
Extruded products were punctured by using a Zwick Z005 testing machine equipped with a 
100 kN load cell (Zwick GmbH & Co., Ulm, Germany) fitted with a 4-mm diameter 
cylindrical flat-faced probe. The speed of advance was 1 mm s-1. The force-deformation 
curves were recorded from the surface of the extrudate and ended after the pin had reached 
the 50% of sample deformation. The work (Nmm) divided by the height of the sample 
(mm) was chosen to represent the textural properties of extrudates that had different 
diameters. 20 measurements were carried out for each sample. 
 
3.2.11.9 Protein solubility 
Protein solubility of extrudates (in the flour form) were determined using three different 
buffers. Thus buffer A: 50mM sodium phosphate monobasic dihydrate and 100mM NaCl 
at pH 7.0; buffer B: 500mM sodium phosphate monobasic dehydrate, 100mM NaCl and 
6M urea at pH 7.0; buffer C: 500mM sodium phosphate monobasic dehydrate, 100mM 
NaCl, 6M urea and 10mM DL-Dithiothreitol (DTT) at pH 7.0. Protein solubility was 
carried out by suspending 0.5 g of finely ground sample in buffer A and 0.25g of finely 
ground samples in buffer B and also in buffer C. Suspensions were vortex and agitated on a 
rotary shaker for 1 hour at room temperature. The samples were then centrifuge at 10,000 
rpm, at a temperature of 20oC for 30min. The supernatant containing the total soluble 
proteins after centrifugation was used to prepare samples for Bradford Protein Assay and 
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SDS-PAGE. The amount of protein in the supernatant was determined by a dye-binding 
method (Bradford, 1976) using bovine serum albumin as a standard. Results are expressed 
as mg proteins/g sample. 
 
3.2.11.10 Electrophoretic pattern of the extracted proteins 
SDS-PAGE was performed according to Iametti et al. (2006). A fixed volume of the 
supernatant obtained after treatment with the various solubilising buffers was diluted 1/1 
(v/v) with SDS-PAGE denaturing buffer (0.125 M Tris-HCl, pH 6.8; 50% w/v glycerol, 
1.7% w/v SDS; 0.01% w/v Bromophenol Blue). The protein samples were denatured by 
boiling at 100oC for 5 min. SDS-PAGE was carried out on a fixed porosity gel at a 
constant 16mA (per gel). Gels were stained with Coomassie Brilliant Blue R250 (Simply 
Blue Safestain, Invitrogen, Carlsbad, CA, USA). Molecular mass markers (Lyophilized 
protein (LMW), 100µl of buffer pH 6.8 (Tris HCl; 1.5M + 0.4% SDS), 100 µl protein 
denaturing solution) covered 96, 65, 45, 30, 21 and 14 kDa. 
 
3.2.11.11 Accessible thiols 
Accessible thiols (expressed as µmol thiols/g sample) were determined by using (Iametti et 
al., 2006) with some modifications. 0.25g of finely ground samples was suspended in 5ml 
of 50mM sodium phosphate, 0.1M NaCl, pH 7.0 in the presence or absence of 6M urea, 
containing 0.2mM of 5, 5’-dithiobis-(2-nitrobenzoate) (DTNB) (Ellman, 1959). After 1 h 
stirring at 25oC, samples were centrifuged (13000 xg, 30 min, 25oC). The blank was 
prepared by suspending 0.25g of samples in 5ml of 50mM sodium phosphate, 0.1M NaCl, 
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pH 7.0 in the presence or absence of 6M urea, without adding DTNB. The supernatant 
absorbance was read at 412 nm. The results were expressed as µmol thiols/g sample. 
 
3.2.11.12 In vitro protein digestibility 
This was carried out using two enzymes thus pepsin and pancreatin. For in vitro pepsin 
digestion, 1.0g of finely ground sample was weighed into polypropylene test tube. 10 ml of 
HCl (0.05 M) was then added. Proteins were hydrolyzed by gastric pepsin (porcine 
stomach mucosa, EC 232-629-3, ref P7012, Sigma) thus by adding 30µl of pepsin at a 
concentration of 2mg/ml. The mixture was then incubated for 60min at 37 °C under mixing 
conditions. In vitro pepsin digestion was terminated by the addition of 10% (final 
concentration) trichloroacetic acid after 60 min. Samples were then centrifuged at 
13000rpm for 15 min, and  the hydrolyzed peptide content in the supernatant was measured 
at 280 nm. 
Protein hydrolysis from pancreatin was preceded by pepsin digestion. Sample pH was 
adjusted to about 8.0 by adding TRIS 1 M. Proteins were hydrolyzed by pancreatic 
enzymes (pancreatin from porcine pancreas, EC 232-468-9, ref P1625, Sigma) by adding 
120 µl of pancreatin  for 60 min at 37 °C under mixing conditions. Pancreatin digestion 
was terminated by the addition of 10% (final concentration) trichloroacetic acid after 
60min in the ratio 1:1. Samples were then centrifuged at 13000rpm for 15 min. This was 
again repeated for 120 and 180min. The hydrolyzed peptide content in the supernatant was 
measured at 280 nm. 
 
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4.0 RESULTS AND DISCUSSION 
 
4.1 Selection of local rice varieties for the preparation of extruded snack. 
There are several local rice varieties in Ghana which are considered low grade due to the 
poor sensory and physical qualities (Tomlins et al., 2005). Awudi (2013), characterized ten 
local rice varieties and Diako et al. (2011) also characterized four local rice varieties based 
on their physicochemical properties as shown in Table 2.4 and 2.5. The low amylose 
content value (19.30%) for Togo marshall rice as shown in Tables 2.4 and 2.5 is 
responsible for it becoming sticky after cooking (Juliano, 1985) and therefore makes it not 
to be preferred by most consumers in Ghana (Fofana et al. 2011). Similarly, grain colour 
has implications for consumer preference. In Ghana there is a high visual appeal for white 
milled rice since most consumers have the perception that white milled rice is superior 
(Adu-Kwarteng et al., 2003) and therefore has a high market value (Wadsworth, 1994). In 
view of this, Viwonor rice variety is least preferred due to its natural reddish colour. This 
therefore, creates the need to diversify these two varieties in the production of ready to eat 
snack products. 
Furthermore, the availability of the local rice serves as an important criterion in the 
selection of rice variety for the production of extruded snack especially for purposes of 
commercialization. A preliminary survey and interactions with rice farmers, millers and 
distributors from three major areas (Ashiaman, Madina and Hohoe) of the Greater Accra 
and Volta region suggest that Togo marshall and Viwonor rice varieties were readily 
available in the markets throughout the year. This is because the two varieties are widely 
cultivated by farmers in the Greater Accra and Volta region in Ghana (Interview with Mr. 
Forson, Ghana Rice Inter-Professional Body (GRIB) 12/09/13). 
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4.2 Physicochemical characterization of two selected local rice varieties. 
The physical and chemical properties of two local rice varieties recognized as low grade 
rice, thus Togo marshall and Viwonor rice (Plate 4.1) were determined.  
 
 
            
 
 
 
Plate 4.1: Two locally cultivated (low grade) rice varieties (Togo marshall and Viwonor).  
 
 
4.2.1 Grain hardness 
Hardness describes a product which displays substantial resistance to deformation or the 
“first bite” that would be perceived (Bourne, 2002). Rice grain hardness is an important 
quality criteria especially for the rice industry since it contributes to changes during 
storage, processing and as well as affecting the extent of grain resistance to pest and insect 
attacks (Fofana et al., 2011). According to Bienvenido (1972), grain hardness is related to 
A: Togo marshall B: Viwonor 
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the packing density of the grain starch. Viwonor rice variety showed a relatively higher 
hardness value of 7.97kg as compared with Togo marshall rice variety with a hardness 
value of 7.46kg. However, the analysis of variance for the data of grain hardness showed 
that there was no significant differences between the rice varieties (Table 4.1). This means 
that the differences in the varieties especially in relation to the arrangement of the starch 
granules of the two varieties did not have an impact on their hardness (Bienvenido, 1972). 
 
4.2.2 Milling recovery (%) 
According to Adu-Kwarteng et al. (2003), milling recovery is a measure of milling quality 
and hence economic value. Thus 50% or less milling recovery is undesirable since it 
suggests that 50% of the rice is discarded as waste or not consumable after milling. The 
data for milling recovery show significant difference between the rice varieties.  The 
Viwonor rice variety showed significantly higher milling recovery than Togo marshall rice 
variety as shown in Table 4.1. The result is in the same order as observed for hardness 
values shown in Table 4.1. It is possible that the higher hardness values for the Viwonor 
rice variety contributed to the relatively higher milling recovery of 52.29% as compared to 
Togo marshall rice variety with a milling recovery value of 45.90% (Correa et al., 2006). 
 
4.2.3 Grain Dimension 
Grain size and shape (length/width) is a varietal property that dictate the marketability and 
commercial viability of rice. According to Rani et al. (2006), preferences for rice grain size 
and shape vary from one group of consumers to another. Grain length is used for the 
classification of grain size thus extra-long, >7.50 mm; long, 6.61 to 7.50 mm; medium, 
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5.51 to 6.60 mm; and short, 5.50 to 4.50 mm (Juliano, 1993). Furthermore, length to width 
(L/W) ratios are used in the classification of grain shape, with a higher ratio indicating 
slender shapes, >3.0; and a lower value indicating medium, 2.1-3.0; bold, 1.1-2.0 or round 
shapes ≤ 1.0 (Juliano, 1993).   
There was no significant difference in relation to both grain length and grain shape at p ≤ 
0.05 as shown in Table 4.1 for both Togo marshall and Viwonor rice varieties. Length of 
the Togo marshall rice variety and Viwonor rice variety were 6.68mm and 6.67mm 
respectively, indicating that they could be classified as long (Juliano, 1993). The length to 
width ratio for Togo marshall rice variety (2.97) and Viwonor rice variety (2.97) as shown 
in Table 4.1 falls within 2.1-3. This means that the two varieties can be classified as 
medium shape according to Juliano (1993). This was also in agreement with the finding by 
Diako et al. (2011) who concluded that Togo marshall together with some local rice 
varieties such as Ex-Baika, Ex-Hohoe were all medium-shaped grains based on FAO 
(1975) categorization. In Ghana, studies have shown a higher demand for long-grain rice 
than for short, round grain types (GLG-SOFRENCO, 1997). 
 
4.2.4 Grain Chalkiness 
Grain appearance is mainly determined by the endosperm opacity. Opacity is as a result of 
chalky texture caused by interruption of final filling of the grain. According to Adu-
Kwarteng et al. (2003), the presence of chalkiness in rice grain is described as a “defect’’ 
that affects milling, marketing and storage properties of rice. Even though, chalkiness 
disappears upon cooking and has no direct effect on cooking and eating qualities, excessive 
chalkiness downgrades the quality and reduces milling recovery (USDA, 2005).  
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On the basis of Standard Evaluation Scale (SES) categorization (USDA, 2005), Togo 
marshall rice variety with percentage chalkiness of 4.93% (Table 4.1) had a chalky score of 
1. The Codex Alimentarius Commission (1990) acceptable tolerance defect for chalkiness 
is 11.0%, therefore, it can be concluded that the percentage chalkiness value for the Togo 
marshall sample falls within the acceptable tolerance level for defect in terms of 
chalkiness. Chalkiness could not be detected in Viwonor rice variety due to its natural 
reddish-brown pigmentation. 
 
