外源褪黑素处理对采后荔枝褐变及活性氧代谢的影响

为探讨外源褪黑素处理对采后荔枝褐变及活性氧代谢的影响，本研究以“妃子笑”荔枝为材料，分别以清水、不同浓度（50、100、200 μmol/L）的外源褪黑素浸泡处理荔枝，于4℃下贮藏，定期取样进行活性氧代谢相关生理指标的测定。结果表明，不同浓度的外源褪黑素处理均可降低荔枝的失重率、褐变指数和细胞膜通透性，保持果实较好的色度（L*:明亮度），降低果实中超氧阴子离（O₂-）产生速率和多酚氧化酶（PPO）活性，减缓丙二醛（MDA）及过氧化氢（H₂O₂）的产生和积累，提高超氧化物歧化酶（SOD）活性和维持荔枝果实细胞膜的良好完整性。尤以50 μmol/L的外源褪黑素处理效果最佳。结果表明黑素处理可以通过调节采后荔枝的活性氧代谢而延缓其衰老进程，为褪黑素的应用及荔枝采后保鲜提供理论支撑。

Effects of Exogenous Melatonin on Browning and Active Oxygen Metabolism of Postharvest Litchi

To investigate the effects of exogenous melatonin treatment on browning and reactive oxygen species metabolism of Postharvest litchi,“Feizixiao”litchi was used as the material in this study.Litchi was treated with clear water and exogenous melatonin at different concentrations(50,100,200μmol/L),and the relevant physiological indexes related with active oxygen metabolism were determinated at regular time during storage at 4℃.The results showed that different concentrations of melatonin could reduce the weight loss rate,browning index and cell membrane permeability of litchi,maintain the original color(L^*:brightness),reduce the production rate of superoxide anion(O₂^-)and the activity of polyphenol oxidase(PPO),slow down the production and accumulation of MDA and hydrogen peroxide(H₂O₂),improve the activity of SOD and maintain the integrity of cell membrane of litchi fruit.In particular,50μmol/L melatonin treatment showed the best effect.It could be speculated that melatonin treatment can delay the aging process of postharvest litchi by regulating its reactive oxygen species metabolism,which provides theoretical support for melatonin application and postharvest preservation of Litchi.