Radiation Physics and Chemistry (1977)最新文献

This paper reviews the international regulatory efforts in the field of food irradiation and deals with the possible role of the International Consultative Group on Food Irradiation to support the implementation of the food irradiation process in industry and trade.

Low dose (less than 30 krad) gamma irradiation of $\text{Trichinella spiralis}$ infected pork renders the parasites sexually sterile and blocks maturation of the ingested larvae in the host gut. Irradiation of freshly slaughtered, market weight hog carcasses indicate that larvae throughout the carcass have essentially identical sensitivities to radiation. The research data indicate that 30 krad of 0.66 MeV gammas can be delivered to market weight, split carcasses with acceptable uniformity, and that such a dose can provide a substantial margin of safety for human consumption of even heavily infected meat.

Feasibility studies of pork irradiation in commercial operations have shown the process to be technically, economically, and financially feasible. Treatment during the first four years of operation in a 2,000 hog per day plant will cost about 0.0034 dollars per pound and 0.0011 dollars per pound thereafter. Social and political feasibility are addressed in a 1,000-family consumer survey completed in the first quarter of 1984.

The International Facility for Food Irradiation Technology (IFFIT) is an international project, jointly established by the IAEA, the FAO and the Ministry of Agriculture and Fisheries of the Netherlands, to speed up progress in the practical introduction of the process of food irradiation in developing countries. The project is hosted by the Pilot Plant for Food Irradiation and the State Institute for Quality Control of Agricultural Products, Wageningen, The Netherlands. The purpose of IFFIT is: 1) to offer training and assist in international co-ordination of development and research in the fields of technology, economics and implementation of food irradiation; 2) to assist national and international agencies in their assessment of the feasibility of applying radiation preservation techniques to foods; 3) to develop and facilitate the dissemination of information on the above topics without proprietary restrictions. The paper summarizes IFFIT's activities of its first five years of active existence, including training courses, long-term applied research training, feasibility studies, evaluation of trial shipments of irradiated commodities, irradiation services, and information activities.

This paper looks at the various design concepts for the irradiation processing of food products, with particular emphasis on handling the products on pallets.

Pallets appear to offer the most attractive method for handling foods from many considerations. Products are transported on pallets. Warehouse space is commonly designed for pallet storage and, if products are already palletized before and after irradiation, then labour could be saved by irradiating on pallets. This is also an advantage for equipment operation since a larger carrier volume means lower operation speeds.

Different pallet irradiator design concepts are examined and their suitability for several applications are discussed. For example, low product holdup for fast turn around will be a consideration for those operating an irradiation “service” business; others may require a very large source where efficiency is the primary requirement and this will not be consistent with low holdup.

The radiation performance characteristics and processing costs of these machines are discussed.

The interaction of collagen and metalloproteins with radiation-generated radicals has been studied using spectrophotometric, chromatographic, and ESR techniques. The hydroxyl radical (·OH) reacted with and caused polymerization of acid soluble collagen. Similar reactions were also observed in a ferrimyoglobin and cytochrome C system. Insoluble collagen from bovine muscle subjected to radiation is followed by a first-order process for the decay of free radicals, depending on relative humidity of the system. When the samples were irradiated with 3 kGy at 25°C by a Cesium-137 Irradiator, the observed half life (hr) of free radicals in the samples decreased with increase of relative humidity RH: 31% > 69% > 100%. When collagen, previously kept dry or under 31% RH, was irradiated with 3 kGy at 77°K (-196°C), the decay of free radicals reached a plateau with annealing at -120°C or higher. The decay kept decreasing with annealing at -100°C or higher temperature when collagen maintained at 69 and 100% RH was used. It is concluded that the free radicals in moistened collagen from bovine muscle decreased at a higher rate than in dried collagen. This suggests that free radicals may persist for a longer period of time in irradiated dry proteins of food or animal feed than in foods of higher moisture extent.

Radiation decontamination of dry ingredients, herbs and enzyme preparations is a technically feasible, economically viable and safe physical process. The procedure is direct, simple, requires no additives, does not leave residues and is highly efficient. Its dose requirement is moderate. Radiation doses of 3 to 10 kGy proved to be sufficient to reduce the viable cell counts to a satisfactory level. Ionizing radiations do not cause any significant rise in temperature and the flavour, texture or other important technological or sensory properties of most ingredients are not influenced at radiation doses necessary for a satisfactory decontamination. The microflora surviving the cell-count reduction by irradiation is more sensitive to subsequent food processing treatments than the microflora of untreated ingredients. Recontamination can be prevented since the product can be irradiated in its final packaging. Irradiation can be carried out in commercial containers and it results in considerable savings of energy and labour as compared to alternative decontamination techniques. Radiation processing of dry ingredients is an emerging technology in several countries and more-and-more clearances on irradiated foods are issued or expected to be granted in the near future.

Oxygen-free aqueous solutions of 0.05 mol dm^-3 malic acid (pH 2.4) were irradiated with ⁶⁰Co λ rays (0.1–92 kGy). Various small molecules were identified: CO, CO₂, CH₄, HCHO, CH₃CHO, (HCO)₂, CH₃COCHO, and CH₃COOH. With the exception of CO₂, they appear in small yields (G< 0.1) and represent minor radiolytic products. About 16 di-and polycarboxylic acids appear in irradiated solution, among them malonic and succinic acids being fairly abundant. Of particular importance is the efficient formation of dimers and trimers of malic acid. From the experimental data the value of k(e^-_aq + (HOOCCH₂CH(OH)COOH) was evaluated as ⩾3 × 10⁹ dm³ mol^-1 s^-1. Probable free-radical reactions leading to the formation of the radiolytic products are considered.

The compressive and bending strengths of a local tropical wood (Kapur-Dryobalanop sp.) were improved significantly by suitable impregnation of polymeric monomers (methylmethacrylate, methylmethacrylate—5% dioxane and vinyl acetate) inot the wood cellular structure and subsequent irradiation to form a wood-polymer composite. Statistical analysis revealed a linear relationship between increase in the strengths and the percentage of polymer impregnated. Fractographic analysis of the impact fractured surfaces under the scanning electron microscope showed the nature of the wood-polymer interface, which could account for the increase in the compressive and bending strengths.