不同低水解度的大米蛋白溶解性与结构变化的关系

Relationship between solubility and structural properties of different low degree of hydrolysis of rice protein

为了研究不同水解度的大米蛋白溶解性与其结构变化之间的关系，本文采用碱性蛋白酶处理大米蛋白，得到不同低水解度的大米蛋白（0％、1％、3％、5％），并表征了不同水解度蛋白的溶解性、二硫键含量、表面疏水性、微观结构和分子量。结果表明，在pH2．0～11．0范围内，各蛋白样品的溶解度均呈现先降低后升高的趋势，且在同-pH下，溶解度随水解度的增大而增大。尤其是在水解度为5％时，蛋白溶解度达到最高为65．93％。随着水解度的增大，蛋白样品的分子量、二硫键含量及表面疏水值发生了显著降低（P≤0．05）。这些变化可能是因为蛋白分子内部结构的变化，导致蛋白质的结构发生去折叠或者解聚现象，促使大米蛋白内部亲水基团暴露，从而提高蛋白质的溶解度。扫描电镜显示原料蛋白颗粒不均一，质地坚硬，而酶解后的蛋白颗粒大小相对均一，表面有较多孔洞且较蓬松。随着水解度的增大，蛋白样品的结构和性质发生更加显著的变化。这些结构变化可能导致大米蛋白溶解性提高。

In order to study the relationship of different degree of hydrolysis of rice protein solubility and the structure change, rice protein was enzymatically modified with alkaline protease to get desired degree of hydrolysis （DH） （0%, 1%, 3%, 5%）.And the solubility and disulfide bond content, surface hydrophobicity, surface microscopic structure and molecular weight of different degree of hydrolysis protein were characterized. In the range of pH2.0-11.0,the solubility of protein samples was decreased firstly,and then increased.At the same pH, solubility was increased with the increase of hydrolysis degree.When the degree of hydrolysis was 5%, maximum protein solubility was 65.93%.1t showed that with the increase of the degree of hydrolysis, rice protein＇s molecular weight,disulphide bond content and surface hydrophobicity were decreased significantly （p〈 0.05 ）.These changes may be because of the change of protein molecule structure, which led to the structure of the protein unfold or depolymerization, prompting rice protein internal hydrophilic group exposure, so as to improve the solubility of protein. From the scanning microscopy analysis=the grain size of rice protein was uneven and the material quality was hard.The size of rice protein hydrolysates was relatively uniform and the surface had more holes and they were fluffier.With the increase of the degree of hydrolysis, the structure and properties of protein samples were significantly changed.The conformational changes may lead to rice protein solubility increase.