Propyl gallate postharvest treatment improves the storability of longans by regulating the metabolisms of respiratory and disease-resistance substances

The influences of 0.5 mM propyl gallate, a ROS scavenger, on the metabolisms of respiratory and disease-resistance substances in 'Fuyan' longan fruit during storage at 15 °C were explored. Compared to the control longan, propyl gallate-treated longan displayed a higher rate of commercially acceptable fruit, the lower indices of pulp breakdown and fruit disease, and a lower rate of fruit weight loss. Additionally, propyl gallate-treated longan exhibited a lower rate of fruit respiration, the lower activities of SDH, PGI, CCO, AAO, PPO and AOX, and the lower levels of NAD and NADH, but the higher activities of NADK and G-6-PDH + 6-PGDH, and the higher levels of NADP and NADPH. Furthermore, propyl gallate-treated longan manifested the higher activities of CHI, GLU, PAL, POD, CAD, C4H and 4-CL, and the higher contents of lignin. These data indicated that, propyl gallate-improved the storability of longan was related to the fact that propyl gallate reduced respiration and increased disease resistance of longan through decreasing the respiratory pathways of EMP and TCA cycle, and raising PPP respiratory pathway, as well as through increasing the metabolism of disease-resistance substances. Above findings suggest that 0.5 mM propyl gallate has potential application in prolonging the shelf-life and restraining the fruit spoilage of postharvest fresh longan.