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.

The mechanism for the beneficial effects of vitamin C (l-ascorbic acid, AsA) on the quality of the heat-induced fish gel, kamaboko, has been proposed by Nishimura et al. to involve the production of thiyl radical (S·). The generation of S· in myosin by the superoxide anion radical (O 2 -), produced by the photoactivation of riboflavin, was then examined by electron spin resonance spectroscopy coupled with spintrapping. Consequently, the production of S· was observed. This generation of S· in myosin was inhibited by the addition of 100 units (u)/ml superoxide dismutase (SOD), whereas heat-inactivated SOD, catalase (1,200 u/ml), and heat-inactivated catalase did not suppress the generation of S·. These results suggested that the generation of S· in myosin occurred due to the presence of O 2 -.