拉曼光谱法分析凡纳滨对虾冻藏过程蛋白质与水分结构变化

Protein and Water Structural Changes in Whiteleg Shrimp(Litopenaeus vannamei) during Frozen Storage as Revealed by Raman Spectroscopy

探明冻藏过程中凡纳滨对虾肌肉蛋白质与水分的结构变化有助于揭示蛋白质冷冻变性机理,采用拉曼光谱技术对凡纳滨对虾肌肉蛋白质在不同冻藏温度条件下的二级结构进行分析,并结合重水置换技术表征肌肉蛋白质的氘代动力学,从蛋白质结构和表层水分子角度研究冻藏温度对蛋白质冷冻变性的影响。结果表明:冻藏过程中蛋白质的二级结构由规整转向松散,肽链展开,且-18℃冻藏的蛋白质结构松散性比-40℃显著;伴随蛋白质结构的展开,表面疏水性增加,蛋白质与表层结合水的相互作用减弱,且冻藏温度越高,相互作用减弱越剧烈,蛋白质结构也越不稳定,水分越容易流失;而冻藏温度越低,蛋白质与水分的相互作用越强,蛋白质结构越稳定,越有利于保持对虾原有品质。

The mechanism of protein denaturation during frozen storage can be revealed by the interaction between muscle protein and water. In this study, the effect of storage temperature on protein denaturation in whiteleg shrimp（Litopenaeus vannamei） muscle was examined in terms of protein structure and surface water molecules. The secondary structure and deuteration kinetics of whiteleg shrimp muscle protein stored at-18 and-40 ℃ were analyzed by Raman spectroscopy and H/D exchange method. The results showed that the secondary structure of protein molecules changed from tight to loose, suggesting protein unfolding. Furthermore, the structure of protein stored at-18 ℃ was more loose than at-40 ℃. With the unfolding of the protein secondary structure, the surface hydrophobicity of the protein increased, while the interaction between protein and bound water was weakened. The higher the storage temperature was, the more intensely the interaction was weakened, the less stable protein structure was and the more easily moisture loss occurred. In contrast, the lower the frozen temperature was, the stronger the interaction between protein and water was. Consequently, protein structure was more stable. The results showed that lower frozen storage temperature was more effective to maintain protein properties.