褪黑素对鲜切梨抗氧化系统和NO合成的影响

目的研究外源褪黑素处理对鲜切梨抗氧化系统及一氧化氮合成途径的影响。方法以“皇冠”梨片为实验材料,分别在0,50,100,150μmol/L褪黑素中进行浸泡处理。结果与对照组相比,褪黑素处理提高了鲜切梨的色差值,降低了鲜切梨呼吸作用、乙烯跃变高峰以及可溶性固形物含量,同时降低了鲜切梨中的菌落总数、霉菌数和酵母菌数。褪黑素处理抑制了多酚氧化酶和过氧化物酶的活性,提高了过氧化氢酶的活性,同时也显著提高了鲜切梨抗坏血酸过氧化物酶活性和超氧化物歧化酶活性,从而降低了活性氧含量。褪黑素处理提高了氧化型谷胱甘肽与还原型谷胱甘肽的含量比例,抗坏血酸与脱氢抗坏血酸的含量比例,同时还提高了谷胱甘肽还原酶活性、单脱氢抗坏血酸还原酶活性以及脱氢抗坏血酸还原酶活性。在外源施加褪黑素后,鲜切梨的硝酸还原酶活性和亚硝酸盐含量与对照组相比变化不明显,一氧化氮合酶活性和L-精氨酸含量得到明显提高。结论经100μmol/L的褪黑素处理对鲜切梨的抗氧化和保鲜效果最为显著,是一种较好的抑制鲜切梨褐变及保持鲜切梨品质的方法。

Effects of Melatonin on Antioxidant System and NO Synthesis Pathway of Fresh-cut Pear

The work aims to explore the effects of exogenous melatonin treatment on the antioxidant system and nitric oxide synthesis pathway of fresh-cut pears.The"Crown"pear slices were used as materials,soaked in 0,50,100,150μmol/L melatonin,respectively.Compared with the control group,melatonin treatment improved chromatic aberration,inhibited the respiration and the ethylene production of fresh-cut pears,and reduced the changes in soluble solids content,the total number of colonies,mold and yeast counts of fresh-cut pears.Melatonin treatment inhibited the activities of polyphenol oxidase and peroxidase,improved the activities of catalase,ascorbate peroxidase and superoxide dismutase,thereby reducing the active oxygen content.And at the same time,melatonin treatment increased the ratio of oxidized glutathione to reduced glutathione,and the ratio of ascorbic acid to dehydroascorbic acid,and enhanced the activities of glutathione reductase,monodehydroascorbate reductase and dehydroascorbate reductase.The activity of nitrate reductase and nitrite content of fresh-cut pears with melatonin treatment were not significantly different from that of the control group,while the activity of nitric oxide synthase and L-arginine content were significantly increased.The results show that 100μmol/L melatonin has the most significant antioxidant and fresh-keeping effects on fresh-cut pears.This is a good method to inhibit the browning of fresh-cut pears and maintain the quality of fresh-cut pears.