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

¹Department of Food Science and Nutrition, Doshisha Women's College of Liberal Arts, Kamigyo-ku, Kyoto, 602-0893, Japan. ²Present address: Department of Home Economics, Shukugawa Gakuin College, 6-58 Koshikiiwa-cho Nishinomiya, 662-8555, Japan. ³Corresponding author. Phone: +81-75-251-4214. Fax: +81-75-251-4289 or 4214. E-mail: knishimu@dwc.doshisha.ac.jp

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.