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