Non-enzymatic browning induced by chlorogenic acid quinone mediated catechin oxidation.

Non-enzymatic oxidation has become a significant issue in the juice industry, inducing browning, flavor deterioration, and nutrient degradation, where catechin oxidation plays a vital role. Here, a novel chlorogenic acid quinone-mediated catechin oxidation was compared with the autoxidation pathway, where the former reaction was significantly faster (0.1326 L·mol-1·min-1) than the autoxidation rate of 4.25E-5 L·mol-1·min-1. The significance of the chlorogenic acid quinone-mediated catechin oxidation was further confirmed in the apple juice showing that chlorogenic acid quinone decreased faster in catechin enriched juice than in chlorogenic acid enriched juice. In addition, chlorogenic acid and catechin quinone hardly changed, but catechin and chlorogenic acid quinone kept decreasing during the browning process. These suggested that chlorogenic acid quinone mediated oxidation dominated the non-enzymatic browning in juice and might act as a self-perpetuating oxidizer, catalyzing the formation of catechin quinone constantly.