Brief Introduction

Vegetables are vital agricultural products for human consumption worldwide. They are herbaceous plants, with soft stems and with a high degree of moisture content. They can be grouped according to the edible parts of different plants which are leaves (lettuce), stalks (celery), root (carrot), tubers (potatoes) and bulbs (onions). Fruits like tomatoes are considered vegetables.

Plant foods are a rich source of nutrients (Steinmetz and Potter, 1996). Vegetables enhance the nutritional quality of diet because of their richness in vitamins and minerals such as carotene (provitamin A), ascorbic acid, riboflavin, iron, iodine, calcium etc (Ihekoronye and Ngoddy, 1985). The deficiency of these nutrients can lead to widespread diseases and in the long run, lead to death. Vegetables are also rich in fibres which are essential for good digestion.

Results from the Global Burden of Disease project for the year 2000 show that up to 2.7 million deaths worldwide and 1.8 per cent of the total global disease burden may be attributed to inadequate consumption of food and vegetables (Lock et al., 2004). There is a proper need to address the production, preservation and storage of vegetables to reduce the death rate caused by the defect of the needed nutrients.

Vegetables should be consumed in a fresh state because they are usually perishable. (Olosunde, 2006) .In Nigeria, the bulk of these items such as tomatoes, bananas, plantains, mangoes and leafy vegetables, are produced and marketed by peasant farmers and these people have an inadequate means of proper handling, transportation and storage (Dzivama, 2000).In their fresh form, most fruits and vegetables contain 80 per cent water with some varieties such as cucumber, lettuce and melons containing about 95 per cent (Sanni, 1999).

Table of Content

TITLE
CERTIFICATION
ABSTRACT
ACKNOWLEDGEMENTS
DEDICATION
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF PLATES

CHAPTER ONE:
INTRODUCTION
1.1 GENERAL BACKGROUND
1.2 STATEMENT OF PROBLEM
1.3 JUSTIFICATION
1.4 OBJECTIVE OF STUDY
1.4.1 SPECIFIC OBJECTIVES

CHAPTER TWO:
LITERATURE REVIEW
2.1 HISTORY OF EVAPORATIVE COOLERS
2.2 ADVANCES IN EVAPORATIVE COOLING TECHNOLOGY
2.3 FACTORS AFFECTING SHELF LIFE OF FRUITS AND VEGETABLES
2.3.1 Ambient conditions
2.3.1.1 Temperature
2.3.1.2 Relative humidity
2.3.2 Variety and stage ripening
2.4 FACTORS ACCOUNTABLE FOR DETERIORATION IN FRUITS AND VEGETABLES
2.4.1 Physiological activity
2.4.2 Pathological infection
2.4.3 Mechanical injury
2.4.4 Water evaporation
2.5 POST-HARVEST CHANGES IN THE QUALITY OF FRUITS AND VEGETABLES
2.5.1 Colour change
2.5.2 Loss of weight
2.5.3 Fruit firmness
2.5.4 Change in total soluble solids
2.6 PRINCIPLES OF EVAPORATIVE COOLING
2.6.1 Evaporative cooling and the Psychrometric chart
2.6.2 Factors affecting evaporative cooling
2.7 METHODS OF EVAPORATIVE COOLING
2.7.1 Direct evaporative cooling
2.7.2 Indirect evaporative cooling
2.8 FORMS OF DIRECT EVAPORATIVE COOLING
2.8.1 Passive-direct evaporative cooling
2.8.2 Non-passive direct evaporative cooling
2.9 ENERGY CHANGES DURING EVAPORATIVE COOLING
2.9.1 Vapour transmission through materials
2.9.2 Heat and mass balance for pad-end
2.10 COOLING PAD MATERIAL

CHAPTER THREE:
MATERIALS AND METHODS
3.1 DESIGN OF THE EXPERIMENTAL COOLING DEVICE
3.1.1 Design principles
3.2 MATERIALS OF CONSTRUCTION
3.3 FEATURES OF THE COOLER
3.3.1 Pad-end
3.3.2 Water distribution system
3.3.3 Storage cabin
3.3.4 Fan position
3.4 PAD MATERIALS SELECTION
3.5 EXPERIMENTAL METHOD AND PROCEDURE
3.5.1 No-load test of the evaporative cooling system
3.5.1.1 Temperature and relative humidity measurement
3.5.2 Heat load of the evaporative cooler
3.5.3 Load test of the evaporative cooling system
3.5.3.1 Physiological weight loss
3.5.3.2 Colour Changes
3.5.3.3 Fruit Firmness

CHAPTER FOUR:
RESULTS AND DISCUSSIONS
4.1 Physical Properties of Pad materials
4.2 No-Load Test of the Evaporative Cooler with Jute Bag
4.2.1 Temperature Readings
4.2.2 Relative Humidity Readings
4.2.3 Cooling Efficiency
4.3 ASSESSMENT OF THE QUALITY OF STORED PRODUCTS
4.3.1 Physiological weight loss
4.3.2 Colour changes
4.3.3 Firmness

CHAPTER FIVE:
CONCLUSIONS AND RECOMMENDATIONS
REFERENCES
APPENDICES