核桃蛋白及其组分构象和功能特性的研究

Study on Conformation and Functional Properties of Walnut Protein and its Components

摘要:

本文研究了核桃蛋白及其主要组分谷蛋白和球蛋白的物化特性与功能特性。研究表明：核桃蛋白的变性温度Td（104.42 ℃）和热焓值ΔH（12.93 J/g）都显著高于谷蛋白和球蛋白的变性温度、热焓值（p<0.05），且变性协同性较好；谷蛋白和球蛋白的巯基含量较核桃蛋白高，且大部分巯基暴露在表面，而核桃蛋白巯基主要包埋在分子内部且二硫键含量为三者中最高（为5.2 μmol/g）；由荧光结果表明核桃蛋白有着较致密的三级结构，而球蛋白结构相对较疏松；表面疏水性指数由高至低依次为谷蛋白、核桃蛋白和球蛋白。谷蛋白表现出较高的乳化活性，但乳化稳定性最差，核桃蛋白的乳化活性较谷蛋白稍差，但乳化稳定性最好；球蛋白的巯基和二硫键含量较高，结构松散，作用位点较多，形成的凝胶强度高，其次是核桃蛋白和谷蛋白。

Abstract:

The physicochemical and functional properties of walnut protein and its main components (glutelin and globulin) were examined. Walnut protein had a higher denaturation temperature (Td=104.42 ℃) and higher enthalpy (ΔH=12.93 J/g) than glutelin and globulin (p<0.05), with higher cooperativity of thermal transition. Walnut protein had the lowest sulfhydryl content while globulin had the highest. Most sulfhydryl groups of walnut protein were embedded within the molecule and it had the highest content of disulfide bonds (5.2 μmol/g), while those of glutelin and globulin were mostly exposed on the surface. The fluorescence results indicated that walnut protein had a dense tertiary structure, while that of globulin was relatively looser. The descending order of surface hydrophobicity of the three proteins was glutelin, walnut protein, and globulin. The emulsifying stability of walnut protein was the strongest among the three, owing to its compact structure and high disulfide content, whereas glutelin exhibited the worst emulsifying stability. Globulin had a loose structure with more active sites, exhibiting greater gel properties than walnut protein and glutelin.