Abstract
In this study, the authors investigated the radiolysis of sulfur-containing amino acids, cysteine and methionine, in aqueous glucose solution to constract models like foods and to elucidate the radiation chemistry of foods.
Cysteine depressed the carbonyl yield produced from glucose to zero at a concentration of one-tenth of glucose.Methionine of one-tenth concentration of glucose lowered the carbonyl yield to about 16% of those from the solution dissolved glucose only (Table I).If methionine acts only as ·OH scavenger, that of one-tenth concentration of glucoseis calculated to suppress carbonyl yield at about half level.This difference may be explained to some extent by the reaction of methionine with radicals secondarily produced from glucose.
When 10-3M cysteine solution was irradiated with the addition of glucose at the concentration of ten-fold of cysteine, the G-value of products produced from cysteine were similar to those from 10-3M cysteine solution. However, in the case that glucose was added at the concentration of a hundred-fold, the high value of G(-cysteine) and disagreement of material balance of sulfur was observed(Table II and III).
These facts suggest that secondary radicals produced from cysteine may react with glucose and/or secondary radicals produced from glucose, resulting that cysteine converted to unknown products which are not listed in the table.
From the results using e-aq scavenger, it was concluded that oxidation to methionine sulfoxide and cleavage to α-aminobutyric acid was caused mainly by ·OH and e-aq attack, respectively (Table IV and V).
