Shelf Life Extension Of Locally Prepared Citrullus Lanatus (Watermelon) Juice Using Species Of Lactobacillus Isolated From Fermented Maize

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