4.2.5 Cooking time 
Cooking time of rice refers to the time taken by the rice starch to gelatinize (Bienvenido, 
1972) when subjected to heating in excess water. At this point the starch granules take in 
water as the temperature is increased to the gelatinization temperature. The starch granules 
also loose their crystalline nature and this change is irreversible. Cooking time is an 
important factor to consumers and it is influenced by the variety, cultivation and 
postharvest practices, degree of milling, and cooking methods (Park et al., 2001). Falade et 
al. in 2014 observed that cooking and eating characteristics of rice such as the cooking time 
are influenced by the ratio of amylose and amylopectin in the rice grain.  
Table 4.1 shows that Viwonor rice variety had a significantly longer cooking time 
(21.00min) than the Togo marshall rice variety (16.00min). The longer cooking time of 
Viwonor rice variety may be due to its relatively higher amylose content shown in Table 
4.2 as suggested by Bahmaniar and Ranjbar (2007) that amylose content directly influence 
the cooking and eating qualities of milled rice. Based on the result, it can be concluded that 
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Togo marshall rice variety will cook faster than Viwonor rice variety and would therefore 
be suitable for products which require shorter cooking time. 
 
Table 4.1: Physical properties of Togo marshall and Viwonor rice varieties. 
Parameter Varieties P-value 
 Togo marshall Viwonor  
Hardness (Kg) 7.46±0.59a 7.97±0.37a 0.3755 
Milling recovery (%) 45.90±0.75a 52.29±0.47b 0.0019 
Length (L) mm 6.68±0.02a 6.67±0.01a 0.2948 
Width (W) mm 2.25±0.01a 2.25±0.02a 0.6366 
L/W 2.97±0.01a 2.97±0.02a 0.8982 
Chalkiness (%) 4.93±1.23 - - 
Cooking time (min) 16.00±0.00a 21.00±0.00b ˂ 0.05 
 
 
4.2.6 Alkaline spreading value (ASV) 
Alkali spreading value is the degree of spreading of individual milled rice kernel in a weak 
alkali solution (1.7% KOH) at room temperature (32±2℃) (Oko et al., 2012). It is used as 
an indicator of gelatinization temperature of milled rice starch granules (Delwiche et al., 
1996). According to Falade et al. (2014), gelatinization temperature is the temperature at 
which 90% of rice starch granules swells in hot water and loose its crystalline structure and 
birefringence or gets swollen irreversibly in hot water. There was a significant difference 
for the Togo marshall rice variety and Viwonor rice variety in their alkaline spreading 
values at p < 0.05 as shown in Table 4.2. The Togo marshall had a significantly higher 
ASV than Viwonor rice variety. The ASV of Togo marshall rice variety (6.67) signifies a 
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gelatinization temperature range of 55-69.5oC (low) (Juliano, 1993). Furthermore, the ASV 
for Viwonor rice variety (5.88) also signifies a gelatinization temperature range of 70-74oC 
(intermediate) (Juliano, 1993). This result is in agreement with the long and short cooking 
time for Viwonor and Togo marshall rice varieties respectively as shown in Table 4.1.  
 
4.2.7 Apparent amylose content (AAC) 
Starch (amylose and amylopectin) constitute about 90% of the dry matter content of milled 
rice.  Rice varieties differ widely in the cooking and eating properties, depending on the 
ratio of the starch fractions, amylose and amylopectin. Amylose is the linear fraction of 
starch, and amylopectin, the branched fraction (Oko et al., 2012). Amylose content is the 
major influence on the eating and cooking qualities of rice. According to Juliano (1985), 
rice with high amylose content cook dry and fluffy and become harder upon cooling while 
low amylose (below 20%) varieties cook moist and sticky. In this study the Viwonor rice 
variety had a significantly higher apparent amylose content (20.62%) than that of Togo 
marshall rice variety (17.45%) as shown in Table 4.2. According to Juliano (1993), 
amylose content in milled rice samples are categorized as follows: waxy (1-2%), very low 
amylose (2-12%), low amylose (12-20%), intermediate (20-25%) and high (25-33%). 
Based on this classification, Viwonor rice variety can be classify as intermediate whiles 
Togo marshall rice variety as low amylose rice. The notable differences in the apparent 
amylose content between the two rice varieties may be due to different factors such as 
genotype, environmental conditions, and agricultural practice (Kim and Wiesenborn, 
1995). According to Fofana et al. (2011), the intermediate amylose varieties are generally 
most preferred in West Africa because they cook dry and fluffy retaining their soft texture 
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even after cooling. This suggests that the Viwonor rice variety would be most preferred to 
Togo marshall rice variety for cooking in West Africa.  
 
Table 4.2: Chemical properties of Togo marshall and Viwonor rice varieties 
Parameter Varieties                    P-value 
 Togo marshall Viwonor  
Alkaline spreading value (ASV) 6.67±0.30a 5.88±0.18b 0.0467 
Amylose % 17.45±0.36a 20.62±0.26b 0.0000 
 
4.3 Physical and chemical analysis of the raw materials used for extruded products 
4.3.1 Colour analysis 
Colour determination was carried out on the raw materials used in the extrusion process.  
These were partially defatted soybean (PDS), Raw Togo marshall (RTM) rice variety, 
Parboiled Togo marshall (PTM) rice variety, Raw Viwonor (RV), Parboiled Viwonor (PV) 
rice variety.  
Data were expressed as L*, a* and b* values, where L* (luminosity) values varied from 
black (0) to white (100), chroma a* values varied from green (-60) to red (+60), and 
chroma b* values varied from blue (-60) to yellow (+60). There were significant 
differences among the values for the raw materials (PDS, RTM, PTM, RV and PV) in 
terms of L*, a* and b* indices at P < 0.05 as shown in Table 4.3. The significantly high L* 
value (93.18) for Raw Togo marshall (RTM) rice variety was because it was polished rice 
and contains about 90% starch which is naturally white in colour. Furthermore, the 
significantly low whiteness (L*) value (79.63) observed for RV was as a result of its 
naturally reddish pericarp (Diako et al., 2011).  The decreased L* values (84.69 and 77.10) 
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for Parboiled Togo marshall (PTM) and Parboiled Viwonor rice varieties as compared to 
their raw form might be as a result of the parboiling treatment of the rice grain which might 
have led to diffusion of husk pigments into the endosperm especially during the soaking 
period of the parboiling treatment. This was also confirmed by Dutta, et al. (2012) who 
reported a decrease in the lightness value of parboiled rice. Furthermore, the least L* value 
(83.89) for Partially Defatted Soybean (PDS) as compared to RTM and PTM may be due to 
its relative darker colour as a result of the high temperature application during the defatting 
process thereby favouring Maillard reaction between reducing sugars and free amino 
groups. The high a* values for RV (4.11) as compared to RTM (-0.31) confirms the 
presence of naturally reddish pericarp in RV rice variety. The negative a* value (-0.31) for 
RTM as compared to PTM (-0.12) suggest the presence of some green pigment in the RTM 
rice variety which was significantly reduced after parboiling as observed in Table 4.3.  
Lastly, the high positive b* value (22.76) for PDS is related to the original yellowish colour 
as a result of some carotenoids pigments in the soybean. The relatively higher b* values for 
parboiled rice (PTM; 15.54 and PV; 12.83) as compared to their raw form (RTM; 6.58 and 
RV; 12.04) suggest that the parboiling process which is a hydrothermal treatment 
significantly improved the yellowish nature of the rice grain as a result of the diffusion of 
yellowish pigment from the rice husk. It can therefore be concluded that parboiling 
treatment significantly affected the L*, a* and the b* indexes of the colour. Grain colour is 
one of the important factors for visual appeal and most consumers are of the perception that 
white rice is superior (Adu-Kwarteng et al., 2003). Therefore based on colour the Togo 
marshall rice variety will be preferred to Viwonor rice variety. 
 
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Table 4.3: Colour measurement of raw materials   
Raw materials         L*         a*        b* 
PDS 83.89±0.73a 0.54±0.18a 22.76±0.83a 
RTM 93.18±0.36b -0.31±0.07b 6.58±0.22b 
PTM 84.69±0.16c -0.12±0.10c 15.54±0.32c 
RV 79.63±0.26d 4.11±0.07d 12.04±0.18d 
PV 77.10±0.51e 3.10±0.10e 12.83±0.53e 
P value  ˂0.0001  ˂0.0001 ˂0.0001 
a, b, c, d, e.  Means and standard deviation with the same superscript in a column are not 
significantly different at p≤0.05. 
Key: PDS: Partially Defatted Soybean, RTM: Raw Togo marshall rice variety, PTM: 
Parboiled Togo marshall rice variety, RV: Raw Viwonor, PV: Parboiled Viwonor rice 
variety. 
 
4.3.2 Protein solubility 
Protein solubility properties of raw and parboiled forms of both rice varieties (Togo 
marshall and Viwonor) as well as partially defatted soybean (PDS) in three different 
extraction buffers were evaluated.  
Generally for all samples, it was observed that protein solubilzation in buffer A (50mM 
sodium phosphate monobasic dihydrate and 100mM NaCl) was less than that in buffer B 
(buffer A and 6M urea) which was also less than the protein solubilzation in buffer C 
(buffer B and 10mM DL-Dithiothreitol (DTT)). This is because, according to Bhattacharya 
(2004), buffer A   which is a saline buffer solubilised water and salt soluble proteins such 
as albumins and globulins. The addition of a denaturing agent (urea) to the saline buffer 
(buffer A) enabled the dissociation of protein aggregates stabilized by hydrophobic 
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interactions there by increasing the quantity of solubilized protein.  Furthermore, buffer C 
which involved the addition of dithiothreitol (DTT) led to an increased solubilisation of the 
proteins since it also ensured the dissociation of aggregates stabilized  by disulphide 
linkages (Bonomi et al., 2012) as shown in Figure 4.1. The high level of solubilized 
proteins from partially defatted soy (PDS) in all buffers as compared to the various rice 
varieties confirms the high protein content in PDS (Shewery, 2007) as compared to rice. 
The protein solubility for the raw rice (of both Togo marshall and Viwonor) in all the 
buffers was higher than their counterparts parboiled rice (PTM and PV).  Thus the 
parboiling process impacted negatively on the solubility of proteins in the rice endosperm. 
Parboiling of rice causes physicochemical transformations such as starch gelatinization and 
retrogradation, leaching of amylose as well as denaturation and aggregation of proteins. 
This confirms the study by Reza et al. (2005) where they stated that many of the peptides 
found in raw rice were absent in the parboiled rice. Harris and Juliano (1977) also noticed 
that the protein bodies in raw rice changed drastically during parboiling process of rice. 
They also observed that the protein fraction were less extracted from parboiled rice. It can 
therefore be concluded that the rice proteins were greatly modified by the parboiling 
treatment. 
 
