Physiological roles of exogenous oxalic acid in delaying ripening of mango fruit during storage.
Zheng XiaoLin, Tian ShiPing, Li BoQiang, Xu Yong
Author Affiliation: Key Laboratory of Photosynthesis and Environmental Molecular Physiology/Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Scientia Agricultura Sinica 40 : 1767-1773
Abstract : The objective of this study is to investigate the effects of exogenous oxalic acid on the ripening process of harvested mango fruit (Mangifera indica cv. Shengxin) and provide an alternative method for the storage of mango fruits. Mango fruit was dipped in 5 mmol oxalic acid/litre solution for 10 min and then stored at room temperature (25°C), and the physiological effects of oxalic acid on delaying ripening process in mango fruits were evaluated during postharvest. Oxalic acid treatment resulted in decrease of the softening rate, and alleviation of the increases of soluble solid content (SSC) and relative leakage, as well as the decrease of titratable acid (TA) during storage. Compared with untreated fruits, superoxide dismutase (SOD) activity in the peel of treated fruit was significantly higher from 6 to 15 days after harvest, while lipoxygenase (LOX) activity was significantly lower at 6 and 9 days, which were associated with the significant decreases of superoxide (O2-) production over the first 12 days and of hydrogen peroxide (H2O2) content at 9 and 12 days during storage, respectively. The ethylene production in treated fruits reduced significantly after 13 days. In addition, the improved peel redness and significant decrease of fruit decay were presented in treated fruits without impairment of the flesh flavour at the end of storage (18 days). The ripening process in mango fruit was delayed by exogenous oxalic acid. The physiological effects of oxalic acid on increasing SOD activity and reducing LOX activity were related to the decrease of radical oxygen species (ROS), and the inhibited ethylene production apparently delayed the ripening process and contributed to disease resistance. It is suggested that oxalic acid treatment in an alternative method for the postharvest storage of mango fruits.