Abstract: To address the issue of rapid browning in litchi fruits during the transition from cold storage to ambient temperature, this study investigated the mitigating effect of exogenous ATP treatment on the quality deterioration of cold-stored litchi fruits and its underlying physiological mechanisms. The results showed that exogenous ATP treatment significantly reduced browning index and decay incidence in cold-stored litchi fruits after 24 hours of storage at ambient temperature by 31.9% and 20.5%, respectively, compared with the control (tap water). In terms of physiological mechanisms, ATP treatment helped to maintain cell membrane integrity by decreasing relative electrical conductivity and malondialdehyde (MDA) content. It also slowed down the degradation of anthocyanins and total phenolics, and significantly inhibited the activity of polyphenol oxidase (PPO) and peroxidase (POD). Meanwhile, ATP treatment alleviated the accumulation of superoxide anion radical and hydrogen peroxide in litchi fruits, and enhanced the activity of superoxide dismutase (SOD) and catalase (CAT), maintaining the balance between the production and scavenging of reactive oxygen species (ROS). Furthermore, ATP treatment alerted the distribution of the respiratory pathways, so that after 6 hours at ambient temperature, the actual operating rate of the alternative pathway was more than twice that of the control group, thereby increasing its proportion among the total respiration. Additionally, ATP treatment maintained a higher level of energy charge, preventing energy metabolism imbalance during the transition from cold storage to ambient conditions. In conclusion, exogenous ATP alleviates the quality degradation of cold-stored litchi fruits during the shelf-life by regulating ROS metabolism, optimizing energy homeostasis and the respiratory pathways, maintaining cell membrane integrity, and inhibiting enzymatic browning. These findings provide a theoretical basis for improving the cold chain circulation of litchi.

Key words: litchi; ATP treatment; energy metabolism; respiratory pathways; cold storage; quality