Studies On The Postharvest Physiology Of Difference Of Storability Between 'Wuye' And 'Lanzhu' Lychee Fruits

The lychee (Litchi chinensis Sonn.) fruit, a native of South China,belong to litchi plant of Sapindaceae,its major producing area is Guangdong,Fujian,Taiwan,Guangxi, Sichuan provinces (or autonomous regions), and so on, and it is one of the most competitive fruits at the domestic and in the international market. However, lychee fruit is produced in hot midsummer and it will rapidly deteiorates once harvested, resulting in a uniform browning of the pericarp surface. Pericarp browning reduced its commercial value and has long been considered the main postharvest problem.Normally,lychee has a very short postharvest life of 3～4 days at ambient temperature.This short postharvest period limits its long-ditance transportation, marketing and consumption.Therefore, the research of postharvest biology and technology of lychee fruit becomes a key problem in the development of lychee production. The fruits of 'Wuye' lychee which tended to have better storage and 'Lanzhu' lychee which tended to have poor storage, the chief cultivars in Fujian province, were used. Fruits harvested from Jiuhu orchard in Zhangzhou city were transported to our laboratory in Fuzhou city under ambient temperature. Fruit were selected for uniformity of maturity, color, shape and size, and any blemished or diseased fruit were discarded. The fruit were dipped for 5 min in 0．1% DECCOZIL(?) (Elf Atochem North America, Inc.), and then the fruits were packed in polychloroethylene (PE) (0．03mm thick) bags and stored at (8±1)℃. Differences of storability and postharvest physiology between 'Wuye' and 'Lanzhu' lychees were investigated in this paper. The results were as follows:1．Storability differed between 'Wuye' and 'Lanzhu' lychees. 'Wuye' lychee tended to have better storage features as compared to 'Lanzhu'. During storage, health rate of 'Wuye' lychee fruit was remarkable higher (P<0．05) than 'Lanzhu'. But the weight loss, pericarp browning degree, pericarp browning index of 'Wuye' lychee were remarkable lower (P<0．05) compared with 'Lanzhu'. There were higher contents of total soluble solids (TSS), total sugars, vitamin C in pulp of 'Wuye' lychee than 'Lanzhu'. During storage, contents of TSS, total sugars and vitamin C in pulp decreased continuously, but the rates of decrease in 'Wuye' lychee were more slowly than 'Lanzhu'. At the same storage, contents of TSS, total sugars and vitamin C in pulp of 'Wuye' lychee were higher than 'Lanzhu'.2．There were defference of rate of O₂ metabolism of pericarp in lychee fruit between 'Wuye' and 'Lanzhu'. Rate of O₂ metabolism in pericarp of 'Wuye' lychee tended to have lower features as compared to 'Lanzhu'. During storage, contents of activities of reactive-oxygen-scavenging enzymes (SOD, CAT, APX) and endogenous antioxidant substances (AsA, GSH) were remarkable higher (P<0．05) compared to 'Lanzhu'. Whereas the productive rate of O₂ and MDA content in pericarp of 'Wuye' lychee were remarkable lower (P<0．05) as compared to 'Lanzhu'. As a result, during storage, 'Wuye' lychee pericarp had a higher antioxidant capacity which reduced the accumulation of active oxygen, degreased membrane lipid peroxidation, kept the integrity of cellular membrane structure and prolong its senescence as compared to 'Lanzhu'. Therefore, 'Wuye' lychee had a longer storage time than 'Lanzhu'.3．There were defference of pericarp browing between 'Wuye' and 'Lanzhu' lychees. 'Lanzhu' lychee tended to have more easily pericarp browing than 'Wuye'. During storage, pericarp browning index of 'Wuye' lychee was remarkable lower (P<0．05) than 'Lanzhu'. There were higher contents of carotenoid and flavonoid in 'Wuye' lychee than 'Lanzhu'. PPO and POD were the key enzymes in pericarp browning. 'Wuye' lychee tended to have lower PPO and POD activities as compared to 'Lanzhu'. During storage, contents of anthocyanin, flavonoid and phenols and PPO activity in pericarp of lychee fruit degreased, whereas POD activity increased. There were less changes of postharvest physiology in 'Wuye' lychee than 'Lanzhu'.From the above results it can be seen that 'Wuye' lychee with higher contents of TSS, total sugars and vitamin C in pulp, higher reactive-oxygen-scavenging enzymes and endogenous antioxidant substances in preicarp which scavenged reactive oxygen, lower rate of water loss and less changes of postharvest physiology, tended to have strong resistant to pericarp browing and more good storage .