Effect of konjac glucomannan coating on antioxidant capacity and phenolic metabolism in fresh-cut lotus roots

Konjac glucomannan (KGM) was used as a natural coating matrix applied on fresh-cut lotus roots at 4 degrees C during 8 days storage. Treatment with 20 g/L KGM significantly maintained the color (L value), inhibited the respiration rate and delayed the decrease of the soluble solid content of lotus roots. For the antioxidant capacity test, KGM can enhance the antioxidant capacity by increasing activities of catalase and superoxide dismutase and increase the antioxidant capacity. Similar to the antioxidant capacity, the total phenolic contents in treated groups also exhibited higher value than untreated ones. Also, konjac glucomannan inhibited the degradation of catechol and increased cinnamic acid contents. In relation with phenolic metabolism, KGM at 20 g/L can improve the activities of peroxidase and phenylalanine ammonia lyase, but inhibit the activity of polyphenol oxidase. These observations indicted that KGM could maintain the quality of fresh-cut lotus root by the phenolic metabolism and antioxidant capacity. Practical applications This study suggested that konjac glucomannan inhibited tissue browning and maintain qualities of fresh-cut lotus roots. This study is also helpful to understand the regulation of tissue browning in fresh-cut lotus roots treated by konjac glucomannan. We have also explored the mechanism of the inhibition of tissue browning in lotus root slices coated with konjac glucomannan by the pathways of reactive oxygens and phenols. Concerned the nontoxic character and the high efficiency to preserve lotus root slices, konjac glucomannan can be a promising potential treatment to preserve qualities of fresh-cut fruits and vegetables, and this natural product could be considered as good candidates to be commercial preservations.