Pre-cut L-cysteine treatment inhibited the browning of fresh-cut apples by regulating enzyme activities and amino acid levels

This work investigated the effect of pre-cut L-cysteine treatment on the browning of fresh-cut apple slices. The results showed that 1% L-cysteine pre-cut treatment for 15 min could significantly inhibit the browning and extend the shelf life of fresh-cut apple slices. Pre-cut L-cysteine treatment was found to significantly inhibit polyphenol oxidase (PPO) activity and its gene expression, and increased superoxide dismutase (SOD) and catalase (CAT) activity as well as DPPH radical scavenging rate. In addition, pre-cut L-cysteine treatment improved the content of total and individual phenolics, particularly the content of chlorogenic acid and epicatechin in pulp. Pre-cut L-cysteine treatment also increased the cysteine, glutamic acid, serine and leucine level in pulp and peel. Therefore, pre-cut L-cysteine treatment is an effective method to control the browning of fresh cut apple by inhibiting PPO activity, improving antioxidant ability and regulating the synthesis of phenolics and free amino acids.