EFFECT OF GINGER AND GARLIC ON THE MICROBIAL LOAD AND SHELF-LIFE OF ZOBO DRINK

ABSTRACT

The preservative effect of garlic, ginger, garlic and ginger combination was compared with that untreated sample in evaluating the shelf quality of locally prepared zobo juice. The zobo juice without treatment (ZB) was used as the control while others were separately treated with garlic (ZBGA), ginger (ZBGI), and a mixture of garlic and ginger (ZBGG). Serially diluted samples were inoculated in duplicates into Nutrient Agar (NA), MacConkey agar (MCA) and Potato dextrose agar (PDA) plates for bacteria and fungi, respectively. The NA and MCA plates were incubated at 370C for 18-24 hours and the PDA plates at 280C for 3-6 days before reading the plates. The total viable counts of the samples during storage showed that the microbial load increased steadily and ranged from 1.19 X 104cfu/ml to 2.6 X 103cfu/ml. The sample containing ginger had the lowest microbial count of 2.6 X 103cfu/ml on the second day of storage, while the sample containing no treatment had the highest microbial load of 1.19 X 104cfu/ml within the storage period. The microbial load data obtained from these Zobo juices suggest that the natural preservatives (ginger, garlic and their mixture) were more effective in prolonging the shelf life compared to untreated sample.

TABLE OF CONTENTS

Title page ﾿ i

Certification ﾿ ii

Dedication ﾿ iii

Acknowledgements ﾿ iv

Table of Contents ﾿ v

List of Tables ﾿ vii

List of Figures ﾿ viii

Abstract ﾿ ix

CHAPTER ONE

1.0 ﾿ Introduction ﾿ 1

1.1 ﾿ Objectives of the Study ﾿ 3

CHAPTER TWO

2.0 ﾿ Literature Review ﾿ 4

2.1 ﾿ Scientific Classification of Roselle (Hibiscus sabdariffa) ﾿ 4

2.2 ﾿ Characteristics of Roselle ﾿ 5

2.3 ﾿ Biochemical Constituents of ﾿ Hibiscus sabdariffa ﾿ 6

2.3.1 ﾿ Phytochemistry ﾿ 6

2.3.2 ﾿ Pharmacology ﾿ 7

2.4 ﾿ Uses of Roselle (Hibiscus sabdariffa) ﾿ 8

2.5 ﾿ Preparation of Zobo Made from Roselle (Hibiscus sabdariffa) ﾿ 9

2.6 ﾿ Medicinal Benefits of Hibiscus sabdariffa ﾿ 9

2.7 ﾿ Herb, Spice and Flavour Oils as Antimicrobials ﾿ 11

2.8 ﾿ Zingiber officinalis (Ginger) ﾿ 12

2.8.2 ﾿ Bioactive components of Ginger ﾿ 13

2.9 ﾿ Allium sativum (Garlic) ﾿ 14

2.9.1 ﾿ Anti-microbial effect of Garlic ﾿ 15 ﾿

CHAPTER THREE

3.0 ﾿ Materials and Methods ﾿ 17

3.1 ﾿ Collection of Samples ﾿ 17

3.2 ﾿ Preparation of Ginger and Garlic Extracts ﾿ 17

3.3 ﾿ Preparation of Zobo Drinks ﾿ 17

3.4 ﾿ Physico-Chemical Analysis ﾿ 18

3.5 ﾿ Microbiological Analysis ﾿ 19

3.6 ﾿ Shelf-Life Evaluation ﾿ 19

3.7 ﾿ Identification of Microbial Associates ﾿ 19

3.8 ﾿ Gram Stain ﾿ 20

3.8.1 ﾿ Biochemical Test ﾿ 20

3.8.2 ﾿ Catalase Test ﾿ 20

3.8.3 ﾿ Citrate Test ﾿ 20

3.8.4 ﾿ Indole Test ﾿ 21

3.9 ﾿ Sensory Analysis ﾿ 21

CHAPTER FOUR

4.0 ﾿ Results ﾿ 22

CHAPTER FIVE

5.0 ﾿ Discussion, Conclusion and Recommendation ﾿ 26

5.1 ﾿ Discussion ﾿ 26

5.2 ﾿ Recommendations ﾿ 29

5.3 ﾿ Conclusion ﾿ 29

REFERENCES

LIST OF TABLES

Table ﾿ Title ﾿ Page

1: ﾿ Total Bacteria Count (cfu/ml) in samples ﾿ 23

2: ﾿ Total Fungal Count (cfu/ml) in samples ﾿ 24

3: ﾿ pH of the samples during the storage period ﾿ 25