Antioxidant activity of Maillard reaction products from a porcine plasma protein–sugar model system

Maillard reaction products (MRPs) were prepared by heating 2% porcine plasma protein (PPP) and reducing sugars (glucose, fructose and galactose) at the levels of 1% or 2% at 100 °C up to 5 h without pH control. Browning and intermediate products, as monitored by absorbance at 420 nm and absorbance at 294 nm, increased as heating time increased (P < 0.05). However, fluorescence (Ex 347 and Em 415 nm) sharply increased within 1 h and subsequently decreased when heating time increased (P < 0.05). Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino groups. Among sugars and concentrations used, galactose at 2% rendered the highest browning and intermediate products. MRPs derived from galactose, especially at a level of 2% possessed greater reducing power and DPPH radical-scavenging activity than those prepared from fructose and glucose. MRPs derived from fructose or galactose at the level of 2% showed the increase in reducing power and DPPH radical-scavenging activity in a concentration-dependent manner. In general, antioxidative activity of PPP–sugar MRPs was coincidental with the browning development and the formation of intermediate products.