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Figure 4.1: Amount of solubilized protein from raw materials.  
(RTM; Raw Togo marshall rice varieties, PTM; Parboiled Togo marshall rice variety, RV; 
Raw Viwonor rice variety, PV; Parboiled Viwonor rice variety and PDS; Partially defatted 
soybean) in different buffers systems. Buffer A: (50mM sodium phosphate monobasic 
dihydrate and 100mM NaCl). Buffer B: (500mM sodium phosphate monobasic dehydrate, 
100mM NaCl and 6M urea) and Buffer C (500mM sodium phosphate dehydrate, 100mM 
NaCl, 6M urea and 10mM DL-Dithiothreitol (DTT). 
 
 
  
4.3.3 Protein electrophoretic patterns 
Electrophoretic patterns shown in Figure 4.2 confirm the solubility data presented in Figure 
4.1 and indicate that the peptides bands from proteins solubilized by urea and DL-
Dithiothreitol (DTT) are more than those soluble in their absence (Mariotti et al., 2011). 
This generally confirms the presence of protein aggregates stabilized by hydrophobic 
interactions and disulfide bonds in both rice varieties and partially defatted soybean (PDS). 
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The high number of peptide bands observed for PDS as compared to both rice varieties 
confirms that cereals and legumes do not have the same types of proteins, hence the 
differences in their peptides bands. Furthermore, the protein electrophoretic patterns of raw 
rice were different from their parboiled rice counterparts. The electrophoretic patterns of 
raw rice (RTM and RV) had a higher number and more intense peptide bands than that of 
their parboiled counterpart (PTM and PV) rice suggesting that parboiled rice gave a poor 
protein extraction characteristics in all buffers as was also confirmed by Reza et al. (2005). 
This clearly shows that parboiling treatment of the rice led to the diffusion of water soluble 
proteins such as albumin from the rice endosperm to the surrounding water especially 
during the soaking stage of the parboiling treatment. Furthermore, the heat treatment during 
the parboiling process might have also led to protein denaturation thereby reducing its 
solubility properties thus confirming the protein solubility results in Figure 4.2.
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Figure 4.2: Electrophoretic patterns of proteins in the raw materials 
RTM; Raw Togo marshall rice varieties, PTM; 
Parboiled Togo marshall rice variety, RV; Raw 
Viwonor rice variety, PV; Parboiled Viwonor 
rice variety and PDS; Partially defatted 
soybean.  
 
M; Marker, A; Buffer A (50mM Sodium 
phosphate monobasic dihydrate + 100mM 
NaCl), B; Buffer B (Buffer A + Urea) and C; 
Buffer C (Buffer B + DTT). 
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4.4 Chemical analysis of soybean 
4.4.1 Changes in fat content due to defatting 
 Raw soybean had a fat content of 21.01%, this was substantially reduced to 16.94% 
(Figure 4.3) by partially defatting it using a screw press. The partially defatting process was 
to reduce the percentage fat content during the inclusion of soybean content in the 
formulation in order to ensure high performance of the extruder (Riaz, 2000).    
 
 
Figure 4.3: Changes in fat content. RS: Raw soybean (full fat soybean); PDS: Partially 
defatted Soybean. 
 
4.5 Evaluation of extrudate quality through visual examination 
In all twenty different formulations were obtained and all extruded. From the visual 
inspection of rice-soybean extrudates variable expansion was noted. The degree of 
expansion decreased gradually as the quantity of partially defatted soybean (PDS) 
increased as observed in Plate 4.2, 4.3, 4.4 and 4.5. This confirms the fact that the addition 
P = 0.0214 
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of protein to starchy raw materials in extrusion cooking reduced the expansion of the 
products by reducing the extensibility of the starch polymer during its extrusion at the die 
exit (Chaiyakul et al., 2009). Moreover, it can be observed that the addition of 40% of PDS 
drastically reduced the expansion of the extrudates made from raw rice in both rice 
varieties (shown in Plate 4.2 and 4.4) from foamy expanded like extrudate to crispy biscuit 
like extrudate. This was actually irrespective of their differences in amylose content; thus 
Togo marshall rice variety being classified as low amylose content and Viwonor rice 
variety as intermediate amylose content as shown in Table 4.2.  This might be that the 
starch matrix of the pre-gelatinized starch with the addition of 40% PDS was able to better 
entrap water vapour during the extrusion cooking as compared with formulation from raw 
rice and 40% PDS. According to Baladran-Quintana et al. (1998) as stated in Asare et al. 
(2012) expansion is the swelling of cells (starch granules) upon the imbibition of water, 
thus the water molecules enter the cell granules causing solvation of the molecules, 
occupying capillary and intramolecular spaces of the molecules. 
In relation to colour, it can be observed that there was no much notable differences with 
respect to extrudates from Viwonor rice variety in both raw of parboiled form. This is 
because the natural red pericarp of the rice variety musk the colour even after extrusion 
cooking as observed in Plate 4.2 and 4.3. With respect to extrudates from raw Togo 
marshall rice variety, there was an observation of yellowish bright colour which was 
gradually changed to a darker colour as the quantity of PDS increased as observed in Plate 
4.4 and 4.5.  The extrudates from parboiled Togo marshall gave a notable difference in 
colour as compared to extrudates from its raw form as shown in Plate 4.5 and 4.4. Thus the 
colour changed during the parboiling process had an impact even after extrusion cooking. 
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Plate 4.2: Extrudates from Raw ‘Viwonor’ rice variety. (Rice: Soybean) 
 
 
 
 
 
 
 
 
 
 
Plate 4.3: Extrudates from Parboiled ‘Viwonor’ rice variety. (Rice: Soybean) 
  
 
 
 
 
 
 
 
90:10                  82.5:17.5         75:25                  67.5:32.5        60:40 (%) 
90:10                 82.5:17.5         75:25             67.5:32.5          60:40 (%) 
 
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Plate 4.4: Extrudates from Raw ‘Togo marshall’ rice variety. (Rice: Soybean) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Plate 4.5: Extrudates from Parboiled ‘Togo marshall’ rice variety. (Rice: Soybean) 
 
 
 
 
 
 
 90:10                82.5:17.5            75:25              67.5:32.5               60:40 (%) 
  90:10               82.5:17.5                 75:25             67.5:32.5             60:40 (%) 
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4.6 Consumer acceptability of twenty extruded snacks     
According to Martinez et al., (2007), sensory evaluation is the nearest to a consumer's 
estimation and still remains the most reliable test for the especially since it allows the 
characteristics of products to be evaluated. Consumer acceptance of extruded foods 
especially snacks is mainly due to sensory attributes such as aroma, mouthfeel, colour, 
aftertaste and more (Majumdar et al. 2014). According to Jin-Soo et al. (1994), several 
extrusion processing variables such as feed moisture, die diameter and differences in 
ingredients composition accounts for the quality of finished products and finally influence 
the success of the product. Pamies et al. (2000) also stated that the success or failure of a 
new extruded snack food product is directly related to sensory attributes, among which 
mouthfeel plays a major role. 
 The sensory results of the twenty extrudates show that there were no significant 
differences among the values for aroma with TMF2 (thus having 60% Togo marshall rice 
variety and 40% PDS) having the highest aroma score value of 6.6±1.07 as shown in Table 
4.4. This might be as a result of the strong beany flavor of the extrudate which was 
generated during the extrusion cooking due to the high percentage of partially defatted 
soybean. The score values in terms for aroma ranged between 6.6-5 shows that the 
extrudates were liked slightly to neither liked nor disliked.  
According to Nisha et al. (2004), colour in many cases acts as a trigger for acceptance of 
products by the consumers, it plays an important role in visual recognition and assessment 
of the surface and the subsurface properties of the food. There was a significant difference 
among the values for colour at p< 0.05 as can be seen in Table 4.4. Extrudate TMF3 (90% 
Togo marshall rice and 10% PDS) had the highest colour preference value of 7.6 which is 
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interpreted on the hedonic scale to be like moderately. This might be as a result of the 
bright colour due to the high percentage of Togo marshall rice variety which is naturally 
white in colour. Extrudate PVF2 (60% Parboiled Viwonor rice variety and 40% PDS) had a 
significant least value of 4.6±2.12 (Dislike Slightly) for colour as can be seen in Table 4.4. 
This might be due to the Viwonor rice variety which naturally had a reddish pericarp and 
the high quantity of PDS. Also the parboiling treatment of the rice further darkened its 
colour. Consumers’ dislike of the colour for PVF2 was not unusual since probably they 
might not be familiar with such darker coloured extruded snack especially since such 
products are not common on the local markets.  
There was a statistically significant difference in relation to mouthfeel, aftertaste and 
overall acceptability at p˂0.05. With regard to mouthfeel, TMF4 (75% Togo marshall rice 
and 25% PDS) was liked moderately with a high preference value of 7 while PVF3 was 
disliked very much with a preference value of 2.8±1.40 (Table 4.4). The addition of high 
percentage of PDS to starch-rich flour could have led to the production of “protein-type” 
extrudates which reduced the stickiness of the products (Obatolu et al., 2006). Extrudate 
TMF4 significantly had a higher aftertaste preference of 6.5±1.78 (like slightly) with 
extrudate PVF5 having the least value of 2.7±1.83 as shown in Table 4.4. The high 
aftertaste value for TMF4 may be as a result of the high PDS content (25%) which led to 
the generation of a soy taste (Shogren et al. 2006) after consumption. With respect to 
overall acceptability, there was no significant difference among the values for TMF1, 
TMF2, TMF3, TMF4, TMF5, PTMF2, PTMF3 and PTMF4 with their preference score 
ranging between 6.8-6.3 (like moderately) and these were significantly higher as compared 
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to the rest of the extrudate with PVF3 being least preferred with a preference value of 3±2 
(dislike moderately) as observed in Table 4.4.  
Based on the mean scores for the overall acceptability values, five extrudates thus TMF3 
(90% raw Togo Marshall (TM), 10% Partially defatted soybean (PDS)); TMF4 (75% raw 
TM, 25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled Togo 
Marshall (TM), 10% PDS); PTMF4 (75% parboiled TM, 25% PDS) were selected from the 
lot not only because they had high preference scores but  also because their formulations 
had a high percentage of rice (especially since the project focused on maximizing the 
utilization of low grade rice varieties in Ghana). (Further analyses were then carried out on 
the five selected extrudates and their formulations). 
  
