冻结及冻藏温度对小龙虾蛋白质理化性质的影响

Effect of Frozen and Freezing Storage Temperatures on Physicochemical Properties of Protein from Red Swamp Crawfish

将小龙虾热烫后置于真空包装盒内,灌水并抽真空,分别于3个冻结温度(-20,-40,-55℃)下冻结至中心温度为-15℃,并置于2个冻藏温度(-20,-40℃)中冻藏24周,测定不同冻结温度处理和冻藏的小龙虾肉的肌原纤维蛋白含量、表面疏水性、内源荧光强度、总巯基和二硫键含量、二级结构的变化。结合冰晶的显微结构观察结果,探讨冻结及冻藏温度对小龙虾蛋白质理化性质的影响,为小龙虾加工原料的周年供应提供理论指导。试验结果显示:在冻藏温度相同时,-20℃冻结小龙虾肉的冰晶较大,导致肌肉结构受到严重的破坏,肌原纤维蛋白含量显著低于-40,-55℃冻结(P<0.05)的表面疏水性、内源荧光强度、总巯基和二硫键含量差异不显著(P>0.05)。在冻结温度相同时,-20℃冻藏小龙虾肉的冰晶更大,出现针形冰晶的时间更早,肌原纤维蛋白含量、总巯基含量显著低于-40℃(P<0.05),表面疏水性、二硫键含量显著高于-40℃(P<0.05),内源荧光强度变化幅度更大。此外,-20℃冻结或冻藏时,α-螺旋的相对含量较高,而β-折叠、β-转角和无规卷曲无明显差别。这些结果表明,较低的冻结及冻藏温度使小龙虾肉蛋白的空间构象更稳定,减轻了蛋白质的变性程度,使冻藏期间小龙虾的品质更好。

In order to provide theoretical guidance for processing all the year, the red swamp crawfish preboiled were placed in the plastic box filled with water, then the boxes with crawfish were vacuumed, followed that the crawfish were frozen in the ice locker at-20,-40,-55 ℃, respectively. After the center temperature of which was fallen to-15 ℃,the frozen crawfish in boxes was stored at-20,-40 ℃ for 24 weeks. The content, surface hydrophobicity, intrinsic fluorescence intensity, total sulfhydryl and disulfide bond contents, and secondary structure of myofibril protein as well as microstructure of ice crystal were measured, to investigate the effect of frozen and freezing storage temperatures on physicochemical properties of protein from red swamp crawfish. The results showed that, at the same freezing storage temperature, the ice crystal with red swamp crawfish frozen at-20 ℃ was bigger, resulting in a heavier damage of meat structure, compare to the frozen temperature with-40 ℃ and-55 ℃. Besides, the myofibril protein content of crayfish frozen at-20 ℃ was significantly lower than that of-40 ℃ and-55 ℃ (P<0.05), while there is a slight difference in the surface hydrophobicity, intrinsic fluorescence intensity, and total sulfhydryl and disulfide bond contents of myofibril protein(P>0.05);at the same frozen temperature, the ice crystals with freezing storage at-20 ℃ was larger, and the needle-shaped ice crystals appear earlier, compared to freezing storage temperature of-40 ℃. The myofibril protein and total sulfhydryl contents of crayfish with-20 ℃ significantly lower than that of-40 ℃ (P<0.05), while the surface hydrophobicity and disulfide bond content were significantly higher than that of-40 ℃ (P<0.05). The intrinsic fluorescence intensity of myofibrillar protein with-20 ℃ changed faster than that of-40 ℃. In addition, the relative content of α-helix with frozen or freezing storage temperatures of-20 ℃ was higher than that of-40 ℃ and-55 ℃ frozen or-40 ℃ of freezing storage, while there is a slight difference in β-sheet, β-turn, and random coil. These results indicated that a lower frozen and freezing storage temperatures may keep a more stable spatial conformation of protein from red swamp crayfish and alleviate the degree of protein denaturation, resulting in better quality attributes of red swamp crayfish during freezing storage.