干制速度对无核白葡萄酚类物质和多酚氧化酶细胞化学定位及褐变的影响

为了探索脱水速度对干制过程中无核白葡萄酚类物质和多酚氧化酶细胞化学定位的影响及其与褐变的关系。利用透射电镜技术观察快速和缓慢脱水过程中的无核白葡萄细胞中酚类物质和多酚氧化酶的精确定位观察及褐变指数的变化。结果表明:酚类物质主要分布于液泡中,多酚氧化酶主要分布于细胞质、叶绿体膜、线粒体膜、液泡膜、细胞膜上。缓慢脱水质量损失40%时和快速脱水质量损失60%时,液泡膜破裂,区室化作用打破,酚类物质流出,与多酚氧化酶反应引起褐变,褐变指数上升,表明无核白葡萄褐变与细胞区室化作用相关。与缓慢脱水相比,快速脱水的无核白葡萄能更好的保持细胞完整性,降低褐变程度。研究结果为快速脱水技术在无核白葡萄干制中的应用提供理论依据。

Effect of Drying Rate on Cytochemical Localization of Phenolic Substance and Polyphenol Oxidase and Browning in Thompson Seedless Grape

In order to explore effect of drying rate on cytochemical localization of phenolic substance and polyphenol oxidase and the relationship for browning in Thompson seedless grape. Transmission electron microscopy was used to observe the precise position of phenolics and polyphenol oxidase and browning index of Thompson seedless grape under both rapid and slow modes. The results showed that phenols were distributed in vacuoles and polyphenol oxidase was distributed in cytoplasm, chloroplast membrane, mitochondrial membrane, tonoplast membrane and cell membrane. When the mass loss of slow dehydration was 40% and the mass loss of rapid dehydration was 60%, the outflow of phenols and brown reaction with polyphenol oxidase, the increase of browning index and the breaking down of compartmentalization. Compared with the slow dehydration, the rapid dehydration of non-nuclear white grapes can maintain cell integrity better, can reduce the occurrence of seedless white grapes browning better. These results can provide a theoretic reference for the application of rapid dehydration in the drying of Thompson seedless grapes.