葡聚糖延缓草鱼肌原纤维蛋白冷冻变性的机理分析

Cryoprotective Effect and Mechanism of Dextran with Different Molecular Weights on Denaturation of Myofibrillar Protein from Grass Carp(Ctenopharyngodon idella)

以草鱼肌原纤维蛋白为研究对象,通过研究盐溶性蛋白质量浓度、Ca^(2+)-ATPase活性、表面疏水性、总巯基和活性巯基含量在冷冻贮藏条件下的变化,比较不同分子质量葡聚糖(添加量0.5%)和传统商业抗冻剂(4%蔗糖+4%山梨糖醇)对冻藏过程中肌原纤维蛋白的冷冻保护效果。结果表明,在冻藏过程中,葡聚糖能有效延缓草鱼肌原纤维蛋白的冷冻变性,效果优于传统商业抗冻剂;分子质量小的葡聚糖(T7)对Ca^(2+)-ATPase活性和活性巯基的保护作用要整体优于分子质量大的葡聚糖(T20),冻藏超过15 d后延缓表面疏水性的上升和总巯基的保护上的效果也显著优于后者;因此,在工业中选用分子质量小的葡聚糖作为淡水鱼及相关制品的冷冻保护剂效果更佳。

The present study investigated the cryoprotective effect of dextran with different molecular weights on denaturation of myofibrillar protein from grass carp（Ctenopharyngodon idella）. The content of salt soluble protein, Ca^2＋-ATPase activity, surface hydrophobicity, total sulfhydryl group and active sulfhydryl group were evaluated. Results showed that the denaturation of grass carp myofibrillar protein was significantly delayed by dextran during frozen storage, and the effect of dextran（0.5%） was better than that of commercial antifreeze（4% sucrose ＋ 4% D-sorbitol）. Low molecular weight dextran（T7） was better than high molecular weight dextran（T20） in protecting the Ca^2＋-ATPase activity and active sulfhydryl group and also in delaying the increase of surface hydrophobicity and the decrease of sulfhydryl group after 15 d frozen storage. Thus, the low molecular weight dextran is recommended to be used in the fishery industry as a promising cryoprotectant.