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 t
he 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 radia
tion dose of 2.5 key losses were within the range of analytical reprod
ucibility for dehydrated spinach, green cabbage and Brussel sprouts. A
t 10 kGy, the highest dose legally permitted for food irradiation in m
any countries, losses of total folates ranged from 0 to about 30% in b
aker's yeast, beef liver, dehydrated spinach, green cabbage and Brusse
ls sprouts, and in Camembert cheese. Losses of polyglutamate folates t
ended to be higher than those of monoglutamate folates, probably indic
ating some radiation-induced conversion of polyglutamates to monogluta
mates Because of the higher bioavailability of monoglutamates the nutr
itional significance of radiation-induced folate losses is even smalle
r than data on total folates would indicate.