褪黑素处理对香菇采后品质及活性氧代谢的影响

实验分别设置不同浓度（0.25、0.50、0.75 mmol/L）褪黑素对香菇进行喷淋处理，通过贮藏42 d内对香菇采后硬度、褐变度、亮度及开伞度等表观品质的测定，筛选得到0.50 mmol/L褪黑素处理浓度效果最好；在该处理浓度下进一步探究了褪黑素处理对香菇采后活性氧代谢的影响，并观察了贮藏28 d时香菇细胞超微结构的变化。结果表明：0.50 mmol/L褪黑素处理可以显著降低香菇采后呼吸强度，抑制细胞内活性氧代谢产物超氧阴离子的生成速率和羟自由基生成能力；贮藏结束（42 d）时，褪黑素处理组香菇的呼吸强度、超氧阴离子自由基的生成速率、羟自由基生成能力与对照组相比分别降低44%、39.1%、24.4%，褪黑素处理还可以减少香菇细胞丙二醛和过氧化氢的积累，维持较低的羰基化蛋白水平和较完整的细胞膜结构；且褪黑素处理组香菇的总酚、抗坏血酸含量及1,1-二苯基-2-三硝基苯肼自由基清除能力均显著高于对照组；超微结构观察表明褪黑素处理组香菇细胞壁和线粒体形态维持较好。综上，褪黑素处理可以有效维持香菇采后品质，降低活性氧代谢产物生成速率，提高机体的抗氧化能力，进而减少活性氧对机体的伤害，其中，0.50 mmol/L处理组效果相对最好。

Effect of Melatonin Treatment on Postharvest Quality and Reactive Oxygen Species Metabolism of Lentinus edodes

In this study, melatonin solutions at different concentrations (0.25, 0.50 and 0.75 mmol/L) were sprayed on fresh shiitake mushrooms (Lentinus edodes). By evaluating the hardness, browning degree, brightness and cap opening of the mushrooms, during the 42-day storage a melatonin concentration of 0.50 mmol/L was selected to further investigate its effect on reactive oxygen species (ROS) metabolism and changes in the ultrastructure of shiitake mushroom cells after 28 days of storage. The results showed that 0.50 mmol/L melatonin treatment significantly decreased the respiration intensity, superoxide anion generation rate and hydroxyl generation capacity compared with the untreated control group, reducing these by 44%, 39.1%, and 24.4% at the end of the 42-day storage period, respectively. The melatonin treatment also decreased the accumulation of malondialdehyde (MDA) and H2O2 in the mushroom cells and maintained lower levels of carbonylation proteins and a more complete cell membrane structure. In addition, the total phenol and ascorbic acid contents, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity in the treatment group were significantly higher than those in the control group. Ultrastructural observations showed that the morphology of the cell wall and mitochondria were maintained well after the treatment. In conclusion, melatonin treatment effectively maintained the quality of postharvest shiitake mushrooms by reducing the production rate of ROS metabolites and improving the antioxidant capacity to reduce oxidative damage caused by ROS to mushrooms, and the best effect was observed at 0.50 mmol/L.