Prevention of the deterioration of polyphenol-rich beverages

Only a small amount of H2O2 was detected in beverages, such as tea or coffee, immediately after opening caps of bottles, but H2O2 was gradually produced in the beverages after opening the caps, i.e. exposure to air. The beverages with high concentrations of polyphenols showed high 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities, but produced relatively high concentrations of H2O2 when they were exposed to air, possibly due to oxygen. The production of H2O2 increased both with duration of the exposure to air and rise in temperature. Since H2O2 is toxic, ways to prevent the deterioration of catechin-enriched green tea, i.e. H2O2 production, were studied. The addition of catalase, which is an enzyme decomposing H2O2, reduced the H2O2 concentration, but it was inactivated at a high temperature. The addition of L-cysteine or glutathione (reduced form), with a thiol residue, reduced the H2O2 concentration. Addition of citric acid, malic acid, succinic acid, fumaric acid, L-ascorbic acid, L-glutamic acid and L-aspartic acid also reduced it, possibly because they lower the pH of the tea. (c) 2005 Elsevier Ltd. All rights reserved.