ABSTRACT
To investigate the effects of fermentation on the proximate, mineral and anti-nutrient compositions of some cassava products, the pulps of 9 varieties of cassava were fermented with pure strains of Saccharomyces cerevisae and Lactobacillus bulgaricus for three days; these were subsequently processed into ‗fufu‘ and ‗gari‘. Similarly, the pulps were also chance fermented without microbial inoculation and made into another set of ‗gari‘ and ‗fufu‘ while some were made directly into ‗lafun‘ without fermentation to allow for comparative studies. Some of the varieties of cassava tubers were collected from Niger State Agricultural Development Project, Minna, Nigeria, while some were sourced from farmers within the areas
under investigations. These tubers were washed, peeled, grated prior to aseptic inoculation with the organisms in liquid nutrient broth. The fermented mash was subsequently dried, pulverised and processed traditionally to ‗gari‘ and ‗fufu‘ while the dried cassava tubers were milled into ‗lafun‘ flours. The physico-chemical compositions of the soil samples where these cassava tubers were planted were also invetigated.The results of the study revealed that microbial fermentation caused significant (p < 0.05) increase in the protein (9I%) and fat (98%) contents and decreased fibre (85%) and carbohydrate (10%) compositions. There were also significant reductions of cyanide, tannins, saponins, phytate and oxalate contents. Conversely, microbial fermentation of the cassava caused increase in Zn, Mg, Ca, Na, K, P and Fe contents, whose values were found to be higher than those of the soil samples. The results of this study suggest that cassava products can be nutritionally improved with S. cerevisiae and Lactobacillus bulgaricus fermentations.
TABLE OF CONTENTS
Fly leaf i
Title page ii
Declaration iii
Certification iv
Acknowledgements v
Abstract vi
Table of contents vii
List of Tables xiv
List of Figures xv
List of Appendices xviii
Glossary xx
1.0 INTRODUCTION 1
1.1 Background to the Study 1
1.2 The Need for Fermentation of Cassava 6
1.3 Microorganisms Used for the Fermentation of Cassava 7
1.4 Description of Cassava 7
1.5 History of the Development of Cassava 10
1.6 Statistics of Cassava Production 11
1.7 Importance of Cassava 15
1.7.1 Human Consumption 15
1.7.2 Livestock Feed 17
1.7.3 Industrial Use 17
1.7.4 Ethno-medicinal usage 18
1.8 Cultivation of Cassava 18
1.9 The Processed Cassava Products 19
1.9.1 ‗Fufu‘ 19
1.9.2 Cassava Chips 20
1.9.3 Gari/Farinha 20
1.9.4 Fermented and Dried Cassava Pulp (‗lafun‘) 21
1.9.5 Smoked Cassava Balls (‗Kumkum‘) 21
1.9.9 Chickwangue 22
1.9.10 Starch 22
1.9.11 Dried Cassava 23
1.10 Varieties of Cassava 23
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1.11 The Anti-Nutritional Factors 25
1.11.1 Cyanide 26
1.11.2 Recommended dietary allowance (RDA) for cyanide 32
1.12 Phytate 33
1.12.1 The Phytate Threshold 34
1.13 The Polyphenols (Tannins) 35
1.13.1 Interaction tannins with other macromolecules 37
1.14 Oxalates 37
1.15 Saponins 38
1.15.1 Recommended dietary allowance (RDA) for cyanide 38
1.16 Effects of Environmental Conditions on the Nutritional and
Antinutritonal Composition of Cassava Products 39
1.17 Aim of the study 41
1.18 Objectives of the study 41
1.19 Justification for the study ` 42
2.0 LITERATURE REVIEW 43
2.1 Methods of Improving the Nutrient Contents of Cassava
Products (Fortification) 43
2.1.1 Nutritional enhancement of cassava products by microbial fermentation 46
2.1.2 Nutritional enhancement of cassava products by supplements 51
2.2 Effects of Processing on the Anti-nutritional Components of Cassava
and the By-Products 57
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2.2.1 Effects of processing on the cyanide level 57
2.2.2 Effects of processing on phytate level 79
2.2.3 Effects of processing on tannins level 83
2.3 Effects of Processing on the Nutritonal Components of Cassava Products 84
2.3.1 Effects of processing on the protein contents 84
2.3.2 Effects of processing on the fat content 90
2.3.3 Effects of processing on Other Nutritional Constituents 90
2.4 The Chemistry of Some Components in Cassava Products 94
2.4.1 Chemistry of phytic acid 94
2.4.2 Phytic acid chelation 96
2.4.3 Significance of phytic acid in agriculture 97
2.4.4 Significance of phytic acid in food science 98
2.4.4 Chemistry of tannins 101
2.4. 5 Chemistry of proteins 106
2.5 Diseases Related to Cassava Toxicity 107
2.5.1 Stunting of children 107
2.5.2 Tropical ataxic neuropathy (TAN) 110
2.5.3 Epidemic spastic paraparesis 111
2.5.4 Konzo 112
2.6 Compositional Studies of Cassava Tubers and Leaves 113
2.7 Hydrolysis of Linamarin by the Endogenous Linamarase Enzyme 120
3.0 MATERIALS AND METHODS 123
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3.1 Materials and Reagents 123
3.2 The Study Area (Evolution of Niger State) 123
3.3 Socio-ecological Mapping of the Study Area 126
3.4 Sampling Scheme and Samples 126
3.4.1 Preparations of cassava samples 126
3.4.2 Sampling of soils where the cassava varieties were planted 126
3.4 3 Method of processiing ‘fufu’ 127
3.4.4 Method of processing ‘gari’ 127
