COLLEGE OF BASIC AND APPLIED SCIENCES SCHOOL OF BIOLOGICAL SCIENCES PHYSICOCHEMICAL, FUNCTIONAL PROPERTIES AND MYCOTOXIN OCCURRENCE OF GHANAIAN TIGERNUTS (Cyperus esculentus L.) THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON BY SARDIA TRIXY BATTUTA-DAWLAH (10083959) IN PARTIAL FUFILMENT OF THE REQUIREMENT FOR THE AWARD OF DOCTOR OF PHILOSOPHY IN FOOD SCIENCE DEGREE DEPARTMENT OF NUTRITION AND FOOD SCIENCE NOVEMBER, 2020 University of Ghana http://ugspace.ug.edu.gh i DECLARATION University of Ghana http://ugspace.ug.edu.gh ii ABSTRACT In Ghana, tigernut (Cyperus esculentus L.) is grossly underutilized in food applications and is mostly consumed raw as a snack. However, the soil and climate conditions of the country are conducive for cultivation of the crop on a large scale for applications in food for local consumption, industrialisation and for the export market. Food applications of tigernut and its derivatives and their possible inclusion as ingredient in the Ghanaian diet would require knowledge on its handling quality and functional properties. The aim of this study was to characterise Ghanaian tigernut as an ingredient for possible food applications. The study design consisted of two parts: (a) a cross-sectional survey of different categories of stakeholders using pre-tested semi-structured questionnaires (b) followed by laboratory designed experiments to study the quality, physicochemical and functional properties of tigernut as a function of tigernut variety and process conditions. For the surveys, a total of 1277 stakeholders in the value chain, comprising of 711 consumers and 487 traders (wholesalers/retailers) in Greater Accra region and 79 tigernut farmers in the Western and Eastern regions of Ghana, were interviewed using semi-structured researcher-administered questionnaires. The questionnaires sought to gain information on respondents’ level of knowledge on mycotoxins, as well as ascertain if measures were in place to mitigate the risk of fungal colonisation of the crop along the supply chain. Additionally, tigernuts collected at various points along the supply chain (farm, wholesale and retail) were analysed for their mycotoxin (aflatoxins and ochratoxin A) levels using reverse phase High-Performance Liquid Chromatography (HPLC), to determine the hot spots of mycotoxin contamination along the value chain. The second part of the study investigated the physical characteristics of tigernut tubers as well as the functional properties of tigernut flour with the aim of determining its suitability in food applications. Additionally, the shelf life of the tigernut flour was determined by accelerated shelf life testing using the Arrhenius model. Fresh tigernut milk is usually University of Ghana http://ugspace.ug.edu.gh iii characterised by the sedimentation of starch which influences its flow behaviour as well as the physical stability. Furthermore, heat treatment of the milk leads to gelatinisation of the starches, which also affects the same properties. Consequently, the effects of heat (by roasting tigernuts) and adding α- amylase to the tigernut milk on the physicochemical and functional properties of tiger nut milk were studied. Tigernut oil was extracted and the phenolic and functional properties were determined as well as the effect of heat on these properties. The macro nutritional composition of tigernut tuber, flour, oil and milk were also investigated. The results of the surveys showed that tigernut farmers and consumers had appreciable knowledge in and displayed better attitude towards the prevention of mycotoxin contamination than the tigernut traders (wholesalers/retailers). The educational level of all stakeholders influenced their attitude and knowledge towards the prevention of mycotoxin contamination. Almost all consumers were willing to try new tigernut products such as the flour, oil and milk and would like to see more of these products on the Ghanaian market. The number of samples and the levels of mycotoxins (Ochratoxin A and aflatoxins) increased as the value chain progressed, with retail samples containing all the mycotoxins analysed. Total mycotoxins ranged from 0-27 µg/kg at the farm stage to 0-52 µg/kg at the wholesale stage and finally to 7.9 to 1115.48 µg/kg at the retail stage. These highlight post-harvest stage of the value chain as the focal point for mycotoxin prevention programs, although mycotoxin prevention can be agreed as a cumulative process. Both black and yellowish-brown tigernut flours contained relatively high and comparable amounts of sucrose, glucose and fructose. The relatively high resistant starch content of the tigernut flour makes the flour ideal for diabetics and weight watchers. The yellowish-brown variety had higher total starch content, higher water-retaining ability and viscosity at heating and holding cycles as compared to the black variety. Titratable acidity was found to be the University of Ghana http://ugspace.ug.edu.gh iv crucial determinant of spoilage in tigernut flour and higher temperature was observed to increase the oxidation of the tigernut flour. This may imply that tigernut flour should be stored below room temperature. Heat and the addition of α- amylase increased the total solids, brix and titratable acidity but caused a decrease in the pH of the tigernut milk. Addition of 0.2% of α- amylase to roasted tigernut milk improved its emulsion stability. Heat and addition of α- amylase caused the tigernut milk to become darker in colour. The flow behaviour of the tigernut milk exhibited shear thinning (pseudoplastic) fluid properties. This implies that commercial production of milk from tigernut must control parameters such as speed of machines during processing as well as concentrations of food additives such as α-amylase. Chemical qualities such as iodine value, peroxide value, ester value, saponification value, free fatty acids and acid value of oil extracted from tigernut tubers, all increased at higher temperatures whilst antioxidant activity and phenolic content decreased. The functional properties of tigernut oil suggested that the oil is good for frying at lower temperatures and for shorter periods. The carbohydrate component of the tigernut tuber was mainly made up of starch and dietary fibre (resistant starches) which reduced in the milk and oil. Crude fat was the second most abundant component in the tigernut tuber. Quercetin and gallic acid were found in appreciable amounts in the tigernut oil. Although, the protein content in the tigernut milk was lower compared to the tuber, it was probably enough to impart desirable functionality to help stabilize the tigernut milk. Tigernut tuber and its derivatives can offer various options in food products. The safety of the tuber and its products can however be improved when stakeholders of the supply chain are educated and supported to implement strategies that prevent mycotoxin contamination. University of Ghana http://ugspace.ug.edu.gh v DEDICATION I dedicate this work to my parents Mr. A.S. Battuta and Mrs Gertrude Adorkor Battuta, my husband, Lawrence Dawlah and my lovely kids, Jayda, Jynelle and Jevon for their support and love throughout this programme. I also dedicate it to my siblings, Rashid, Khalid and Trudy for their prayers and support. University of Ghana http://ugspace.ug.edu.gh vi ACKNOWLEDGEMENT I first and foremost want to thank the Almighty God for His loving kindness and tender mercies that have sustained me and seen me through this project. I am grateful to my supervisors; Prof. Firibu Saalia, Prof. Agnes Simpson Budu and Prof. Emmanuel Ohene-Afoakwa, for their time and guidance in this work. To my family, I say, I appreciate all their prayers, financial support and encouragement that urged me on throughout this research. I owe much gratitude to Dr. Naa Dodua Dodoo of the Regional Institute for Population Studies, University of Ghana; Eric Boafo and Joyce Duah of the Nutrition and Food Science Department of University of Ghana; William Appaw of the Food Science and Technology Laboratory, Kwame Nkrumah University of Science and Technology; Jochebed Graham, Ezekiel Coffie and Noel Appiah of Nestlé Ghana Limited for the support they offered me in diverse ways throughout this project. University of Ghana http://ugspace.ug.edu.gh vii TABLE OF CONTENTS DECLARATION ........................................................................................................................ i ABSTRACT ............................................................................................................................... ii DEDICATION ........................................................................................................................... v ACKNOWLEDGEMENT ........................................................................................................ vi TABLE OF CONTENTS ......................................................................................................... vii LIST OF FIGURES ............................................................................................................. xviii LIST OF TABLES .................................................................................................................. xxi LIST OF ABBREVIATIONS ............................................................................................... xxiv CHAPTER ONE ........................................................................................................................ 1 1. Introduction ........................................................................................................................ 1 1.1 Development of the Agricultural Sector in Ghana ...................................................... 1 1.1.1 Tigernuts .................................................................................................................. 2 1.1.2 Farming/Cultivation of Tigernuts in Ghana ............................................................ 2 1.1.3 Nutritive and Nutraceutical Value of Tigernuts ...................................................... 3 1.1.4 Food applications of Tigernuts ................................................................................ 4 1.1.5 Occurrence of Mycotoxins in Tigernuts .................................................................. 4 1.2 Problem Statement and Justification ........................................................................... 5 1.3 Objectives .................................................................................................................... 6 1.3.1 Specific Objectives .............................................................................................. 6 1.4 Significance of the Study ..................................................................................... 7 University of Ghana http://ugspace.ug.edu.gh viii CHAPTER TWO ....................................................................................................................... 8 2. Literature ............................................................................................................................ 8 2.1 Overview of the Agricultural Sector of Ghana ........................................................... 8 2.2 One District One Factory (1D1F) Program ................................................................. 9 2.3 Tigernut as a Potential for 1D1F in Kwahu-East District of Ghana ......................... 10 2.4 Overview of Tigernuts .............................................................................................. 10 2.4.1 Description............................................................................................................. 11 2.4.2 Horticulture ............................................................................................................ 12 2.4.3 Composition of Tigernuts ...................................................................................... 14 2.4.3.1 Health benefits of tigernuts ................................................................................ 