¬ Production And Proximate Analyses Of Yoghurts From Tiger Nuts And Soybean Using Lactic Acid Bacteria As Starter Cultures

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