ISOLATION AND CHARACTERIZATION OF FUNGI ASSOCIATED WITH “SPOILED” TOMATOES IN GWAGWALADA

1.1 Introduction

Tomato is the most perishable vegetable during handling, transportation and storage. This is because tomato contains large amount of water which makes them susceptible to spoilage by the action of microorganisms such as fungi, bacteria and protozoans (Ross, 1975). Estimates have shown that about one third of the produce is lost before reaching the consumer (Erinle, 2007), this loss has been attributed to a number of factors which include physical (mechanical breakage, bruises), physiological and also damages caused by pathological agents (Thompson and Kelly, 2000), market value of the tomato are mainly reduced by this factors.

As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.

---

1.2 Background to the Study

Tomatoes are tomatoes usually peeled that are sealed into a canned after having been processed by heat. This product is considered important worldwide (Robinso, et al, 1994). In Nigeria tomato paste is the most important tomato product because of its wide spread use for preparation of various food/menus. It contain on the average about 6.4% total solids, of which 3.5% is invert sugar, 0.5% citric acid,0.6% ash, 0.9% protein, 0.53% crude fibre and about 0.05% fat.

When spoil as a result of the life processes of bacteria, yeast and molds, the sugars are rapidly used up being changes into acetic acid, lactic acid, alcohol and carbon dioxide, the amount of these substances depending on the types of organism which are most active in the particular sample in question. Until recent years, nearly all the tomato paste consumed in Nigeria was important from European countries with Italy being the leading country. However, today, limited brands are produced locally. Although both the imported and the local brands are available on the market, consumers prefer the former in spite of its relatively higher cost.

In general, adequate heat processing is given to tomato paste to achieve commercial sterility (speck, 1984), but subsequent abusive post-process handling/storage may lead to undesirable microbiological changes (Anon, 1980). It is public knowledge that can of tomato paste often show external evidence of spoilage under tropical retail conditions. In addition, and interestingly, these d effective products are sold (especially to the less informed) at the same cost as the normal (non-defective- product. The structural systematic approach for the control of food safety “Hazard Analytsis and critical control point-HACCP” identifies, evaluated and controls hazards that are significant for food safety. The control parameters include various factors such as time of harvesting, temperature and moisture during storage, selection of agricultural products prior to processing, decontamination conditions, addition of chemicals at final product storage ((Sango, 1995).

Tomato (lycopersicumesculentum) is an animal plant, having a weak woody stem covered with glistering red iscultivated in many parts of the world. The tomato plant is widely cultivated in many parts of the world and also has a smooth stain. It is green when immature but becomes bright red or yellow as it ripens. These products are considered important worldwide (Robins et al; 1994).

Tomato fruit is a well vegetable eaten raw as salad or for garnishing various foods in Nigeria as well as in many part of the world. The fruit contains high amount of carbohydrate, fat, organic acid, water, minerals, vitamins and pigments (Reddy, 2009). When spoilt as a result of life process of bacteria, yeast and molds, the sugar are rapidly used up being changes into acetic acid lactic acid, alcohol and carbondioxide, the amount of these substances depending on their types of organism which are most activities particular sample in question.

In generally, adequate heat processing is given to tomato paste to achieve commercial sterility (speck 1994), but subsequent abusive post process handling /storage may lead to understand microbiological changes. It is public knowledge that can of tomato paste often show external evidence of spoilage under tropical retail condition (Anon, 1980).

Tomato fruit contains a lot of water which makes them susceptible to spoilage by microorganism. Also, the high water content makes storage and transportation of vegetable difficult. The microorganism reduces not only the nutritional values but also the market value s of tomato fruit. Micro organisms also affect the seller due to the spoilage of tomato. Hazard analysis and critical control point − HACCP identifies evaluate and control hazards that control or significant for food safety (De Rover, C. 1998)food safety (De Rover, C 1998). The control of parameter include various factors such as time of harvesting, temperature and moisture during storage, selection of agricultural product prior to processing, decontamination conditions, addition of chemicals at final product storage (Sango, 1995).

Tomatoes were chosen for this study because they are referred to as ready-to-eat food since they are manually processed and many people take tomatoes raw directly or via meals of salad usually served cold. Microbial spoilage and contaminating pathogens on this product poses a serious problem in food safety. Ecological factors influencing survival and growth of human pathogens or raw growth of human pathogen on raw fruit and vegetables. There are vew reports of studies on micro-organism associated with spoilage of tomato fruit in Nigeria. Similar research cost of test ripened tomato fruits sold in local markets in Benue State has tended to turn the worry public to patronize spoilt tomato fruit because they are relatively cheap. (Benchat, L.R.:2002).

