Antioxidant activity of vinegar melanoidins

Melanoidins, the brown polymers formed through Maillard reaction during vinegar process, are one of major high-molecular-weight fractions of vinegar. In this study the antioxidant activity of high-molecular-weight fractions (MW > 3500 Da) separated from ethanol-supernatant extraction of concentrated Zhenjiang aromatic vinegar was evaluated by different in vitro tests: the DPPH radical scavenging activity, the reducing power, total phenolic content, and the inhibitory effect on hydroxyl radical. Each individual fraction was found to have antioxidant activity in all the model systems tested. The high-molecular-weight fractions of vinegar (MW > 3500 Da) were separated into different fractions by DEAE-Sepharose fast flow. The fractions eluted by 0.2 mol/L NaCl and 0.3 mol/L NaCl with higher phenolic content have stronger DPPH radical scavenging activity and reducing power. Antioxidant activity in hydroxyl radical system was not correlated with phenolic content. Two phases which have stronger effects on Maillard reaction products (MRPs) in production process were examined. Decoction, storing and aging may affect vinegar’s antioxidant activity. The present results support the concept that melanoidins formed during vinegar production process may have health promotion activity.