Riboflavin-sensitized photochemical changes in beta-lactoglobulin in an aqueous buffer solution as affected by ascorbic acid

The effects of ascorbic acid on the riboflavin-sensitized photochemical cha nges in beta-lactoglobulin in an aqueous buffer solution as determined by h igh performance gel permeation liquid chromatography (HPGPLC), insoluble pr otein content, and individual amino acid content during fluorescent light i llumination were studied. The riboflavin-sensitized photochemical degradati on of beta-lactoglobulin was effectively inhibited by ascorbic acid, and it s inhibitory effectiveness wa's concentration dependent. The 0.1% ascorbic acid treatment showed 74.4% inhibition of beta-lactoglobulin degradation as determined by a HPGPLC during 6 h light illumination. Insolubility of beta -lactoglobulin in a buffer solution during light illumination was also effe ctively decreased by ascorbic acid treatment. The riboflavin-sensitized pho tochemical reduction of cysteine, histidine, lysine, methionine, and trypto phan in beta-lactoglobulin was high during 6 h fluorescent light illuminati on. The 0.1% ascorbic acid treatment exhibited 20.8% inhibition of total am ino acid degradation in beta-lactoglobulin during 6 h light illumination, s howing strong inhibitory activity against the degradation of arginine, aspa rtic acid, cystein, glycine, histidine, phenylalanine, proline, serine, and tryptophan.