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

LIST OF FIGURES

Fig. 1: Flow chart of Zobo Preparation 18

CHAPTER 1

1.0 INTRODUCTION

Zobo, a non-alcoholic beverage popularly consumed in Northern Nigeria (Aliyu, 2000; Ogiehor and Nwafor, 2004), is produced from the dried calyces of the roselle plant Hibiscus sabdariffa by boiling and filtration. It is gaining wide acceptance, being consumed by several millions of people from different socio-economic classes and background. Zobo drink has been shown to be

good source of natural carbohydrate, protein and vitamin C which constitutes the major reason for consuming soft drink and fruit juice (Ogiehor and Nwafor, 2004). Hibiscus sabdarffa belongs to the super order Malvaceae and it is believed to originate from East Africa (Ilondu and Iloh, 2007). H. sabdariffa plants are cultivated and consumed as vegetable and tea, whereas other Hibiscus varieties are planted for the fibres they produce. It is called different names like Roselle and Sorrel in English and it is locally called zobo and Isapa in Nigeria (Adebayo-Taye and Samuel, 2000).

In spite of the increasing popularity of Zobo beverage, one of its limitations for large scale production is that it deteriorates rapidly. The drink contains microorganisms which can cause food spoilage (Omemu et al., 2006). Several groups of microorganisms (Bacillus, Streptococcus, Staphylococcus, Leuconostoc, Lactobacillus, Aspergillus, Penicillium, Geotrichum, Fusarium and Alternaria) have been associated with Zobo beverage during storage (Akinyosoye and Akinyele, 2000; Ogiehor and Nwafor, 2004). Some health implications of these spoilage microorganisms include: food poisoning, food intoxication and sometimes death in severe cases. At present, the production process is neither standardized nor mechanized. The proliferation of the associated microorganisms within the short shelf life of 4 days (Ogiehor and Nwafor, 2004) potentiates the spoilage of this relished beverage. Zobo drink is often contaminated with

enteropathogenic microorganisms with as much as 2.49x10⁴cfu/ml, which could be harmful to persons who consume large quantities of the drink (Bukar et al., 2009). Major points of contamination of the Zobo drink include: the packaging material, as most retailers package the drink in already used plastic bottles and polyethene bags, which are not properly, disinfected prior to packaging (Nwafor and Ikenebomeh, 2009). The dried calyces are also a major point of contamination as they harbor spoilage organisms such as Penicillium and Aspergillus sp. (Amusa et al., 2005) and the retailers, who seldom prepare the drink under aseptic conditions and often do not do enough boiling to reduce the microbial load in the preparation of the beverage.  Considering the increasing acceptance, socio-economic potentials and ready sources of vitamin C, the need to enhance and extend the shelf life by an effective means becomes imperative.

The deleterious role of Aspergillus niger and Penicillium citrinum in low pH and high sugar content foods have been reported (Efiuwevwere and Akoma, 1997; Prescott et al., 2002). The use of chemical preservatives at an acceptable concentration to control the growth of microorganisms in beverages is desirable and gaining research interest worldwide (Efiuwevwere and Akoma, 1997).

It is possible to improve the shelf life of Zobo beverage by slowing down the fermentation process, thus inhibiting deterioration discoloration of the zobo drink and possibly permitting large-scale production and preservation for a longer period with maximum retention of nutritive values. Ilondu and lloh (2007), Akpomedeya and Ejechi (1998), Ogiehor et al. (1998), Akinyosoye and Akinyele (2000) have demonstrated different methods of zobo preservation.

Many parts of Roselle including seeds, leaves, fruits and roots, are used in various food preparations. Among them, the fleshy red calyces are the most popular (Yadeng et al., 2005). Roselle is used in many folk medicines. In Nigeria, the dry red calyces are processed into a refreshing non-alcoholic beverage known as Zobo. Despite the fact that the popularity of Zobo juice is increasing, one of its greatest limitation for large scale production is that it has a very short shelf life of 24 hours if not refrigerated (Omemu et al., 2006). Therefore, there is urgent need to explore various preservation methods that could be employed to extend the shelf life of this product.

Dougheri et al. (2007) employed some chemical preservatives to improve the shelf life of Zobo drink. They reported that only samples treated with benzoic acid remained organoleptically attractive after 14 days of storage. However, the problem with the use of chemical preservatives in food is that they tend to have adverse effects on the health of consumers (Adesokan et al., 2010). Therefore, naturally occurring plant extracts with proven antimicrobial properties will be preferred in food preservation (Kolapo et al., 2007). The use of natural preservatives has become more popular as compared to synthetic antimicrobials and antioxidants (Aliu et al., 2007).

Ginger (Zingiber officinale) and garlic (Allium sativum) are two plants traditionally used as spices in food preparation but have been demonstrated to have both antioxidant and antimicrobial activities (Kolapo et al., 2007). Therefore, the objective of this present study was to evaluate the physico-chemical and microbiological qualities of zobo drinks blended with ginger and garlic extracts.

1.1  OBJECTIVES OF THE STUDY

1) To determine the effect of ginger on the microbial load and shelf life of zobo

2) To determine the effect of garlic on the microbial load and shelf life of zobo

3) To determine the effect of ginger and garlic on the microbial load and shelf life of zobo

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