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Table 4.4: Mean scores of sensory attributes of twenty extruded snacks from different rice 
varieties and partially defatted soybean. 
     Sensory      attribute   
Extrudates Aroma Colour Mouthfeel Aftertaste Overall 
acceptability 
TMF1 6.3±0.82a 7.1±0.74ab 5.6±1.58abc 6.1±0.99bc 6.5±0.71b 
TMF2 6.6±1.07a 5.7±1.83ab 5.5±2.59abc 5.6±2.59abc 6.8±1.55b 
TMF3 6.2±1.81a 7.6±1.58b 5.9±2.08bc 5.7±2abc 6.6±2.12b 
TMF4 6.5±1.18a 6.4±1.71ab 7±1.83c 6.5±1.78c 6.8±1.69b 
TMF5 6.4±1.07a 6.4±1.65ab 6.2±1.32bc 5.9±1.60bc 6.5±1.27b 
PTMF1 5.2±0.92a 6.4±1.07ab 5.1±1.45abc 4.7±1.25abc 5.4±0.84ab 
PTMF2 5.9±1.37a 6.6±1.84ab 5.6±1.78abc 5±1.94abc 6.3±0.95b 
PTMF3 6.2±1.40a 6.7±1.49ab 6±2bc 5.6±2.5abc 6.7±1.83b 
PTMF4 6.3±1.34a 7.1±0.99ab 5.4±1.51abc 5.8±1.81abc 6.3±1.25b 
PTMF5 5.9±1.73a 5.5±1.84ab 5.4±1.90abc 4.7±2.11abc 5.7±1.16ab 
VF1 5±1.05a 5.6±1.96ab 5.3±1.49abc 4.8±1.81abc 5.1±1.45ab 
VF2 6.5±1.43a 5.1±2.28ab 5.2±1.81abc 6±2bc 5.4±1.96ab 
VF3 5.5±2.07a 5.9±1.52ab 4.1±1.85abc 3.9±2.18abc 4.2±2.04ab 
VF4 6.2±1.03a 6±1.15ab 5.3±2.06abc 4.8±2.2abc 4.2±2.49ab 
VF5 5.5±1.96a 6.3±1.34ab 5.4±1.51abc 5.1±1.60abc 5.2±1.81ab 
PVF1 5±1.15a 5.3±1.83ab 4.6±2.01abc 3.9±1.79abc 4.6±1.78ab 
PVF2 5.1±1.45a 4.6±2.12a 4.5±1.96abc 4±2abc 4.7±2.31ab 
PVF3 5±2.11a 5.7±1.06ab 2.8±1.40a 3±2.49ab 3±2a 
PVF4 6.2±1.23a 5.6±1.43ab 3.9±1.79ab 3.2±1.81ab 4.6±2.63ab 
PVF5 5±2.40a 5.3±2.67ab 3.5±2.59ab 2.7±1.83a 3.2±1.87a 
P value 0.0641 0.0081 0.0002 0.0000 0.0000 
a, b, c: Means and standard deviation with the same superscript in a column are not 
significantly different at p˂0.05. Scale: 9 - like extremely, 8 - like very much, 7 - like 
moderately, 6 - like slightly, 5 - neither like nor dislike, 4 - dislike slightly, 3 - dislike 
moderately, 2 - dislike very much, 1 - dislike extremely.  
KEY: TM (Raw Togo Marshall rice variety), PTM (Parboiled Togo Marshall rice variety), 
V (Raw Viwonor rice variety), PV (Parboiled Viwonor rice variety), F1 (Rice, 67.5%: 
Soybean, 32.5), F2 (Rice, 60%: Soybean, 40), F3 (Rice, 90%: Soybean, 10), F4 (Rice, 
75%: Soybean, 25), F5 (Rice, 82.5%: Soybean, 17.5) 
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4.7 Chemical analysis of the formulations of the selected extrudates 
 4.7.1 Apparent amylose content (AAC)  
According to Singh et al. (2006), amylose constitutes larger percentage of the amorphous 
component of the starch granules where water penetration into the granule is more 
pronounced. Furthermore, Hamaker and Griffin (1993) as cited in Adu-Kwarteng et al. 
(2003) concluded that amylose content is an important factor in determining the cooking 
and pasting behaviour of rice and its end use. Results show that, there was a significant 
difference in the values for amylose content for all formulations at p ≤ 0.05 as shown in 
Figure 4.4. There was an obvious trend indicating that formulation with high rice content 
had high amylose content for both untreated (raw) rice and parboiled rice based 
formulations. This was as a result of the rice being the main source of amylose in the 
formulations. It was also noticed that the parboiled rice based formulations generally had 
higher amylose content than those of untreated rice (Figure 4.4). The parboiling treatment 
probably led to extensive gelatinization of the rice starches (thus the amylose leaching out) 
and retrogradation of the amylose molecules which tend to associate or bind strongly 
together upon cooling (Adu-Kwarteng et al., 2003). This suggests that parboiling as a 
treatment affects the availability of the amylose content of rice products during extraction 
and analyses. 
Noda et al. (2003) and Riley et al. (2004) stated that amylose content plays a key role in 
the digestion of starches, as starches with low amylose content digest more easily than 
those of high amylose content.  Therefore based on this it can be concluded that products 
from TMF4 (Raw rice 75 % and PDS 25 %) formulation are likely to digest more easily as 
compared to products from the other formulations. 
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Figure 4.4: Apparent Amylose Content (AAC) for five formulations from Togo marshall 
rice variety and Partially Defatted Soybean.  
TMF3 (90% raw Togo Marshall (TM) rice, 10% Partially defatted soybean (PDS)); TMF4 
(75% raw TM rice, 25% PDS); TMF5 (82.5% raw TM rice, 17.5% PDS); PTMF3 (90% 
parboiled Togo Marshall (TM) rice, 10% PDS) and PTMF4 (75% parboiled TM rice, 25% 
PDS). 
 
 
4.8 Functional properties of the formulations of the selected extrudates 
4.8.1 Pasting properties of the five formulations 
The Brabender viscoamylograph was used for the characterization of starches in the five 
different formulations. The viscosity of a paste depends on a large extent on the degree of 
gelatinization of the starch granules and the extent of their molecular breakdown (E-Dash 
et al., 1983). Thus pasting viscosity allows one to determine the degree of modification of 
the starches or flours when subjected to heat treatment under moist conditions.  
 
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4.8.1.1 Beginning of gelatinization/Initial viscosity 
Beginning of gelatinization/initial viscosity refers to the viscosity of the suspension in 
Brabender Unit (BU) at the start of heating. The initial viscosity of the flour in water at 30 
ºC is called the cold viscosity. In the preparation of instant foods this property indicates the 
capacity of the flour to absorb water at room temperature to form a paste, gel or viscous 
liquid. In this work, it was noted that formulations were not significantly different from one 
another at p≤0.05 and that the rice treatment and the various formulations have no 
significant effects on the initial viscosity. Formulations from the parboiled rice had greater 
initial viscosity (thus before gelatinization) with viscosity values from 26.50-27.00 BU as 
against 16.50-20.00 BU for raw rice (Table 4.5). The high initial viscosity is typical of 
gelatinized starch products, which indicates a high level of polymer breakage with a 
consequent increased in water absorption even at room temperature.  The TMF4 (Raw rice 
75 % and PDS 25 %) had the lowest initial viscosity value (16.50±6.36) BU because it had 
a relatively high percentage of partially defatted soybean. Shimelis et al. (2006) concluded 
that legumes have a diluting effect by forming complexes with starch during gelatinization 
thereby restricting swelling of the suspension at the start of heating. The high initial 
viscosity values for the formulations with parboiled rice (PTMF4 and PTMF3) imply that 
they could be used directly in the preparation of foods with water or cold milk, since they 
show good ability to absorb water at room temperature as was also confirmed by Souza et 
al. (2012).  
 
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4.8.1.2 Maximum/peak viscosity 
The maximum/peak viscosity which is the highest viscosity attained during the heating 
cycle before their physical breakdown was noted to be significantly different for the 
formulations at p≤0.05 as shown in Table 4.5. The formulation that was composed of 90% 
raw rice (Togo marshall) and 10% partially defatted soybean (TMF3) had a peak viscosity 
of 1036.50±6.36 BU. This formulation had the highest raw rice composition and the least 
amount of partially defatted soybean. Its peak viscosity was significantly higher than 
formulations with relatively lower amounts of raw rice, such as for TMF5 (82.5% raw rice; 
17.5% PDS) (965.50±2.12) BU and TMF4 (739.00±35.36) BU. The increasing presence of 
partially defatted soybean in the formulation only served to dilute the starch content and 
consequently lowered the peak viscosity. Zaidul et al. (2007) observed that peak viscosity 
is influenced by starch granule swelling, amylose leaching, starch crystallinity, amylose 
content, branch chain length distribution of amylopectins as well as the content of other 
components such as proteins and lipids.  
Parboiling of rice seemed to influence peak viscosity of the formulations. Even for 
formulations that had the same ratio of rice (90%) and PDS (10%), those with parboiled 
rice showed significantly lower peak viscosities than with raw rice. This is because the 
parboiling treatment of the rice which involved heating under moist condition led to the 
pre-gelatinization of the rice starch. According to Shimelis et al. (2006), peak viscosity is 
the maximum viscosity attained by gelatinized starch during heating in water, indicating 
the water binding capacity of the starch granule. Peak viscosity has also been closely linked 
with the degree of starch damage and that high starch damage results in high peak viscosity 
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(Sanni et al., 2001). Therefore the high peak viscosity of TMF3 (1036.50±6.36 BU) is 
likely to lead to its high starch damage.  
 
4.8.1.3 Hot paste viscosity 
The hot paste viscosity is the viscosity of the paste at the end of the heating phase at 95oC. 
There were significant differences in the hot paste values of the different formulations 
(Table 4.5). High raw rice concentration led to higher hot paste viscosity in the 
formulations. The hot paste viscosities of the formulations made using parboiled rice 
showed significantly lower values. The values further decreased with increasing partially 
defatted soybean concentration. According to Bainbridge et al. (1996), high paste stability 
is a requirement for industrial use of starch and that starch with low paste stability will 
have a greater need for cross-linking than that with high value.  
 
4.8.1.4 Breakdown 
The hold period after the heating phase of 95oC is often accompanied by a breakdown in 
viscosity. Breakdown viscosity according to Falade et al. (2014), measures the 
vulnerability or susceptibility of the cooked starch to disintegrate. Breakdown viscosities of 
the formulations were significantly influenced by rice treatment, and also by soybean 
content in the formulation. Formulations with raw rice showed tremendously high 
breakdown viscosities. On the other hand formulations with parboiled rice showed 
extremely low breakdown viscosity. According to Dutta et al. (2012) the decrease of 
breakdown viscosity might be due to the failure of complete pasting and swelling of starch 
granules induced by the reduction of water absorption of starch granules. For all 
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formulations however, increasing soybean content decreased the breakdown viscosity 
(Table 4.5). Adebowale et al. (2005) stated that the higher the breakdown in viscosity, the 
lower the ability of the starch sample to withstand heating and shear stress during cooking. 
Therefore, TMF3 (90% raw Togo marshall rice; 10% PDS) formulation showing higher 
breakdown viscosity value (624.50±6.36) will not be able to withstand more heating and 
shear stress compared to the other formulations. 
 
