Radurization of Fresh-Water Fish in the Federal Republic of Germany

Fresh gwyniad trout and carp were vacuum-packed in plastic foil impermeable to gas and water vapour, irradiated with 10-MeV electrons, and stored under melting ice. Sensory, chemical and microbiological tests were then carried out over a period of four to two weeks. In the case of gwyniad, best results were obtained with a dose of 0.1 Mrad which prolonged Grade-1 quality shelf life from nine to 23 days. With trout a dose of 0.05 Mrad improved the shelf life from 15 to 21 days. Doses higher than 0.1 Mrad for gwyniad and 0.05 Mrad for trout caused a noticeable loss of flavour. In this respect trout appears to be particularly radiation-sensitive in comparison with other species of fish. In contrast, carp turned out to be particularly well suited for radiation-preservation treatments, as its flavour is not negatively affected even by relatively high radiation doses. While unirradiated carp could be stored for 15 days', a dose of 0.5 Mrad preserved the Grade-1 quality shelf life for 35 days. Higher doses, up to 1.5 Mrad, caused a further reduction of microbial counts without improving the shelf life beyond the results obtained with 0.5 Mrad. The latter dose, which does not affect flavour, can therefore be considered optimal for carp. (author)