16 2.4.4 Food applications of tigernuts ............................................................................... 16 2.4.4.1 Tigernut milk ..................................................................................................... 16 2.4.4.2 Tigernut flour ..................................................................................................... 18 2.4.4.3 Economic importance of tigernuts ..................................................................... 20 2.5 The other side of the coin: Food Safety of Tigernuts ................................................ 21 2.5.1 Mycotoxins in Tigernuts ........................................................................................ 22 2.5.2 Conditions for Fungal growth................................................................................ 24 2.5.3 Effects of mycotoxins on the economy ................................................................. 25 2.5.3.1 Health effects of mycotoxins on the economy ................................................... 25 2.5.3.2 Effect on trade and Agricultural export ............................................................. 28 2.5.3.3 Impact on National budget ................................................................................. 29 University of Ghana http://ugspace.ug.edu.gh ix 2.6 Conclusion ................................................................................................................. 30 CHAPTER THREE ................................................................................................................. 32 3. OBJECTIVE 1: To assess the level of mycotoxin knowledge of the stakeholders in the tigernut value chain .................................................................................................................. 32 3.1 Introduction ............................................................................................................... 32 3.2 Methodology ............................................................................................................. 33 3.3 The Study Area.......................................................................................................... 34 3.4 Sampling and sample size determination for farmers ............................................... 37 3.5 Sampling and sample size determination for traders ................................................ 37 3.5.1.1 Inclusion Criteria for Traders (wholesalers/retailers) .................................... 41 3.5.2 Sampling and sample size determination for consumers ................................... 41 3.5.2.1 Inclusion Criteria for consumers ........................................................................ 44 3.6 Ethical Clearance....................................................................................................... 44 3.7 Statistical analysis of survey data.............................................................................. 44 3.8 Results and Discussion .............................................................................................. 44 3.8.1 Mapping out the Artisanal Tigernut Value chain .................................................. 44 3.8.2 Demographic Characteristics of Tigernut stakeholders......................................... 46 3.8.3 Raw Material Supply for Tigernut Farmers .......................................................... 49 3.8.4 Raw Material Supply of Traders (retailers/wholesalers) ....................................... 50 3.8.5 Raw material supply and Knowledge on tigernut products by consumers ............ 52 3.8.6 Food safety practices of tigernut farmers .............................................................. 53 3.8.7 Food safety practices by Tigernut Traders ............................................................ 58 University of Ghana http://ugspace.ug.edu.gh x 3.8.8 Food safety practices by tigernut consumers ......................................................... 61 3.8.9 Mycotoxin Awareness of tigernut stakeholders .................................................... 62 3.8.10 Association between demographic characteristics and knowledge categories ...... 66 3.8.11 Attitude of tigernut stakeholders ........................................................................... 67 3.8.12 Association between demographic characteristics and attitude categories ........... 70 3.8.13 Logistic Regression of Knowledge of tigernut farmers on mycotoxins ................ 71 3.8.14 Logistic Regression of Knowledge of Traders (wholesalers/retailers) on mycotoxins ........................................................................................................................... 72 3.9 Conclusion ................................................................................................................. 73 CHAPTER FOUR .................................................................................................................... 75 4. OBJECTIVE 2: To determine the occurrence and level of mycotoxins (Aflatoxins and Ochratoxin A) in tigernut along the supply chain .................................................................... 75 4.1 Introduction ............................................................................................................... 75 4.2 Methods and Materials .............................................................................................. 76 4.3 Sources of Materials .................................................................................................. 76 4.4 Methods ..................................................................................................................... 80 4.4.1 Mycotoxin (Aflatoxins and Ochratoxin A) Analysis ............................................ 81 4.4.2 Determination of Aflatoxin levels .................................................................. 81 4.4.3 Analysis of Ochratoxin A contamination in Tigernut samples. ..................... 83 4.5 Statistical Analysis .................................................................................................... 84 4.6 Results and Discussion .............................................................................................. 84 4.6.1 Occurrence of mycotoxins in Ghanaian Tigernuts ................................................ 84 University of Ghana http://ugspace.ug.edu.gh xi 4.6.2 Concentration of mycotoxins in Ghanaian Tigernuts ............................................ 88 4.7 Conclusion ................................................................................................................. 92 CHAPTER FIVE ..................................................................................................................... 94 5. OBJECTIVE 3: To evaluate some compositional and functional properties as well as the shelf life of tigernut flour ......................................................................................................... 94 5.1 Introduction ............................................................................................................... 94 5.2 Materials and Methods .............................................................................................. 96 5.3 Sample Preparation: Preparation of Tigernut flour ................................................... 96 5.4 Methods ................................................................................................................. 97 5.4.1 Determination of Compositional properties of tigernut flour ............................ 97 5.4.1.1 Sugar profiling of tigernut flour ..................................................................... 97 5.4.1.2 Total Starch determination ............................................................................. 97 5.4.1.3 Determination of Polysaccharides ............................................................ 100 5.4.1.4 Determination of Resistant starch content ................................................ 101 5.4.2 Determination of the Functional properties of Tigernut Flour ..................... 102 5.4.2.1 Pasting Properties of Tigernut starch ........................................................ 102 5.4.2.2 Determination of oil absorption of tigernut flour ..................................... 102 5.4.2.3 Determination of water absorption of tigernut flour ................................ 102 5.4.2.4 Determination of swelling capacity of tigernut flour ............................... 103 5.4.2.5 Determination of foam capacity and foam stability of tigernut flour ....... 104 5.4.2.6 Determination of emulsion capacity and stability of tigernut flour ............. 104 5.4.3 Accelerated shelf life study of tigernut flour ............................................... 105 University of Ghana http://ugspace.ug.edu.gh xii 5.5 Statistical Analysis .............................................................................................. 106 5.6 Results and Discussion ........................................................................................ 106 5.6.1 Sugar profile of tigernut flour .......................................................................... 106 5.6.2 Starch profile of Tigernut Flour ....................................................................... 107 5.6.3 Pasting Properties of starch from tigernut flour ............................................... 110 5.6.4 Emulsion capacity and Emulsion stability of Tigernut flour ........................... 115 5.6.5 Foam capacity and Foam stability of Tigernut flour ....................................... 116 5.6.6 Bulk density and swelling capacity of Tigernut flour ...................................... 118 5.6.7 Water absorption capacity and Oil absorption capacity of Tigernut flour ....... 120 5.6.8 Estimation of Shelf life of Tigernut flour using accelerative experimental shelf- life studies ....................................................................................................................... 122 5.6.8.1 Reaction kinetics of moisture against tigernut flour quality ........................ 123 5.6.8.2 Reaction kinetics of pH against tigernut flour quality ................................. 125 5.6.8.3 Reaction kinetics of titratable acidity against tigernut flour quality ............ 127 5.6.8.4 Determination of shelf life of flour .............................................................. 129 5.7 Conclusion ........................................................................................................... 132 CHAPTER SIX ...................................................................................................................... 134 6. OBJECTIVE 4: Effects of roasting and addition of alpha amylase on the functional properties of the tigernut milk ................................................................................................ 134 6.1 Introduction ............................................................................................................. 134 6.2 Materials and Methods ........................................................................................ 136 6.2.1 Sources of materials ......................................................................................... 136 University of Ghana http://ugspace.ug.edu.gh xiii 6.2.2 Sample Preparation of Variants of Tigernut Milk ........................................... 136 6.3 Physico-functional properties .............................................................................. 138 6.3.1 Determination of total solids in tigernut milk .................................................. 138 6.3.2 Determination of pH of tigernut milk .............................................................. 139 6.3.3 Determination of titratable acidity (TA) of tigernut milk ................................ 139 6.3.4 Determination of %brix of tigernut milk ......................................................... 139 6.3.5 Determination of emulsion capacity of tigernut milk ...................................... 