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. University of Ghana http://ugspace.ug.edu.gh i 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) University of Ghana http://ugspace.ug.edu.gh ii 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. University of Ghana http://ugspace.ug.edu.gh iii 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. University of Ghana http://ugspace.ug.edu.gh iv 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. University of Ghana http://ugspace.ug.edu.gh v 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. University of Ghana http://ugspace.ug.edu.gh vi 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 University of Ghana http://ugspace.ug.edu.gh vii 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 University of Ghana http://ugspace.ug.edu.gh viii 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 University of Ghana http://ugspace.ug.edu.gh ix 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 University of Ghana http://ugspace.ug.edu.gh x 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 University of Ghana http://ugspace.ug.edu.gh xi 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 University of Ghana http://ugspace.ug.edu.gh xii 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 University of Ghana http://ugspace.ug.edu.gh xiii 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 University of Ghana http://ugspace.ug.edu.gh xiv 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 University of Ghana http://ugspace.ug.edu.gh xv 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 University of Ghana http://ugspace.ug.edu.gh xvi 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 University of Ghana http://ugspace.ug.edu.gh xvii 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 University of Ghana http://ugspace.ug.edu.gh 1 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). University of Ghana http://ugspace.ug.edu.gh 2 . 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. University of Ghana http://ugspace.ug.edu.gh 3 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 University of Ghana http://ugspace.ug.edu.gh 4 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. University of Ghana http://ugspace.ug.edu.gh 5 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 University of Ghana http://ugspace.ug.edu.gh 6 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) University of Ghana http://ugspace.ug.edu.gh 7 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 University of Ghana http://ugspace.ug.edu.gh 8 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). University of Ghana http://ugspace.ug.edu.gh 9 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 University of Ghana http://ugspace.ug.edu.gh 10 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 University of Ghana http://ugspace.ug.edu.gh 11 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. University of Ghana http://ugspace.ug.edu.gh 12 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. University of Ghana http://ugspace.ug.edu.gh 13 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 University of Ghana http://ugspace.ug.edu.gh 14 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). University of Ghana http://ugspace.ug.edu.gh 15 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 University of Ghana http://ugspace.ug.edu.gh 16 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). University of Ghana http://ugspace.ug.edu.gh 17 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. University of Ghana http://ugspace.ug.edu.gh 18 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. University of Ghana http://ugspace.ug.edu.gh 19 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). University of Ghana http://ugspace.ug.edu.gh 20 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 University of Ghana http://ugspace.ug.edu.gh http://www.google.com.gh/search?tbo=p&tbm=bks&q=inauthor:%22Arun+S.+Mujumdar%22&source=gbs_metadata_r&cad=5 http://www.google.com.gh/search?tbo=p&tbm=bks&q=inauthor:%22Randall+G.+Mutters%22&source=gbs_metadata_r&cad=5 http://www.google.com.gh/search?tbo=p&tbm=bks&q=inauthor:%22Randall+G.+Mutters%22&source=gbs_metadata_r&cad=5 21 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 University of Ghana http://ugspace.ug.edu.gh http://www.google.com.gh/search?tbo=p&tbm=bks&q=inauthor:%22Sewa+Ram%22&source=gbs_metadata_r&cad=4 http://www.google.com.gh/search?tbo=p&tbm=bks&q=inauthor:%22Sewa+Ram%22&source=gbs_metadata_r&cad=4 22 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). University of Ghana http://ugspace.ug.edu.gh 23 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. University of Ghana http://ugspace.ug.edu.gh 24 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. University of Ghana http://ugspace.ug.edu.gh 25 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 University of Ghana http://ugspace.ug.edu.gh 26 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 University of Ghana http://ugspace.ug.edu.gh 27 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 University of Ghana http://ugspace.ug.edu.gh 28 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 University of Ghana http://ugspace.ug.edu.gh 29 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. University of Ghana http://ugspace.ug.edu.gh 30 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 University of Ghana http://ugspace.ug.edu.gh 31 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. University of Ghana http://ugspace.ug.edu.gh 32 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. University of Ghana http://ugspace.ug.edu.gh 33 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 University of Ghana http://ugspace.ug.edu.gh 34 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 University of Ghana http://ugspace.ug.edu.gh 35 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, University of Ghana http://ugspace.ug.edu.gh 36 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 University of Ghana http://ugspace.ug.edu.gh 37 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 University of Ghana http://ugspace.ug.edu.gh 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