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 degrees 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. (C) 2012 Elsevier Ltd. All rights reserved.