140 6.3.6 Determination of emulsion stability of tigernut milk ...................................... 140 6.3.7 Determination of foam capability and stability of tigernut milk ..................... 140 6.3.8 Determination colour of tigernut milk ............................................................. 141 6.3.9 Determination of flow behaviour of tigernut milk ........................................... 141 6.3.9.1 Calculation of Power -law model’s coefficients and thixotropic index of tigernut milk ................................................................................................................... 142 6.4 Statistical Analyses .......................................................................................... 142 6.5 Results and Discussion .................................................................................... 143 6.1.1. Total Solids and % Brix of tigernut milk variants ............................................... 143 6.1.2. pH and titratable acidity of tigernut milk ............................................................ 145 6.1.3. Emulsion capacity and Emulsion stability of tigernut milk ................................ 148 6.1.4. Foam capacity and foam stability of tigernut milk .............................................. 151 6.1.5. Colour of tigernut milk variants .......................................................................... 153 6.1.6. Flow behaviour of tigernut milk variants ............................................................ 156 6.6 Conclusion ....................................................................................................... 163 University of Ghana http://ugspace.ug.edu.gh xiv CHAPTER SEVEN ............................................................................................................... 165 7. OBJECTIVE 5: To evaluate the polyphenol content and stability of tigernut oil during heating at different temperatures ........................................................................................... 165 7.1 Introduction ............................................................................................................. 165 7.2 Materials and Methods ..................................................................................... 167 7.2.1 Sample preparation: Soxhlet extraction and fat content determination of tigernut tubers ............................................................................................................ 167 7.3 Methods............................................................................................................ 168 7.3.1 Determination of the compositional properties of tigernut oil ..................... 168 7.3.1.1 Fatty Acid Profile ..................................................................................... 168 7.3.1.2 Determination of the smoke point of tigernut oil ..................................... 168 7.3.1.3 Determination of Flash point of tigernut oil ............................................. 169 7.3.2 Determination of the changes in the polyphenol content and compositional properties of tigernut oil at different temperatures .................................................... 169 7.3.2.1 Determination of Polyphenol content of tigernut tubers and tigernut oil (fresh and after heat applications) .............................................................................. 169 7.3.3 Determination of the functional properties of tigernut oil ........................... 171 7.3.3.1 Determination of Peroxide Value (PV) of tigernut oil ............................. 171 7.3.3.2 Determination of the saponification value of tigernut oils ....................... 172 7.3.3.3 Determination of the iodine value ............................................................ 172 7.3.3.4 Acid value determination. ......................................................................... 174 7.3.3.5 Determination of Ester value of Tigernut oil ............................................ 174 University of Ghana http://ugspace.ug.edu.gh xv 7.4 Statistical analysis ............................................................................................ 174 7.5 Results and Discussion .................................................................................... 175 7.5.1 Oil yield from Tigernut tubers ..................................................................... 175 7.5.2 Fatty acid profile of Tigernut ....................................................................... 175 7.5.3 Smoke point of tigernut oil .......................................................................... 177 7.5.4 Flash point of tigernut oil ............................................................................. 177 7.5.5 Effect of processing on the phenolics of tigernut ......................................... 178 7.5.6 Changes in the levels of the total phenolics of tigernut tuber as it is processed into tigernut oil ........................................................................................................... 178 7.5.7 Effect of heating on the levels of specific polyphenols of tigernut oil ........ 182 7.1. Effect of heating on the compositional properties of tigernut oil ........................... 184 7.1.1. Effect of heating on the Acid Value and free fatty acids of tigernut oil .............. 184 7.1.2. Effect of heating on the Peroxide value of tigernut oil ........................................ 186 7.1.3. Effect of heating on the Saponification value and Ester value of tigernut oil ..... 188 7.1.4. Effect of heating on the Iodine value of tigernut oil ............................................ 190 7.2. Conclusion ............................................................................................................... 192 CHAPTER EIGHT ................................................................................................................ 194 8. OBJECTIVE 6: Physical and Nutritional parameters of Tigernut tuber and its products 194 8.1 Introduction ............................................................................................................. 194 8.2 Materials and Methods ............................................................................................ 195 8.3 Sources of Materials ................................................................................................ 195 University of Ghana http://ugspace.ug.edu.gh xvi 8.4 Sample Preparation ................................................................................................. 196 8.4.1 Sample Preparation of tigernut tubers ................................................................. 196 8.4.2 Sorting ................................................................................................................. 196 8.4.2.1 Washing and Drying ................................................................................. 196 8.4.3 Preparation of Tigernut Milk Extract ........................................................... 196 8.4.4 Oil Extraction ............................................................................................... 197 8.5 Methods of analyses ............................................................................................ 197 8.5.1 Physical analysis of tigernut tubers .............................................................. 197 8.5.1.1 Bulk Density of tigernut tubers ................................................................ 197 8.5.1.2 Size and shape determination of tigernut tubers ....................................... 197 8.5.2 Changes in the proximate composition of tigernut tuber when processed into its milk and oil ........................................................................................................... 198 8.5.2.1 Moisture Content determination of tigernut tubers, fresh tigernut milk and tigernut oil .................................................................................................................. 199 8.5.3 Mineral Ash content of tigernut tubers, fresh tigernut milk extract and tigernut oil 199 8.5.4 Crude Fibre Determination of tigernut tubers and fresh tigernut milk ........ 200 8.5.5 Determination of Protein Content (Macrokjeldahl method) tigernut tubers, fresh tigernut milk and tigernut oil ............................................................................ 201 8.5.6 Carbohydrate Content tigernut tubers, fresh tigernut milk extract and tigernut oil 202 8.6 Statistical Analyses .............................................................................................. 202 University of Ghana http://ugspace.ug.edu.gh xvii 8.7 Results and Discussion ........................................................................................ 202 8.7.1 Physical Properties of Tigernut tuber .............................................................. 202 8.7.1.1 Classification of shape of Ghanaian tigernut tubers..................................... 203 8.7.1.2 Bulk density and size of Ghanaian Tigernuts tubers .................................... 204 8.7.2 Macro-nutritional composition of Tigernuts tubers, milk and oil .................... 205 8.7.2.1 Moisture content ........................................................................................... 205 8.7.2.2 Mineral Ash content of Tigernut tubers, milk extract and tigernut oil ........ 209 8.7.2.3 Protein content of tigernut ............................................................................ 211 8.7.2.4 Fat content of Tigernut ................................................................................. 213 8.7.2.5 Carbohydrate content of tigernut tuber and tigernut milk ............................ 215 8.7.2.6 Dietary fibre content of tigernut tuber and tigernut milk ............................. 217 8.8 Conclusion ........................................................................................................... 218 CHAPTER NINE ................................................................................................................... 220 9. Summary and Conclusion ............................................................................................... 220 9.1. Recommendations ................................................................................................... 222 REFERENCES ...................................................................................................................... 224 APPENDICES ....................................................................................................................... 285 APPENDIX 1 ......................................................................................................................... 285 APPENDIX 2 ......................................................................................................................... 290 APPENDIX 3 ......................................................................................................................... 297 APPENDIX 4 ......................................................................................................................... 304 University of Ghana http://ugspace.ug.edu.gh xviii LIST OF FIGURES Figure 2.1: Varieties of tigernut on the Ghanaian market ....................................................... 12 Figure 2.2: Distribution of mycotoxins in African countries ................................................... 28 Figure 3.1: Map of Ghana indicating study area...................................................................... 36 Figure 3.2: Artisanal Tigernut Value Chain ............................................................................ 45 Figure 3.3: Source of tigernut seeds for tigernut cultivation ................................................... 50 Figure 3.4: Cultivated tigernut varieties and methods of tigernut storage by farmers ............ 56 Figure 3.5: Methods of tigernut preservation and yield of tigernut ......................................... 