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

In the current study, we examined the role of superoxide anion radical (superoxide) 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 superoxide upon photoactivation. Nitro blue tetrazolium dye confirmed that superoxide 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 superoxide 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.