ABSTRACT

Starch from cormels of cocoyam Xanthosoma sagutzfoliuin), cullivar Ede ocha and cultivar Ede uhie were extracted and milled into starch of fine texture and were further subjected to acid arid enzyme modification treatments. Proximate composition, funcfional and amylograph pasting properties of the starches were evaluated. The starch samples were also used in the production of cookies at 5%, 10%, 15%, 20% and 25% lvel of substitution with wheat flour. The cookies produced were subjected to proximate analysis and sensory evaluation. The result of the sensory evaluation showed that cookies prepared at 5% level of substitution were most acceptable. After eight weeks of storage in light polythene bags, the cookies prepared at 5% and 10% levels of substitution with wheat flour were found to be more acceptable by the panelists. Observations on the functional properties showed that the modified cocoyam starches exhibited higher bulk densities than the untreated starches. Native and modified starches with the high water absorption capacity and swelling index were produced from cultivar Ede uhie. There was no significant difference (P> 0.05) in the solubihity of the starch samples.

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgement iv

Table of contents v

List of Table ix

List of Figures x

Abstract - xi

CHAPTER 1

INTRODUCTION

1.1 Objectives 4

CHAPTER 2

LITERATURE REVIEW 5

2.1 World Production arid Trade 5

2.2 Nutritional Quality of Cocoyam 7

2.3 Post harvest Losses and Storage of Cocoyam 9

2.4 Cocoyarn Processing and Utilization 10

2.5 Oxalates in Cocoyarn Ill

2.6 Cocoyani Starch 13

2.7 Starch: Composition and Properties 15

2.8 Starch Extraction 16

2.9 Modified Starches 17

2.9.1 Enzyme Modification 18

2.9.2 Chemical Modification 19

2.9.3 Acid Modification 20

2.10 Starch Utilization 21

2.11 Sensory Properties of Foods 22

CHAPTER 3

MATERIALS AND METHODS 24

3.1 Materials 24

3.2 Methods 24

3.3 Starch Modification 24

3.3.1 Acid Modification 24

3.3.2 Enzyme Modification 25

3.4 Proximate Analysis 26

3.4.1 Moisture Content 26

3.4.2 Ash Content 26

3.4.3 Crude Protein 27

3.4.4 Crude Fat 27

3.4.5 Crude Fibre 27

3.4.6 Total Carbohydrate 28

3.5 Functional Properties 28

3.5.1 Wettability 29

3.5.2 Packed Bulk Density 29

3.5.3 Loose Bulk Density 29

3.5.4 Swelling Index 29

3.5.5 Least Gelation Property 30

3.5.6 Water Absorption Capacity 30

3.5.7 Foam Capacity/Stability 30

3.5.8 Solubility in Water 31

3.5.9 Gelatinization 31

3.6 Oxalate Determination 32

3.7 Baking Properties of Composite Cocoyarn-wheat 33

based cookies

3.7.1 Production of Cookies 33

3.7.2 Sensoty Evaluation 35

CHAPTER 4

RESULTS AND DISCUSSION 36

4.1 Proximate Composition of the Cocoyam Starch samples 36

4.2 Functional Properties of the Cocoyam Starch samples 39

4.2.1 Bulk Density 39

4.2.2 Water Absorption Capacity 39

4.2.3 Swelling Index 40

4.2.4 Solubility in Water 42

4.2.5 Foam Capacity! Foam Stability 42

4.2.6 Wettability 43

4.2.7 Least Gelation Property 43

4.2.8 Viscosity 46

4.3 Oxalate 48

4.4 Sensory Evaluation of Cocoyam-Wheat Based Cookies 49

4.4.1 Taste 49

4.4.2 Appearance 51

4.4.3 Texture 51

4.4.4 Flavour 54

4.4.5 Acceptability 54

4.5 Proximate Composition of the Cocoyam-Wheat based Cookies 57

4.6 Effect of Ageing on the Sensory Attributes of Cookies Produced from

Cocoyam Starch/Wheat Flour after Eight weeks of Storage 59

4.7 Recovery of Starches after Modification Treatments 67

CHAPTER 5

CONCLUSION AND RECOMMENDATION 68

5.1 Conclusion 68

5.2 Recommendation 68

REFERENCES 70

APPENDIX