57 Figure 3.6: Level of Mycotoxin knowledge of farmers, traders (wholesalers/retailers) of consumers ................................................................................................................................ 65 Figure 3.7: Attitude of Tigernut farmers, traders (wholesalers/retailers) and consumers in relation to mycotoxin contamination ....................................................................................... 69 Figure 4.1: Map of Ghana indicating tigernut sampling area .................................................. 78 Figure 4.2: Occurrence of mycotoxins (aflatoxins and Ochratoxin A) in samples at the different stages of the supply chain ........................................................................................................ 85 Figure 4.3: Percentage of samples contaminated with various types of mycotoxin at each stage of the supply chain ................................................................................................................... 86 Figure 4.4: The variations in mycotoxin contamination at each stage of the value chain ....... 87 Figure 5.1: Yellowish Brown and Black Tigernut tubers and their corresponding Flours ...... 96 Figure 5.2: Storage of tigernut flour and tigernut oil in oven for shelf life studies ............... 105 Figure 5.3: Zero and first plots for moisture value against storage period for the different temperatures of the yellowish-brown and black tigernut flours ........................................... 124 Figure 5.4: Zero and first plots for pH value against storage period for the different temperatures of the yellowish-brown and black tigernut flours ............................................ 126 University of Ghana http://ugspace.ug.edu.gh xix Figure 5.5: Zero and first plots for titratable value against storage period for the different temperatures of the black and yellowish-brown variety ........................................................ 128 Figure 5.6: Arrhenius plots of the tigernut flours .................................................................. 129 Figure 6.1: Process flow for the preparation of tigernut milk variants used in this study ..... 137 Figure 6.2: Refractive Index and % brix of Variants of Tigernut Milk ................................. 143 Figure 6.3: pH and Titratable acidity of Variants of Tigernut Milk extracts ......................... 146 Figure 6.4: Emulsion Capacity and Emulsion Stability of Variants of Tigernut Milk .......... 149 Figure 6.5: Foam capacity and Foam stability of Variants of Tigernut Milk ........................ 151 Figure 6.6: Colour Coordinate L* of tigernut milk................................................................ 153 Figure 6.7: Colour Coordinate a* and b* of tigernut milk .................................................... 154 Figure 6.8: Flow Behavior of Black Tigernut Milk Variants ................................................ 157 Figure 6.9: Flow Behavior of Yellowish-Brown Tigernut Milk Variants ............................. 158 Figure 6.10:Thixotropic index of all Tigernut Milk Variants ................................................ 163 Figure 7.1: Changes in the levels of quercetin in tigernut oil at different temperatures ........ 182 Figure 7.2: Changes in the levels of quercetin and gallic acid in tigernut oil at different temperatures ........................................................................................................................... 183 Figure 7.3: Changes in the levels of acid value in tigernut oil at different temperatures ...... 184 Figure 7.4: Changes in the levels of free fatty acids in tigernut oil at different temperatures ................................................................................................................................................ 185 Figure 7.5: Changes in peroxide value (PV) of tigernut oil at different temperatures .......... 187 Figure 7.6: Changes in saponification value of tigernut oil at different temperatures .......... 189 Figure 7.7: Changes in ester value of tigernut oil at different temperatures .......................... 190 Figure 7.8: Changes in iodine value of tigernut oil at different temperatures ....................... 191 Figure 8.1: Tigernut shape and Size chart ............................................................................. 198 Figure 8.2: Display of tigernut in the market ......................................................................... 208 University of Ghana http://ugspace.ug.edu.gh xx Figure 8.3: Packaging of tigernut in Polyethene bags by street hawkers .............................. 208 University of Ghana http://ugspace.ug.edu.gh xxi LIST OF TABLES Table 2-1: Nutritional composition of tigernut tubers and beverage ....................................... 15 Table 2-2: Common Mycotoxin causing fungi and their conditions for growth ..................... 24 Table 3-1: List of Selected Markets in the Districts in Greater Accra Region ........................ 38 Table 3-2: List of selected streets in the Districts in Greater Accra Region ............................ 39 Table 3-3: Sample size allocation of traders (wholesalers/retailers) in each district ............... 40 Table 3-4: Sample size allocation for each street and selected per district ............................. 43 Table 3-5: Demographic characteristics of tigernut stakeholders ............................................ 47 Table 3-6: Responses to questions on raw material supply by traders (retailers/wholesalers) 51 Table 3-7: Responses to questions on raw material supply by consumers .............................. 53 Table 3-8: Tigernut safety practices of farmers ....................................................................... 54 Table 3-9: Tigernut safety practices of tigernut traders ........................................................... 59 Table 3-10: Tigernut safety practices of consumers ................................................................ 61 Table 3-11: Mycotoxin Awareness of tigernut stakeholders ................................................... 63 Table 3-12: Association between demographic characteristics and period of trading in tigernut .................................................................................................................................................. 66 Table 3-13: Summary of attitude of tigernut farmers, traders (wholesalers/retailers) and consumers ................................................................................................................................ 68 Table 3-14: Association between demographic characteristic and period of trading in tigernuts with respect to attitude ............................................................................................................. 70 Table 3-15: Logistic regression analysis of effects of demographics on the mycotoxin knowledge of farmers .............................................................................................................. 71 Table 3-16: Logistic regression analysis of effects of demographics on the mycotoxin knowledge of Traders (wholesalers/retailers) .......................................................................... 72 Table 4-1: List of Selected Markets in the Districts in Greater Accra Region ........................ 79 University of Ghana http://ugspace.ug.edu.gh xxii Table 4-2: List of Selected Streets in the Districts in Greater Accra Region .......................... 80 Table 4-3: The concentration of mycotoxins at each stage of distribution .............................. 88 Table 4-4: The range of the levels of individual mycotoxins detected at different stages ...... 90 Table 4-5: The percentage of samples exceeding regulatory limits for total aflatoxin ........... 91 Table 4-6: The total mycotoxin concentration at the street vs. marketplaces .......................... 91 Table 5-1: Sugar profile of tigernut tubers ............................................................................ 107 Table 5-2: Starch Profile of tigernut tubers ........................................................................... 108 Table 5-3:Pasting properties of the tigernut cultivars ............................................................ 110 Table 5-4: Emulsion capacity and stability of tigernut flour ................................................. 115 Table 5-5: Foam capacity and stability of tigernut flour ....................................................... 116 Table 5-6: Bulk density and swelling capacity of tigernut flour ........................................... 118 Table 5-7: Water absorption and oil absorption capacity of tigernut flour ............................ 120 Table 5-8: R2 value and Residual Mean Square Errors (RMSE) for each parameter for the Tigernut Flour ........................................................................................................................ 130 Table 5-9: Estimating the shelf life of the tigernut flour using the titratable acidity ............. 131 Table 6-1: Flow behaviour index, consistency index and R2 of tigernut milk ...................... 160 Table 7-1: Required quantity of dry oil for estimation of iodine value ................................. 173 Table 7-2: Free Fatty Acids composition of tigernut tubers .................................................. 175 Table 7-3: Total phenolic content of tigernut tubers and tigernut oil .................................... 178 Table 7-4: Polyphenol content of tigernut tubers and tigernut oil ......................................... 180 Table 8-1: Summary of results on the shape of samples ....................................................... 203 Table 8-2: Summary of the bulk density and size of Ghanaian Tigernut ............................. 204 Table 8-3: Moisture content of tigernut tubers, milk extract and tigernut oil ........................ 205 Table 8-4: Moisture content of Tigernuts purchased from markets and streets .................... 207 Table 8-5: Mineral Ash composition of tigernut tuber, milk and oil ..................................... 209 University of Ghana http://ugspace.ug.edu.gh xxiii Table 8-6: Protein composition of tigernut tubers, milk extract and oil ................................ 211 Table 8-7: Fat composition of tigernut tubers, milk extract and oil ...................................... 213 Table 8-8: Carbohydrate composition of tigernut tubers and tigernut milk .......................... 215 Table 8-9: Dietary fibre composition of tigernut tubers and milk ......................................... 217 University of Ghana http://ugspace.ug.edu.gh xxiv LIST OF ABBREVIATIONS AACC - American Association for Clinical Chemistry AFB1- Aflatoxin B1 AFB2- Aflatoxin B2 AFG1- Aflatoxin G1 AFG2- Aflatoxin G2 AOAC - Association of Analytical Chemist AOCS - American Oil Chemists' Society FUMs - Fumonisins GDP - Gross Domestic Product GEPC -Ghana Export Promotion Council GIPC - Ghana Investment Promotion Centre HPLC - High Performance Liquid Chromatography 1D1F - One District One Factory OTA - Ochratoxin A WHO - World Health Organisation University of Ghana http://ugspace.ug.edu.gh 1 CHAPTER ONE 1. Introduction This chapter presents the background and rationale of the study. The problem statement is also presented together with the justification of the study. The concluding section contains the study objectives and significance. 