ABSTRACT

Corms and cormels of cocoyams (Colocasia esculenta cv. Cocomdia and Xanthosoma sagithfolium cv, Ede ocha) were each milled into flour. The flours were subjected to proximate analysis , evaluation of calcium and phosphorus compositions of the two cocoyams varieties - The results showed crude protein; 7:12% for Colocasia esculeiita and 5.83% for Xanthosma sagithfolziim . They were exceptionally rich in ash , 4.74% (Colocasici esciilenla) and 3.84%( Xanthosom sagittfelum), but were low in fibre ; 1.63% (Colocasia esculejila ) and I .24%( Xanthosoma sagittfoluim)They formed a fair source of fats, containing 0.38% for taro and 0.61% for tannia . Taro seems lightly superior to tannia in its content of crude proteins, although the latter were richer in carbohydrates ; 75.87% (tannia), 73.54% (Taro). Both were fairly good sources of calcium and phosphorus taro Ca 24. 05 (mg/bOg) and p, 359.66mg/lOOg Tannia: Ca, 8.02 mg/l0og and p;56.00mg/loOg.The qualitative detection of sugars using thin layer chromatographic techniques indicated the following sugars in the two varieties of cocoyams fructose , dextrose, maltose , mannose, xylose and stachyose.. The estimations of starch in cocoyam tubers were 23.21% and 23.95% for taro and tannia respectively - The total sugars and reducing sugars for taro (Colocasia esculenta) and tannia (Xanthosoma sagitEfolizim ) were 0.62% and 0.66% and 0.50% and 0.52% respectively. The high carbohydrates content of Xau/hosoma sagiutfo1iurn and its wide availability makes it a very good source of starch for both domestic and industrial uses in Nigeria and tropical Africa.

TABLE OF CONTENTS

TITLE PAGE

Title Page

Certification ii

Declaration iii

Dedication iv

Acknowledgement v

Table of contents vi—vii

List of tables viii

List of abbreviations and acronyms ix

List of figures x

Abstract xi

CHAPTERS

1.0 INTRODUCTION 1-3

2.0 LITERATURE REVIEW 4

2.1 Cocoyam processing and Nutrition 4

2.2 Anti Nutrition factor 9

2.3 Agents of food toxicity 10

2.3.1 Microbial agents of food toxicity 10

2.4 Rheology and texture of foods 13

2.4.1 Food Rheology 13

2.4.2 Starch gelatinization and viscosity of foods 14

2.4.3 Food texture 18

2.5 Spoilage, Preservation, and Packaging of foods 19

2.5.1 Foodspoilage 19

2.5.2 Food Preservation 21

2.5.3 Food packaging 22

3.0 MATERIALS AND METHODS 25

3.1 Sources of experimental materials 25

3.2 Preparation of sample 25

3.3 Proximate Analyses 25

3.4 Qualitative, detection of sugars 26

3.5 Estimation of starch in cocoyam tubers 26

3.6 Determination of total soluble sugars 27

3.7 Determination of reducing sugars 28

4.0 RESULTS AND DISCUSSION 30

4.1 Proximate and mineral composition of cocoyam 34

4.2 Sugars presenting cocoyam 34

4.3 Contents, % sugars and % Reducing sugars 35

5.0 CONCLUSION AND RECOMMENDATION 36

REFERENCES 39

APPENDICES 48