鸭梨果心褐变过程中膜质过氧化及细胞内膜微粘度的变化

Changes of Superoxidation and Endomembrane Microviscosity of the Core of Ya pears during Browning Development

采用急降温和缓降温两种方法处理鸭梨果实，并对冷藏中果心褐变指数、保护酶活性、膜质过氧化水平和细胞内膜微粘度进行测定。结果表明：急降温处理的果实约３０天果心出现褐变症状，６０天后褐变指数达到１００％，而缓降温处理的果实在贮藏中无褐变产生。在６０天的贮藏过程中，急降温处理的果实果心组织的超氧化物歧化酶（ＳＯＤ）、过氧化物酶（ＰＯＤ）、过氧化氢酶（ＣＡＴ）活性均呈下降趋势，丙二醛（ＭＤＡ）水平和细胞内膜微粘度则显著升高。缓降温果实果心组织中ＳＯＤ、ＰＯＤ活性呈上升趋势，ＣＡＴ活性虽呈下降趋势，但下降水平明显低于急降温处理。ＭＤＡ水平及细胞内膜微粘度的上升率明显低于急降温处理组。实验结果说明：急降温处理导致果心细胞膜质过氧化作用加剧，同时造成细胞内膜流动性下降，从而造成细胞膜系统组分及功能发生变化，导致细胞中区域化分布被打破，造成果实组织褐变。

Ya pear fruits were treated with slow cooling and rapid cooling. brown index, activities of SOD, POD and CAT, MDA level and endomembrane microviscosity of the core tissue were investigated. The results showed that rapid cooling induced the browning of the fruits and the brown index reached 100% after 60 days storage. Activities of SOD, POD, CAT were decreased notably and MDA level and endomembrane microviscosity increased sharply by the treatment. The fruits under slow cooling treatment did not show any incidence of core browning. Activities of SOD and POD increased remarkably, CAT activity and MDA level decreased and endomembrane microviscosity kept steady. The data suggested that rapid cooling could result in the changes of superoxidation and phase of the membrane of the core cells of the fruits. This, in turn, results in the leakage and decomposition of the cell membrane system. Further more, the compartment of polyphenols and PPO can be destroyed and the browning of the fruits developed.