[en] In the task of alleviating the distress caused by the world-wide food shortage it is essential to preserve what has been grown and harvested in the fields. Clearly all suitable methods for preserving agricultural produce and food should be made use of. In this context treatment with ionizing radiation has proved its value as an environmentally clean, physical method of food preservation which is low in its energy requirement, but the volume of food being processed in this way is still low. The introduction of food irradiation on a global basis poses certain economic, legal, regulatory and health-related questions, the solution of which requires close international collaboration. Such collaboration between many international, intergovernmental and national organizations began over a decade ago. The need for dissemination and discussion of information gained through research and development work on this subject became apparent, and a number of inter-regional meetings were held. The last international symposium on the topic was held jointly by FAO and the IAEA in 1972 in Bombay. To review progress made since then, FAO and the IAEA, together with WHO, convened the present Symposium on 21-25 November 1977. It appeared timely to hold this Symposium for the following reasons: (1) Apart from significant scientific work reported in the literature, progress in other directions between 1972 and 1977 had also been made. For example, the number of food items authorized by governments, with or without restriction, had grown from 19 to 26, and the number of countries accepting one or more irradiated foods for human consumption had increased from 11 to 19. (2) Largely on the basis of the work of the International Project in the Field of Food Irradiation (Karlsruhe), already described at the Bombay Symposium, an international expert committee, jointly convened by FAO, the IAEA and WHO in August-September 1976, had made important statements on the philosophy of wholesomeness studies, as well as on the public health acceptability of a number of irradiated food items. These matters had been reported in WHO Technical Reports Series No.604, Wholesomeness of Irradiated Food, published in Geneva, 1977. (3) The Joint FAO/WHO Food Standards Programme, through the Codex Alimentarius, had examined food irradiation and developed a proposed General Standard on Irradiated Foods and a proposed Code of Practice for the Operation of Radiation Facilities used for the Treatment of Foods at step 5 of the 9-10 step procedure of the Codex. (4) FAO and the IAEA were about to join forces with the Government of the Netherlands in establishing an International Facility for Food Irradiation Technology at Wageningen for the purposes of technological and economic training and research in food irradiation. Sessions of the Symposium dealt with such topics as the control of animal infestation, toxicological studies, public health aspects and economics, and many papers were concerned with chemical changes in irradiated foods and with the control of microbial spoilage. The present Proceedings contain the papers given and the ensuing discussions, including the extensive round-table discussion on a plan of action for the future. The order of publication of the papers does not strictly follow that of presentation at the Symposium where, for technical reasons, it was not always possible to preserve the logical sequence. Viewed against the new developments recorded here, the outlook for the food irradiation community is encouraging, and the tasks ahead appear less formidable. The sponsoring organizations hope that the publication of this material will be a useful contribution towards accelerated progress in the practical application of food processing by irradiation

[en] The experience obtained in Israel regarding procedures for petitioning and granting clearance for irradiated food is briefly reviewed. The Israel Ministry of Health deliberated on the approach to be taken towards irradiated farm animal feed, since feed is normally dealt with under Ministry of Agriculture Plant Protection Division regulations. A similar situation existed in Canada, where the Feed and Fertilizer Section, Plant Products Division, granted clearance of radicidized poultry feed. However, since the meat of farm animals raised on radicidized feed is to be consumed by humans, and is thus included in the definition of food in the Public Health (Rules as to Food) Ordinance, the Ministry of Health finally decided that it would require a regular petition. The petition to clear irradiated poultry feed is described in detail. It is based on local studies as well as on the detailed material prepared by the Canadian authorities in their petition and the clearance. The petition was submitted in October 1972 and clearance was obtained in July 1973. The implementation of the legislative requirements in the forthcoming pilot scale test, aimed at radicidization of 300 tons of poultry feed, is considered in detail. (author)

