1.1 Introduction
Food Irradiation is the process of exposing food to ionizing radiation to disinfect, sanitize, sterilize, preserve food or to provide insect disinfestation (Wikipedia, 2021).
Food irradiation is sometimes referred to as cold pasteurization or electronic pasteurization to emphasize its similarity to the process of pasteurization. Like pasteurization of milk and pressure cooking of canned foods, treating food with ionizing radiation can kill bacteria and parasites that would otherwise cause food borne diseases (Wikipedia, 2021; CDC, 2021).
By irradiating food, depending on the dose, some or all of the microbes, fungi, viruses or insects present are killed. This prolongs the life of the food in cases where microbial spoilage is the limiting factor in shelf life. Some foods (e.g. herbs and spices) are irradiated at such high doses (5kGy or more) that they show microbial counts reduced by several orders of magnitude. It has also been shown that irradiation can delay the ripening or sprouting of fruits and vegetables and replace the need for pesticides.
Studies have shown that when Irradiation is used as approved on foods:
- Disease-causing germs are reduced or eliminated.
- The food does not become radioactive
- Dangerous substances do not appear in foods
- The nutritional value of the food is essentially unchanged (CDC, 2021).
In the food industries, specific types of radiation treatments are used, they are Radurization, Radicidation, and Radappertization. However, in the actual process of irradiation, three different irradiation technologies are used namely; gamma irradiation, electron-beam irradiation and x-ray radiation (CDC, 2021).
The dose of irradiation is usually measured in a unit called the Gray, abbreviated (Gy). This is a measure of the amount of energy transferred to food, microbes or other substances being irradiated. To measure the amount of irradiation something is exposed to, photographic film is exposed to irradiation at the same time.
The killing effect of irradiation on microbes is measured in D-values. One D-value is the amount of irradiation to kill 90% of that organism. For example, it takes 0.3kGy to kill 90% of Escherichia Coli, so the D-value of E.coli is 0.3 kGy. (www.cdc.gov).
A distinctive logo has been developed for use on food packaging, in order to identify a product as irradiated. This symbol is called the “radura” and is used internationally to mean that the food in the package has been irradiated. (www.cdc.gov)
1.2 Food Irradiation Developments
There is a widening gap in the less developed countries (LDC’s) of Africa, Asia and Latin America between the growth rates of population and food production. Yet, in LDC’s over a quarter of the harvested food is lost due to wastage and spoilage. In Nigeria, very high losses of foods, especially highly perishable foods such as fish, fruits, vegetable and some dietary staples such as yam, maize, millet and sorghum occur in the time lag between harvest and consumption and during storage. There is, therefore, the need for greater utilization of the available appropriate technologies of food preservation in these countries (Aworh, 1986).
In the last three decades a new technology, food irradiation, has been developed which has the potential of reducing food losses in LDC’s (Aworh, 1986).
Research on Food irradiation dates back to the turn of the 20th century. The first US and British patents were issued for use of ionizing radiation to kill bacteria in foods in 1905. Food irradiation gained significant momentum in 1947 when researchers found that meat and other foods could be sterilized by high energy and the process was seen to have potential to preserve food for military troops in the field. To establish the safety and effectiveness of the irradiation process, the U.S. Army began a series of experiments with fruits, vegetables, dairy products, fish and meat in the early 1950’s. (www.ccr.uc davis.edu).
In 1958, Congress gave the FDA authority over the food irradiation process under the 1958 Food Additive Amendment to the Food, Drug and Cosmetic Act. The FDA has approved food irradiation process for wheat, potatoes, pork, spices, poultry, fruits, vegetables and red meat (www.ccr.uc davis.edu).
Food irradiation was recognised by the United Nations which established the Joint Expert Committee on Food Irradiation. Their first meeting was in 1964. The committee concluded in 1980 that “irradiation of foods up to the dose of 10kGy introduces no special nutritional or microbiological problems” (www.ccr.uc davis.edu).
In 1999, the World Health Organisation determined the dose limitation at very high dose is palatability etc. Irradiation should be considered parallel to cooking in all aspects of safety (www.ccr.uc davis.edu).
Tremendous progress has been made, in the past few decades, in the design and construction of safe radiation facilities and chances of radiation accidents are now very remote provided that personnel have been properly trained in the operation of radiation facilities (Aworh, 1986).