4.8.1.5 Setback 
According to Lee et al. (2004), setback values indicate the hardness of gel paste upon 
cooling and it is considered by Zaidul et al. (2003) to be an indirect measurement of 
retrogradation tendency or syneresis of starch upon cooling of cooked starch pastes. There 
were significant differences among the formulations in terms of setback viscosity. 
Formulations with raw rice, such as TMF3 had very high setback values (535.00±25.46), 
while formulations with parboiled rice such as PTMF4 had very low setback viscosities 
value (170.50±2.12) (Table 4.5). The low setback viscosity indicates a low tendency to 
retrograde and the low likelihood of syneresis taking place upon cooling. According to 
Adebowale et al. (2003), the lesser tendencies of starch to retrograde is an advantage in 
food products such as soups and sauces, which undergo loss of viscosity and precipitation 
as a result of retrogradation. 
 
 4.8.1.6 Pasting temperature 
Shimelis et al. (2006) observed that pasting temperature is one of the properties that 
determines the temperature at which the viscosity begins to increase during the heating 
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process. This gives an indication of the minimum temperature required for sample cooking, 
as well as the energy cost involved and the stability of other components. There were no 
significant differences among the formulations in terms of pasting temperature. From Table 
4.5, it can be observed that formulations from raw rice had higher pasting temperatures 
than formulations from parboiled rice. TMF5 had the highest pasting temperature of 
(68.60±0.14) oC followed by TMF3 (68.10±0.14) oC and TMF4 (57.05±17.75) oC while 
PTMF4 (51.40±0.00) oC and PTMF3 (47.85±1.34) oC had the lowest pasting temperature. 
This is because the parboiling process which required a heat treatment might have caused a 
partial starch degradation which led to the decrease in pasting temperature. This contradicts 
the findings by Swasdisevi et al. (2010) that parboiling treatment of rice causes the increase 
in pasting temperature. The contradiction could be due to the presence of proteins and 
lipids from PDS which interacted with the starch from rice as was observed with the initial 
viscosities as noted in Table 4.5. Starches with lower pasting temperatures are generally 
considered to be easier to cook. However, very low pasting temperatures are associated 
with low paste stability, which is usually considered to be an undesirable property (Aishat 
et al., 2007).  
 
 
 
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Table 4.5: Pasting parameters of five formulations (Rice and Partially Defatted Soybean (PDS)). 
 Parameters 
Samples Beginning of 
gelatinization 
[BU] 
Maximum 
viscosity [BU] 
 
Hot Paste 
Viscosity [BU] 
 
Breakdown [BU] Setback [BU] 
 
Pasting 
temperature[oC] 
TMF3 20.00±1.41 abc 
 
1036.50±6.36e 412.00±0.00e 624.50±6.36c 535.00±25.46d 68.10±0.14 ab 
 
TMF4 16.50±6.36 a 
 
739.00±35.36c 310.50±9.19c 428.50±26.16b 491.00±5.66c 57.05±17.75 ab 
 
TMF5 19.00±0.00 ab 
 
965.50±2.12d 360.00 ±12.73d 
 
605.50 ±14.85c 529.50±14.85 d 68.60±0.14 b 
 
PTMF3 26.50±0.71 bc 
 
194.00±0.00b 192.50±0.71b 1.50 ±0.71a 251.50±0.71b 47.85±1.34 a 
 
PTMF4 27.00±0.00 c 
 
130.50±0.71a 130.00±1.41a 0.50±0.71a 170.50±2.12a 51.40±0.00 ab 
 
p-value 0.0511 ˂0.0001 ˂0.0001 ˂0.0001 ˂0.0001 0.1412 
 
 
* Values are means ± standard deviations. Different letters (a, b, c, d, e) in the same column for each parameter indicate 
significant differences between means (p≤0.05). BU= Brabender Unit. TMF3 (90% raw Togo Marshall (TM) rice, 10% 
Partially defatted soybean (PDS)); TMF4 (75% raw TM rice, 25% PDS); TMF5 (82.5% raw TM rice, 17.5% PDS); 
PTMF3 (90% parboiled Togo Marshall (TM) rice, 10% PDS) and PTMF4 (75% parboiled TM rice, 25% PDS). 
 
 
 
 
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4.9 Chemical analysis of the five formulation and their extrudates 
4.9.1 Changes in moisture content for formulation and their extrudates 
Moisture content is an important determinant of shelf stability of food products. The 
moisture content of the formulations ranged from 10.10-12.57% with formulation TMF5 
having the highest moisture content of 12.57%. The highest moisture content for TMF5 led 
to the highest expansion ratio of 3.79 and the least bulk density of 0.07 when the 
formulation was extruded as shown in Table 4.7. There was also a substantial decrease in 
moisture content for all extudates after extrusion and this might be as a result of the 
pressure differences in and outside the extruder die enabling the release of water vapour to 
the outside of the die thereby forming vacuoles leading to product expansion. Ashworth 
and Draper in 1992 stated that high moisture products (>12%) usually have shorter shelf 
stability compared to lower moisture products (˂12%). Therefore, the low moisture content 
of the extrudates ranging 6.04-8.77% will allow easy handling, storage and extended shelf 
life of the extrudates. This is because products with higher moisture content have high 
water activity, which enhances microbial activity leading to spoilage. 
 
Table 4.6: Changes in moisture content 
 Samples  
Moisture  
content % 
TMF3 TMF4 TMF5 PTMF3 PTMF4 p-value 
Formulation  
 
11.95±0.13a 11.67±0.35a 12.57±1.94a 11.03±0.47a 10.1±0.14a 0.2116 
 
Extrudates 
 
8.77±0.17c 
 
6.05±0.04a 
 
6.04±0.0a 
 
7.74±0.25b 
 
7.93±0.29b 
 
0.0001 
Values are means ± standard deviations. Different letters (a, b, c) in the same row for each 
parameter indicate significant differences between means (p≤0.05). TMF3 (90% raw Togo 
Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 (75% raw TM, 25% PDS); 
TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled Togo Marshall (TM), 10% 
PDS); PTMF4 (75% parboiled TM, 25% PDS). 
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4.10 Physical properties of the selected Rice extrudates 
The physical properties determined included expansion ratio, bulk density, colour and 
hardness of extrudates. 
 
4.10.1 Expansion ratio (ER) 
When starch is extrusion-cooked, expansion is dependent on the formation of a starch 
matrix that entraps the water vapour, resulting in formation of bubbles (Guy et al., 1988). 
There was a significant difference among the extrudates in their expansion ratio (Table 
4.7). Extrudates made with raw rice had significantly higher expansion ratios than those 
from parboiled rice. The expansion ratio value (2.31±0.11) for PTMF4 (Parboiled rice 75 
% and PDS 25 %) was significantly low as compared to the others. Among all the 
formulations increasing amount of soybean content generally decreased the expansion 
ratio. This is a confirmation of Chaiyakul et al. (2009) study which found that the addition 
of protein to starchy raw materials in extrusion cooking reduced the expansion of the 
products by reducing the extensibility of the starch polymer during its extrusion at the die 
exit.   
 
4.10.2 Bulk density (BD)  
Bulk density (BD) is an index of the extent of puffing and it considers expansion in all 
directions. The bulk density values for the extrudates were in the range 0.07-0.13 g/cm3. 
From Table 4.7, it can be observed that parboiled rice based samples had higher density 
than that of raw rice products (thus PTMF3 (0.13) and TMF3 (0.11) g/cm3; PTMF4 (0.13) 
and TMF4 (0.08) g/cm3), suggesting that the parboiling treatment modified starch matrix 
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leading to a more compact structure that is less able to organize under high temperature and 
pressure conditions.  
 
4.10.3 Colour  
Colour is one of the important quality factor directly related to the acceptability of food 
products and it is therefore an important physical property of extruded products. Altan et 
al. (2008) observed that colour changes can give information about the extent of browning 
reactions such as caramelization, Maillard reaction, degree of cooking and pigment 
degradation that take place during the extrusion process. There was a significant difference 
in the L* values of the extrudates as shown in Table 4.7. There was generally a decrease in 
L* values as the level of PDS increased. Obatolu et al. (2006) and Yagci et al. (2009) 
confirmed this by reporting that extrudates turn to be slightly darker when the quantity of a 
partially defatted legume in the formulation is increased. It was also observed that 
extrudates obtained from parboiled rice formulations had significantly lower L* values as 
compared to those obtained from raw rice formulations (Table 4.7). This suggest that the 
diffusion of husk pigments into the endosperm during the parboiling treatment significantly 
had an impact on the L* index. 
There was also a significant difference among the values for a* of the extrudates at p≤0.05 
as shown in Table 4.7. This implies that the parboiling treatment positively impacted on the 
redness of the extrudates.   
Table 4.7 shows that b* index increased as the amount of PDS in the formulation increased, 
suggesting that the yellowness of the extrudates increased with increasing soybean content.   
This was in agreement with work by Obatolu et al., (2006) that the incorporation of PDS 
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enhanced the b* of puffed extrudates. This can be attributed to the presence of carotenoids 
pigments in the soybean which was not totally degraded after the extrusion cooking. 
Furthermore, it was also observed that b* values for extrudates from parboiled rice were 
significantly higher than that from raw rice extrudates. This might be that the diffusion of 
colour pigments from the rice husk into the endosperm during the parboiling process 
significantly affected the b* thus the yellowness. It can therefore be concluded that soybean 
level in the formulation and the parboiling treatment has an impact on the colour of the 
extrudates.  
 
Table 4.7: Expansion ratio, bulk density and colour characteristics of five extrudates      
 Parameter 
   Colour 
Samples Expansion 
ratio 
Bulk density 
(g/cm
3
) 
L* a* b* 
TMF3 3.73± 0.30
c
 0.11±0.02
b
 87.37±0.51
a
 -0.63±0.06
a
 15.14±0.24
a
 
TMF4 3.30± 0.16
b
 0.08±0.00
a
 85.04±0.61
b
 -0.04±0.06
b
 20.42±0.29
b
 
TMF5 3.79± 0.21
c
 0.07 ±0.00
a
 84.10±0.24
c
 0.11±0.02
c
 19.72±0.19
b
 
PTMF3 3.14±0.15
b
 0.13±0.01
c
 82.61±0.56
d
 0.31±0.06
d
 19.31±0.35
c
 
PTMF4 2.31± 0.11
a
 0.13±0.01
c
 81.74±0.92
e
 0.62±0.11
e
 21.25±0.63
d
 
p-value <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 
Values are means ± standard deviations. Different letters (a, b, c, d, e) in the same column 
for each parameter indicate significant differences between means (p≤0.05).  TMF3 (90% 
raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 (75% raw TM, 
25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled Togo Marshall 
(TM), 10% PDS); PTMF4 (75% parboiled TM, 25% PDS). 
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4.10.4 Hardness of five extrudates 
Hardness was determined by puncturing the eatrudates.  Ding et al. (2005) stated that 
hardness is the average force required for a probe to penetrate an extrudate. There were 
significant differences among the values for hardness as shown in Figure 4.5. Choudhury 
and Gautam (2003) as well as Onwulata et al. (2001) concluded that extrudate hardness 
was strongly influenced by protein content. Increased protein content in feed material 
produced a less expanded product and more rigid network, resulting in higher resistance to 
shear and thereby increasing extrudates hardness (Chaiyakul et al., 2009).  This was largely 
observed in extrudates obtained from formulations with parboiled rice.  It was also noted 
that extrudates obtained from formulations with parboiled rice had higher hardness as 
compared to those obtained from raw rice formulations.This has been explained by 
Bhattacharya (2004) to be as a result of the more homogeneous and compact ultrastructure 
obtained as a result of starch gelatinization during the parboiling treatment. It can therefore 
be concluded that the parboiling treatment and amount of protein as determined by the 
level of PDS in the formulation significantly affected hardness. 
 
