Antioxidant properties of Maillard reaction products obtained by gamma-irradiation of whey proteins

The radiation processing of sugar–amino acid solutions results in formation of Maillard reaction products (MRPs). In the present study, the efficacy of gamma-irradiation in the formation of MRPs from whey protein powder was investigated. The formation of MRPs in whey protein suspension was studied by monitoring spectrophotometeric and chemical changes. A dose-dependent increase in UV absorbance and development of fluorescence was observed. Formation of brown pigments was established by increased A420 nm and Hunter colour upon irradiation. These MRPs exhibited antioxidant activity as measured by 1,1-diphenyl-2-picrylhydrazyl and β-carotene bleaching assays. Reducing power and iron-chelating abilities of MRPs also increased upon irradiation. These MRPs were able to scavenge hydroxyl and superoxide anion radicals under in vitro conditions. Dose-dependent decrease in free amino groups and lactose suggested the formation of glycated proteins upon irradiation treatment. SDS–PAGE analyses indicated formation of crosslinked proteins upon irradiation.