1.1 Development of the Agricultural Sector in Ghana It is estimated that the agricultural sector provides employment to about 60% of the Ghanaian population, thereby placing second to the service sector, in order of contribution, to the nation’s Gross Domestic Product (GDP) (Sam & Dzandu, 2015). In 2018, the country enjoyed 34% increase in export earnings from the Agricultural sector, which was valued at US$591.036 million (Ghana Export Promotion Authority, 2019). These earnings were mainly from a few crops such as cashew nuts, banana, shea nuts, mangoes, medicinal plants, pineapples, yams, rice and seafoods such as cuttlefish, squid and tuna. In Ghana, the Agricultural sector is regarded as vital to the alleviation of poverty and improvement in food security. In congruence with this, the Ghanaian Government has directed its efforts to the enhancement of the sector through the improvement of agricultural practices to increase yield, and the industrialisation of food crops, under the One District One Factory (1D1F) Initiative, amongst others. The 1D1F initiative seeks to industrialise the major agricultural produce in every district to ensure supply, create jobs and improve the nation’s export prospects (Dzansi et al., 2018). The Government of Ghana, under the 1D1F initiative, has identified tigernut as an underutilized crop with huge potential (Agoo Fm, 2017). With the 1D1F, the nation intends to increase the availability of the tubers to Ghanaians, especially since University of Ghana http://ugspace.ug.edu.gh 2 the crop is not new to most of the population, considering the occasional media awareness made on the goodness of the tigernut tuber (Yeboah, 2014). 1.1.1 Tigernuts Tigernut (Cyperus esculentus L.), which has its roots in Egypt, is a tuber, contrary to popular beliefs that it is a nut (Negbi, 1992). Nonetheless, its chemical composition has both properties of tubers and nuts (Sánchez‐Zapata et al., 2012). It is a perennial grass-like plant with sweet nut-like rhizome/tubers. Tigernut has many local names such as “chufa” (in Spanish), “souchet” (in French) and “ermandeln” (in German), “earth almonds, earth nut, edible galingale, yellow nut sedge, ground almond, and rush nut (Coşkuner et al, 2002). In Ghana, tigernut is commonly called “atadwe”, “atangme”, “nansaxa” and “fie” by the Akans, Gas, Dagombas and Ewes respectively (Dokosi, 1998). It is classified under the division of Magnoliophyta and the class of Liliopsida. Furthermore, it belongs to the order Cyperales and family of Cyperaceae (Orhevba & Bankole, 2019). 1.1.2 Farming/Cultivation of Tigernuts in Ghana Tigernut is regarded as one of the underutilised crops in Ghana. It is a food commodity cultivated in many parts of Ghana in very small scales, with the Kwahu East district being one of the major hubs for tigernut cultivation. For this reason, tigernut has been considered as the major raw material for a factory in that district, as per the 1D1F initiative (Dzansi et al., 2018). Colour is the commonest criterion used for the classification of tigernut, of which four varieties exist: yellow, yellowish-brown, red and black (Ejoh et al., 2006; Abano & Amoah, 2011). Among these, the yellowish-brown and black varieties are common in the Ghanaian markets (Ayeh-Kumi et al., 2014). The yellowish-brown type is more preferred to the black variety due to its innate characteristics, such as its eye-catching colour, fuller body and larger size. The University of Ghana http://ugspace.ug.edu.gh 3 yellowish-brown variety also contains more protein, fewer anti-nutritional elements, mainly, polyphenols and produces more milk with less fat. (Okafor et al., 2003). There are two tigernut planting periods in Ghana; minor planting period (September to November) and major planting period (April to July) (Tetteh & Ofori, 1998). Harvest time ranges from 90 to 120 days. In Ghana, tigernut farmers dry the harvested tubers under the sun for about 2 to 3 months until the tubers are dried, shrivelled and wrinkled. Dried tubers are then sold immediately after harvesting or stored in a well-ventilated area until sold or consumed. 1.1.3 Nutritive and Nutraceutical Value of Tigernuts According to Suleiman et al., (2018), a fresh tigernut tuber weighs between 70mg to 900mg whilst that of a dried tuber is between 30mg to 350mg. The major components of tigernuts are carbohydrates (mainly starch and fibre) and fat. Carbohydrates represent 43.4g/100g, starch content is 29.9g/100g and fibre content is 8.81g/100g. The fat content is between 22% to 45% in dry matter. The key fatty acids present in tigernuts are oleic (56% to 85%), linoleic acid (8% to 12%), palmitic (10% to 20%), and stearic acid (0.3% to 5%). Tigernuts also contain high calcium and phosphorus. However, iron, zinc, magnesium, manganese and copper are present in small concentrations (Arafat et al., 2009). Many researchers have reported on the numerous health benefits of tigernut including the lessened occurrences of cardiovascular disease, diabetes, cancer (specifically colon cancer), thrombosis and obesity, following significant consumption of the tubers. The tubers have been said to preserve the internal mechanisms, stimulate blood circulation and inhibit both constipation and diarrhoea and are ideal for children, older persons and sportsmen (Adejuyitan et al., 2009). According to Belewu and Abodunrin, (2008), allergic reactions from the consumption of tigernut have not been reported. University of Ghana http://ugspace.ug.edu.gh 4 1.1.4 Food applications of Tigernuts In Ghana, tigernut is mostly consumed in its raw state as a snack. The most popular processed form of the tuber is the tigernut porridge, locally known as “Atadwe” milk. This porridge is consumed as a complementary food by babies. It is also consumed by the elderly, weight-loss aspirants, adults and convalescents at health centres (Chukwuma et al., 2010). A few industries in the country have incorporated tigernut as an ingredient in their manufacturing process for alcoholic drinks and for yoghurt. However, tigernut is used in food applications in various other forms across the globe. Tigernut has been applied in the ice-cream and baking industries as a flavouring agent and as flour respectively. It is combined with cereal and spices in the production of a popular local Nigerian beverage (“Kunnu”). Oil, soap and starch extracts have been successfully made from tigernut (Ezekiel et al., 2019). “Horchata de chufa”, which is a sweetened water extract from tigernut, is the most globally recognised food application of the tuber (Sanchez-Zapata et al., 2012). Researchers across the globe have established that, tigernut and its by-products encounter challenges with fungal growth as the tuber travels along the value chain. As a result of this, there has been reports of the presence of mycotoxins in varying concentrations, along the value chain of tigernuts in other parts of the world. 1.1.5 Occurrence of Mycotoxins in Tigernuts Mycotoxins including aflatoxins, ochratoxin A and fusarium have been identified in tigernuts (Rubert et al., 2011) in various parts of the world. Fungal colonisation and subsequent mycotoxin production are promoted by physical (temperature, moisture, mechanical damage, and relative humidity), biological (spore load, stress, and insects) and chemical (fungicides, oxygen, substrate composition, pesticide, carbon dioxide) factors. The climatic conditions of University of Ghana http://ugspace.ug.edu.gh 5 Ghana and most sub-Saharan African countries are ideal for the growth of mycotoxin- producing fungi, which require an optimal temperature of 25°C to 30°C; water activity of 0.83 aw to 0.99 aw and moisture greater than 9% (Ribeiro et al., 2006). The conditions surrounding the pre-harvest, harvest and post- harvest of the tubers, as well as other parts of the value chain, are conducive for mycotoxin contamination (Bhat & Vasanthi, 2003). Global attention is given to mycotoxins due to the weighty economic loss it imposes on human health, animal productivity and trade (Cinar & Onbaşı 2019). Effects of ingestion, inhalation and absorption of mycotoxins in the skin cause animal and human mortality as well as general performance decrease. According to Campos-Mondragon et al. (2009), chronic and acute exposure to aflatoxins can lead to liver cancer (10% adults’ death) and immunosuppression in adults; stunting (35%), mental impairments and acute poisoning in children. Nearly $670 million is lost by African countries for the non-compliance of African produce to aflatoxin levels outlined by European Union (Otsuki et al., 2001). Fungi colonisation can occur at any stage of the supply chain of mycotoxin-susceptible crops. For this reason, prevention mechanisms can be applied throughout the supply chain, especially at stages where the risk of colonisation has been identified as most likely. This requires analysis of the players in each stage of the supply chain to identify the vantage points. Regulation of the mycotoxin levels in food helps to ensure control along the supply chain and avoid the detriments of its presence in unacceptable levels. 1.2 Problem Statement and Justification As mentioned in section 1.1 above, the government of Ghana has called for the industrialization of tigernut under the 1D1F initiative, which would result in increase in local consumption and demand for the crop, as well as may become a revenue generating crop for the nation through exports. This venture has high prospects since the soil profile in many parts of the nation is University of Ghana http://ugspace.ug.edu.gh 6 favorable for tigernut cultivation. As industrial application of tigernut tubers is underdeveloped in Ghana, an increase in the demand for the tuber and subsequent increase in its production may not be sustained unless the food applications of tigernuts are known. This study will enlighten the industry and general public on the functional and physicochemical properties of Ghanaian tigernuts and its derivatives in order to increase its use in Ghanaian diets. Eventually, the demand of the tubers will increase, in line with the Government of Ghana’s agenda of increased production of food crops such as tigernuts. It is well-known that tigernuts are susceptible to mycotoxin contamination. In many of such nations, where the presence of mycotoxins such as aflatoxins and Ochratoxin A have been established in tigernuts through numerous research studies, measures have been put in place to minimise fungal colonisation on the tubers. In Ghana, however, there is inadequate published data on the mycotoxin levels of tigernuts grown in the country. Furthermore, there is limited available information that shows that measures have been specifically put in place to reduce the contamination of the tigernuts along the value chain by mycotoxin-producing fungi. Lack of information on its levels of contamination across the value chain hampers remedial strategies to minimise contamination. Additionally, there is no standard on the maximum mycotoxin level in tigernut specifically in Ghana. Lack of regulatory measures pose a risk of increasing financial drain on health systems as well as reducing international trading in the form of exports. 1.3 Objectives The main objective of the study is to characterize Ghanaian tigernut as an ingredient for possible food applications. 1.3.1 Specific Objectives The specific objectives of the study are: University of Ghana http://ugspace.ug.edu.gh 7 • To assess the level of mycotoxin knowledge of the stakeholders in the tigernut value chain. • To determine the occurrence and level of mycotoxins (Aflatoxins and Ochratoxin A) in tigernut along the supply chain. • To evaluate some compositional and functional properties as well as the shelf life of tigernut flour • To determine the effect of roasting and addition of alpha amylase on the functional properties of tigernut milk. • To evaluate the polyphenol content and stability of tigernut oil during heating at different temperatures. • To determine the physical properties of tigernut tuber and some of the nutritional composition of tigernut tuber, milk and oil. 1.4 Significance of the Study Data gathered in this study will offer baseline information on the level of mycotoxin contamination of Ghanaian tigernuts. It will also establish the level of mycotoxin information that players in the tigernut value chain have. Furthermore, it will highlight the focus areas for mycotoxin control programs along the value chain. The information on the mycotoxin levels will provide a basis for regulation of the mycotoxin level of the tigernuts. Published results of the study will create awareness on mycotoxins in tigernuts for the general public to minimise their effects on the health of tigernut consumers. Furthermore, data on the functional properties of tigernut tuber, tigernut flour, tigernut oil and tigernut milk would direct industry on the food application to industrialise. In the long term, information shared from this study will lead to increase in demand of the tuber and revenue for stakeholders of the tigernut value chain as well as serve as a cash crop for the country. University of Ghana http://ugspace.ug.edu.gh 8 CHAPTER TWO 2. Literature This section provides theoretical and empirical basis for the study. The chapter begins with an overview of the agricultural sector of Ghana and the Government of Ghana’s One District One Factory (1D1F) initiative. It then delves into the identification of tigernut as an input to the 1D1F program. The chapter also provides an overview on tigernuts, its composition, horticulture and its uses. The safety of tigernut in terms of the presence of mycotoxins is introduced in this chapter. There is also a review of empirical works on the effect of fungal colonisation in the value chain. Finally, gaps in available literature pertaining to the topic are highlighted. 