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

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 p H2.0~11.0,the solubility of protein samples was decreased firstly,and then increased.At the same p H,solubility was increased with the increase of hydrolysis degree.When the degree of hydrolysis was 5%,maximum protein solubility was 65.93%.It 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.