中文摘要：

为探索杨桃采后果实保鲜新方法，研究外源柠檬酸对采后杨桃后熟衰老及保鲜效果的影响。以广东湛江红杨桃为试材，采用5、10mmol／L的柠檬酸溶液浸泡果实20min并在15℃下贮藏，研究柠檬酸处理对果实的后熟软化及相关生理指标的影响。结果表明：柠檬酸处理有效延缓’了杨桃果实硬度的下降、可溶性固形物含量的上升、可滴定酸含量的降低、细胞膜透性的上升以及果实V，含量的下降；柠檬酸处理还能提高果实贮藏后期POD的活性；同时，柠檬酸处理也抑制了果实中PPO活性的升高和MDA含量的积累。相关性分析表明，柠檬酸处理果实的硬度与POD活性、PPO活性及可滴定酸含量密切相关。外源柠檬酸能有效地抑制采后杨桃的后熟衰老进程，有较好的保鲜效果。

英文摘要：

The objective of the study is to investigate a new method for the preservation of carambola fruits and the effects of exogenous citric acid on ripening, senescence and preservation of post harvested carambola fruits. Ca- rambola fruits were subjected to treatments of citric acid at the concentrations of 0 （as control）, 5mmol/L and 10mmol/L for 20min, and then were stored at 15℃. The physiological parameters related to delaying ripening and softening process were measured. The results showed that citric acid treatments decreased the softening rate, delayed the increase of total soluble solids（TSS） and delayed titratable acid（TA）decreasing. Compared with the control, the membrane permeability was distinctly inhibited, and the loss of VC content was decreased. Citric acid treatment can promote the activities of peroxidase （POD） in later period of storage, and decrease polyphenol oxidase （PPO） activity and malondialdehyde（MDA） content. Correlation analysis showed that the physiological parameters of POD activity, PPO activity and TA content were related to the firmness in carambola fruits. It is suggested that exogenous citric acid treatment could delay the ripening and senescence rate of carambola fruits.