2.1 Overview of the Agricultural Sector of Ghana The primary cash crops produced in Ghana include beans, cocoa, palm oil, pineapple, cotton, tomato, banana, citrus fruits, coconut, cashew, tobacco, and fresh vegetables. The cocoa industry is known to be vital to the strength of the economy (GIPC, 2020). The export returns from the agricultural sector depend mainly on cocoa and a few other unprocessed commodities (Business and Financial Times, 2015). According to this report, the estimated non-traditional export earnings were valued at $2.4 billion as at 2019. The agricultural sector in Ghana is marked by low yields for both staple and cash crops (Ghana Agriculture Sector Policy Note, 2017). It would be very beneficial to the country if a few more crops provide economic benefits to the scale of cocoa’s contribution. The Government of Ghana has, over the years, implemented policies aimed at increasing the nation’s raw agricultural products (GIPC, 2020). Additionally, University of Ghana http://ugspace.ug.edu.gh 9 the Ghanaian Government has made intensive efforts to process most of the nation’s raw agricultural products (GIPC, 2020). 2.2 One District One Factory (1D1F) Program Industrially, measures and initiatives have been put in place by the Government of Ghana to revamp and increase the production of the nation’s cash crops. A prominent initiative is the "One District One Factory" (1D1F) program. The 1D1F program is a vital element of the Industrial Transformation Agenda of the Government. The Government's role in this program is to provide support in the creation of District Enterprises through the creation of the right setting such as the provision of amenities including good roads, regular flow of water and undisrupted power. The program aims at establishing at least one medium scale to large scale factory in all the 254 districts in the country. This means that, a district could have more than one factory depending on its resource base. The emphasis on the establishment of medium to large scale factories is because the enterprises to be established are expected to impact positively and significantly on the economies of the districts through the creation of jobs, stable income for the residents and improved livelihoods. The implementation of this program will restore the industrial sector of the economy through the implementation of targeted initiatives to make industrial production competitive and attractive to the private sector. In this regard, the 1D1F program has become a vital component for the revolution and transformation of the industries and the Agricultural sector of the economy. With the implementation of this program, the economies of the Districts would be positively impacted and improved significantly through the creation of jobs, and provision of stable income for the resident as well as a source of livelihood. University of Ghana http://ugspace.ug.edu.gh 10 2.3 Tigernut as a Potential for 1D1F in Kwahu-East District of Ghana Despite the numerous health and economic benefits that the production of tigernut promises, its production and utilization have not received the due attention as compared to other cash crops by the Government of Ghana (Wongnaa et al., 2019). Efforts to popularise and commercialise this crop are left in the hands of rural indigenous farmers and small-scale traders (Wongnaa et al., 2019). Added to these, the high cost of land preparation and cultivation has been a major setback to tigernut production. It has been one of the many underutilized crops which is yet to attract the attention of relevant institutions and receive the needed support to uncover its full significance (Business and Financial Times, 2015). The climatic and soil profile of most parts of Ghana have been found to be favourable for the cultivation of this food commodity. Nonetheless, Aduamoah is regarded as the tigernut hub of the nation. Under the 1D1F initiative, measures have been put in place to increase the production and cultivation of tigernuts. The development of tigernut industries may improve the livelihood of the rural populace in the districts and eventually create foreign exchange earnings for the country (Agoo FM, 2017). 2.4 Overview of Tigernuts The use of tigernut (Cyperus esculentus L.) as food originated from ancient times. It was cherished food in ancient Egypt (Pascual et al., 2000). There have also been reports revealing that the edible tuber originated from Spain and Africa (Deatra, 1999). It is known to be among the first domesticated crops cultivated by ancient Egyptians at the Nile valley. According to Kaufman (2006), paintings of tigernut have been found in Egyptian tombs with inscriptions, giving instructions on how small loaves of a combination of tigernut and honey were made. In other reports, the paintings depicted the weighing of tigernuts by labourers whilst a scribe took University of Ghana http://ugspace.ug.edu.gh 11 records of their work (Deatra, 1999). In Egypt and the Mediterranean, tigernuts were used for medicine and perfumes. They were also roasted and eaten by nursing mothers. In places such as Southern Europe, tigernut has been grown for hundreds of years (Sánchez- Zapata et al., 2012). It has been reported to have been introduced by the Arabs into Europe in the Middle ages. In the 13th century, beverages made from tigernuts were consumed in the Southeast of Spain (Pascual et al., 2000). The use of tigernut in industry is not prominent and as such, has been poorly studied (Shikhov et al. 2011). 2.4.1 Description Cyperus esculentus (tigernut) is a plant from the family Cyperaceae (Omoniyi et al., 2014), which is a perennial grass-like plant that produces somewhat spherical rhizomes and tubers from its base (Cortes et al., 2005). Daniel and Maria (2000) argued the plant to be a tuber rather than a nut. According to Deatra, (1999), the tigernut plant grows to a height of about 90 cm and bears slender leaves of 3-10 mm wide. It has very rough and fibrous plant foliage, which is often mistaken for a grass and the edible brown spike-like flowers mostly grow to a height of 1cm to 1.5 cm long. There are different varieties of tigernut tubers. However, the prominent ones are the yellow, brown, and black, which come in various shapes and sizes (Barminas et al., 2001). The most ubiquitous varieties are mostly long and round. These varieties are: Cyperus esculentus var. leptostachyus, Cyperus esculentus var. sativus, Cyperus esculentus var. hermannii., Cyperus esculentus var. esculentus, Cyperus esculentus var. rotundus, Cyperus esculentus var. macrostachyus. Each variety has a distinct morphological feature. For example, the leaves of Cyperus esculentus var. leptostachyus are narrow, shiny and long and are arranged in rows of 3 with a triangular stem (FAO, 1988). Cyperus eculentus var. rotundus is non-flowering and dark brown in colour with blunt tipped leaves with no shoulders. University of Ghana http://ugspace.ug.edu.gh 12 Cyperus esculentus is the common name used for both the useful and weedy sedge in most literature. The difference however is that, the weedy esculentus produces a lot of seeds whereas the cultivated variety sativus produces few seeds (Lapham & Drennan, 1990). The two varieties which are of most interest to many are the Cyperus esculentus var. sativus (cultivated) and Cyperus esculentus var. esculentus (weedy). According to Ayeh-Kumi et al. (2014), the light brown or yellowish-brown and the black tigernut are the two types sold in the Ghanaian market (Figure 2.1). Figure 2.1: Varieties of tigernut on the Ghanaian market (Source: Ayeh-Kumi et al.,2014) 2.4.2 Horticulture Tigernuts are prevalent in damp grasslands and periodic wet grassland. Fluvial soils with moderately high concentration of manganese (Mn), sulphur (S), calcium (Ca) and boron (Bo) are specifically suitable for the cultivation of tigernut. Sandy soil and a mild climate have been proven by research to be the most suitable for the cultivation of tigernut. Cyperus esculentus is prevalent in temperate and tropical zones (Holm et al., 1997; Larridon et al., 2011). It is a plant University of Ghana http://ugspace.ug.edu.gh 13 that tolerates cold temperatures but is mostly found in warmer zones (Holm et al., 1977). According to Mulligan and Junkins (1976), it is found in moderately dry environments such as fields. Cyperus esculentus var. esculentus is prevalent in Asia, Africa and South Europe (Schippers et al., 1995). Cyperus esculentus var. hermannii have been reported only to be found in Southern USA (Schippers et al., 1995). Cyperus esculentus var. eptostachyus was reported by Guillerm (1987) to be widespread in Europe because of its ability to adapt to the cold climate. Lastly, Cyperus esculentus var. macrostachyus was found mostly in Central America and Southern USA (Schippers et al., 1995). In Ghana, cultivation of tigernut for commercial purposes are prevalent in areas such as Aduamoah and Esereso in the Kwahu province of the Eastern Region of Ghana (Obeng- Koranteng et al., 2017; Tetteh & Ofori, 1998). It is also cultivated in other areas such Bewjiase and the surrounding villages in the Awutu Senya East District, Ampenyi and its environs in the Komenda Edna Eguafo District (Obeng-Koranteng et al., 2017). In the Ashanti Region, the cultivation of tigernut is found in areas like Adansi Danyameso in the Adansi South District and Tanoso and its peripheral villages. Asante (2015), also reported cultivation of tigernut in areas of the Western Region (Adowa), and in some parts of the Northern Region (Tampong in the Savelugu Nantom District). The survey conducted by Tetteh and Ofori (1998) on the cultivation of tigernut in Kwahu-Aduamoah showed that, men constituted approximately 30% of the farmers whiles women were about 70%. Donkor et al. (2019) studied the variation in the local accessions of tigernut in Ghana. The results proved that the variations were wide, therefore buttressing the point that breeding of improved variations of tigernuts was possible. They also highlighted the fact that the tigernuts from Twifo Praso, Kasoa, Bawku, Bodwiase, Asukese Donkokrom, Krachi, Kwanyako, Wa and Bewjiase produce high yield. This means that tigernuts from these areas could be further exploited for future large-scale farming. University of Ghana http://ugspace.ug.edu.gh 14 So far, tigernut cultivation has contributed slightly to Ghana’s economy in terms of foreign exchange from its exportation (Donkor et al., 2019). In 1998, Ghana’s revenue for the export of tigernut was $8, 687.78 (Tetteh & Ofori, 1998). However, this trend increased in 2010, when Ghana exported 63,462 tonnes of tigernut, which was valued at $25,130.82 (GEPC, 2010). 