Physiological changes during the process of pericarp browning in the postharvest litchi | 采后荔枝果皮褐变过程中的生理变化研究

[Objective] Pericarp browning in the postharvest litchi significantly reduced its commercial value and limited the expanding of litchi markets. Physiological changes during the process of pericarp browning were determined in order to identify the underlying mechanisms. [Method] Matured Feizixiao fruits were stored at 25 ℃ and 70%±5% relative humidity. The physiological changes happened in pericarp during storage were tested at an 8-hour interval. [Result] The fruit of Feizixiao (Litchi chinensis Sonn. cv Feizixiao) turned completely brown within 72 h after being harvested under the experimental conditions. Sharp increase of the browning index occurred from 48 to 64 hours after harvest (HAH). With the browning of pericarp, water content of the whole fruit and pericarp decreased continuingly. In contrast, there were no significant changes in the water content of pulp during the same period. MDA content, pH value and relative leakage rate of pericarp were increased during storage. Most of pigment contents including anthocyanin, flavonoid, phenols, chlorophyll a and total chlorophyll decreased. POD activity was initially increased in 32 HAH and then decreased afterwards. PPO activity was decreased continuously, while the activities of catalase and superoxide dismutase exhibited the pattern of “increasingCdecreasingCincreasing” as the storage time progressed. Correlation, stepwise regression and path analyses showed that water loss of pericarp was the major factor of pericarp browning. Principal and cluster analyses showed that there were two stages of pericarp browning during the course of litchi storage. [Conclusion] Water status of pericarp was the most important factor affecting pericarp browning. The pericarp browning happened by stages, which was mainly determined by the water loss of pericarp.