Abstract:Maillard reaction products (MRPs) from silver carp peptide were isolated using a 5-kDa and 1-kDa ultrafiltration system, which was followed by solvent fractionation in order to investigate the antioxidant activity and chemical properties of different fractions. Measurements of the free-radical scavenging activity, metal ion chelating activity, and total antioxidant capacity of different fractions showed that high molecular weight (HMW) compounds displayed higher antioxidant activity than that of low molecular weight (LMW) compounds in the water-soluble fraction. In contrast, the antioxidant activity of HMW compounds was lower than that of LMW compounds in the alcohol-soluble fraction. The DPPH radical scavenging activity, metal ion chelating activity, and ferric reducing/antioxidant power (FRAP) of the water-soluble fraction F-3 (> 5 kDa) in silver carp peptide MRPs were the highest. The browning intensities of F-3 and F-2 (1~5 kDa) were the strongest and the fluorescence intensity of F-3 was the highest. Fourier transform infrared spectroscopy (FT-IR) showed that MRPs had a strong absorption peak at 860.66 cm-1, while F-2 and F-3 had sharp absorption peaks at 860.01 cm-1 and 948.61 cm-1, respectively, indicating that the reducing sugar may be linked to the peptide skeleton, which thus, leads to structural changes. Therefore, the water-soluble substances from MRPs play a major antioxidant role, and the colored water-soluble products with relatively HMW show strong antioxidant activity.
