Advisory Council on Food and Environmental Hygiene
Use of Irradiation in Food Technology
This paper sets out the application of irradiation in food technology, the related safety concerns and control measures.
2. Application of irradiation in food technology has been developed and studied extensively for over 50 years. To date, around 35 countries have set up irradiation plants to treat over 40 kinds of foodstuffs, including spices, fruits, vegetables, cereals, poultry and fish.
Principle of Food Irradiation
3. Food irradiation is treatment of foods by ionizing radiation. It is quite different from thermal processing, such as cooking by heat or microwave. The unique feature of irradiation process is that it causes no increase in temperature of treated foodstuffs and is therefore often termed as a "cold" process. Codex Almentarius Commission (Codex) has recommended two types of sources for food irradiation. They are -
- Machine sources of ionizing radiation: They refer to electron accelerators and X-ray generators. Both emit forms of energy that can penetrate into food substances.
- Radionuclides: They are isotopes that give off ionizing gamma-rays during its degradation. Cobalt-60 and caesium-137 are commonly used in the food industry.
4. Irradiation may be applied at various levels of food processing. It does not make food radioactive. It reduces or eliminates pathogenic bacteria, insects and parasites. It also reduces spoilage. In certain fruits and vegetables, it inhibits sprouting and delays the ripening process. Through food irradiation, harmful bacteria such as E. coli 0157:H7, Salmonella and Campylobacter can be effectively reduced. In general, irradiation does not compromise the nutritional quality of food, or noticeably change their taste, texture or appearance as long as it is properly applied to a suitable product.
5. Food irradiation has advantages over other food preservation methods. The use of some chemical treatment can be reduced. For example, it can reduce the use of the fumigants, ethylene oxide1(ETO), in sanitizing herbs, spices, nuts and oilseeds. Food irradiation also has an advantage over the traditional thermal treatment in cases where heating is undesirable for the commodities in question, e.g. frozen food, fresh fruits and vegetables.
6. However, irradiation does have its limitations. Certain microorganisms such as viruses are more resistant to the usual doses of irradiation. When the radiation dose is high enough for sterilizing these substances, side effects such as undesirable colours, odours, tastes, etc. may occur.
Safety Concerns Related to Food Irradiation
7. Assessment of the safety and wholesomeness of irradiated food for human consumption have been extensively assessed under the following aspects: (i) toxicological safety, (ii) microbiological safety, (iii) radiological safety, and (iv) nutritional adequacy. The Joint Food and Agriculture Organisation / International Atomic Energy Agency / World Health Organisation (FAO/IAEA/WHO) Study Group on Irradiation completed an assessment on the safety and wholesomeness of irradiated food in 1999. In terms of health risk, the Study Group came to the following conclusions -
- Food irradiated to any dose appropriate to achieve the intended technological objective is both safe to consume and nutritionally adequate; and
- Irradiation to high doses is essentially analogous to conventional thermal processing in order to eliminate biological hazards, including pathogenic and spoilage microorganisms, but does not result in the formation of physical or chemical entities that could constitute a hazard.
Labelling of Irradiated Food Products
8. In 1999, Codex developed a set of labelling guidelines for irradiated food. It recommended that pre-packaged food products which have been treated with ionizing radiation should carry written statements indicating that the products have been treated with irradiation.
9. In Hong Kong, the Food and Drugs (Composition and Labelling) Regulations, Public Health and Municipal Services Ordinance (Cap. 132) stipulate that irradiated food sold for human consumption should be clearly and legibly marked with the words "IRRADIATED" or "TREATED WITH IONIZING RADIATION" in English capital lettering, "��ӭ��~" in Chinese characters.
10. We carry out regular surveillance on the proper labelling of irradiated food. In 2000, 69 food samples were taken for detection of ionizing treatment. 6 samples were found positive. As these products do not bear proper irradiation labelling, warning letters were issued to their sellers requesting the products either be withdrawn from the market or properly labelled. In all cases, the products were withdrawn from the market and no further non-compliance was detected.
Food and Environmental Hygiene Department
1Ethylene oxide is a colourless and flammable gas. It may reasonably be anticipated to be a carcinogen. Potential symptoms of overexposure are irritation of eyes, nose and throat; peculiar taste; headache; nausea, vomiting and diarrohea, etc.