ABSTRACT
Preservation of food is a pre-requisite for food safety and security, bridging the gap between the site of production and site of consumption and the rising between demand and supply.
There has been a problem of preserving seasonal food properly and disinfesting food without noticeable hazard to the consumer. There is also a noticeable increase in the incidence of food borne disease.
The study is aimed at determine the shelf life extension of avocado, carrot, okra and tomatoes when preserved by irradiation. To investigate the proper dose range suitable for irradiation and determine the physical changes incurred by the fruits during irradiation.
The result of the research will help to determine the shelf life extension possible when the fruits/vegetable preserved by radiation.
The assessment of the effect of radiation in the food preservation was studied using of avocado, tomatoes, carrot and okra. These fruits/vegetables were treated with three radiation doses of 30 Gy; 40 Gy and 50 Gy respectively and
stored in a under room temperature (25±2°C). The physical conditions of the radiation treated and control these fruits/vegetables were observed daily for their organoleptic properties till spoilage. In avocado, there was 100% rotting of fruit in control while 75%,87.5%,87.5% in30 Gy; 40 Gy and 50 Gy respectively indicating that 30Gy,rotting rate in avocado can be delayed. In tomatoes, at the end of the 10 days 75% of the control was rotten while 12.5%,12.5% and 25% were rotten in the 30Gy,40Gy,50Gy respectively showing that shelf life of the tomatoes can be extended with irradiation. In okra, there was 50% rotting in the control while 12.5%,12.5% and 25% was rotten in 30Gy ,40Gy, 50Gy.They shelf life of okra was extended from 3days to 8 days. In carrot, there was 100% spoilage in the control, while 50%,37.5% in the group irradiated with 50Gy,30Gy and 40Gy.The study showed that radiation doses of 30Gy and 40Gy will preserve the fruits and vegetables with less physical changes.
TABLE OF CONTENT
Title page----------i
Certificate page-----------ii
Approval page-----------iii
Dedication-------------iv
Acknowledgement---------v
Abstact ----------vi
List of tables ----------vii
List of figures ----------viii
Table of content---------ix
LIST OF FIGURES
Figure i Particle-particle collision-----24
Figure ii radioactive decay------25
Figure iii radioactive decay----- 25
Fig. iv Acceleration of Charged Particles---26
Figure v Photoelectric process ------- 29
Figure vi . Compton scattering ----- 31
Figure vii Pair production -------32
LIST OF TABLES
Table 1---------- 46
Table 2. Effect of irradiation on the delay of rotting of avocado --49
Table 3: Effect of irradiation on the delay of rotting of tomatoes---- 51
Table 4. Effect of irradiation on the delay of rotting of okra -53-
Table 5. Effect of irradiation on the delay of rotting of carrot---54
CHAPTER ONE
1.0 Background of the study------ 1
1.1 STATEMENT OF THE PROBLEM ---- 4
1.2 OBJECTIVES OF THE STUDY----- 4
1.3 SIGNIFICANCE OF THE STUDY---- 5
1.4 SCOPE OF THE STUDY------5
1.5 LITERATURE REVIEW-------5
CHAPTER TWO
THEORETICAL BACKGROUND-------23
2.0 DEFINITIONS--------23
2.1 Generation of photon particle-------24
2.2 Photon interaction with matter------27
2.3 Electron interaction with matter------34
2.4 Radiation sources use in food irradiation-----36
2.5 Dose distribution----------38
2.6 Effect of ionizing radiation on foods and food- borne microorganisms----39
2.7 DNA as the target biological molecule------41
2.8 Radiolysis of water---------42
CHAPTER THREE
RESEARCH METHODOLOGY
3.1 Research Design-----------44
3.2 Sampling Technique--------44
3.3 SAMPLE SIZE---------45
3.4 MATERIALS--------- 47
3.5 FRUITS/ VEGETABLE IRRADIATION----47
3.6 Observation---------48
3.7 Method of data collection--------- 48
CHAPTER FOUR
DATA PRESENTATION--------49
CHAPTER FIVE
DISCUSSION, SUMMARY, CONCLUSION, AND RECOMMENDATION
5.1 AVOCADO---------- 58
5.2 TOMATOES----------- 59
5.3 OKRA ---------- 60
5.4 CARROT---------60
5.5 SUMMARY OF FINDINGS------62
CONCLUSION-------- 62
RECOMMENDATION ------- 62
REFERENCES-------- 63
INTRODUCTION
Food plays a vital role in maintaining proper health and also helps in the prevention of disease. Good nutritive food makes health but unhealthy food gives rise to several diseases1. Preservation of food is a pre-requisite for food safety and security. The factors that affect food availability include: the seasonal nature of most food items, long distance between the site of food production and the site of consumption, rising gap between demand and supply.