 
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Figure 4.5: Hardness (N) of five extrudates.  
Different letters (a, b, c) represent statistically significant differences between the samples 
(p<0.05).  
TMF3 (90% raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 
(75% raw TM, 25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled 
Togo Marshall (TM), 10% PDS); PTMF4 (75% parboiled TM, 25% PDS). 
 
 
4.11 Functional properties of selected extrudates 
The functional properties determined included water absorption index (WAI) and water 
solubility index (WSI).  
 
 
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4.11.1 Water absorption index (WAI)  
Water absorption index, an indicator of the ability of flour to absorb water, depends on the 
availability of hydrophilic groups which bind water molecules and on the gel-forming 
capacity of macromolecules. Anderson et al. (1969) stated that WAI measures the amount 
of water absorbed by starch and can be used as an index of gelatinization. The order for 
WAI in this study is as follows TMF4˂TMF5˂PTMF4˂PTMF3˂TMF3 as shown in Table 
4.8. There was a significant difference among the values for WAI at p≤0.05. According to 
Colonna et al. (1989) starch granules damaged or gelatinized during extrusion cooking 
absorb water and swell at room temperature unlike native starches which do not absorb 
water at room temperature. It can therefore be deduced that the significantly higher WAI 
value for TMF3 (90% raw Togo Marshall (TM), 10% partially defatted soybean (PDS)) 
after the extrusion cooking may be as a result of its great starch damage or degradation due 
to its high raw rice quantity.   
 
4.11.2 Water solubility index (WSI)  
According to Hernandez-Diaz et al. (2007), water solubility index (WSI) is used as an 
indicator  of starch degradation and also measures the degree of starch conversion during 
extrusion cooking thus at lower WSI there is minimal degradation of starch and such 
condition leads to low amounts of soluble molecules of the extrudates. There were 
significance differences in the WSI values at p≤0.05 (Table 4.8). The significantly higher 
WSI value for extrudate TMF5 implies that the amount of free polysaccharide or soluble 
molecule released from the extrudate after addition of excess water was higher than that of 
the other extrudates (Yang et al., 2008).  
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Table 4.8: Water Absorption (WAI) and water solubility indexes (WSI) of five extrudates.  
             Parameters 
Samples WAI WSI 
TMF3 6.10±0.10d 19.62±0.40b 
TMF4 4.91±0.05a 23.27±0.61d 
TMF5 5.02±0.15a 25.27±0.49e 
PTMF3 5.63±0.03c 21.57±0.12c 
PTMF4 5.33±0.10b 18.02±0.27a 
p-value 0.0003 0.0001 
 
TMF3 (90% raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 
(75% raw TM, 25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled 
TM, 10% PDS); PTMF4 (75% parboiled TM, 25% PDS). 
 
 
 
4.12 Molecular characterization of protein from five extrudates 
The protein molecular analysis determined included protein solubility, protein 
electrophoretic pattern, accessible protein thiols and in-vitro protein digestibility of 
extrudates. 
 
4.12.1 Protein solubility  
Structural features of proteins in rice-soybean extrudates were evaluated by extraction in 
three different buffers thus buffer A (50mM sodium phosphate monobasic dihydrate and 
100mM NaCl), buffer B: (buffer A and 6M urea) and Buffer C (buffer B and 10mM DL-
Dithiothreitol (DTT)) with different dissociating abilities towards covalent and non-
covalent inter-protein bonds. In particular saline buffer (buffer A) enables the solubilisation 
of water and salt soluble proteins such as albumins and globulins (Bhattacharya, 2004). As 
shown in Figure 4.6, the amount of soluble proteins in buffer A appears very low and 
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comparable in all extrudates. Addition of a denaturing agent such as urea to the saline 
extractant resulted in an increase in protein solubility as shown in Figure 4.6. This is due to 
the fact that urea promoted the dissociation of aggregates stabilized by hydrophobic 
interactions (Moroni et al., 2009). A further increase in the amount of soluble proteins was 
evident when both urea and dithiothreitol (DTT) were present in the extractant (buffer C). 
This is because the addition of dithiothreitol (DTT) further reduced disulphide bonds thus 
by destabilizing some tertiary protein folding and breaking up of quaternary protein 
structure (Lukesh et al., 2012).  
This was confirmed by Cabrera-Chávez et al. (2012) and Mariotti et al. (2011) who 
concluded that combining urea and DTT in the extraction medium further increased the 
amount of solubilized protein. Comparing extrudates from raw rice (ie TMF3, TMF4 and 
TMF5), it was obvious that the amount of soluble proteins in all buffers (A, B and C) 
increased as the percentage of partially defatted soybean (high protein source) increased. 
In terms of TMF4 (raw Togo marshall (TM) 75% and partially defatted soybean (PDS) 
25%) and PTMF4 (parboiled (TM) 75% and PDS 25%), the highest amount of solubilised 
proteins for PTMF4 as compared to TMF4 in all buffers  suggests that both hydrophobic 
interactions and inter-protein disulphide bonds play a fundamental role in the overall 
stabilization of the proteins. This was similarly observed by Barbiroli et al. (2013) while 
addressing the effects of processing conditions on rice macromolecular structure and 
protein-protein and protein-macromolecules interactions in rice pasta. In relation to TMF3 
and PTMF3 the same observation for TMF4 and PTMF4 was made during the 
solubilisation with buffer C but for buffer A and B, a vice versa observation was made 
(Figure 4.6). This may suggest the presence of strong aggregation phenomena especially 
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due to the high percentage of parboiled rice (90%) in PTMF3. Cabrera-Chávez et al. (2012) 
suggested that the sequential starch gelatinization/retrogradation cycles might have resulted 
in protein entrapment in an organized starch structure. The presence of a highly denatured 
network is more evident since a significant fraction of the total proteins is not solubilised in 
buffer A and B but unlike protein solubilisation using buffer C, the presence of disulphide-
reducing agent, DL-Dithiothreitol (DTT), enabled an increase in protein solubilisation 
(Moroni et al., 2009). This also confirms the role of disulphide bonds in the stabilisation of 
insoluble protein aggregates (Bonomi et al., 2012). It can therefore be concluded that a 
structured protein network is present and is stabilized by inter-protein disulphide bonds. 
Furthermore, parboiling treatment and the quantity of PDS affects the proteins structural 
features in the rice-soybean extrudates. 
 
 
 
  
 
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0
20
40
60
80
100
120
140
Buffer A Buffer B Buffer C
s
o
l
u
b
l
e
 
p
r
o
t
e
i
n
s
,
 
m
g
/
g
 
s
a
m
p
l
e
TMF3
TMF4
TMF5
PTMF3
PTMF4
 
Figure 4.6: Amount of solubilized protein in different buffers systems.   
Buffer A: (50mM sodium phosphate monobasic dihydrate and 100mM NaCl). Buffer B: 
(Buffer A+ 6M urea) and Buffer C (Buffer B+ 10mM DL-Dithiothreitol (DTT)). TMF3 
(90% raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 (75% raw 
TM, 25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled TM, 10% 
PDS); PTMF4 (75% parboiled TM, 25% PDS). 
 
 
4.12.2 Electrophoretic patterns of extracted proteins from the selected extrudates 
Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) has been used as 
a qualitative tool for the separation and eventual molecular weight determination of 
proteins in foods sources (Luo et al., 2004). Separation of proteins in the extrudates by 
SDS-PAGE allowed for a qualitative comparison among samples in terms of representative 
protein families and to estimate their molecular weight, as shown in Figure 4.7.  
In relation to all  five extrudates, it can be noted that the number and the intensity of 
peptide bands increased when urea (buffer B) or urea and DTT (buffer C) were used for 
protein extraction, thus confirming the presence of protein aggregates stabilized by 
hydrophobic interactions and disulfide bonds.  The electrophoretic patterns of the 
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extrudates confirm the solubility data presented in Figure 4.6 and their tracings or peptide 
bands indicate that the proteins solubilized by urea and DTT (buffer C) are derived from 
disulfide-linked aggregates and are larger than those solubilized in the absence of 
chaotrope eg. urea and reductants such as DTT (Mariotti et al., 2011). Comparing all the 
five extrudates, those with high percentage of partially defatted soybean (PDS) gave more 
peptide bands and had higher molecular weight. This suggest that extrudates with more 
PDS percentages are much diversified in types of proteins as compared to those with lower 
percentage of PDS.   
 
 
 
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Figure 4.7: Electrophoretic patterns of proteins in five extrudates 
(from raw/parboiled rice and partially defatted soybean) by using different extraction 
buffers.  
Thus Buffer A: 50mM sodium phosphate monobasic dihydrate and 100mM NaCl; |Buffer 
B: buffer A + 6M urea; Buffer C: buffer B + 10mMDTT. M: Protein marker, TMF3 (90% 
raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 (75% raw TM, 
25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled TM, 10% PDS); 
PTMF4 (75% parboiled TM, 25% PDS). 
 
