CHARACTERIZATION AND TECHNOLOGICAL POTENTIALS OF LACTIC ACID BACTERIA ISOLATED FROM FERMENTED TIGER NUT MILK

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