ABSTRACT
This study investigated the microorganisms associated with the spoilage of tomatoes (Lycopersicon esculentum) fruit obtained from five markets namely: Orie Ugba, Ubani, Nkwoegwu, Ubakala and Ogwumabiri markets in Umuahia, Abia State, Nigeria. A total of five species of bacteria isolated and identified are: Staphylococcus, Proteus, Bacillus, Escherichia, and Pseudomonas species. The most prevalent bacterial isolate was Staphylococcus spp. with 100% and was found in all the samples while Proteus spp. was the least prevalent isolate with 40%. The fungal isolates were Aspergillus, Penicillium, Saccharomyces, Rhizopus, Mucor and Botrytis species. The most prevalent among the fungal isolates was Saccharomyces with 100% and was also found in fruit samples from all the markets. The mean bacterial load ranges were 17.33 x104 Cfu/g – 38.33 x104 Cfu/g for Orie Ugba market; 25.33 x104 Cfu/g for Ubani market; 40.00 x104 Cfu/g – 93.67 x104 for Nkwoegwu market; 21.33 x104 Cfu/g – 47.33 x104 Cfu/g for Ogwumabiri market. The mean fungal load ranges were 4.00 x102 Cfu/g – 8.33 x102 Cfu/g for Orie Ugba market; 3.67 x102 Cfu/g – 9.67 x102 Cfu/g for Ubani market; 3.67 x102 Cfu/g – 10.67 x102 Cfu/g for Nkwoegwu market; 7.00 x102 Cfu/g – 9.67 x102 Cfu/g for Ubakala market and 7.00 x102 Cfu/g – 11.67 x102 Cfu/g for Ogwumabiri market. Based on this research work, it can be agreed that the intake of spoilt tomatoes could be dangerous, since these organisms produce spores and toxins that could cause severe food poisoning that will result in fatal outcome. Moreso, fruit storage room kept at high sanitary conditions, treatment of fruits with antimicrobial agents, as well as some forms of refrigeration is necessary to increase shelf-life and reduce the rise of microbial toxins which are disastrous to human health.
TABLE OF CONTENTS
Title page - - - - - - - - - - i
Certification - - - - - - - - - - ii
Dedication - - - - - - - - - - iii
Acknowledgement - - - - - - - - - iv
Table of Contents - - - - - - - - - v
List of Tables - - - - - - - - - - viii
Abstract - - - - - - - - - - ix
CHAPTER ONE
1.0 INTRODUCTION - - - - - - - - 1
1.1 Aims and Objective of Study - - - - - - - 2
CHAPTER TWO
2.0 LITERATURE REVIEW - - - - - - - 3
2.1 Brief history and Distribution of Tomato Fruit - - - - 4
2.2 Varieties of Tomato Fruit - - - - - - - 4
2.3 Disease Symptoms due to Fungi and Bacteria in Tomato - - - 6
2.3.1 Bacterial Diseases - - - - - - - - 6
2.3.1.1 Bacterial Spot - - - - - - - - - 6
2.3.1.2 Bacterial canker: - - - - - - - - 6
2.3.2 Fungal Diseases - - - - - - - - 7
2.3.2.1 Sour Rot - - - - - - - - - 7
2.3.2.2 Rhizopus Rot: - - - - - - - - - 7
2.3.2.3 Buckeye Rot - - - - - - - - - 8
2.3.2.4 Black Mold - - - - - - - - - 8
2.4 Physiological Disorders of Tomato - - - - - - 8
2.5 Control of Postharvest Diseases and Losses of Tomato - - - 9
2.5.1 Biological Control - - - - - - - - 9
2.5.2 Chemical Control: - - - - - - - - 10
2.5.3 Physical methods: - - - - - - - - 11
2.5.3.1 Heat Treatment: - - - - - - - - 11
2.5.3.2 Waxing and coating - - - - - - - - 12
2.6 Mineral Nutrition of Tomato - - - - - - - 12
2.6.0 Responses to specific nutrients and nutrient ratios - - - - 13
2.6.1 Nitrogen - - - - - - - - - 13
2.6.2 Phosphorous - - - - - - - - - 14
2.6.3 Potassium - - - - - - - - - 14
2.6.4 Calcium - - - - - - - - - 15
2.6.5 Magnesium - - - - - - - - - 16
2.6.6 Iron - - - - - - - - - - 16
2.6.7 Manganese - - - - - - - - - 17
2.6.8 Zinc - - - - - - - - - - 17
2.6.9 Copper - - - - - - - - - - 18
2.6.10 Molybdenum - - - - - - - - - 18
2.7 Medicinal uses of Tomato - - - - - - - 19
2.8 Health Benefits of Tomato - - - - - - - 21
2.9 Spoilage of Tomatoes - - - - - - - - 27
2.10 Prevention of tomato spoilage - - - - - - 27
CHAPTER THREE
3.0 MATERIALS AND METHODS
3.1 Source of Materials - - - - - - - - 29
3.2 Sample and Media Preparation- - - - - - - 29
3.2.1 Sample and Sampling - - - - - - - - 29
3.2.2 Media Preparation - - - - - - - - 29
3.3 Isolation of Microorganism and Determination Load - - - 30
3.3.1 Spread Plate Technique - - - - - - - 30
3.3.2 Direct Placement Technique - - - - - - - 31
3.4 Purification of Pure Isolates - - - - - - - 31
3.5 Characterization and Identification of Isolates - - - - 32
3.5.1 Characterization of Fungi Isolates - - - - - - 32
3.5.2 Characterization of Bacteria - - - - - - - 32
CHAPTER FOUR
4.0 RESULTS - - - - - - - - - 38
CHAPTER FIVE
5.1 Discussion - - - - - - - - - 50