 
4.12.3 Accessible protein thiols from extrudates  
According to Iametti et al. (2013), thiol–disulfide exchange reactions, are major 
contributors to the formation of a covalently-linked protein networks in many foods, where 
disulfides represent the most “natural” type of inter protein covalent bond. In this frame it 
may be pointed out that thiol–disulfide exchange reactions occur as a function of the 
accessibility of the involved thiols, which in turn depends on structural features of the 
proteins. The degree of structural “stiffness” of the protein network or the extent of 
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modification induced in the individual extrudates was evaluated through thiol accessibility 
studies in the presence and absence of urea. These studies were carried out independently 
of protein solubility  and the measurements provide two separate parameters, namely the 
total content in reactive thiol (measured under denaturing conditions on both the soluble 
and insoluble fraction) and the increment in thiol accessibility due to denaturation (Iametti 
et al., 2006). Generally, the accessible thiols values for all extrudates suggest a loose 
protein network and this is as a result of the extrusion cooking due to the high temperature 
involved. It is also noted that the number of accessible thiols increased in the presence of 
urea for all extrudates as shown in Figure 4.8. This increase might be due to the fact that 
the hydrophobically stabilized compact structure of the protein matrix must be destabilized 
by the chaotrope enabling thiols to readily become accessible (Mariotti et al., 2011). The 
relatively lower values for extrudes obtained using parboiled rice formulations (PTMF4 
(0.9559 µmol/g) and PTMF3 (0.9191µmol/g)) as compared to extrudates obtained from 
raw rice formulations (TMF4 (1.2647 µmol/g) and TMF3 (1.0662 µmol/g) in the presence 
of urea confirm the impact of parboiling treatment on the compactness of the protein matrix 
making thiols not easily accessible. It can therefore be concluded that rice parboiling had 
an effect on the overall protein organization of the extrudates.  
 
 
 
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Figure 4.8: Accessible thiols of five extrudates from rice and partially defatted soybean.  
 
TMF3 (90% raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 
(75% raw TM, 25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled 
TM, 10% PDS); PTMF4 (75% parboiled TM, 25% PDS). 
 
4.12.4 In vitro protein digestibility 
Protein digestibility is one of the most important factors determining protein quality of raw 
materials and their products (Parsons et al., 1991). The results show that with the exception 
of TMF5, all the other extrudates showed almost an equal digestibility by pepsin after 1 
hour incubation time (Figure 4.9). All the extrudates were however hydrolyzed by 
pancreatin but at significantly different rates.  Extrudates made from raw rice formulations 
were generally more digestible by pancreatin. However increasing amounts of the partially 
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defatted soybean in the formulation decreased the protein digestibility by pancreatin.  Thus 
among the extrudates made with raw rice formulation, those with high percentage of PDS 
(25%) showed the least protein digestibility after the fourth hour. This might suggest the 
presence of quite a substantial amount of antinutritional factor such as trypsin inhibitors 
that bind to trypsin and thereby reducing the extent of protein-digestion (Stauffer, 1990). 
Petitot et al. (2009) and de Zorzi et al. (2007) also concluded that resistance of proteins to 
digestion could be attributed to the presence of highly aggregated proteins stabilized by 
covalent protein interactions, such as inter peptide cross-linking. Extrudates obtained from 
parboiled rice had low pancreatin digestibility, irrespective of the amount of soybean in the 
formulations. Starch modification induced by the parboiling treatment may have resulted in 
the decrease of protein digestibility by pancreatin. This could be related to the presence of 
the pre-gelatinized starch-rich rice matrix that could have changed the pattern and outcome 
of protein structural reorganization. 
 
 
 
 
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Figure 4.9: In-vitro protein digestibility of five extrudates from rice and partially defatted 
soybean.  
TMF3 (90% raw Togo Marshall (TM), 10% partially defatted soybean (PDS)); TMF4 
(75% raw TM, 25% PDS); TMF5 (82.5% raw TM, 17.5% PDS); PTMF3 (90% parboiled 
TM, 10% PDS); PTMF4 (75% parboiled TM, 25% PDS). 
 
 
4.13 Aroma and taste determination using electronic nose and tongue  
According to Baldwin et al. (2011), electronic noses (e-noses) and electronic tongues (e-
tongues) mimic the human smell and taste, and their communication with the human brain. 
 
4.13.1 Aroma analysis of the five extrudates 
The electronic nose is the common name of electrochemical sensor systems responding to 
flavour/odour (volatiles) using an array of simple and non-specific gas sensors and a 
pattern recognition software system (Buratti et al., 2004). Essentially, it is particularly 
useful for the analysis of headspace of liquid or solid food samples (Schaller et al. 1998) 
  PEPSIN 
PANCREATIN 
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and each odour leaves a characteristic pattern or fingerprint on the sensor array, and a 
pattern recognition is use to distinguish and recognize the odours. 
The electronic nose was used to evaluate the aromatic profile of extrudates (Figure 4.10a) 
obtained from different formulations. For each sample the electronic nose responses were 
collected and analyzed using multivariate procedures (Principal Component Analysis 
(PCA)) performed in a correlation matrix to achieve a partial visualization of the data set in 
a reduced dimension. By examining the score plot (Figure 4.10a), the first two principal 
components (PCs) could explain 81.4% of total variance, and it can be seen that the 
extrudates are distributed along both PC1 and PC2 from right to the left part of the plots 
describing a trend related to changes in aroma compounds.  
Considering the PC1 (thus assessing sample similarity in a vertical direction), it can be 
observed that extrudates were discriminated into two folds thus raw rice based extrudates 
with PDS content not less than 17.5% on the right and parboiled rice based extrudates; raw 
rice based extrudate with PDS content of 10% on the left. Generally on the loading plot 
(Figure 4.10b) which explains 45.5% of the total variation, it is noticed that only W1W 
(sulphur-organic) had the least magnitude and therefore had no substantial influence on 
PC1 while the others had a higher influence  (W1C (aromatic), W3C (aromatic), W6S 
(hydrogen), W5C (arom-aliph), W1S (broad-methane), W2S (broad-alcohol), W2W (sulph-
chlor) and W3S (methane-aliph) having negative PC scores while W5S (broad range) had a 
positive PC score.  
Extrudate made using raw rice with at least 17.5% PDS (a and c) located in the positive 
part of the plot suggests similar odorous compounds due to the response of W5S (broad 
range) sensor on the loading plot. This might be as a result of oxidation of their relatively 
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high lipid content from the PDS as compared to the raw rice based extrudate with 10% 
PDS. This was confirmed by Choe et al. (2006) who stated that the unsaturated fatty acids 
present in food lipids such as oleic, linoleic, α and γ-linolenic can undergo thermally 
induced oxidation during cooking to generate volatile compounds which determine the 
aroma characteristics of the foods.  
Extrudates obtained from parboiled rice based formulations with any amount of partially 
defatted soybean (d and e), are located to the left (or negative) half of PC1. Thus the 
parboiling treatment according to Sareepuang et al. (2008) which involves gelatinization 
and pigment transfers from the rice husks to the rice endosperm affects the organoleptic 
properties of cooked rice. Maarse (1991), Parnsakhorn and Noomhorm (2008) also 
concluded that parboiling treatment of the rice gave rise to some peculiar flavonoids 
thereby leading to their similar aromatic profile. 
The second principal component (PC2) could explain 35.9% of the total variation in the 
sensory scores. The sensory scores for extrudates  in the negative half of PC2 were 
influenced by WC sensor series (Figure 4.10b).The samples in this location were either 
extrudates made with raw rice with 25% PDS, or with any type of rice treatment (raw or 
parboiled) with low (10%) PDS.  
 
 
 
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First Component (45.5%)
S
e
c
o
n
d
 
C
o
m
p
o
n
e
n
t
 
(
3
5
.
9
%
)
210-1-2
3
2
1
0
-1
-2
a
b
c
d
e
 
Figure 4. 10a: PCA score plot of five extrudates.  
a: TMF5 (raw ‘Togo marshall’ rice variety-82.5%, Partially defatted soybean (PDS)-
17.5%); b: TMF3 (raw ‘Togo marshall’ rice variety-90%, PDS-10%); c: TMF4 (raw ‘Togo 
marshall’ rice variety-75%, PDS-25%); d: PTMF3 (parboiled ‘Togo marshall’ rice variety-
90%, PDS-10%); e: PTMF4 (parboiled ‘Togo marshall’ rice variety-75%, PDS-25%). 
 
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First Component
S
e
c
o
n
d
 
C
o
m
p
o
n
e
n
t
0.20.10.0-0.1-0.2-0.3-0.4-0.5
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
W3S
W2W
W2S
W1W
W1S
W5C
W6S
W3C
W5S
W1C
 
Figure 4.10b: PCA loading plot of five extrudates. 
W1C (aromatic) W5S (broadrange) W3C (aromatic) W6S (hydrogen) W5C (arom-aliph) 
W1S (broad-methane) W1W (sulphur-organic) W2S (broad-alcohol) W2W (sulph-chlor) 
W3S (methane-aliph). 
 
 
4.9.4.2 Taste analysis of the five extrudates  
Taste analysis was conducted using the electronic tongue (ET). ET is a liquid analytical 
device that mimics the taste-sensing mechanism of the gustatory system; it comprises 
sensor arrays that are specific for liquid 
Taste has an important role in the development of food products such as snacks. In relation 
to consumer acceptability and compliance to quality standards, taste is one of the prime 
factors determining the market penetration and commercial success of products (Jain et al. 
2010). The taste values collected by ET were analysed using multivariate techniques, in 
particular Principal Component Analysis (PCA). Principal component analyses could 
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account for 96.5% of the total variation in the taste of the extrudates based on the data from 
e-tongue. PC1 alone accounted for 65.8% of the total variations in the taste of the 
extrudates, and separated the extrudates based on the percentage of PDS in the formulation 
and irrespective to the rice treatment (either raw or parboiled): extrudates that were 
obtained from either raw or parboiled rice but with high partially defatted soybeans (25%) 
(C and E) clustered to the left (negative half), while those that were obtained from low 
levels of soybean (10%) (B and D) were located to the right half (Figure 4.11a). The 
loadings plot (Figure 4.11b) shows that extrudates that were located to the left (negative) 
half of the plot were based on umami and salty taste. On the other hand, extrudates that 
were separated to the right based on low PDS content (10%) tasted bitter, sour and 
astringent. It can therefore be concluded that the amount of PDS in the formulation affected 
the taste properties of the extrudates. 
 
 
 
 
 
 
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3210-1-2-3
2
1
0
-1
-2
First Principal Component (65.8%)
S
e
c
o
n
d
 
P
r
i
n
c
i
p
a
l
 
C
o
m
p
o
n
e
n
t
 
(
3
0
.
7
%
)
E
D
C
B
A
 
Figure 4.11a: Score plot of samples (A-E) in the plane defined by the first two principal 
component.  
 
A: TMF5 (raw ‘Togo marshall’ rice variety-82.5%, Partially defatted soybean (PDS)-
17.5%); B: TMF3 (raw ‘Togo marshall’ rice variety-90%, PDS-10%); C: TMF4 (raw 
‘Togo marshall’ rice variety-75%, PDS-25%); D: PTMF3 (parboiled ‘Togo marshall’ rice 
variety-90%, PDS-10%); E: PTMF4 (parboiled ‘Togo marshall’ rice variety-75%, PDS-
25%). 
 
