Antioxidant effects of Maillard reaction products obtained from ovalbumin and different D-aldohexoses

Nonenzymatic glycation between ovalbumin (OVA) and seven D-aldohexoses was carried out to study the chemical and antioxidant characteristics of sugar-protein complexes formed in the dry state at 55 degrees C and 65% relative humidity for 2 d through the Maillard reaction (MR). The effects of Maillard reaction products (MRPs) modified with different aldohexoses on radical scavenging, lipid oxidation, and tetrazolium salt (XTT) reducibility were investigated. The results showed that the degree of browning and aggregation and the tryptophan-related fluorescent intensity of glycated proteins displayed a noticeable difference that depended on the sugars used for modification. All the glycated proteins exhibited higher antioxidant activity as compared to a heated control and native OVA, and the antioxidant activity was well correlated with browning development. Furthermore, the order of antioxidant activities for the seven complexes was as follows: altrose/allose-OVAs > talose/galactose-OVAs > glucose-OVA > mannose/glucose-OVAs. This implies that sugar-protein complexes with two sugars known as epimers about C-2 showed a similar antioxidant capacity. From these results, the configuration of a hydroxyl (OH) group about position C-2 did not influence the advanced cross-linking reaction, but the configuration of OH groups about C-3 and C-4 might be very important for formation of MRPs and their antioxidant behaviors.