The effect of irradiation (0.6 Mrad), cooking and a combination of both treatments has been measured on the protein nutritive value and on the B-complex vitamins, nicotinic acid, riboflavin and thiamine, in cod fish fillets. Microbiological assay methods were used throughout. Protein nutritive value was unaffected by irradiation, whereas cooking caused a 9% loss: this loss was not increased by prior irradiation treatment. Irradiation did not affect nicotinic acid and a 4 % loss caused by cooking was again not increased by a combination of treatments. Riboflavin was reduced 6 % by radiation, 9 % by cooking, and 16% after both treatments, whilst for thiamine the losses were 47% by radiation, I0 % by cooking and 54 % by combined treatment.It was concluded that irradiation followed by cooking produced a total loss which was the sum of the losses produced by each treatment. The importance of loss of nutrients in fish due to radiation processing is discussed.

No abstract

The use of a gamma radiation process for the elimination of Salmonella from frozen meat is considered with particular reference to the treatment of boned-out horsemeat and kangaroo meat imported into the UK and intended for use as pet meat.Examination of dose/survival curves produced for several serotypes of Salmonella in frozen meat shows that a radiation dose of 0.6 Mrad. will reduce a population by at least a factor of 10(5). The influence on the radiation resistance of salmonellas of such factors as preirradiation growth in the meat and temperature during irradiation have been examined and considered. It is also demonstrated with both preinoculated and naturally contaminated meat that postirradiation storage in the frozen state does not lead to the revival of irradiated salmonellas.The properties of Salmonella survivors deliberately produced in meat using conditions of irradiation designed to simulate a commercial process are studied after six recycling treatments through the process. There were no important changes in characteristics normally used for identification of Salmonella but radiation resistance was lowered. Survivors grown in situ in meat after irradiation showed an abnormally long lag phase, and removal of competitive microflora in meat by the radiation treatment can influence the growth of salmonellas.

The effect of y-radiation on the protein nutritive value of certain animal feeds (protein concentrates), frozen whole egg, whole wheat and wheat gluten was measured by use of a microbiological method. There was little change in nutritive value of the animal feeds with doses of 0.5 and 1.0 Mrad and no change with frozen egg aL0.5 and 5.0 Mrad. Whole wheat showed no loss a t 0.2 Mrad; a 6% loss at 1 . 0 Mrad was not increased further a t 5.0 Mrad. Gluten prepared from wheat and then irradiated was unchanged a t 0.02.Mrad but losses of 5. 7 and 26% were shown with doses of 0.2, 1.0 and 5.0 Mrad respectively. Following amino-acid supplementation studies and microbiological assays for methionine, loss of availability of this amino-acid was demonstrated to be principally responsible for the lowering of the nutritive value of the 5-o-Mrad-irradiated wheat gluten.

By use of microbiological methods of assay, the effect of y-radiation at doses of 0.5 Mrad and 5.0 Mrad on the content of some B-complex vitamins in frozen whole egg has been studied. For comparative purposes, analyses were also performed on egg treated by a heat-pasteurisation process designed to eliminate salmonellae food-poisoning organisms. No change was apparent in pantothenic acid, biotin and riboflavin after any of the treatments. A 24% loss of thiamine occurred at 0.5 Mrad and this was increased t o 61% at j.0 Mrads. Similar analyses were made on Manitoba wheat irradiated a t 0.02 Mrad, which is approximately the dose required for grain disinfestation, and also a t ten times this dose. No apparent change was observed in the contents of nicotinic acid, thiamine, riboflavin, biotin and total vitamin B, after irradiation a t 0.02 Mrad ; pantothenic acid showed a slight loss a t this dose. At 0.2 Mrad a loss of 12% nicotinic acid, 11% pantothenic acid and 10% biotin occurred. IntroductionBefore the introduction of any radiation process for the treatment of food, its possible effect on wholesomeness with respect to both toxicity and nutritive value requires investigation. Wheat and egg have been chosen for study of vitamin destruction since promising processes for the disinfestation of grain2 and for the elimination of salmonellae from frozen egg3 have been proposed. Furthermore, long-term animal feeding studies on these commodities have been undertaken at this laboratory in order to investigate their possible toxicity after irradiation ; such studies require that the test diets be nutritionally adequate. Some of the evidence obtained showing the non-toxicity of irradiated wheat has recently been publi~hed.~ Microbiological methods of vitamin assay were employed and the foods treated at the radiation doses recommended for practical application, and, in order to exaggerate any destniction and to conform to some of the diet treatments in the animal studies previously mentioned, also at doses ten times higher. In addition, the effect of a newly-proposed heat-pasteurisation process for eggs5 was studied for comparative purposes. The vitamins involved were nicotinic acid, pantothenic acid, biotin, thiamine and riboflavin for both wheat and egg, plus vitamin B, in the case of wheat.