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.