Effect of ionizing radiation on folates in food

A radiation dose of 2.5 kGy, the highest dose practically feasible for fresh vegetables, caused about 10% loss of total folates in spinach, green cabbage and Brussel sprouts. No consistent differences between the radiation resistance of tetrahydrofolic acid and its 5-methyl and 5-formyl derivatives were observed. Radiation stability of folates was higher in dehydrated vegetables than in the fresh material. At a radiation dose of 2.5 key losses were within the range of analytical reproducibility for dehydrated spinach, green cabbage and Brussel sprouts. At 10 kGy, the highest dose legally permitted for food irradiation in many countries, losses of total folates ranged from 0 to about 30% in baker's yeast, beef liver, dehydrated spinach, green cabbage and Brussels sprouts, and in Camembert cheese. Losses of polyglutamate folates tended to be higher than those of monoglutamate folates, probably indicating some radiation-induced conversion of polyglutamates to monoglutamates Because of the higher bioavailability of monoglutamates the nutritional significance of radiation-induced folate losses is even smaller than data on total folates would indicate.