该研究比较了添加三种分子量分别为149.03、118.75和36.48 ku的魔芋葡甘聚糖酶解产物EK1、EK2和EK3对草鱼肌原纤维蛋白在-18 ℃冻藏过程中物理、化学和结构特性的变化，通过盐溶性蛋白含量、Ca2+-ATPase活性、总巯基、表面疏水性、粒径、Zeta电位、SDS-PAGE、紫外和荧光光谱分析其变化特征。研究结果表明，与空白对照组、商业抗冻剂、EK1和EK2相比，冻藏20 d，EK3组的盐溶性蛋白浓度和总巯基含量最大，分别为1.51 mg/mL和19.76×10-5 mol/g。与此同时，冻藏30 d，EK3组的Ca2+-ATPase活性含量最大，且表面疏水性和Zeta电位最小，分别为1.31 μmol Pi/（mg prot•h）、8 689.07和-13.35 mV。冻藏30 d，SDS-PAGE结果表明EK3组的肌球蛋白和肌动蛋白降解程度最小，有利于抑制肌原纤维蛋白的氧化。冻藏30 d，紫外和荧光光谱结果表明EK3组的色氨酸和酪氨酸残基的暴露程度减小，有利于维持蛋白空间结构稳定性。因此，该实验添加小分子量的魔芋葡甘聚糖酶解产物EK3（36.48 ku）对肌原纤维蛋白冷冻保护作用最佳，这为水产品冷冻过程中使用小分子多糖作为抗冻剂提供了理论支持。

Changes in the physical, chemical, and structural properties of myofibrillar protein of grass carp caused by adding konjac glucomannan enzymatic products EK1, EK2 and EK3 with molecular weights of 149.03, 118.75 and 36.48 ku, respectively, during the frozen storage at –18 ℃, were compared. The samples were analyzed for salt-soluble protein content, Ca2+-ATPase activity, total sulfhydryl groups, surface hydrophobicity, particle size, Zeta potential, SDS-PAGE, and UV and fluorescence spectra. The results manifested that the salt-soluble protein content and total sulfhydryl content in the EK3 group were at maximum at 1.51 mg/mL and 19.76×10-5 mol/g, respectively, after 20 d of freezing, compared with the blank control, commercial antifreeze, EK1, and EK2. At same time, the Ca2+-ATPase activity, in the EK3, were at maximum at 1.31 μmol Pi/(mg prot•h), while the Zeta potential were at minimum at 8 689.07 and –13.35 mV, respectively, after 30 d of freezing. After 30 d of freezing, the SDS-PAGE results showed that the EK3 group had the least degradation of myosin and actin, which inhibited the oxidation of myogenic fibronectin. Furthermore, the exposure of tryptophan and tyrosine residues was reduced in the EK3 group, which indicated that the stability of the protein spatial structure was maintained. Therefore, it was concluded that the addition of small molecular weight konjac glucomannan enzymatic digestion product EK3 (36.48 ku) had the best cryoprotective effect on myofibrillar protein in this experiment, which supports the use of small molecule polysaccharides as antifreeze agents for aquatic products.

国家自然科学基金项目（31871870）