ABTRACT

Two Lactobacillus specie isolates designated L1 and L2, isolated from fermented maize (Akamu) and identified as Lactobacillus plantarum and Lactobacillus brevis respectively. Each isolate was used at three different treatment concentrations (0.5ml, 1.0ml and 2.0ml) to treat and preserve locally produced watermelon juice stored at ambient temperature for seven days. Bacteriocin extracted from each isolate was also used in the preservation of watermelon juice. The watermelon juice was divided into nine samples (control, L1 0.5ml, L1 1.0ml, L1 2.0ml, L2 0.5ml, L2 1.0ml, L2 2.0ml, L1Bacteriocin and L2Bactriocin). After inoculation, the juice samples were subjected to chemical and microbial analyses on 24 hour-interval for seven days. The microbial analysis showed that the control, L1 0.5ml and L2 0.5ml had higher bacterial load of 5.9 x 105cfu/ml 4.4 x105cfu/ml and 4.6 x 105cfu/ml respectively for four storage days, and decreased later, and fungal load of 5.9 x 103cfu/ml 5.2 x 103cfu/ml and 5.2 x 103cfu/ml respectively. The samples preserved with L1 2.0ml and L2 2.0ml had lower bacterial load of 2.8 x 105cfu/ml and 2.9 x 105cfu/ml respectively and fungal load of 2.3 x 103cfu/ml for each. The results of this study revealed that the concentration of preservative affects the nature and microbial load of micro-organisms found in fruit juices during storage.

TABLE OF CONTENTS

Title i

Certification ii

Dedication iii

Acknowledge iv

Table of contents v

List of tables viii

List of figures ix

Abstract x

Chapter One

1.1 Introduction 1

1.2 Aim and objectives of the study 6

Chapter Two

2.1 Origin and distribution of watermelon 7

2.2 History Review of watermelon 7

2.3 Watermelon varieties 9

2.4 Nutritional and medicinal value of watermelon 12

2.5 Economic importance and uses of watermelon 16

2.6 Lactic acid bacteria 17

2.7 Lactobacillus 19

2.7.1 Classification of Lactobacillus species 19

2.7.2 Metabolites from Lactobacillus 21

2.7.3 Antimicrobial activity of Lactobacillus 23

Chapter Three 

3.1 Procurement of materials 25

3.2 Isolation of Lactobacillus species 25

3.2.1 Characterization of isolates 25

3.2.2 Biochemical tests 26

3.2.3 Sugar utilization test 26

3.3 Identification of Lactobacillus isolates 26

3.4 Production of watermelon juice 26

3.5 Treatment of juice with Lactobacillus 27

3.6 Shelf life studies 28

3.6.1 Determination of total solid content 28

3.6.2 Determination of total titratable acidity 29

3.6.3 Determination of pH 30

3.6.4 Determination of microbial load 30

3.6.5 Sensory evaluation 31

3.7 Statistical analyses 32

Chapter Four

Results 33

Chapter Five

5.1 Discussion 48

5.6 Conclusion 50

5.2 Recommendation 50

References 51