[en] Many experiments have been carried out at our institute during the last four years while studying the prolongation of the shelf-life of prepacked fillets of cod (Gadus callarias) and plaice (Pleuronectes platessa) and cooked shrimp (Crangon crangon) by irradiation at a dose of 100 krad. For the bacteriological analysis in these experiments modified Long and Hammer's medium was used as enumeration medium. On this medium colonies of Pseudomonas putrefaciens, Photobacterium spp. and 'typical shrimp spoiling' bacteria (presumably Alteromonas spp.) can be differentiated. These and several other species that are involved in the spoilage of unirradiated fish and shrimp are eliminated by irradiation. In irradiated fish and shrimp Moraxella spp. predominated during the whole storage period. Their colonies typically differ from the colonies of the former species. Simple tests can be applied for the confirmation of the latter species. The predominance of Moraxella-type colonies on the plates in combination with the absence of colonies of the radiosensitive species mentioned above is indicative of irradiated samples. (author)

[en] Poultry is a major local meat source which is often contaminated with salmonella. A major source of contamination was found to be salmonella-infected poultry feed. Since gamma radiation at doses of up to 1 Mrad reduced salmonella populations in feed by 6 to 7 logs, this study was undertaken to determine if radicidized poultry feed can be used as a step in reducing contamination of poultry without affecting breeder flock performance and longevity. Two breeder flocks, each comprising 300 hens and 50 roosters, were kept in separate coops. One flock was fed untreated feed, while the feed of the other was radicidized at 1 Mrad, which resulted in a level of less than 10 enterobacteria per gram. The flocks Were studied for over 12 months, from the emergence of chicks to the end of 6 months of egg production. The quantity of feed supply was controlled to ensure early detection of detrimental effects on the biological value of the feed. For the first 8 weeks, when the feed was freely supplied, no differences were observed in feed utilization or growth. After limited feeding was started, no significant differences were observed in feed utilization and in total amount of feed consumed. The number of fertile eggs, the feed consumption per egg, the age at which the first egg was laid, mortality and the total weight after 22 weeks and 12¼ months were practically equivalent in both flocks. Chicks obtained from both flocks showed no significant differences in weight or in feed utilization. (author)

[en] The energy used in food systems in the US amounts to about 16.5% of total US energy. An analysis has been made of the energy used in the many steps of the food-irradiation process. It is found that irradiation pasteurization uses only 21 kJ/kg and radappertization 157 kJ/kg, which is much less than the energy used in the other food processes. A comparison has also been made with other methods of preserving, distributing and preparing the meat for servings. It is found that the food irradiation can save significant amounts of energy. In the case of heatsterilized and radiation-sterilized meats the largest fraction of the energy is used in the packaging, while in the frozen meats the largest energy consumption is by refrigeration in the distribution channels and in the home. (author)

[en] A biological dose meter using specially prepared and packaged spores of Bacillus subtilis var. niger has been shown to be reliable. The spore preparations used as dose meters contain about 10⁸ spores and are stable at room temperature for many months. The procedure for the preparation and assaying of the dose meters is described. It is found that post-irradiation repair is significant and that dried, irradiated spores are sensitive to oxygen, even when first exposed to oxygen several hours after irradiation. The spore repair and sensitivity to oxygen can be quenched by exposure to water before the exposure to oxygen. This biological dose meter is found to be dose-rate independent in the range of dose rate from 10^-1 to 10¹¹ Gy/s. The dose D₁₀ required to reduce the survival by a factor of 10 is found to decrease linearly with increase in temperature in the range of - 190 to + 90°C according to D₁₀ = 3.13 - 0.0059-T. (author)

