LAUSR

Enzymatic browning is a main problem encountered in the preparation and further storage of apple juice, thus shortening shelf-life of products. Preliminary screening of the chitosan samples with different molecular weights, determined by antioxidant capacity in vitro, showed that oligochitosan with a molecular weight of 1 kDa (OCS1) was the most potent antioxidant among those tested. OCS1 at three different concentrations was added during juice processing and then the juice were stored at 25C for 48 h to investigate its effects on browning. The application of oligochitosan effectively retarded juice browning and had little effect on the content of nutritional components. OCS1-treated apple juice exhibited lower levels of protein and total phenols, as well as superoxide anion radicals ( O2−·), compared to nontreatment control. Oligochitosan treatment also enhanced the activities of antioxidases (superoxide dismutase and peroxidase) and inhibited the activity of polyphenol oxidase, which may be beneficial in scavenging O2−·. Practical Applications Apple juice is one of the most popular fruit beverages in the world. But during processing of fruit juice and also during storage, it is easy for them to undergo enzymatic browning reaction, which has an influence on the color and nutritional quality of apple juice. The main approach to reduce enzymatic browning is the use of antioxidants. This work studied the antioxidant activity of chitosans with different molecular weights in vitro, and further research was focused on the application of the most potent antioxidant among those tested as an enzymatic browning inhibitor of apple juice. The study demonstrated that oligochitosan may be potentially used for controlling browning of apple juice without affecting nutritional quality.