Enzymatic browning in fresh-cut apples causes a decrease in sensory quality, commodity value reduction and economic losses. Various physical, chemical and biotechnological methods have been developed to inhibit browning in fresh-cut apples. In the present study, we propose a promising alternative approach using a combination of lysine (Lys) and arginine (Arg)—two natural amino acids—which effectively delayed browning in fresh-cut apples. Lys/Arg treatment impeded weight loss while maintaining firmness and soluble solid content. Molecular docking and phenolic contents showed that Lys/Arg could delay browning in fresh-cut apples by inhibiting polyphenol oxidase (PPO) activity and reducing phenolic substrates. Furthermore, transcriptomic analysis showed that Lys/Arg treatment improved stress tolerance and reactive oxygen species (ROS) scavenging capacity. RT-qPCR confirmed that Lys/Arg treatment inhibited the transcription of key PPO-related genes and induced the expression of genes associated with antioxidant capacity, which collectively reduced PPO activity and enhanced the antioxidant capacity of fresh-cut apples. In conclusion, Lys/Arg treatment can delay fresh-cut apple browning by decreasing PPO activity, regulating phenolic metabolism and enhancing ROS scavenging, which provides a promising alternative approach to delaying visual browning and maintaining selected physicochemical attributes of fresh-cut apples.
Liu et al. (Mon,) studied this question.