 
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0.500.250.00-0.25-0.50
0.50
0.25
0.00
-0.25
-0.50
First Principal  Component (65.8%)
S
e
c
o
n
d
 
P
r
i
n
c
i
p
a
l
 
C
o
m
p
o
n
e
n
t
 
(
3
0
.
7
%
)
Saltiness
Umami
Sourness
Aftertaste Astringency
Astringency
Aftertaste Bitterness
Bitterness
 
Figure 4.11b: Loading plot of samples (A-E) in the plane defined by the first two 
principal component 
 
 
 
 
 
 
 
 
 
 
 
 
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5.0 CONCLUSION AND RECOMMENDATION 
 
5.1 Conclusion 
i. The ‘Togo marshall’ rice and ‘Viwonor’ rice differed based on physicochemical 
properties such as milling recovery, cooking time, alkaline spreading value and 
amylose content. This implies the milling recovery, alkaline spreading value and 
amylose content are parameters that can be used to characterize ‘Togo marshall’ 
rice and ‘Viwonor’ rice. ‘Togo marshall’ rice variety can be characterized as rice 
with low milling recovery, lesser cooking time, low gelatization temperature and 
amylose content. ‘Viwonor’ rice variety can also be characterized as rice having 
higher milling recovery, longer cooking time, intermediate gelatinization 
temperature and amylose content.  
ii. There are differences in the raw materials (thus Partially Defatted Soybean: PDS, 
Raw Togo marshall rice variety: RTM, Parboiled Togo marshall rice variety: PTM, 
Raw Viwonor: RV and parboiled Viwonor rice variety: PV) in terms of colour, 
protein solubility and electrophoretic patterns. RTM was whiter whilst RV was 
more reddish and PDS more yellowish. PDS had a higher protein solubility and 
more peptides bands as compared to the other raw materials. This confirms that rice 
varieties and soybean do not have the same types and amount of proteins. 
iii. Extruded rice-soybean snack from ‘Togo Marshall’ formulations are more 
acceptable to consumers than those from ‘Viwonor’ rice. This implies that ‘Togo 
Marshall’ would make a better extruded rice-soybean snack. 
iv. High levels of Partially Defatted Soybean in the formulation lowers the in vitro 
protein digestibility, and influences the flavour and taste of the extrudate. 
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v. Based on physical, chemical, functional and tastes properties, formulation with 
82.5% raw Togo marshall; 17.5% PDS is suitable for the production of extruded 
rice-soybean snack. 
 
 
5.2 Recommendation 
i. Microbial analysis and shelf-life studies of the rice-soybean snack is recommended 
to assess the stability and microbial safety of the product. 
ii. The application of gas chromatography mass spectrometry (GC-MS) is required to 
establish the exact flavour compounds present in the extrudates. 
iii. Nutritional analysis of the extrudates is required to ascertain the effect of the 
extrusion cooking on major and micronutrients in the product.  
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6.0 REFERENCES 
1. Abbas, A., Murtaza, S., Aslam, F., Khawar, A., Rafique, S. and Naheed, S. (2011). Effect 
of Processing on Nutritional Value of Rice (Oryza sativa). World Journal of Medical 
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2. Abd El-Hady, E.A. and Habiba R.A. (2003). Effect of soaking and extrusion conditions 
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(36): 285–293. 
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APPENDICES 
 
APPENDIX I: SENSORY SCORE SHEET 
SAMPLE CODING: 
0 in the middle is sample 1 (Raw Togo Marshall) 
Samples ending with 8 means sample 2 (Parboiled Togo Maeshall) 
3 in the middle is sample 3 (Raw Viwonor) 
6 in the middle is sample 4 (Parbioled Viwonor) 
 Sample 
Pan
elist 
T
M
F1 
T
M
F2 
T
M
F3 
T
M
F4 
T
M
F5 
PT
M
F1 
PT
M
F2 
PT
M
F3 
PT
M
F4 
PT
M
F5 
V
F
1 
V
F
2 
V
F
3 
V
F
4 
V
F
5 
P
V
F
1 
P
V
F
2 
P
V
F
3 
P
V
F
4 
P
V
F
5 
1 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
2  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
3         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
4    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
5 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
6  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
7         67    5
3
9
3
   46 86  
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8 1 4 7 9 
8    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
9 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
10  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
11         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
12    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
13 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
14  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
15         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
16    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
17    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
18         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
19  10 50    22 31    7         
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3 6 8 8 3
6 
20 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
21    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
22         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
23  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
24 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
25    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
26         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
27  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
28 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
29    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
30         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
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31  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
32 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
33 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
34  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
35         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
36    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
37 20
4 
    41
8 
    6
3
9 
    26
3 
56
4 
   
38  10
3 
50
6 
   22
8 
31
8 
   7
3
6 
        
39         67
8 
   5
3
1 
9
3
4 
   46
7 
86
9 
 
40    30
7 
40
6 
    74
8 
    8
3
5 
    36
1 
 
 
 
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APPENDIX II: BALLOT SHEET FOR CONSUMER ACCEPTANCE OF EXTRUDED 
RICE-SOYBEAN SNACK 
           
Date………………… 
Panellist No. ……….. 
Instructions:  
You have been provided with five samples of extruded rice-soybean snack; which you are to 
evaluate by indicating your degree of liking for each sample attribute of the sample.  
Please clean your palates or rinse your mouth with water or cream crackers in between samples. 
Also allow a period of at least 2min interval before smelling the next sample.  
 
Scale/Interpretation 
9. Like Extremely 
8. Like Very much 
7. Like Moderately 
6. Like Slightly 
5. Nether Like nor Dislike 
4. Dislike Slightly 
3. Dislike Moderately 
2. Dislike Very much 
1.Dislike Extremely 
 
 
Attributes            
(pick and smell) 
Aroma                --------------         --------------           --------------             ------------            --------- 
(observe the product) 
     
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Colour                 --------------         --------------           --------------             ------------          --------- 
 
(take a bite) 
Mouthfeel           --------------         --------------           --------------             ------------          --------- 
(take a bite) 
Aftertaste           --------------         --------------           --------------             ------------          --------- 
Overall - 
acceptability      --------------         --------------           --------------             ------------          --------- 
 
Please turn over 
Any additional comments?  
………………………………………………………………………………………………… 
 
………………………………………………………………………………………………………
………………………………… 
 
………………………………………………………………………………………………………
………………………………… 
 
………………………………………………………………………………………………………
………………………………… 
 
………………………………………………………………………………………………………
……………………………….... 
 
 
 
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APPENDIX III: ANOVA TABLES 
Beginning of gelatinization 
ANOVA Table for Beginning of gelatin by Sample 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 176.6 4 44.15 5.13 0.0511 
Within groups 43.0 5 8.6   
Total (Corr.) 219.6 9    
 
 
ANOVA Table for Breakdown [BU] by Sample 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 777586. 4 194397. 1026.92 0.0000 
Within groups 946.5 5 189.3   
Total (Corr.) 778533. 9    
 
ANOVA Table for Maximum viscosity [B by Sample 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 1.4557E6 4 363926. 1404.58 0.0000 
Within groups 1295.5 5 259.1   
Total (Corr.) 1.457E6 9    
 
 
ANOVA Table for Pasting temperature by Sample 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 720.11 4 180.028 2.84 0.1412 
Within groups 316.85 5 63.37   
Total (Corr.) 1036.96 9    
 
ANOVA Table for Setback [BU] by Sample 
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Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 235795. 4 58948.8 325.50 0.0000 
Within groups 905.5 5 181.1   
Total (Corr.) 236701. 9    
 
ANOVA Table for Start of cooling per by Sample 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 109811. 4 27452.8 551.26 0.0000 
Within groups 249.0 5 49.8   
Total (Corr.) 110060. 9    
 
ANOVA Table for Start of holding per by Sample 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 523437. 4 130859. 1222.98 0.0000 
Within groups 535.0 5 107.0   
Total (Corr.) 523972. 9    
 
ANOVA Table for L by Samples 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 788.887 5 157.777 465.37 0.0000 
Within groups 8.1368 24 0.339033   
Total (Corr.) 797.024 29    
 
 
ANOVA Table for b by Samples 
Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 1179.72 5 235.943 766.64 0.0000 
Within groups 7.38628 24 0.307762   
Total (Corr.) 1187.1 29    
 
ANOVA Table for a by Samples 
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Source Sum of Squares Df Mean Square F-Ratio P-Value 
Between groups 116.325 5 23.2649 1655.47 0.0000 
Within groups 0.33728 24 0.0140533   
Total (Corr.) 116.662 29    
 
 
APPENDIX IV: MULTIPLE RANGE TESTS 
  
Multiple Range Tests for Beginning of gelatin by Sample 
Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
TMF4 2 16.5 X 
TMF5 2 19.0 XX 
TMF3 2 20.0 XXX 
PTMF3 2 26.5  XX 
PTMF4 2 27.0   X 
 
 
Multiple Range Tests for Breakdown [BU] by Sample 
 
Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
PTMF4 2 0.5 X 
PTMF3 2 1.5 X 
TMF4 2 428.5  X 
TMF5 2 605.5   X 
TMF3 2 624.5   X 
 
 
Multiple Range Tests for Maximum viscosity [B by Sample 
 
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Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
PTMF4 2 130.5 X 
PTMF3 2 194.0  X 
TMF4 2 739.0   X 
TMF5 2 965.5    X 
TMF3 2 1036.5     X 
 
 
Multiple Range Tests for Pasting temperature by Sample 
 
Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
PTMF3 2 47.85 X 
PTMF4 2 51.4 XX 
TMF4 2 57.05 XX 
TMF3 2 68.1 XX 
TMF5 2 68.6  X 
 
* denotes a statistically significant difference. 
 
Multiple Range Tests for Setback [BU] by Sample 
 
Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
PTMF4 2 170.5 X 
PTMF3 2 251.5  X 
TMF4 2 491.0   X 
TMF5 2 529.5    X 
TMF3 2 535.0    X 
 
* denotes a statistically significant difference. 
 
 
Multiple Range Tests for Start of cooling per by Sample 
 
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Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
PTMF4 2 130.0 X 
PTMF3 2 192.5  X 
TMF4 2 310.5   X 
TMF5 2 360.0    X 
TMF3 2 412.0     X 
 
* denotes a statistically significant difference. 
 
 
 
Multiple Range Tests for Start of holding per by Sample 
 
Method: 95.0 percent LSD 
Sample Count Mean Homogeneous Groups 
PTMF4 2 85.0 X 
PTMF3 2 133.5  X 
TMF4 2 494.0   X 
TMF5 2 577.5    X 
TMF3 2 629.0     X 
 
* denotes a statistically significant difference. 
 
Multiple Range Tests for L by Samples 
 
Method: 95.0 percent LSD 
Samples Count Mean Homogeneous Groups 
PV 5 77.096 X 
RV 5 79.63  X 
PDS 5 83.888   X 
PTM 5 84.692    X 
RSB 5 86.55     X 
RTM 5 93.176      X 
 
 
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Multiple Range Tests for b by Samples 
 
Method: 95.0 percent LSD 
Samples Count Mean Homogeneous Groups 
RTM 5 6.578 X 
RV 5 12.036  X 
PV 5 12.828   X 
PTM 5 15.54    X 
PDS 5 22.764     X 
RSB 5 24.708      X 
 
 
 
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