ABSTRACT

The possibility of producing African yam bean (AYB) yoghurt from AYB seeds was explored in this research. The AYB milk equivalent was prepare& from the grains of AYB. The grains were sorted, dehulled,blended with 1 75% water into slurry, diluted with distilled water in the ratio of 1:5 (w/v) and sieved with a muslin cloth. A 1 5- member untrained panelists using a nine point Hedonic scale scores, was used to evaluate the acceptability of the AYB yoghurt. The AYB milk equivalent incubated at 42°C for 15 hours using a lyophilized thermophilic starter culture gave yoghurt with the characteristic sour taste and good consistency. The colour, consistency,sour taste,flavour and overall acceptability scored the means of 6.53, 7.27, 6.87, 6.13, and 7.20 respectively. The means respectively represented 72.56%, 80.78%, 76.33%, 68.11%, and 80.00% acceptance. The proximate composition of the AYB Yoghurt showed 83.250% moisture, 3.326% cnide protein, 0.278% ash, 0.03 1 % crude fibre, 1 .900% ether extract and 11 .215% carbohydrate. Some quality parameters investigated on the AYB yoghurt showed a pH of 3.67,1.08% lactic acid and 317.597Kj/100g energy value. The microbial analysis on the AYB yoghurt revealed only the presence of the two symbiotic cultures- L. hu/garicus and S. iliermophilus inoculated. One-in-ten (10-') serial dilution showed 4.8x 10 cells of each bacteria strains.

TABLE OF CONTENTS

Title page

Certification

Dedication

Acknowledgements

Table of contents

List of tables

Abstract

CHAPTER ONE

1 .0 Introduction

CHAPTER TWO

2.0 Literature review 3

2.1 African Yam bean 3

2.1.0 Origin and description 3

2.1.1 Nutritional status of AYB 4

2. 1 .2 Anti-Physiological Factors of AYB 5

2. 1.3 Therapuetic value of AYB 6

2.2 Yoghurt 6

2.2.0 History and composition of yoghurt 6

2.2. 1 Therapeutic function of yoghurt 7

2.2.2 Nutritional value of yoghurt 8

2.3.0 Gelatin 9

2.4. Microbiology of yoghurt organisms 10

2.4.1 Effects of inhibitory agent on the yoghurt mixed cultures 15

2.4.1 a Natural yoghurt culture inhibitors 15

2.4.lb Chemical inhibition on yoghurt starters 16

2.4. Ic Bacteriophages (phages) 20

CHAPTER THREE

3.0 Material and methods 21

3.1 AYB milk equivalent preparation 21

3.2 AYB yoghurt preparation 21

3.3 Chemical analysis of AYB yoghurt 22

3.3.1 Crude protein 22

3.3.2 Moisture content 22

3.3.3 Fat determination 23

3.3.4 Crude fibre determination 23

3.3.5 Ash content determination 24

3.3.6 Carbohydrate determination 24

3.3.7 Detennination of pH value of AYB yoghurt 25

3.3.8 Titratable Acidity(TTA) 25

3.4 Evaluation of the energy value of the AYB yoghurt 26

3.5 Sensory evaluation 26

3.6 Microbial analysis of the AYB yoghurt 27

CHAPTER FOUR

4.0 Results and discussion 29

4.1 Sensory evaluation of AYB yoghurt 30

4.2 Proximate composition of AYB yoghurt 31

CHAPTER FIVE

5.0 Conclusion and Recommendation

References 36

Appendices

Appendix 1. Calculation of the proximate analysis 45

Appendix 2. Calculation of the energy value of AYB yoghurt 46