DETERMINATION OF MICROBIAL LOAD ON SOME COMMON SALAD VEGETABLES SOLD IN AHIA EKE MARKET, UMUAHIA

ABSTRACT

Salad vegetables are consumed without any heat treatment, sometimes without washing or peeling. Salad vegetables also promote good health but harbor a wide range of microbial contaminants. Vegetables get contaminated with pathogenic microorganisms while growing fields or orchard or during harvesting, post harvesting, handling, processing and distribution. To assess the microbial \quality of salad vegetables sold in Ahia-Eke market, 5 samples of different salad vegetables were purchased from two different vendors. Samples were analyzed to determine the microbial load using MacConkey and Sabouraud agar Microbial load ranged from 9.9  105 to 1.2  106 Cfu/ml for vendor A and 2.9 106 to 9.7 106 Cfu/ml for vendor B for the bacteria isolates; the microbial load for the fungal isolates ranged from 3.0 5 to 6.3 105Cfu/ml for vendor A and 2.6 6 to 5.96Cfu/ml for vendor B. Six bacterial isolates were identified and Staphylococcus aureus was more predominant (24.6%), Bacillus species (11.5%) and Pseudomonas species(11.5%) were the least; four fungal isolates were identified and Aspergillus species were more predominant (29.4%) and Geotrichum was the least predominant (14.9%). The present study revealed the potential hazard of consuming pathogen contaminated salad vegetables; therefore there is need for thorough washing with safe running water before consumption to reduce the number of microorganisms and to safeguard health.

TABLE OF CONTENTS

Title page

Certification i

Dedication ii

Acknowledgements iii

Table of Contents iv

List of Tables viii

Abstract ix

CHAPTER ONE

INTRODUCTION

1.0 Introduction 1

1.1 Aim 3

CHAPTER TWO

LITERATURE REVIEW

2.0 Overview 4

2.1 Salad vegetables 5

2.1.1 Cabbage 5

2.1.1.1 Green cabbage 6

2.1.1.2 Red cabbage 6

2.1.1.3 White cabbage 7

2.1.1.4 Chinese cabbage 7

2.1.1.5 Nutritional and medical properties of salad cabbage 7

2.1.2 Carrot 8

2.1.2.1 Nutritional importance of salad carrot 9

2.1.3 Cucumber 9

2.1.3.1 Nutritional and medical properties of salad cucumber 10

2.1.4 Green peas 12

2.1.4.1 Nutritional value of green peas 13

2.1.5 Green pepper 13

2.1.5.1 Nutritional value of green pepper 14

2.2 Pathogenic microorganism associated with fresh produce of salad vegetables 14

2.2.1 Pathogens of concern – Bacteria 15

2.2.2 Spore-forming pathogenic bacteria 20

2.2.3 Pathogens of great concern – Viruses 20

2.3 Sources of contamination 21

2.3.1 Pre-harvest 22

2.3.2 Harvest 24

2.3.3 Post- harvest 25

CHAPTER THREE

MATERIALS AND METHODS

3.1 Sample collection 26

3.2 Sample processing 26

3.3 Media preparation 26

3.4 Identification of isolates 27

3.5 Biochemical tests 27

3.5.1 Catalase test 27

3.5.2 Coagulase test 28

3.5.3 Oxidase test 28

3.5.4 Indole test 28

3.5.5 Citrate test 29

3.6 Motility test 29

3.7 Gram staining

CHAPTER FOUR

RESULTS 31

CHAPTER FIVE

5.0 Discussion 39

5.1 Conclusion and Recommendation 40

REFERENCES 42

LIST OF TABLES

Table Title Pages

1 Biochemical characterization of isolates 32

2 Microscopic characterization of fungal isolates 33

3 Total bacterial count (Cfu/ml) of Salad vegetable samples 34

4  Total fungal count (Cfu/ml) of Salad vegetable samples 35

5 Isolated organisms 36

6 Prevalence of bacteria isolated 37

7 Prevalence of fungal isolates 38

CHAPTER ONE

INTRODUCTION

1.0 INTRODUCTION

Vegetables are defined as plants, usually herbaceous plants that contain an edible portion which suitably is served with the main course of a meal. Although the line between fruits and vegetables is sometimes vague, the stipulation that the plant should be herbaceous helps to clarify the issue. This definition is useful in classifying some of the plant foods that might otherwise be confusing. For example, tomatoes are conveniently designated as vegetable because they grow on a vine that withers at the end of the growing season, and they are generally served with the main course than as dessert. (Beuchat, 1996).

