MICROORGANISMS ASSOCIATED WITH SPOILAGE OF TOMATOES AND PEPPER

ABSTRACT

Tomato and pepper are rich source of vitamins and also rich source of minerals which makes it an essential component of food. The microorganisms associated with the spoilage of physical damaged tomatoes (Lycopersicon esculentum) and pepper obtained from three markets ( Isi gate, Ubani and Orie-ugba) in Umuahia, Abia State, Nigeria were evaluated. This analyses was conducted at two(2) days interval for a period of six days, using standard microbiological techniques. A total of five species of bacteria were isolated and identified as Staphylococcus, Salmonella, Klebsiella, Bacillus and Lactobacillus species,  while the fungal isolates isolated were Aspergillus and Penicillium species. The most prevalent bacteria isolated was Staphylococcus species with 27.3% in tomato and was found in all the samples while Klebsiella and Lactobacillus species was the least prevalent isolate with 9.1%. The most prevalent bacteria isolate in pepper was Bacillus species with 22.2% while Staphylococcus and Salmonella species were the least prevalent isolate with 11.1%. The most prevalent among the fungal isolate was Aspergillus with 27.3% in tomato and 33.3% in pepper. The microbial count of the physically damaged tomato and pepper fruit was higher compared to the count observed for fresh tomato and pepper fruit which was used as the control sample. Findings from this work revealed that the intake of spoilt tomatoes and pepper could be dangerous, since these organisms produced spores and toxins that could cause severe food poisoning that will result in disastrous outcome.

TABLE OF CONTENTS

Title page                                                                                                                                i

Certification                                                                                                                            iii

Dedication                                                                                                                               iv

Acknowledgements                                                                                                                v

Table of contents                                                                                                                    vi

List of tables                                                                                                                           ix

List of figures                                                                                                                         x

List of Plates                                                                                                                           xi

Abstract                                                                                                                                   xii

CHAPTER ONE

1.0       Introduction                                                                                                                1

1.1       Aims and Objectives                                                                                                   3

CHAPTER TWO

2.0       Literature Review                                                                                                       4

2.1       General description and scientific classification                                                        4

2.1.1    Description of Tomato                                                                                               4

2.1.2    Description of Pepper                                                                                                 5

2.1.3    Classification of Tomato                                                                                            7

2.1.4    Classification and taxonomy of Pepper                                                                      8

2.2       Origin                                                                                                                          9

2.2.1    Origin of Tomato                                                                                                        9

2.2.2    Origin of Pepper                                                                                                         10

2.3       Varieties                                                                                                                     10

2.3.1    Varieties of Tomato                                                                                                    10

2.3.2    Varieties of Pepper                                                                                                     11

2.4       Diseases and Pests                                                                                                      12

2.4.1    Diseases and Pests of Tomato                                                                                    12

2.4.2    Diseases and Pest of Pepper                                                                                       13

2.5       Nutritional Value                                                                                                        14

2.5.1    Nutritional Value of Tomato                                                                                      14

2.5.2    Nutritional Value of Pepper                                                                                       15

2.6       Medicinal Uses                                                                                                           15

2.6.1    Medicinal Uses of Tomato                                                                                         15

2.6.2    Medicinal Uses of Pepper                                                                                           17

2.7       Health Benefits                                                                                                           17

2.7.1    Health Benefits of Tomato                                                                                         17

2.7.2    Health Benefits of Pepper                                                                                           21

2.8       Spoilage                                                                                                                      22

2.8.1    Microorganisms associated with spoilage of tomatoes and pepper                                    22

2.9       Prevention of spoilage                                                                                                            24

CHAPTER THREE

3.0       Materials and Method                                                                                                 25

3.1       Sample Collection                                                                                                      25

3.2       Preparation of media                                                                                                  25

3.3       Preparation of samples                                                                                               25

3.4       Isolation and enumeration of microorganism                                                            26

3.5       Purification and maintenance of pure isolates                                                           26

3.6       Characterization and identification of bacterial isolates                                            26

3.7       Biochemical tests                                                                                                        27

3.7.1    Gram stain                                                                                                                  27

3.7.2    Indole test                                                                                                                   27

3.7.3    Methyl red (MR)                                                                                                         27

3.7.4    Voges proskauer (VP)                                                                                                28

3.7.5    Hydrogen sulphide test (H₂S)                                                                                     28

3.7.6    Citrate test                                                                                                                   28

3.7.7    Urease test                                                                                                                  29

3.7.8    Catalase test                                                                                                                29

3.7.9    Coagulase test                                                                                                             29

3.7.10  Motility Test (Stab method)                                                                                       29

3.7.11  Sugar fermentation test                                                                                               30

3.7.12  Starch test                                                                                                                   30

3.8       Fungal Characterization                                                                                             30

3.9       Statistical Analysis                                                                                                     31

CHAPTER FOUR

4.0       Results                                                                                                                        32

CHAPTER FIVE

5.0       Discussion, Conclusion and Recommendations                                                         46

5.1       Discussion                                                                                                                   46

5.2       Conclusion                                                                                                                  49

5.3       Recommendations                                                                                                      50

References                                                                                                                  53

Appendix                                                                                                                    60

