Abstract: In order to obtain high dry protein content of soy isolate protein,using the physical methods controlling pH gradient to change acid precipitating step,and adding sodium chloride to alter ion intensity of solution,in order to separating 11S and 7S orderly.Therefore,it could enhance the dry protein content of soy isolate protein.On the basis of single factor test of material fluid proportion,temperature,sodium chloride addition,response surface optimization design was carried on to enhance the dry protein content of soy isolate protein on the most superior parameter condition.The result indicates the best condition that material fluid proportion is 1:11.35,the extract temperature is 48.63℃,NaCl addition is 0.126 mol/L,which leads to the dry protein content of soy isolate protein to achieve 96.04%,and is better than the market products that is 93.31% to increasing 2. 67%.

Key words: soy isolate protein, dry protein content, response surface methodology, technology