Food safety

High-dose irradiation: wholesomeness of food irradiated with doses above 10 KGy, a joint FAO/IAEA/WHO study group. Geneva, Switzerland, 15-20 September 1997

Technical Report Series, No 890
ISBN: 92 4 120890 2

Summary

This report presents the conclusions and recommendations of a group of experts convened to assess the safety and nutritional adequacy of food irradiated to doses above 10 kGy. Noting growing concern over the microbiological safety of the food supply, the report responds to the need for average doses higher than 10 kGy to ensure that food items, particularly meat and poultry, are rendered consistently free of pathogens. Other technological objectives of high-dose irradiation include the decontamination of low-moisture products, such as spices, herbs, and dried vegetables, the preparation of sterilized meals or meal components for hospitalized patients, and the production of shelf-stable hygienic products that reduce the need for refrigeration and frozen storage and can thus facilitate safe food distribution under tropical and subtropical conditions.

With these public health applications in mind, the report draws on over four decades of research to address the complete range of questions raised by high-dose food irradiation. Some 500 references to the literature are included. In reviewing this vast body of evidence, the experts also identify several conditions and procedures that constitute good irradiation practices for specific applications. Principles of risk assessment, important for regulatory authorities, are likewise considered in this comprehensive assessment.

The report opens with a brief history of food irradiation, its regulatory control, and the rationale for the upper limit of 10 kGy established by WHO in 1980. The importance of food irradiation as a public health technology is also briefly discussed. Against this background, section two, on radiation chemistry, reviews studies of the chemical changes in foods and food constituents detected after high-dose irradiation, giving particular attention to the complex physical and physicochemical processes observed in muscle foods. The experts also considered evidence that foods of similar composition show similar chemical and microbiological responses when similarly irradiated, thus supporting the validity of granting broadly-based generic approvals of high-dose irradiated foods.

A section devoted to nutritional considerations reviews findings from numerous studies of the effects of high-dose irradiation on macro- and micronutrients. Apart from confirming the commonality and predictability of radiation effects, these studies support the conclusion that irradiated foods are, from a nutritional viewpoint, substantially equivalent or superior to thermally sterilized foods.

Microbiological considerations are addressed in section five, which reviews the effects of irradiation on microorganisms and the factors influencing their radiation resistance. Studies evaluated cover vegetative bacterial cells, animal parasites, yeasts, mould propagules, bacterial spores, viruses, and preformed microbial toxins. On the basis of this exhaustive review, the report concludes that high-dose irradiation is no different from thermal processing in producing shelf-stable, microbiologically safe foods.

A section devoted to toxicological safety reviews findings from a considerable number of animal investigations and clinical studies using human volunteers. Animal investigations, which are summarized in 39 pages of tables, include carcinogenicity bioassays and multigeneration reproductive toxicity evaluations. Together, these studies support the conclusion that irradiated foods using a variety of sources under a variety of conditions are toxicologically safe for human consumption.

Section seven addresses the important role packaging plays in facilitating irradiation processing, in protecting irradiated food from recontamination, and in maintaining the quality of the food. Although studies of flexible packaging are stressed, the report also assesses the suitability of all available packaging materials for use in high-dose applications, and recommends the best candidate materials and processes for the development of future generations of packaging for radiation-sterilized food. The final section considers the processing and environmental conditions and control procedures essential for ensuring that a food product is sterilized within the targeted dose range.

On the basis of the extensive scientific evidence reviewed, the report concludes that food irradiated to any dose appropriate to achieve the intended technological objective is both safe to consume and nutritionally adequate. The experts further conclude that no upper dose limit need be imposed, and that irradiated foods are deemed wholesome throughout the technologically useful dose range from below 10 kGy to envisioned doses above 10 kGy.

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