Abstract

This study aimed to evaluate the antioxidant activity of the Maillard reaction products (MRPs) derived from stingray non-protein nitrogenous (NPN) fraction and sugar (glucose, galactose and fructose) model systems. MRPs were prepared by heating the solution containing NPN (2g nitrogen/100ml) and sugar (2g/100ml) in 0.05M sodium hydrogen carbonate buffer, pH 12 for 120min at 100°C. Reducing power and capacity to scavenge hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>), hydroxyl radical (OH<sup/>), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTS⁺) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH<sup/>)of all MRPs were greater than those of original NPN solution (P<0.05). The MRPs derived from NPN-fructose tended to have the highest reducing capacity and free radical scavenging ability. However, the ferrous (Fe²⁺) chelating activity of all MRPs was lower than the original NPN solution (P<0.05). Therefore, reducing power and scavenging activity toward free radicals and reactive oxygen species of NPN from stingray muscle can be improved significantly by reacting NPN with sugar particularly fructose via the Maillard reaction. However, the Maillard reaction seemed to show a negative impact on the Fe²⁺ chelating activity of stingray NPN. © 2014 Elsevier Ltd.