桑椹采后自溶过程中的质地与细胞壁结构变化

Changes in Texture and Cell Wall Structure of Postharvest Mulberry Fruits During Aril Breakdown

将果实采摘后发生果肉变软、溶解、流汁,甚至糜烂的现象称为果实自溶。为了解桑椹采后自溶现象发生与质地参数及细胞壁结构变化的关系,对大10和白玉王2个果桑品种的桑椹进行采后自溶指数、质构参数及细胞壁组分、细胞膜透性与降解酶活性的变化分析。4℃低温贮藏过程中,2个果桑品种桑椹的硬度、弹性和咀嚼性均呈下降变化,而自溶指数均明显上升,即果实的硬度、弹性、咀嚼性与自溶指数均呈显著负相关,3项参数均能较好地反映桑椹采后的质地特性。黏附性和内聚性均能较好地反映因细胞壁结构变化而导致的桑椹采后自溶现象：采后桑椹的黏附性上升,与细胞壁物质含量呈显著负相关,验证了细胞壁组分发生了降解;采后桑椹的内聚性下降,与细胞膜透性呈显著负相关,验证了细胞膜的完整性受到破坏。研究结果证实质地多面分析（TPA）参数可以评价桑椹采后质地变化和自溶现象。此外,桑椹采后自溶时,细胞壁降解酶（果胶酯酶、多聚半乳糖醛酸酶、β-半乳糖苷酶、纤维素酶）活性发生改变,引起细胞壁结构变化,导致果实质地软化,这种变化在2个果桑品种间存在差异。

The pulp of some fruits will become soft,soluble,juice leaking or even rotten after picking. This phenomenon is called fruit aril breakdown. To get a better understanding on the relationship of aril breakdown with texture parameters and cell wall structure changes in postharvest mulberry fruit,changes in aril breakdown indexes,texture parameters,cell wall components,cell membrane permeability and cell wall degradation enzyme activity of mulberry fruits from Da 10 and Baiyuwang fruit mulberry cultivars were analyzed. During storage under 4 ℃,firmness,elasticity and chewiness of the stored fruits from the 2 cultivars all decreased,while aril breakdown indexes increased obviously. There were significant negative correlations between breakdown index and all the 3 parameters,i. e. firmness,elasticity and chewiness. These3 parameters could well reflect the mulberry postharvest texture characteristics. Adhesiveness and cohesiveness could well reflect the aril breakdown of postharvest mulberry fruits caused by the changes of cell wall structure.The increase in adhesiveness has significant negative correlation with cell wall material content,which verifies that the degradation of cell wall components had occurred.The decrease in cohesiveness has significant negative correlation with cell membrane permeability,which verifies that cell membrane integrity was damaged. Results indi-cated that texture changes and aril breakdown of postharvest mulberry fruits can be evaluated by texture profile analysis（ TPA）. The activities of cell wall degradation enzymes（ pectinesterase,polygalacturonase,β-galactosidase,celluase,etc.） changed during aril breakdown in postharvest mulberry,which caused the cell wall structure change and the fruit texture softening. Such change was different between the two mulberry varieties.