Radiation Physics and Chemistry (1977)最新文献

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 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.

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.

The radiation induced hydrogen abstraction from hydrogen-containing substrates, by CF₂Cl radical was studied in CF₂Cl₂ solution as a function of the RH concentration (where RH is cyclohexane, cyclohexene, and ethanol) and as a function of temperature in the range of -80 to +20°C. For the CF₂Cl₂-ethanol system it was found that the ratio between the concentration of the abstraction product CHF₂Cl and the square root of the concentration of the recombination product (CF₂Cl)₂ is linearly dependent on the ethanol concentration (as was expected). However, for the two other systems, no dependence was found between this ratio and the concentration of the hydrogen containing substrate. A new mechanism for explaining those results was suggested.

A study of optical properties of H[AuCl₄]-containing polyvinyl alcohol (PVA) films allows the basis of a chain mechanism of their photolysis and radiolysis to be put forward. A suggestion is made, that in these chain reactions the Cl radical functions as an active particle, initiating the formation of two interacting chains in reactions of this radical with PVA and [AuCl₄]^- ions correspondingly.

The radiation-chemical yields of ionic species formed upon irradiation of water by 3.5 MeV electrons have been determined directly using dc conductivity and optical measurements. Yields (expressed in μmol J^-1) at 10 and 110 ns after the end of a 10 ns pulse are: for H₃O⁺ = 0.371, 0.320; for OH^- = 0.082, 0.045, and for e^-_aq = 0.299 and 0.275, respectively.

Neutralization reaction was investigated in negative ferric hydrous oxide sols. The adsorption isotherm of OH^- ions on the surface of colloidal particles was measured to provide the variation of their charge with pH. Impulse radiolysis generated the reacting ions in the sol. Using a fast DC conductivity setup for detection, a significant increase in the neutralization rate coefficient was found at low OH^- concentrations. The phenomenon was discussed in terms of the theory of diffusion controlled reactions for particles interacting with Coulomb and Yukawa potential.

The isothermal luminescence of γ-irradiated frozen 3-methylpentane (3MP)-methylcyclohexane (MCH) mixtures (3MP mole fraction from 0 to 0.96) containing naphthalene (Nph) was investigated at 77K. At high Nph concentration (2.5 x 10⁻²mol dm^−>3) the luminescence is due to molecular ion recombination by tunnelling. In the soft glass (0.96 mole fraction 3MP) at low Nph concentration (10^-3 mol dm^-3) electron thermal detrapping seems to contribute to the emission. The experimental decay curves were interpreted based on the Bagdasar'yan relation as well as the continuous-time- random-walk formalism (assuming a first-order rate equation with a time dependent rate constant of the form k(t) = Bt^(α−1).