Effects of γ-irradiation and cooking on vitamins B6 and B12 in grass prawns (Penaeus monodon)

The effects of irradiation doses, irradiation temperature and a combined treatment of irradiation and cooking on the vitamin B₆ and B₁₂ contents of grass prawns have been studied. Grass prawns were irradiated at refrigerated (4°C) or frozen (-20°C) temperatures with different doses. A domestic cooking procedure was followed after irradiation. The changes in vitamins B₆ and B₁₂ of both raw and cooked grass prawns were evaluated. Results showed no significant changes of vitamin B₆ and B₁₂ in grass prawns with a radiation dose up to 7 kGy at either 4°C or -20°C. Irradiation at 4°C caused more destruction of vitamin B₁₂ but not vitamin B₆ than did irradiation at -20°C in grass prawns. There was significant destruction of both vitamins B₆ and B₁₂ in unirradiated samples during cooking. The introduction of the irradiation process before cooking had no effect on either vitamin. These results indicate that the loss of vitamins B₆ and B₁₂ in the combined treatments was caused mainly by thermal destruction.