3.4.5 Method of procssing ‘lafun’ 128
3.4.6 Inoculation of the ‗gari‘ and ‗fufu‘ during processing 128
3.5 Analyses of Soil 128
3.5.1 Particle size analysis (Bouyoucos hydrometer method) 129
3.5.2 Determination of soil pH 130
3.5.3 Determination of organic carbon and organic matter (Walk –Black method) 130
3.5.4 Determination of available phosphorus (Bray PI or dilute
acid – fluoride extraction Method) 131
3.5.5 Determination of exchageable bases (NA+, K+, Ca2+ and Mg2+) 132
3.5.5a Extraction of Exchageable Bases from soil 132
3.5.5b Determination of Na+ and K+ in the extract 133
3.6 Chemical Analysis of Cassava Products (inoculated and uninoculated) 134
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3.6.1 Determination of moisture content of cassava products using
evaporation method 134
3.6.2 Determination of total dry matter (TDM) and total organic
matter (TOM) of the cassava products 134
3.6.3 Determination of ash content of the cassava products 135
3.6.4 Determination of crude fat in the cassava products using
the Ministry of Agriculture Fish Food Method 135
3.6.5 Determination of crude fibre in the ‗fufu‘, ‗gari‘ and ‗lafun‘ products 136
3.6.6 Determination of the nitrogen free extract (NFE) in each of the
cassava products 136
3.6.7 Determination of carbohydrate of ‗gari‘, ‗fufu‘ and ‗lafun‘
product samples 137
3.6.8 Determination of crude protein in the cassava products using
the Micro Kjeldahl digestion and distillation methods 137
3.6.9 Perchloric acid digestion (wet oxidation) of the samples for P, Ca,
Mg, Fe, Mn, Zn, Cu, K and other minerals determinations 139
3.6.10 Phosphorus determination using the Association of Official Analytical
Chemists (AOAC) Vanado-Molybdate official method 139
3.6.11 Determination of potassium and sodium by flame emission
spectrphotometer (FES) method 140
3.6.12 Preparation of the standards for the determination of Ca, Mg, Zn, Fe Cu
and P in ‗fufu‘, ‗gari‘ and ‗lafun‘, using atomic absorption
spectrophotometric method 141
3.6.13a Determination of cyanides in the samples (The alkaline Picrate method) 142
3.6.13b Preparation of standard plot for cyanide determination 142
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3.6.13c Determination of total cyanide in the samples 143
3.6.14 Determination of phytates using anion exchange method 143
3.6.15 Determination of saponins in the cassava product samples
(‗gari‘, ‗fufu‘ and ‗lafun‘) 146
3.6.16 Determination of the oxalic acid contents of the cassava product samples 148
3.7 Methods of Statistical Analysis 149
4.0 RESULTS 150
4.1 The Percntage Increase or Decrese of Proximate Compositions
of the Cassava Samples 150
4.2 The Percentage Decrease in Anti-nutrient Compositions of the
Cassava Samples. 182
4.3 The Percntage Increase in Elemental Compositions of the
Cassava Samples 201
4.4 The results of Physico-chemical Compositions of Soil Samples from the Three
Sampling Areas 228
5.0 DISSCUSION 232
5.1 Proximate Composition of the Inoculated and Uninoculated Cassava Products 232 5.1.1 Effects of inoculation on the crude protein contents the products 232 5.1.2 Effect of inoculation on the crude fibre content of the products 236 5.1.3 Effect of inoculation on the crude fat content of the products 238
5.1.4 Effect of inoculation on the carbohydrate content of the products 240 5.1.5 Effect of inoculation on the moisture composition of the products 242
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5.1.6 Effect of inoculation on the ash content of the products 242 5.1.7 Effect of inoculation on the total dry matter (TDM) of the products 243
5.2 Anti-nutrient contents of the Inoculated and Uninoculated Cassava Products 245 5.2.1 Effect of inoculation on the cyanide content of the products 245
5.2.2 Effect of inoculation on the oxalate content of the produicts 248
5.2.3 Effect of inoculation on the phytate composition of the products 250 5.2.4 Effect of inoculation on the tannin contents of the products 252 5.2.5 Effect of inoculation on the saponin composition of the products 254
5.3 Mineral Composition of the Inoculated and the Uninoculated Cassava Products 254 5.3.1 Effect of inoculation on the zinc contents of the products 254
5.3.2 Effect of inoculation on the level of magnsium content in the products 256 5.3.3 Effect of inoculation on the level of sodium composition in the products 258 5.3.4 Effect of inoculation on the level of potassium composition in the products 259 5.3.5 Effect of inoculation on the level of calcium composition in the products 261 5.3.6 Effect of inoculation on the level of iron composition in the products 262 5.3.7 Effect of inoculation on the level of phosphorus cootent in the products 264
5.4 Soil Composition of the areas where cassava samples were planted 265 5.4.1 Physico-chemical contents of soil samples of Kontagora town 265
5.4.2 Physico-chemical contents of soil samples of Suleja town 267 5.4.3 Physico-chemical contents of soil samples of Bida town 269
6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 272
REFERENCES 275
APPENDICES 307
CHAPTER ONE
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