The study was under taken to isolate and identify micro-organisms that are associated or responsible for the spoilage of Tomato sold in some market within Benin City. In addition, the study investigated the toxin producing capacity and the susceptibility of micro-organisms to some antibiotics.

---

1.3 Statement of the Problem

Tomatoes are an attractive cash crop for small scale farmers and provide potential source of employment to many rural and urban people. The tomato fruits have been marketed freshly picked from the field and is the best selling fresh market vegetable crop (AVRDC, 2006).

Despite the human need of tomato, damage as a result of post-bacteria spoilage micro-organisms has been of serious concern. Microbial decay is one of the main factors that determine losses and compromises the quality of the produce. The extent of the losses especially through microbial decay has not been quantified in most areas and on this has been quantified the result are short lived.

Periodic surveys may help to understanding the seventy of losses in a specific place and at a specific time. Estimates of post harvest losses in Benue State have of been established. Therefore, the study aims at establishing estimates of post harvest losses in Nigeria, identify pathogens involved in post a harvest decay of tomato fruits and evaluate ways of managing them using crude plant extracts.

Several kinds of synthetic fungicides have been successfully used to control the post harvest decay of fruits and vegetable (Adasaveg et al, 2009, Kanetis et al, 2002). However, there are three major concerns the increasing consumer concern over pesticide residues on foods which are toxic and caranogenic, predominance of fungicide resistance strains of fungi due to excessive use of fungicides.

− Environmental pollution. Therefore there is need for effective means of post harvest disease control that poses less risk to human health and the environment.

Natural plant products and their analoges have been found as important sources of agricultural bio-pesticides which serve as anti-microbial properties of the plant extracts (Cardelina, 1995, Okigbo, 2009). Arokiyaraj et al (2008), (2009), reported that plants are sources of natural pesticides that lead in new pesticide development. Anti-fungal and anti-bacterial components of neem plant leaf, ginger rhizome, and garlic bulb crude extracts on root pathogen of post harvest tomatoes fruits were also targeted in this study.

---

1.4 Aim and Objectives of Study

The aim of the Study is to identify the various fungi organisms associated with the spoilage of fresh tomatoes in Gwagwalada with the view of mapping out strategies to curtail these fungal attacks and also to determine the effects of the isolated fungi on the spoiled tomatoes. In achieving this aim, the following specific objectives were laid out as follows:

• To isolate of fungi organism from spoilt tomatoes in Gwagwalada.
• To characterize and identify of the fungi in spoilt tomatoes.
• To determine the prevalence and pathogenicity of fungal organisms.
• To create public health awareness about the preponderance of fungal organisms.

---

1.5 Research Questions

The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:

• What are the microorganisms associated with the spoilage of Tomatoes?
• What are the isolates using morphological and biochemical characteristics?

---

1.6 Research Hypothesis

In order to pursue the objective of this study, the following generalized statements have been designed to guide and aids in obtaining the result for the experiment to be conducted. For this work, the null hypothesis will be represented with H0 while the alternative hypothesis will be represented with hypothesis H1.

• H0: Fungi are not responsible in the spoilage of tomatoes.
• H1: Fungi are responsible in the spoilage of tomatoes.

---

1.7 Significance/Justification of the Study

Since microorganisms have been identified with the major cause of spoilage in fruits and vegetables due to their high water content, proper isolation and characterization of these organisms in tomatoes will greatly reduce the spoilage of this perishable fruit and as such producers and consumers will be able to protect their vegetables (tomato) and also identify spoiled tomatoes that have been attacked by fungi.

Works have been done on the isolation and identification of bacteria and fungi on fruits (Okoli, 1998). Little or no work has been done on the isolation and characterization fungi on spoiled tomatoes in Gwagwalada. Therefore, the major organisms responsible for field and market diseases will be majorly identified and checked.

---

1.8 Scope of Study

The study focuses on the Isolation and Characterization of Fungi Associated with “spoiled” Tomatoes in Gwagwalada, FCT Abuja.

---

1.9 Limitations of the Study

During the course of this study, many things militated against its completion, some of which are:

1. Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
2. Research material: availability of research material is a major setback to the scope of the study.
3. Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
4. Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).