ABSTRACT

This study was aimed to characterize and determine the functional potentials of lactic acid bacteria isolated from fermenting tiger nut milk. The specific objectives were to isolate lactic acid bacteria from fermenting tiger nut milk, characterize and identify lactic acid bacteria using morphological, physiological and biochemical techniques and to ascertain the functional potentials of lactic acid bacteria isolated from fermenting tiger nut milk. The result of the analysis showed that tiger nuts are high in carbohydrate, fat and fibre content. . All the isolates were negative for Catalase test. Many isolates were negative for gas production from glucose and few isolates were positive. All the isolates indicated negative haemolytic test. The antimicrobial properties of the samples was determined by measuring the diameter of zone of inhibition, the maximum zone of inhibition was observed in case of (TMP2472) Lactobacillus pentosus with 14mm zone of inhibition while the minimum was observed in (TMP 051) Lactobacillus fermentum with 3mm zone of inhibition. It has been reported that lower temperature slows down chemical reactions, enzyme actions and microbial growth; it is therefore recommended that when tiger nut milk is not to be served immediately, it should be stored at low temperatures (i.e. in the refrigerator) so as to prevent the growth of spoilage organisms and maintain the quality of the milk.

TABLE OF CONTENTS 

Title page i

Certification ii

Dedication iii

Acknowledgements iv

Table of contents v

List of tables vii

List of figures viii

Abstract ix

CHAPTER ONE

1.0 Introduction 1

1.1 Aim and Objectives 4

CHAPTER TWO

2.0 Literature Review 5

2.1 Lactic Acid Bacteria (LAB) 5

2.2 Taxonomy of Lactic Acid Bacteria 5

2.3 Sources of Lactic Acid Bacteria 6

2.4 Classification of Lactic Acid Bacteria 6

2.5 Food fermentation 7

2.6 Benefits of Food Fermentation 9

2.7 Advantages of Food Fermentation 10

2.8 Importance of Lactic Acid Bacteria 10

2.9 Beneficial Role of Lactic Acid Bacteria 11

2.10 Importance of LAB and their Effect on Human Health 12

2.11 Lactic Acid Bacteria and Other Effects on the Immune System 13

2.12 Lactic acid fermentation 14

2.13 Importance of Tiger nuts 15

CHAPTER THREE

3.0 Materials and Methods 19

3.1 Sample Collection and Preparation 19

3.1.1 Tiger nut milk extraction 19

3.1.2 Glass wares and media preparation 20

3.1.3 pH determination 20

3.2 Proximate Analysis 21

3.3 Microbiological Analyses 23

3.3.1 Enumeration of total bacteria 23

3.3.2   Enumeration of Coliform 24

3.3.3 Enumeration of Yeast 25

3.3.4    Enumeration of Lactic acid bacteria 25

3.3.5   Isolation of Lactic Acid Bacteria 26

3.3.6. Characterization of Lactic Acid Bacteria 26

3.3.6.1 Morphological characterisation 27

3.3.6.2 Biochemical characterization 27

3.3.6.3 Physiological characterization 29

3.3.7 Identification of Lactic Acid Bacteria 30

3.4 Safety Properties of Lactic Acid Bacteria 30

3.4.1 Haemolytic test 30

3.4.2 Antibiotic resistance pattern    31

3.5    Determination of Functional Potentials 31

3.5.1   Tolerance to low pH 3.5 and 2.5 31

3.5.2   Tolerance to 0.3% Bile salt 31

3.5.3   Antimicrobial properties 32

CHAPTER FOUR

4.0 Results 34

CHAPTER FIVE

Discussion, Conclusion and Recommendations 45

5.1 Discussion 45

5.2 Conclusion 46

5.3 Recommendations 47

References 48

LIST OF TABLES

Table Title Page 

1: Proximate Composition of Fermenting Tiger nut milk 33

2: pH and microbial load of tiger nut milk during fermentation 34

3: Morphological Characteristics of Lactic Acid Bacteria Isolated from Tiger 

nut milk 36

4: Biochemical and physiological characteristics of Lactic Acid Bacteria 

isolated from fermenting Tiger nut milk 37

5: Haemolytic activity of Lactic Acid Bacteria isolated from fermenting 

Tiger nut milk 40

6: Result for antibiotic sensitivity 41

7: Antimicrobial properties of lactic acid bacteria 44

LIST OF FIGURES

Figure Title Page 

1: Tiger nut milk extraction 19

2: Tolerance to low pH 42

3: Tolerance to 0.3% bile salt 43