Antioxidant activity of Maillard reaction products (MRPs) derived from fructose–lysine and ribose–lysine model systems

Maillard reaction products (MRPs) were prepared from aqueous ribose–lysine (RL) and fructose–lysine (FL) model systems at pH 9, heated at 60, 80 and 120 °C for 15, 60 and 120 min. Browning intensity (BI) and pH reduction were monitored throughout the reaction. 1,1-Diphenyl-2-picryl-hydrazyl (DPPH-RS), peroxyl (PRS), and hydroxyl radical scavenging (HRS) and reducing power (RP) measured their antioxidant activity. The pH of FL and RL system decreased (p < 0.05) as reaction temperatures and times increased. This reduction coincided with the increase (p < 0.05) in BI for all MRPs. With the exception of HRS activity, the antioxidant activity of FL increased (p < 0.05) with increased reaction temperature, while that of RL systems decreased (p < 0.05). Concerning sugar reactivity, RL systems exhibited higher (p < 0.05) reduction in pH, BI, DPPH-RS, PRS and RP than FL model systems, with no considerable differences (p > 0.05) in HRS activity.