Yuka Miyamoto

Beneficial Effects of Ascorbic Acid on Heat-Induced Fish Gel (Kamaboko) from the Superoxide Anion Radical

We examined the participation of the superoxide anion radical (O2 −) in the beneficial effects of L-ascorbic acid on heat-induced fish gel (Kamaboko). The generation of a thiyl radical (S·) in glutathione, ovalbumin, and actomyosin was examined by electron spin resonance spectroscopy coupled with spin trapping. O2 − was provided by the photoactivation of riboflavin. The typical line shape for S· was observed with the glutathione and ovalbumin samples. A signal different from that for S· was detected with the actomyosin sample, and its intensity markedly decreased when the SH groups of actomyosin had been modified. The signal was eliminated when superoxide dismutase was added, but unaffected when catalase or an equivalent amount of heat-inactivated superoxide dismutase or catalase were added. These results suggest that S· in actomyosin was produced by the reaction with O2 − and that the beneficial effects of L-ascorbic acid are due to a different mechanism in Kamaboko from that in bread.

Production of Thiyl Radical on a Peptide Derived from Wheat Protein by Superoxide Anion Radical

ABSTRACT In the current study, we examined the role of superoxide anion radical (O-2) in the improvement of bread dough by l-ascorbic acid. Because of difficulties in detecting thiyl radicals in the presence of l-ascorbic acid, we replaced the latter with riboflavin, which produces O-2 upon photoactivation. Nitro blue tetrazolium dye confirmed that O-2 was produced in dough upon photoactivation of riboflavin. Electron spin resonance spectroscopy coupled with spin trapping showed that, in a solution containing riboflavin and the hydrolyzed gluten peptide (GP-1), thiyl radicals are produced upon photoactivation. Addition of superoxide dismutase but not catalase suppressed the production of thiyl radicals on GP-1. These results suggest that the O-2 produced during the oxidation of l-ascorbic acid in dough generates thiyl radicals on gluten proteins. This, in turn, would increase the production of interprotein disulfide bonds and result in an improvement in bread structure.

Action of ascorbic acid on a myosin molecule derived from carp

The influence of L-ascorbic acid at 40 °C incubation on the subfragment-1 and rod regions, prepared by chymotryptic digestion of myosin, and myosin was investigated by SDS–polyacrylamide gel electrophoresis and transmission electron microscopy respectively. It was observed that L-ascorbic acid acted more readily on the subfragment-1 region of myosin. Further, circular dichroism measurement indicated that L-ascorbic acid did not affect the structure of myosin. These results suggest that L-ascorbic acid acts more readily on the myosin subfragment-1 region and promotes the gelation of myosin without producing a conformational change in this protein.