[en] As a result of the recent evaluations of a joint FAO/IAEA/WHO Expert Committee almost all scientific hesitations against the use of irradiation for the preservation of food have been removed. This opens wide perspectives for the augmentation of the quantity of food available for consumption. This also offers great possibilities for less-developed countries with an agricultural economy to export products to the developed countries. Two obstacles to the internationalization of trade in irradiated food remain, however. Only if these last obstacles are removed will food irradiation be able to play an important role. The first obstacle is that no simple test exists to determine whether a food item has been irradiated with what dose. The second obstacle is the public acceptance of irradiated food, as the public is highly sensitive to imagined or real dangers associated with the word radiation. Ways are suggested for overcoming both obstacles, stressing the importance of international cooperation and international organizations such as the IAEA, FAO and WHO. (author)

[en] A system was elaborated to determine whether strawberries have been irradiated, using 3 criteria, namely the number of Enterobacteriaceae, the percentage of yeasts on total microflora (or total absence of microorganisms) and the number of Pseudomonas. The higher the numbers of Enterobacteriaceae and/or Pseudomonas, the lower the probability that the strawberries have been irradiated. The higher the yeast percentage, the more the conclusion is justified that irradiation has taken place. The same holds true for total absence of microorganisms. By combining results for the 3 criteria an identification scheme was drawn up that would have led to 189 correct decisions (92.2%) on 205 samples (102 irradiated with 200krad, 103 unirradiated). In only 3 samples (1.5%) the combination of properties resembled that generally shown by the opposite group in such a way that they would have been classified in the wrong category. Some combinations of results for the 3 criteria were found in about equal numbers for both irradiated and unirradiated samples. These samples and others showing contradictory results, totalling 13 samples (6.3%), had to be placed in a separate 'intermediate' category, about which no opinion could be given. The only possibility in such cases is to investigate new samples. Sixty of the samples were investigated without the investigators knowing whether the samples had been irradiated; 56 of them would have been classified in the right category with the help of the scheme made up using the previous data; the remaining 4 had to be classified in the intermediate category. (author)

[en] Fresh eviscerated broiler chicken, both with salt treatment (part of kosher processing) and without, were gamma irradiated and stored at -1, 0, +1.6 and +4.4⁰C for up to 31 days. At intervals samples were withdrawn for microbial, physical and sensory evaluations. Combination of a 250 krad irradiation dose and storage at 1.6⁰C were adequate for a radurized chicken process. The product was free from microbial spoilage and of excellent quality for at least 15 days and, in addition, was essentially free from Salmonella and other organisms of public-health significance. It is therefore proposed that the doses recommended recently by the Joint FAO/IAEA/WHO Committee are unnecessarily high and should be markedly reduced. A 500 krad dose caused marked flesh discolouring without improving the microbiological or enzymatic preservation, and this is likely to be found generally true for commercial poultry flocks under veterinary inspection. Flesh discolouring of chicken treated with 300 krad is unlikely to be detectable by the untrained eye and a maximum dose of 300 krad should be the target for non-frozen chicken irradiation processes. (author)

[en] The concept of using a simple aqueous solution model to predict the chemical changes that take place when fruits are irradiated is discussed. Using relative rate constants determined by irradiating binary systems containing glucose, it has been possible to calculate the protective effect due to the high concentration of sugars present in fruit. The validity of the predicted effect was then tested by irradiating a model solution containing the components present in a typical subtropical fruit. The yield of products due to the radiolysis of sugars in this solution was shown to be similar to the yield obtained when aqueous solutions of pure sugars are irradiated. Thus the other components do not compete for the primary radicals formed in the radiolysis of aqueous solutions. On the basis of these experiments it has been concluded that the only significant radiolysis products formed during the radiation processing of fruits are sugar degradation products. The yields of these products are known and the toxicological implications of their formation may be assessed and shown to be insignificant. The limitations of the aqueous model have been considered and its validity tested by comparing the yields of sugar degradation products in the model solution with those obtained from irradiated fruit juice, fruit pulp and fresh fruit. The results indicate that the aqueous model provides a satisfactory basis for predicting the chemical changes in a wide variety of fruits. The significance of this finding with respect to toxicological considerations is discussed. (author)