ABSTRACT

The aim of this study was to produce tiger nut and soybean yoghurt and determine it’s proximate values. The yoghurt was produced by inoculation of isolates of lactic acid bacteria (Lactobacillus acidiophilus, Lactobacillus Bulgaricus and Streptococcus thermophilus) into milk extract of tiger nut and soybean. pH, temperature, optical density, titratable acidity, sensory characteristics and proximate composition of produced samples were analyzed. After fermentation, tiger nut yoghurt had the lowest pH (3.6) while the commercial milk yoghurt had initial pH of 6.0. The tiger nut yoghurt and soybean yoghurt had optimum fermentation temperature of 31.50C while the dairy milk yoghurt had a maximum fermentation temperature of 290C. The tiger nut yoghurt had a maximum optical density of 1.39 while the lowest optical density (1.13) was recorded in dairy milk yoghurt. Tiger nut had a maximum titratable acidity of 1.38 while the dairy milk yoghurt had the lowest titratable acidity of 0.52.The proximate result showed that the soy milk yoghurt had the highest protein and fiber content (3.69 ±0.10 and 0.39±0.03) respectively. The commercial dairy milk had the highest fat (3.87 ±0.03), ash (2.96 ±0.16) and moisture (87.54±0.07) content while tiger nut yoghurt had the highest carbohydrate content (4.90±0.31). Yoghurts from tiger nut and soybean were considered generally accepted based on the sensory evaluation by 11 man panel. The results obtained from this study shows that it is possible to produce yoghurts using tiger nut and soybean which are beneficial to human health compared to yoghurt produced from dairy milk

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgements iv

Table of contents v

List of tables ix

Abstract x

CHAPTER ONE

1.0 Introduction 1

1.1 Scope of study 2

1.2 Statement of Problem 3

1.3 Significance of the Study 3

1.4 Aims and Objectives 4

CHAPTER TWO

2.0 Literature Review 5

2.1 Chemical Structure of Yoghurt 5

2.2 Starter Culture 5

2.3 Important Metabolic Activities of Yoghurt Technology 6

2.3.1 Acid Production 7

2.3.2 Flavour Compounds of Yoghurt 7

2.3.3 Production of Polysaccharides 8

2.3.4 Proteolytiç Activity 8

2.3.5 Urease Activity 9

2.4 Interaction between Yoghurt Bacteria 10

2.5 Health Concerns/ Challenges about Dairy Milk 10

2.5.1 Fat Content and Cardiovascular Diseases 10

2.5.2 Dairy and Cancer 11

2.5.3 Lactose Intolerance 11

2.5.4 Dairy Contaminants 12

2.5.5 Dairy Protein and Diabetes 13

2.6 Tiger Nut 13

2.6.1 Uses and Product 14

2.6.2 Economic and Nutritional Benefits of Tiger Nut 16

2.7 Soybean 17

2.7.1 Physical Characteristics 17

2.7.2 Chemical Composition of Soybean 18

2.7.3 Soybean and Health 18

2.7.3.1 Effects on Hypercholesterolemia and Cardiovascular Diseases 19

2.7.3.2 Effects on Osteoporosis and Menopause 20

2.7.3.3 Hypertension Activity 20

2.7.3.4 Effects on Insulin Secretion and Energy Metabolism 20

CHAPTER THREE

3.0 Materials and Methods 21

3.1 Source of Materials 21

3.2 Isolation of Lactic Acid Bacteria 21

3.3 Gram Staining 22

3.4 Motility Test 22

3.5 Biochemical Tests 23

3.6 Milk Extraction 25

3.7 Production of Yoghurt 25

3.8 Proximate Analysis 26

3.8.1 Determination of Total Solids/ Moisture Content 26

3.8.2 Determination of Ash Content 26

3.8.3 Determination of Fat Content 27

3.8.4 Determination of Protein Content 27

3.8.5 Determination of Crude Fibre 28

3.8.6 Determination of Carbohydrate 29

3.9 Sensory Evaluation 29

3.10 Statistical Analysis 29

CHAPTER FOUR

4.0 Results 30

CHAPTER FIVE

5.0 Discussion 36

5.1 Conclusion 39

5.2 Recommendation 40

REFERENCES 41

LIST OF TABLES

Table 1 Microbiological Result of Isolates 32

Table 2 Proximate Analysis of Yoghurt Samples 33

Table 3 Fermentation Parameters of Yoghurt Samples 34

Table 4 Sensory Analysis of Samples 35