Abstract: The purpose of this study was to explore the physiological mechanism for browning inhibition in fresh-cut apple by cysteine. Fresh-cut apples were dipped in 0.5 g/L cysteine solution for 1 min. The effect of cysteine treatment on browning index (BI), the activities of polyphenol oxidase (PPO) and antioxidant enzymes, the contents of antioxidant substances and malondialdehyde (MDA) and non-enzymatic antioxidant capacities was evaluated. The results showed that cysteine treatment significantly inhibited surface browning in fresh-cut apples during storage and resulted in lower PPO activity at the early stage of storage. Furthermore, cysteine treatment enhanced the activities of antioxidant enzymes, improved antioxidant capacity and the contents of antioxidant substances, and inhibited the accumulation of MDA at the same time. Statistical analysis indicated that BI was significantly negatively correlated with ascorbic acid content, catalase (CAT) activity, and antioxidant activity (P < 0.01), while there was a positive correlation between BI and MDA content (P < 0.01). Collectively, these finds suggest that cysteine treatment can inhibit PPO activity and enhance antioxidant capacity, thereby retarding the browning of fresh-cut apples during storage.

Key words: fresh-cut apples, browning, cysteine, physiological mechanism