A contrast is presented by rhubarb which does grow vigorously and then withers but this plant food is classified as a fruit because its common use is in desserts, such as A\ pies and sauces.

Vegetable salad is composed of different kinds of fresh raw vegetables, they include leafy vegetables (lettuce), stem vegetables (asparagus), root vegetable (carrot), flower vegetables (broccoli), bulbs (onions and garlic) and botanical fruits such as cucumbers, squashes, pumpkins, legumes such as green peas, as well as leafy immature seeds such as those of peas or beans (Beuchat, 1996).

Vegetables have been cherished for their nutritional values. They provide little protein and fat. Apart from being rich in crude fibers, they contain water – soluble vitamin, like vitamin B and vitamin C; fat soluble vitamins including vitamin A and vitamin D, they also contain carbohydrates and minerals. Fresh produce provide anti-oxidants and other compounds that may lower the risk of cancer and other chronic diseases such as heart diseases. Vegetables are important as part of a healthy diet (Little, et al. 1999).

Salad vegetables are consumed without any heat treatment, sometimes without washing and peeling and therefore the possibility of food borne diseases are more. Vegetables can become contaminated with pathogenic microorganisms during harvesting through human handling, harvesting equipment, transport containers, wild and domestic animals (Beuchat, 1996). The pathogenic microorganisms which reside in intestinal tracts of animals or humans are more likely to contaminate vegetables through feces, sewage, untreated irrigation water or surface water (Nguyen – the dan Carlin, 1994; Dunn, et al., 1995, Carmo, et al, 2004).

Unsafe water used for rinsing the vegetables and sprinkling to keep them fresh is also a source of contamination (Mensah, et al., 2002)

Also, in developing countries such as Nigeria, continued use of untreated waste water and manure as fertilizers for the production of vegetables is a major contributing factor to contaminations (Olayemi, 2007; Amoah, et al., 2009).

Thus despite their nutritional and health benefits, outbreaks of human infections associated with the consumption of fresh or minimally processed vegetables have increased (Hedberg, 1994; Altekruse and Swerdlow, 1996; and Beuchat, 2002). Enteric pathogens such as Escherichia Coli and Salmonella are among the greatest concerns during food related outbreaks (Buck et al., 2003). Several cases of typhoid fever outbreak have been associated with eating contaminated vegetables grown in or fertilized with soil or sewage (Beuchat, 1998).

Also, several outbreaks of gastroenteritis have been linked to the consumption of contaminated fresh vegetables. The worlds’ largest reported vegetable borne outbreak occurred in Japan in 1996 in which 11,000 people were affected and about 6,000 cultures were confirmed. The outbreak involved the death of three (3) children and was carried by
Escherichia coli (Beuchat, 1995). Beuchat also reported the presence of Aeromonas, Bacillus cereus, Campylobacter, Escherichia coli, Salmonella, Shigella and Staphylococcus species on salad vegetables (Beuchat, 1998).

1.1 AIM

Salad vegetables pick microorganisms from the soil on which they are planted, the manure used to improve the quality of the soil and water used for irrigation purposes. Also, salad vegetables can be contaminated during handling, packaging and storage and while on transit. When these vegetables are consumed raw or unwashed, the likelihood of endangering the health of consumers especially when the microorganism present includes the pathogenic ones increases.

Therefore, this project/research work is aimed at:

1. Determining the microbial load of some common salad vegetables sold in Ahiaeke market in Umuahia, Abia State.

2. Characterizing pathogens present in the salad vegetables

3. Highlighting possible health implications of eating raw salad vegetables

4. To reduce the risk of microbial contamination from farm-to-fork and to assure safe product and food safety.

5. Protection of salad vegetables from contamination and spoilage during subsequent handling, packaging and while on transit. 

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