Optimization of extraction process of protein isolate from corn germ by response surface analysis

The protein isolate was extracted from defatted corn germ powder by alkali-solution and acid precipitation.The effect of 4 factors,pH value,ratio of solid to liquid,the extraction time and temperature,on protein extraction rate was studied by single factor experiment.According to the results of single factor experiment the response surface methodology related to pH value,ratio of solid to liquid,temperature and the extraction rate was established.The result showed that the main factors affecting the extraction rate were in turn of pH value,ratio of solid to liquid,the extraction time and temperature.Under the optimum condition of pH value 9,liquid-solid ratio 10.79∶ 1(mL∶ g),at 50.46 ℃ for 60 min,the extraction rate of corn germ protein isolate was 55.71%,the purity could reach about 90%.