2.4.3 Composition of Tigernuts Carbohydrates have been found to be the principal component in tigernuts. Starch and dietary fibre are the main composition of the carbohydrate content in tigernut. The starch content in tigernut is reported to decrease when reducing sugar levels elevate during storage (Sánchez- Zapata et al., 2012; Coşkuner et al., 2002). According to Ros (2010), the fibre composition of tigernut were found to be like that of nuts. However, the moisture and carbohydrate levels were found to be higher. The lipid and protein levels were also found to be lower than in tree nuts (Ros, 2010; Sánchez-Zapata et al., 2012). Researchers such as Yeboah et al. (2011) found some levels of phytosterols and vitamin E in tigernut oil. The appreciable content of phytosterol have been found to enrich the quality and commodity value of tigernut as a source of food (Sánchez-Zapata et al., 2012). The fatty acid composition in tigernut have also been studied. Linssen et al. (1988) have analysed and compared the composition of fatty acids and triglycerides in tigernuts and olive oil. They found out that, both showed great resemblance in composition even though the tigernut is a tuber and the olive is a fruit. This showed that tigernut oil could be a suitable alternative for imported olive oil (Deatra, 1999). Table 2-1 shows the proximate composition of tigernut tuber and a few of its beverages. University of Ghana http://ugspace.ug.edu.gh 15 Table 2-1: Nutritional composition of tigernut tubers and beverage (Source: Sanchez-Zapata et al., 2012) According to Sanchez-Zapata et al. (2012), tigernut contains essential vitamins and minerals such as calcium, potassium, Vitamin C and E (Belewu & Belewu, 2007). Besides the main composition of tigernuts, the phenolic and anti-nutrient compounds have also been analysed and studied. Ekeanyanwu et al. (2010) showed that, the main phenolic compounds found in tigernut oils are the trans-ferulic, vanillic acid, vanillin and trans-cinnamic acid (Roselló-Soto et al., 2018). The concentration of quercetin in tigernut has also been studied and found to be 3.76× 10-3 -60.63 mg GAE/100 g (Oladele et al., 2017). Additionally, tigernut contains gallic acid and catechin in concentrations of 3.95 × 10−3 − 1.74 mg GAE/100 g and 8.83 × 10−4 − 6.58 mg GAE/100 g respectively (Oladele et al., 2017). Nutrient Tigernut Tuber (g/100g) Horchata De Chufa (g/100g) Tigernut Beverage (g/100g) Total fat 24.49 3.09 1.26-1.59 1.88-2.27 SFA (% total fatty acid) 17.5 MUFA (% total fatty acid) 72.9 PUFA (% total fatty acid) 9.3 Ratio n-6/n-3 22 Proteins 5.04 0.91 2.34-2.51 0.47-0.54 Ash 1.7 0.25 0.31-0.39 0.16-0.18 Carbohydrates 43.3 Not detected 1.93-2.34 2.31-2.74 Total dietary fibre 8.91 1.03 0.23-0.31 0.53-0.65 Sucrose 13.03 >10 Total energy (kcal/100g) 413.8 >71.45 28.42- 33.71 28.04- 33.55 University of Ghana http://ugspace.ug.edu.gh 16 2.4.3.1 Health benefits of tigernuts Studies conducted by Salem et al. (2005) revealed that, tigernuts exhibit anti-inflammatory properties. It has also been confirmed that arginine, the prevalent amino acid in tigernut, significantly lowers blood and peripheral vascular resistance in healthy adults and in patients with vascular diseases (Moore, 2004). The milk of tigernut has been found to be good for the prevention of arteriosclerosis (Sánchez- Zapata et al., 2012). According to Chukwuma et al. (2010), its consumption, leads to the prevention of heart related problems and the facilitation of blood circulation. Tigernut milk has also been found to be a suitable beverage for celiac patients who are lactose intolerant (Sánchez-Zapata et al., 2012). It has also been found to be beneficial to those who have problems with digestion and diarrhoea, as it aids in the production of the essential digestive enzymes such as amylase and catalase (Adejuyitan, 2011). The nutritional analysis conducted by Bixquert (2003), concluded that tigernut contained high levels of oleic acid, which lowers the cholesterol levels, owing to its high vitamin E content. It has also been found to prevent colon cancer (Zimmerman, 1987). In Ghana, tigernuts have attracted numerous unproven or unsubstantiated health claims. The tubers are mostly consumed for its nutritional and health benefits as well as for its aphrodisiac properties (Ayeh-Kumi, 2014). For this reason, it has been labelled as a substitute to Viagra. It is also believed to improve fertility in women. 2.4.4 Food applications of tigernuts 2.4.4.1 Tigernut milk The use of tigernut as milk had its origin from Spain, which according to literature, may have been introduced by the Arabs. Many names have been ascribed to it; the Spaniards call it “chufa de horchata” whilst Northern Nigerians call their variant ‘kunnu aya’ (Bamishaiye & University of Ghana http://ugspace.ug.edu.gh 17 Bamishaiye, 2011). It has been proven to be a rich source of magnesium, potassium, calcium, carbohydrates, protein and enzymes which aid in digestion (TTSL, 2005). The tigernut milk has also been found to be a rich source of vitamin C and E (Bamishaiye & Bamishaiye, 2011). Tigernut milk is not readily available on the Ghanaian market as compared to its pudding (“Atadwe” milk), which is sold in markets, by street sellers, a few supermarkets, few restaurants and some eateries. According to Tapsoba (2015), there are six kinds of tigernut milk in Spain. These include the untreated or fresh, pasteurized, sterilized, Ultra High Temperature (UHT), condensed pasteurized and the powdered tigernut milk. TTSL (2005) however, acknowledged the concentrate tigernut milk as the 7th type in addition to the six mentioned above. These different types of tigernut milk have different modes of preparation and characteristics. According to TTSL (2005), “the natural or fresh tigernut milk is prepared with the right quantity of tigernuts, water and sugar to get a product with not less than 12% of soluble solids, 2.2% of starch, 2.5% of fats, a pH of 6.3 and not more than 10% of sugar in form of sucrose.” The pasteurized tigernut milk is prepared by subjecting the milk to a pasteurization treatment below 72ºC, without the addition of additives or technologic fertilizers while the sterilized tigernut milk is obtained by submitting the tigernut milk into a technological process, which transforms or removes its contents of starch totally or partially (TTSL, 2005). The sterilized tigernut milk must be thermally treated after being packaged, in order to destroy microorganisms and inactivate its forms of resistance. The Ultrahigh temperature tigernut milk is the type of tigernut milk submitted to a process that eliminates the starch and is processed by a thermal treatment (UHT) which ensures that after its aseptic packaging, microbes especially pathogens are destroyed (TTSL, 2005). University of Ghana http://ugspace.ug.edu.gh 18 The concentrate tigernut milk is the type of milk with the right proportions of tigernut, water and sugar to obtain a product that has at least a concentration of dissolved solids of 42% and a pH of 6 (TTSL, 2005). It is the milk which when dissolved in water, results in a product which has the same characteristics as the natural tigernut milk. According to TTSL, (2005), the condensed tigernut milk can be pasteurized (with about 60% or more of dissolved solids, 4% of starch and 5% of fats) or frozen (at least 50% of dissolved solids, 5% of starch and 7% of fats). The powdered tigernut milk is subjected to a technological process which can eliminate or partially or totally transform its starch components into solid granulates or particles. It is obtained through a drying process with not more than 5% content of water (TTSL, 2005). As compared to the other forms of milk, it is required to consume the natural tigernut milk within 2 to 3 days after opening or keep in the fridge to prevent spoilage. 2.4.4.2 Tigernut flour As a result of its gluten free content, tigernut flour has been found to be a suitable substitute to several other flours. It is utilized in the confectionery industry as a component or main flour (Bamishaiye & Bamishaiye, 2011). According to Ade-Omowaye et al. (2009), tigernut flour is considered a good substitute to cassava flour in the baking industry and has been used to flavour biscuits and ice creams (Osagie & Eka, 1998). Additionally, tigernut flour has been regarded as a potential ingredient for the bakery industry due to its moderate natural sugar content (Anderson et al., 1994). In Keta (Ghana), sugar is added to the sun-dried tigernut flour to be eaten raw or as a beverage when water is added (Adejuyitan et al., 2009). It is used to supplement flavour to ice creams and biscuits (Osagie & Eka, 1998). Tigernut has been confirmed to have more essential amino acids than the ones purported in the protein standard by the FAO/WHO (FAO/WHO, 1985). It is also a rich source of calcium and iron, which are University of Ghana http://ugspace.ug.edu.gh 19 necessary for body development and growth (Oladele & Aina, 2007). Tigernut flour maintains its nutritional properties in the milling process. Due to the therapeutic and nutritional benefits, tigernut flour could work as a suitable substitute to cassava flour in the baking industry (Ade- Omowaye et al., 2008). The evaluation of the nutritional application and sensory properties of tigernut flour products have been reported in literature. Akajiaku et al. (2018) evaluated the sensory and proximate properties of cookies made from tigernut flour. The results obtained showed that, cookies made from tigernut have good nutritional profile with carbohydrates and proteins relative to that of cookies made from wheat flour. In their analysis, Eke-Ejiofor and Deedam (2015) stated an increase in proximate composition of cakes and biscuits made from a composite flour of wheat and tigernut. Twum et al. (2015) investigated the physicochemical properties of a composite flour mixture of tigernut, maize and soybeans flour in different percentage compositions. The results reported an increase in physicochemical properties (ash content, moisture content, pH and protein content) of the composite flour relative to that of the individual flours. The increase in weight of cakes prepared from a mix of tigernut and wheat flour has been ascribed to the bulkiness of tigernut flour in wheat-based cakes (Chinma et al., 2010). Oladele and Aina (2007) concluded that, tigernut flour could be used as an ingredient in food applications owing to its little to no retrogradation effect, low bulk density as well as its peculiar setback and breakdown viscosities. The term oil is generally used to define greasy or oily materials that are fluid at room temperature (Buba, 2005). Lipid is a collective name for fats and oils that are naturally occurring. Lipids are of massive commercial use in terms of frying operations since they are a suitable way of transferring heat rapidly (Andrew et al., 2012). They occur naturally along with carbohydrates and protein in main crops and are extensively present in nature. In chemical terms, esterification is used to describe the reaction between three molecules of fatty acids and University of Ghana http://ugspace.ug.edu.gh 20 a triol (glycerol). Fats and oils are mainly acquired from two sources: vegetable sources and animal sources (O'brien, 2008). Fats and oils from animals are obtained from both land- dwelling and aquatic animals. Vegetable oils, that is, oils obtained from plant sources, occur most abundantly in seeds and fruits. These include tigernut oil, groundnut oil, cotton seed oil, sunflower oil, palm oil etc. Plant-source oils suitable for human consumption have gained much interest in several food processes and factories as they give distinctive flavour and texture qualities to foods as vital dietary elements (Odoemelam, 2005), while serving as a derivative of oleo compounds (Morrison et al., 1995). Vegetable oils contribute positively to the diet in various nations, providing a rich basis of lipid and fatty acids as well as protein for human nutrition by restoring worn-out tissues, developing new cells and functioning as a useful source of energy (Gaydon et al., 1983; Grosso & Guzman, 1995; Grosso et al., 1997; Aremu et al., 2015). The core nutrients essential to the human body include carbohydrates, proteins, fats and oil, together with vitamins and minerals. The principal significance of the vegetable oils is in their food value. Tigernut oil has been found to be a good source of oleic acid and low polyunsaturated fatty acid (Okladnikov et al., 1977). According to Bamishaiye and Bamishaiye, (2011), tigernut oil is suitable for salads because of its ability to form a uniform liquid at cold temperature. They also noted that it is classified as a high-quality oil since it is extracted without the application of heat. Furthermore, the oil serves as a suitable substitute for other oils such as soybeans, olive, cotton seed oil and corn oil. He et al. (1996) reported that tigernut oil could be the future source of biodiesel. 