Studies on the combined effect of gamma radiation and cooking on the nutritional value of fish

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, 10 % 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.