外源褪黑素对甜樱桃果实褐变和品质的影响

为探讨外源褪黑素处理对采后甜樱桃褐变和品质的影响，本研究以‘萨米脱’甜樱桃为材料，分别以蒸馏水、100 μmol·L?1外源褪黑素浸泡处理甜樱桃果实5 min，于0±1 ℃下贮藏，定期取样进行褐变和品质相关生理指标的测定。结果表明:外源褪黑素处理能够显著（P<0.05）抑制褐变指数上升，降低了33.3%腐烂率，并显著（P<0.05）延缓了硬度、可滴定酸、可溶性固形物和抗坏血酸含量的下降。褪黑素处理还显著（P<0.05）提高了超氧化物歧化酶和过氧化氢酶活性，显著（P<0.05）抑制了脂氧合酶活性、O₂?·产生速率、H₂O₂水平、丙二醛含量和相对膜透性的上升。同时，褪黑素处理显著（P<0.05）延缓了过氧化物酶、多酚氧化酶、苯丙氨酸解氨酶活性的上升，并显著（P<0.05）提高了多酚含量。这些结果表明，外源褪黑素处理抑制甜樱桃果实褐变可能与提高抗氧化酶活性，降低膜脂过氧化程度，保持细胞膜结构完整性和抑制褐变相关酶活性密切相关。

Effect of Exogenous Melatonin Treatment on Browning and Quality of Sweet Cherry

To investigate the effects of melatonin on the browning and quality of postharvest sweet cherry fruits, ‘Samituo’sweet cherry was used as the material in this study. Sweet cherry was treated with distilled water and 100 μmol·L?1 exogenous melatonin, and the relevant physiological indexes related with browning and quality were determinated at regular time during storage at 0±1 ℃. The results showed that melatonin treatment significantly (P<0.05) inhibited the increase of browning index, reduced the decay rate by 33.3%, significantly (P<0.05) delayed the decrease of firmness, total soluble solids, titratable acidity, and ascorbic acid content. The melatonin significantly (P<0.05） increased the activities of superoxide dismutase and catalase, significantly (P<0.05) inhibited the increase of lipoxygenase activity, O₂?· generation rate, H₂O₂, malondialdehyde content , and relative membrane permeability. Meanwhile, melatonin treatment significantly (P<0.05) delayed the increase of peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase, and significantly (P<0.05) increased polyphenol content. These results indicated that the inhibiting fruit browning via exogenous melatonin treatment in sweet cherries might be closely associated with the improvement of antioxidant enzyme activities, the reduction of membrane lipid peroxidation degree, the maintenance of structural integrity of cell membrane and the inhibition of browning related enzyme activities.