Food preservation has been a major anxiety of man since time immemorial. Food preservation involves treating and handling food to stop or slow down food spoilage. It also helps in retaining the edibility and nutritional value of food, thereby allowing longer storage of food2.The measure of self-sufficiency and economic stability of a country is viewed through their food security which speaks volume of the preservation measures adopted3.Spoilage of stored foods is as a result of the following factors; physical/physiological, chemical, enzymatic and microbiological changes. The factor that affects food spoilage most is activity and growth of microorganism4.These organisms are the major cause of food-borne disease, they include Escherichia coli, Salmonella and Campylobacter spp. E.coli is found in leafy green vegetables, Salmonella is found in pepper, tomatoes and meat. Campylobacter is found in meat, milk or cheese5.
Food irradiation is the process of exposing food to certain amount of energy in the form of speed particles or rays for improving food safety, eliminating and reducing organisms that destroy the food product.6It is regarded as a cold and mild process because it does not significantly increase the temperature or sensory characteristics of food, it can only increase its temperature by 0.36ºC.5,7
Irradiation of food can be used in both large and small quantities and has a wide range of potentials which includes:
• Reduction of microorganism; Irradiation is a tool that can be used to reduce microorganisms particularly E.coli, Salmonella and a number of other food pathogens. Using approved doses for meat and poultry can reduce Salmonella and E.coli population up to 99.9%-99.999%.8
• Disinfestations: Parasites and insect pests, which have large DNA, are rapidly killed by radiation.
• Delay ripening and inhibiting sprouting.
Furthermore, food irradiation, being a mild process of food treatment, does not greatly affect the food quality as does other method of preservation. In thermal processing of food with high temperature, heterocyclic ring and carcinogenic aromatic compound produced.6Most food micronutrients are not affected by radiation less than 10KGy (carbohydrate, proteins and lipids) but low and medium dose affects Vitamins.
The idea of using ionizing radiation in food preservation almost immediately followed Henri Becquerel’s discovery of radioactivity in 1895. The suggestion to use ionizing energy to destroy pathogenic and spoilage microorganisms in food was published in a German medical journal, the same year. In the early 1900’s, patents were issued in the United States and the United Kingdom describing the use of ionizing radiation to destroy microorganisms in food.
Labeling of foods treated with ionizing energy has been one of the most controversial issues related to commercial production. The Joint FAO/IAEA/WHO Expert Committee concluded that for irradiated foods which had been approved as safe to eat, there was no valid scientific reason for identifying the products with a label at the retail level when similar labeling is not required for the other commonly used processing methods. Wholly irradiated foods, which are sold either in pre-packaged or bulk form, must be identified as having been irradiated, by using the international irradiation symbol. Additionally, the statement “Treated with Radiation”, “Treated by Irradiation” or “Irradiated” is required. Other statements that explain the reason for irradiation, or the benefits, may be used on the same label. The main purpose of the label is to advise consumers of the choice, rather than to warn9.
The effectiveness of processing of food by ionizing radiation depends on proper
Delivery of absorbed dose and its reliable measurement. For food destined for
International trade, it is of the utmost importance that the dosimetry techniques used for dose determination are carried out accurately and that the process is monitored in accordance with the internationally accepted procedures. Such dosimetry should be traceable to national or international standards, and thus the quality of the dosimetry results allows for the evaluation of the process reliability10.