LIST OF TABLES

4.1       Total viable count of the tomato samples at different days intervals                                  33

4.2       Total viable count of the pepper samples at different days intervals                                  35

4.3       Morphological identification, Biochemical Identification, Gram Reaction

and Sugar Utilization Profile of isolates from the tomato and pepper samples           37

4.4       Cultural Morphology and Microscopic Characteristics of the Fungal Isolates

from the tomato and pepper samples sold in Umuahia                                              39

4.5       Percentage occurrence of the isolates from the tomato samples                              41

4.6       Percentage occurrence of the isolates from the pepper samples                              43

4.7       Distribution of isolates from the tomato and pepper samples                                              45

LIST OF FIGURES

1          Picture showing spoilt tomatoes                                                        60

2          Pictures of some displayed fresh tomatoes and pepper in the market             60

LIST OF PLATES

1          Showing Salmonella in SSA agar                                                                              61

2          Showing S. aureus in MSA agar                                                                                61

CHAPTER ONE

1.0       INTRODUCTION

Food spoilage refers to various changes in which the food becomes less palatable or even toxic to consumers; these changes may be accompanied by alterations in taste, smell, appearance or texture. Numerous microbial defects of tomatoes and pepper are characterized by the types of microorganisms responsible for their deterioration (Akinmusire, 2011). Tomato (Lycopersicon esculentum) is a perishable vegetable widely cultivated and consumed worldwide (Agrios, 2005). It is rich in nutrients, vitamins dietary bres, and phytochemicals (Mariga, 2012). Tomato has long been used as food both in cooked as well as raw form. The deep red colouration of ripened tomato fruit is due to the presence of lycopene, a form of β- carotenoid pigment which forms the precursor of vitamin A and hence is of great nutritional value. It is a rich source of water and its composition includes 95%. Today, with an increased number of ailments of vision, these fruits rich in carotenoid pigment forms prime importance to minimize the problems related to vision. Also, tomato forms a major food component because of its wide distribution and application in a number of food stuff, they are eaten fresh in salads or processed and can be stewed, fried, baked and also used to produce soup, or used as juice.

Tomato is one of the widely consumed fresh fruit worldwide since it contributes to a healthy well balanced diet which is rich in vitamins such as vitamin, B, C, and E. Carbohydrates such as fructose and glucose; and trace elements like iron, copper, zinc, and dietary fiber ( Faostat, 2010). It is known to be a very protable crop that provides high returns for small scale farmers in most developing countries (Lemma et al., 2014). Due to its nutritive value, taste, affordability, and accessibility, there has been an increase in demand by consumers (Behravesh et al., 2012). However, isolation and identification of microorganisms that are associated with spoilage of tomatoes have gained some research focus. In most developing countries, microbial infestation of tomatoes can occur during the harvesting period, post harvesting, handling, storage, transportation, and processing by customers (Yeboah, 2011 and Barth et al., 2009), but there is a huge loss of tomato across the globe due to microbial spoilage. Since it is composed mostly of water, microbes grow best using it as its substrate. Baiyewu et al. (2007) have also reported that another means of bacterial contamination is by exposing them on benches and baskets in the open markets for customers. The proliferation of bacteria more especially in damaged tomatoes could be considered to be more harmful when such contaminated tomatoes are consumed in improperly cooked food (Valadez et al., 2012). Some studies have been carried out on bacteria associated with tomatoes and tomato products in some countries.

The fruits of pepper is drupe and when dried, it is a pepper corn. It is grown in soil that is neither too dry nor susceptible to flooding, moist, well drained and rich in organic matter. Although, peppers are used as spice all over the world, their flavour and pungent smell vary widely just as their content of the major active ingredient, Capsicum and Capsaicinoid analoques vary(Dorantes et al., 2000). Pepper play substantial roles and occupy an important nutritional consequences.

 Peppers are also good sources of nutrients - Vitamins A, C, K, and B6, calcium, iron, zinc, and fiber. The nutrient and other phytochemical composition of peppers vary with color and/or maturity stage (Deepa et al., 2007). The wide variability in capsaicin and nutrient content of peppers allows more breeding to be undertaken for improvement. Since peppers are easy to grow, harvest, process and utilize, efforts should be undertaken by extension workers, nutrition and health promoting specialists to disseminate and promote improved varieties.

The biological structure of tomato and pepper when disrupted (during harvesting, transportation and storage or by insect) can serve as a route of entry for opportunistic pathogen (Salik et al., 2008). Due to their soft textures the fruits, are easily bruised through harvesting and other postharvest handling operations such as packaging, transportation and storage (Sani and Alao, 2007). Tefera et al. (2007) states that due to poor storage conditions, resistance of fruits and  vegetables to natural disease usually decline, leading to infection by pathogens.

1.2       AIM AND OBJECTIVE

The aim of the study is concerned with isolation and identification of pathogenic bacterial and fungi agents associated with tomatoes and pepper(fresh and spoilt) sold in three central markets in Umuahia.

Objectives

The specific objectives are to;

1.      Isolate and characterize microorganisms (bacteria and fungi) from fresh healthy (unspoilt) and physically damaged (spoilt) tomatoes and pepper sold in Umuahia market.

2.      To determine the average microbial load of tomato and pepper (spoilt and unspoilt).

3.      To determine the percentage occurrence of the microbial isolates in the spoilt tomatoes and pepper.

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