冻融次数对镜鲤鱼肌原纤维蛋白功能和结构特性变化的影响

本实验通过测定肌原纤维蛋白溶解性、乳化性、δ-电势、巯基含量、自由氨基酸含量、二聚酪氨酸含量、表面疏水性和α-螺旋含量的变化，探究反复冻融过程引起镜鲤鱼肌原纤维蛋白功能特性和结构特性的变化。结果表明：当冻融次数增加到5 次时，肌原纤维蛋白的溶解度、乳化活性、乳化稳定性分别显著下降至62.85%、20.67 m2/g、34.83%（P＜0.05）；在冻融过程中随着冻融次数的增加，蛋白质的δ-电势、表面疏水性和二聚酪氨酸含量不断增加，而巯基、自由氨基酸和α-螺旋含量不断下降。蛋白质的这些变化表明，冷冻-解冻循环破坏了镜鲤鱼肌原纤维蛋白的完整结构，降低了蛋白质的功能特性。

Effect of Freeze-Thaw Cycles on Changes in Functional and Structural Properties of Myofibrillar Protein from Mirror Carp (Cyprinus carpio var. specularis)

The effect of freeze-thaw cycles on the functional and structural properties of myofibrillar protein from mirror carp (Cyprinus carpio var. specularis) was investigated by measuring the changes in the emulsifying properties, solubility, δ-potential, surface hydrophobicity and content of sulfydryl, free amino acids, dityrosine, surface hydrophobicity and α-helix. The results indicated that the solubility, emulsifying activity and emulsion stability of myofibrillar protein decreased to 62.85%, 20.67 m2/g and 34.83%, respectively after five freeze-thaw cycles (P < 0.05). The δ-potential, surface hydrophobicity and dityrosine content increased constantly with the increase of freeze-thaw cycles, while the sulfydryl, free amino acid and α-helical contents decreased gradually. These changes suggested that freeze-thaw cycles damaged the structural integrity and functional properties of fish myofibrillar protein.