5.2 Conclusion - - - - - - - - - 51
5.3 Recommendations - - - - - - - - 52
References - - - - - - - - - 53
Appendix
LIST OF TABLES
Table | Title | Page |
1 | Microbial load of spoilt tomatoes. | 39 |
2 | Occurrence of bacterial isolates in spoilt tomatoes | 41 |
3 | Occurrence of Fungal isolates in spoilt tomatoes | 43 |
4 | Occurrence of Fungal Isolate in Spoilt Tomatoes | 44 |
5 | Occurrence of Bacterial Isolate in Spoilt Tomatoes | 45 |
6 | Colonial and Morphological Characteristics of Fungal Isolates | 46 |
7A | Characterization and Identification of Bacterial Isolates | 47 |
7B | Characterization and Identification of Bacterial Isolate | 48 |
7C | Characterization and identification of bacterial isolate | 49 |
CHAPTER ONE
3.0 INTRODUCTION
Tomato (Lycopersicon esculentum) is a berry plant in the Solanaceae family. It is a short lived perennial plant grown as an annual plant, typically growing about 3-5m approximately in height. The fruit is edible, bright red coloured berry. The tomato plant is widely cultivated in many parts of the world. The tomato fruit has a smooth skin and it is green when immature but becomes bright red or yellow as it ripens (Maddox, 1998).
Tomato fruits are very rich in vitamins such as vitamin A, B, C, and E, carbohydrates such as fructose and glucose; minerals include phosphorous, sodium, calcium, magnesium and trace elements like iron, copper, and zinc (Udoh et al., 2005). It is estimated that ripe tomato fruits contain approximately 94% water, 4.3% carbohydrates, 1% fat, and 0.6% fibre and vitamins. The nutrients support the growth of microorganisms such as fungi and bacteria, which produce enzymes that degrade the nutrients (Maddox, 1998). Tomato fruits contain a lot of water which makes them more susceptible to spoilage by microorganisms and also the high water content makes storage and transportation of this fruit difficult. The microorganisms reduce not only the nutritional value but also the market value of tomato fruits.
Tomato, however, have serious challenges to their existence these include; climatic condition, pest, bacterial and fungal attack. Over the years, there has been an increase in the need to identify and isolate the microorganisms associated with their spoilage (Akinyele and Akinkumi, 2012).
Spoilage refers to any change in the condition of food 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 agricultural crops are characterized by the types of microorganisms responsible for their deterioration (Akinmusire, 2011). Susceptibility of tomato to microbial colonization is due to its differential chemical composition such as high level of sugar, low pH (4.9-6.5) and its high water activity which favours the growth of micro-organisms in tomato is recognized as a source of potential health hazard to man and animals, this is due to their production of toxins which are capable of causing disease like respiratory infection, meningitis, gastroenteritis, diarrhoea in man following ingestion (Beuchat, 2006).
Tomato fruits are usually displayed on benches and in baskets for prospective customers in the open markets until sold, thereby exposing their further microbial infection beside those associated with these whole fruit surface and those from adjacent fruits (Baiyewu et al., 2001). In developing countries, post harvest deterioration are often more severe due to inadequate storage and transportation facilities. Microbial fruits infection may occur during the growth season, harvesting, handling, transport and post harvest storage and marketing conditions, or after purchasing by the consumer (Singh and Sharma, 2007). Those types of soil borne spoilage microbes that occur on produce are the same spoilage microorganism that are present on harvesting equipment, on handling equipment, in the packaging house, in the storage facility, and on food contact surfaces throughout the distribution chain (Barth et al., 2009).
Therefore, early intervention measures during crop developments and harvesting through the use of good agricultural practices (GAP) will provide dramatic reductions in the yield loss due to deterioration at all subsequent steps in the food (Barth et al., 2009).
1.1 Aims and Objective of Study
This research aimed at the following:
· To isolate and identify the microorganisms associated with spoilage of tomatoes.
To enumerate and characterize the microorganisms involved in spoilage of tomatoes.
Login To Comment