荔枝采后果皮花色素苷的降解与花色素苷酶活性变化

 荔枝果实外观颜色在很大程度上取决于果皮花色素苷含量及其存在的状态 ,果皮褐变与花色素苷含量呈显著的负相关。荔枝果皮存在高活性的花色素苷酶 ,而同样富含花色素苷的水果如苹果、葡萄、草莓和杨梅等则不含花色素苷酶活性。容易褐变的糯米糍荔枝含有较高的花色素苷酶和PPO活性 ;不容易褐变的桂味、兰竹则含有较低量的花色素苷酶和PPO活性。在荔枝采后褐变过程中 ,花色素苷酶活性一直维持在较高水平并呈逐渐上升的趋势 ,PPO活性随褐变加重而下降 ,POD活性则逐渐升高。因此推测 ,荔枝果皮花色素苷的降解及果皮褐变除了与PPO和POD有关之外 ,还可能与花色素苷酶有关。

The Anthocyanin Degradation and Anthocyanase Activity During the Dericarp Browning of Lychee Fruit

The pericarp color of lychee fruit is mainly dermined by its anthocyanin content. A significant inverse relationship between anthocyanin content and pericarp browning index was established. A high activity of anthocyanase (anthocyanin-3-glucosidase) in lychee pericarp was identified, whereas, under the same conditions, no anthocyanase activity could be detected in red apple, red grape, red bayberry and strawberry. Furthermore, a higher anthocyanase and PPO activity was recorded in Nuomici fruit, which is sensitive to pericarp browning, compared to lower activity in Guiwei and Lanzhu fruit, which are less sensitive to pericarp browning. Anthocyanase activity maintained at high level and increased gradually along with postharvest pericarp browning. In the same condition, PPO activity decreased gradually, whereas POD activity increased gradually during the pericarp browning, which implied that anthocyanase was involved in anthocyanin degradation and pericarp browning of lychee fruit as PPO and POD.