2.4.4.3 Economic importance of tigernuts There is no denying the fact that, the production and export of tigernuts has brought considerable economic returns to many countries. Reports from Rubert et al. (2011) indicated University of Ghana http://ugspace.ug.edu.gh 21 that, the ‘horchata’ industry has been of a great economic benefit to Spain. Approximately, 40 to 50 million litres of ‘horchata’ are produced annually in Spain (Maduka & Ire, 2019). This is valued at about $60 million according to Sánchez-Zapata et al. (2012). The use of tigernut to produce lactose-free products have led to an increase in tigernut cultivation globally (Maduka & Ire, 2019). According to Decker & Kurnik (2018), there has been a considerable increase in the value of gluten-free market from $ 1.7 billion in 2011 to $ 3.5 billion in 2016. This was expected to be valued at $ 4.7 billion in 2020. Tigernut is cultivated and used as a side dish in countries like Ghana, Northern-Nigeria, Mali, Senegal and Togo (Omode et al., 1995). Some of the tigernuts are exported from these countries to Spain (Sánchez-Zapata et al., 2012), where the tubers are used to- process ‘‘horchata de chufa” (Beneyto et al., 2000). Countries such as Chile, Brazil, Mexico, and Missouri cultivate tigernuts mainly for animal feed (Sánchez-Zapata et al., 2012). Tigernut oil can be used as a waterproofing agent in textile fibres (Hleba et al., 2020). Presently, tigernuts are planted for medicinal and food purposes in Africa, Asia and Europe (Pascual- Seva et al., 2013; Bamishaiye & Bamishaiye, 2011). 2.5 The other side of the coin: Food Safety of Tigernuts Though there is scarce literature on mycotoxin contamination in tigernuts, a few researchers have evaluated the levels of mycotoxins in tigernut tubers in different countries to assess the danger to the consumer. Mycotoxins are lethal chemical compounds produced naturally by mycotoxigenic fungi like Claviceps, Stachybotrys, Aspergillus, Fusarium, Penicillium and Alternaria (Bankole & Adebanjo, 2003; Custódio et al., 2019). These fungi sprout on many agricultural commodities such as cereals, dried fruits, tubers, nuts and spices (WHO, 2018). Mycotoxins can occur either before, after or during storage and are mostly detected in humid University of Ghana http://ugspace.ug.edu.gh 22 and moist environments. Research has showed that, most mycotoxins are chemically stable and can survive the rigorous operation of food processes (WHO, 2018). 2.5.1 Mycotoxins in Tigernuts Aflatoxins are harmful secondary ancillary generated by Aspergillus parasiticus and Aspergillus flavus (Omoniyi et al., 2014). These fungi, which primarily contaminate cereal (corn, wheat, sorghum and rice), spices, tubers and tree nuts survive in soil, hay, decaying vegetation and grains. Four main types of aflatoxins have been identified in tigernuts; Aflatoxin B1 (AFB1), Aflatoxin B2 (AFB2), Aflatoxin G1 (AFG1) and Aflatoxin G2 (AFG2) (Moss, 1998). Of all the identified mycotoxins in tigernuts, Aflatoxin B1 is considered the most dangerous since it is placed in the Class 1A human carcinogen category (Rothschild, 1992). Omoniyi et al. (2014) studied the aflatoxin contamination of tigernut sampled randomly from various markets in Kano, Kaduna, and Gombe states of Nigeria. The report indicated that, 90% of the tigernuts were above the 10μg/kg limit while 17% exceeded the alarm limit of 20 μg/kg established by United States Food Regulation and the Codex Alimentarius. Bankole and Adebanjo (2003) also reported aflatoxin concentrations extending from 10-20 μg/kg in 35% of tigernut samples from various marketplaces in Nigeria. Ochratoxin A has also been identified in tigernuts in other countries in the world. Ochratoxin A (OTA) is a chemical substance yielded by Aspergillus ochraceus and various species of Penicillium and Aspergillus. It is the predominant of the Ochratoxin family (Mitchell et al., 2014) and is known to be the common mycotoxin that contaminates food commodities such as spice, juice, coffee beans, cereals and cereal products (WHO, 2018). It is produced during crop storage and is known to cause harmful effects in animal species. OTA has been connected to a few diseases in both animals and humans including hepatotoxic and immunotoxic effect University of Ghana http://ugspace.ug.edu.gh 23 (Mitchell et al., 2014). It has been confirmed to cause adverse influence on cocoa beans exported from West Africa (Bankole & Adebanjo, 2003). In certain parts of Africa, OTA have been identified in tigernuts (Rubert et al., 2011). In Nigeria, a study conducted by Adebajo (1993) to determine how moisture content and pH levels affected mycotoxin levels in tigernut tubers as storage time increases, observed that, contamination of samples with aflatoxin B1, B2 and Ochratoxin A increased with increasing storage time as moisture content increased and pH levels declined. From the analysis conducted by Bankole and Eseigbe (1996), 35% of tigernuts from Nigeria contained aflatoxin levels extending from 10 to 20 μg/kg and therefore labelled tigernut as a food commodity susceptible to aflatoxin concentration. In Europe, Sebastia et al. (2012) identified Fusarium-emerging mycotoxins in Spanish tigernuts in concentrations between 32.1 and 4400 µg/kg. In West Africa, Adebajo (1993) and Bankole and Eseigbe (1996) detected mycotoxins in Nigerian tigernuts in concentrations between 10 and 120 µg/kg. Couvillion et al. (1991) did not identify mycotoxin in all samples of tigernuts in Mississippi. Tigernut tubers sampled from different marketplaces in Ghana were reported to have significant levels of Aflatoxins B1, and G1 and Ochratoxin A (Rubert et al., 2011). Agyeman (2011) also isolated fungi of the genera Aspergillus, Fusarium, Cladosproium, Mucor, Neosartorya, Monoascus, Neurospora, Penicillium, Paecilomyces, Rhizopu, Syncephalastrum, Torula, Rhodotorula, and Saccharomyces in tigernuts from Ghana. Studies have also been organized to ascertain the levels of mycotoxins in tigernut-related products. Rubert et al. (2011) investigated the concentrations of mycotoxins in tigernut and tigernut beverages sampled from different markets in Spain. Out of a total of 238 analysed samples, 32 were detected to be contaminated with OTA, AFB1, AFB2 and AFG2. University of Ghana http://ugspace.ug.edu.gh 24 Mycotoxin contaminated tigernut tubers have been rejected by importing nations as experienced in 2002, when on three occasions, mycotoxin-contaminated tigernuts were refused entry into the European Union. Added to this, Malian tigernuts imported to Europe in April 2004, which contained mycotoxin concentration of 300 µg/kg AfB1, were also refused entry (European Commission, 2019). 2.5.2 Conditions for Fungal growth Mycotoxins can develop on food commodities at any stage of the supply chain: processing, transport, and storage (Ferrăo et al., 2017). There are numerous factors which are responsible for the growth of mycotoxins. These include temperature, relative humidity, fertilizers, geographical location and insect infestation (Ferrăo et al., 2017). Table 2-2 shows the conditions for growth of common fungi. Table 2-2: Common Mycotoxin causing fungi and their conditions for growth Fungi Mycotoxins Growth Temperature Optimal Toxin Production Temperature Optimal Growth pH Water Activity A. flavus AFB1, AFB2 25-30°C 28-35°C 5-6 0.94- 0.97 A. parasiticus AFB1, AFB2, AFG1, AFG2 15-33°C 28-35°C 5 0.95- 0.99 A. niger FB2 24-37°C 25-30°C 5 0.97- 0.99 A. ochraceus OTA 24-37°C 31°C 3-10 Min. 0.8 A. fumigatus GTX Under 42°C 37°C 7.35-7.45 0.92- 0.97 (Source: Ráduly et al., 2020) University of Ghana http://ugspace.ug.edu.gh 25 The incidence of fungal growth and infection have been connected predominantly to the presence of moisture (Kortei et al., 2019). Improper drying of stored food commodities such as cereals, tubers and legumes increases their susceptibility to the increase in mycotoxigenic fungi like Aspergillus species (Kortei et al., 2019). The susceptibility is speculated to increase with storage time (Pinotti et al., 2016). Kortei et al. (2019) established the fact that, contamination of food crops with the metabolites of Aspergillus flavus could increase at maturity and harvest periods at the terminus of the raining season. Methods used for traditional drying of the food crops entails bare ground and field drying as well as improper handling. These methods significantly impact fungal infectivity. According to Mitchell et al. (2014), crops prone to mycotoxin contamination are those harvested and stored in tropical and subtropical regions susceptible to humid and dry environment (Mitchell et al., 2014). Aflatoxin production has been declared to be facilitated by tropical and Mediterranean climates (Ráduly et al., 2020). This was backed by the fact that, the production of toxins secreted by A. flavus and A. parasiticus occurs between 28 and 35 ℃ (Ryu et al., 2008). This buttresses the point that food commodities produced from these regions are susceptible to aflatoxin contamination. 2.5.3 Effects of mycotoxins on the economy According to the World Health Organization’s report on mycotoxins, mycotoxins have caused a lot of agricultural loss and pose a serious threat to both human and livestock, when consumed in high concentration. 2.5.3.1 Health effects of mycotoxins on the economy The extent of biological damage elicited by mycotoxins differs based on many factors including the class and source, exposure route and dosage, species vulnerability and contributory University of Ghana http://ugspace.ug.edu.gh 26 subclinical circumstances of the consumer (Mitchell et al., 2014). When consumed in high concentrations, mycotoxins can elicit diseases called mycotoxicosis. Hepatic disease and alimentary toxic aleukia are the most common mycotoxicosis (Armenda´riz et al., 2014). Intake of large amounts of food commodities containing mycotoxins within a short period of time will initiate severe toxicity leading to death (Darwish et al., 2014). Aflatoxins have been marked to cause human ailments including Kwashiorkor, occupational respiratory diseases, liver cancer, Indian childhood cirrhosis and Reye’s syndrome (Darwish et al., 2014). Humans are most sensitive to acute AFB1 toxicity (Mitchell et al., 2014). Symptoms of acute aflatoxicosis include; anorexia, depression, ataxia, dyspnoea, anaemia and haemorrhage (Mitchell et al., 2014). Aflatoxins also have deleterious effects when exposed to high concentrations which includes immune suppression, gastroenteritis and hematomas (Mitchell et al., 2014). Aflatoxins can cause acute hepatitis by causing damage to the hepatocytes which can lead to death (Ráduly et al., 2020). Protracted aflatoxin contamination causes flawed DNA multiplication in the bone marrow which lowers leucocyte concentrations (Ráduly et al., 2020; Benedict et al., 2016). Chronic toxicity occurs from long periods of exposure to moderate levels of aflatoxin concentrations. (Wagacha & Muthomi, 2008). Symptoms includes decreased egg or milk production in animals, immuno-suppression, and decline in rate of development (Wagacha & Muthomi, 2008). Kenya recorded the largest outburst of Aflatoxicosis to date, which resulted in 215 deaths out of 317 cases recorded (Darwish et al., 2014). In Nigeria, a study conducted by Uri