Effects of pectolytic treatment of Ziziphus mauritiana L. mash on theantioxidant content and activity of the fruit juice

Jujube (Ziziphus mauritiana L.) is a tropical fruit which is rich in phenolic compounds and ascorbic acid. In this study, jujube mash was treated with pectinase preparation for juice extraction. The effects of pectinase concentration and pectolytic time on the total phenolic and ascorbic acid content, as well as the antioxidant capacity of jujube juice, were investigated. Response surface methodology was then used to optimize the conditions of the pectolytic treatment. An increase in pectinase concentration and pectolytic time significantly improved the antioxidant level of jujube juice; nevertheless, so high pectinase concentration and prolonged pectolytic time reduced the total phenolic and ascorbic acid content of the fruit juice. The optimal pectinase concentration and pectolytic time were 0.07 U/g dry weight of jujube mash and 120 min, respectively under which, the content of total phenolics, ascorbic acid and the antioxidant capacity evaluated by 1,1- diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays were 41%, 82%, 133% and 83%, respectively higher than those of the control without pectolytic treatment. Enzyme-assisted extraction was therefore potentially useful for the development of fruit juice products with high antioxidant levels.