Effect of sucrose on the anthocyanin and antioxidant capacity of mulberry extract during high temperature heating

This study aimed to elucidate how sucrose affects the anthocyanin and antioxidant capacity at low pH under high temperature. The interactive role of different sucrose concentrations (20%, 40%, 60%) and pH values (2, 3, 4) on a mulberry anthocyanin model system at different heating times was investigated. A520 (red color) decreased from 0 to 4 h and increased thereafter, degradation index of anthocyanin (DI) increased in the pure anthocyanin system during 68 h of heating. The samples with sucrose showed a DI peak at 17 h, which indicated that severe browning occurred after this period should be along with lower ratio of A420 and A520, and the latter high A520 came from a brown pigment instead of anthocyanin. Furfural content reached a maximum at 26 h during heating, and other caramelization intermediates showed a similar trend during this period. All samples, with or without sucrose, showed increase in polymeric and copigmented anthocyanin and a decrease in the monomeric ones during heating. The browning depends on the pH and sucrose concentration. Samples at pH 2 with higher sucrose showed the most significant browning and the increase of ferric reducing ability of plasma (FRAP) indicated that hydrolysis of sucrose might increase the antioxidant capacity. Further correlation analysis indicated that changes of antioxidant capacity during heating were closely related to the caramelization intermediate developed from sucrose in the sugar added system. (c) 2005 Elsevier Ltd. All rights reserved.