ABSTRACT

This study was aimed at characterizing and determining the technological potentials of lactic acid bacteria isolated from fermented tiger nut milk. The result of the studies showed that tigernuts are high in carbohydrate, fat and fibre contents. All the isolates were negative for Catalase test. Some of the isolates were negative for gas production from glucose while few of the isolates were positive. All the isolates indicated negative haemolytic test. In the antibiotic sensitivity test, majority of the isolates tested were antibiotic sensitive while others were antibiotic resistance. Production of exopolysaccharides investigated in this study was considered a positive characteristic for the fermentation of tiger nut milk, except (TMT2464, TMT2472 and TMT2462). Amylase abilities by the lactic acid bacterial isolates from the tiger nut milk were all negative. The results showed fermented tiger nut milk contain both homofermentative and hetrofermentative lactic acid bacteria. Lactic acid bacteria also produce exopolysaccharides which are essential as texture formation. It is therefore recommended that lactic acid bacteria also produce exopolysaccharides which are essential as texture formation. Considering the existing reports on several health-promoting properties as well as their generally recognized as safe (GRAS) status of LAB, they can be widely used in the developing of new fermented milk products including yoghurt. 

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgements iv

Table of contents v

List of figures vii

List of tables viii

Abstract ix 

CHAPTER ONE

1.0 Introduction 1

1.1 Aims and Objectives 4

CHAPTER TWO

2.0 Literature Review 5

2.1 Classification, Taxonomy and Sources of Lactic Acid Bacteria 5

2.1.1 Lactic Acid Bacteria 5

2.1.2 Sources of Lactic Acid Bacteria 5

2.1.3 Classification of Lactic Acid Bacteria 5

2.2 Lactic acid bacteria as source of exopolysaccharides 7

2.2.1 Definition and classification of exopolysaccharides 7

2.3 Food fermentation 8

2.3.1 Benefits of Food Fermentation 10

2.4 Fermentation of Foods by Lactic Acid Bacteria 12

2.5 Fermentation of Tiger Nut by Lactic Acid Bacteria 14

2.6 Economic and Nutritional Benefits of Tiger Nut 15

CHAPTER THREE

3.0       Materials and Methods 17

3.1 Source of Materials 17

3.1.1 Sample Preparation 17

3.2 Glass Wares and Media Used and Their Preparation 17

3.3 pH Determination 18

3.4 Proximate Analysis 18

3.4 Microbiological Analyses 22

3.4.1 Enumeration of total bacteria 22

3.4.2 Enumeration of Coliform 23

3.4.3 Enumeration of Yeast 23

3.4.4 Enumeration of Lactic acid bacteria 24

3.4.5 Isolation of Lactic Acid Bacteria 24

3.4.6 Characterization of Lactic Acid Bacteria 25

3.4.6.1 Morphological characterisation 26

3.4.6.2   Biochemical characterization 26

3.4.6.3 Physiological Characterization 28

3.4.7 Identification of Lactic acid bacteria 29

3.5 Safety Properties of Lactic Acid Bacteria 29

3.5.1 Haemolytic test 29

3.5.2 Antibiotic resistance pattern    30

3.6 Determination of Technological Properties 30

3.6.1 Screening for Amylase Production 30

3.6.2 Screening for Esopolysaccaride Production 31

3.6.3 Rate of Acid Production 31

CHAPTER FOUR

4.0 Results 32

CHAPTER FIVE

5.0 Discussion, Conclusion and Recommendations 43

5.1 Discussion 43

5.2 Conclusion 45

5.3 Recommendations 46

References 47