Effect of Citric Acid on Shelf-life and Quality of Fresh-cut Chinese Water Chestnut (Eleocharis dulcis)

Polyphenol oxidase (PPO) and peroxidase (POD) of fresh-cut Chinese water chestnut (CWC) (Eleocharis dulcis) were extracted; use of citric acid at a concentration of 0.04 M or higher suppressed markedly PPO and POD activities. On the basis of the inhibition of PPO and POD activities in vitro, fresh-cut CWC were respectively dipped in the solutions of 0.05, 0.1 and 0.2 M citric acid, placed in trays over-wrapped by plastic films, and then stored at 4°C. Changes in surface discoloration, eating quality and disease development were evaluated, while the content of total phenols and the activities of PPO, POD and phenylalanine ammonia lyase (PAL) were analysed. Among treatments, the best beneficial effects were observed when 0.1 M citric acid was used. Treatment with 0.1 M citric acid prevented surface discoloration, delayed the increase in the activities of PPO, POD, PAL, reduced the loss in the contents of ascorbic acid and total soluble solid (TSS) and, thus, maintained eating quality and extended shelf-life. The results also exhibited that fresh-cut CWC treated with 0.1 M citric acid had a shelf-life of about 9 days. The potential use of citric acid as an anti-browning agent on fresh-cut CWC is discussed.