Effect of sucrose on the anthocyanin and antioxidant capacity of mulberry extract during high temperature heating P.J. Tsai a, * , L. Delva a , T.Y. Yu a , Y.T. Huang a , L. Dufosse ´ b a Department of Food Science, National Pingtung University of Science and Technology, 1 Hsueh Fu Road, Nei Pu Hsiang, 91207 Pingtung, Taiwan, ROC b Laboratoire ANTiOX, Universite ´ de Bretagne Occidentale, IUP Innovation en Industries Alimentaires, Po ˆle Technologique de Cre ´acÕh Gwen, F-29018 Quimper Cedex, France Received 2 June 2004; accepted 20 March 2005 Abstract 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. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Sucrose; Anthocyanin; Antioxidant capacity; Mulberry extract 1. Introduction Anthocyanins are a good source of natural antioxi- dant, but they are quite unstable during processing and storage. Temperature, pH, oxygen, and water activ- ity are considered to be important factors influencing its stability. During heating, degradation and polymeriza- tion usually lead to its discoloration (Markakis, 1982; Tsai & Huang, 2004). Sugar protection via hyperchro- mic effect was reported to stabilize the anthocyanin pig- ment in strawberries (Ohta, Watanabe, & Osaiima, 1979; Wrolstad, Skrede, Lea, & Enersen, 1990) and ro- selles (Tsai, Hsieh, & Huang, 2004) due to reduced water activity or availability. In contrast, thermal degradation products of sucrose like furfural, caramel or maillard reaction products (MRP) are also well known to be browning agents (Granados, Mir, Serrana, & Martinez, 1996) and furfural has been found to be involved in anthocyanin deterioration (Debick-pospisil, Lovric, Tri- najstic, & Sabljic, 1983). Temperature and duration of heating, pH and concentration of reactant are parame- ters that should be taken into consideration (Davies & Labuza, 2005) for the browning reaction. In general, acidic media favor sucrose hydrolysis and carameliza- tion while the maillard reaction is favored by alkaline 0963-9969/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2005.03.017 * Corresponding author. Tel.: +886 8 7740408; fax: +886 8 7740378. E-mail address: pijen@mail.npust.edu.tw (P.J. Tsai). www.elsevier.com/locate/foodres Food Research International 38 (2005) 1059–1065