Response Surface Optimization for the Extraction and Properties of Walnut Protein
Using walnuts as the main raw material,the method of extracting walnut protein is the alkaline solution and acid deposition method,and the auxiliary mean is the ultrasonic method.The effects of enzyme addition,temperature,time,material-to-liquid ratio and pH on the extraction of walnut protein are investigated by single-factor test.The optimal process for the extraction of walnut protein is obtained by using the Plackett-Burman design to screen the optimal factors.The optimum process for walnut protein extraction is obtained as follows:enzyme addition 1.5% ,temperature 55 ℃,time 2.0 h,material-liquid ratio 1∶12(g/mL),pH 9.0,and the extraction rate of walnut protein can reach 68.44% under this condition.The significant effects of factors and their interactions on the extraction rate of walnut protein are obtained using response surface analysis.The three factors that have significant effects on the protein extraction rate are pH,temperature and time,and the order of the factors affecting the extraction of walnut protein is pH＞time＞temperature.Under the optimal extraction process,investigate the effect of different pH on the properties of walnut proteins,which include the ability to dissolve,the ability to produce bubbles and the ability of the foam sheet to remain stable.At pH 5.0,the solubility of walnut protein is 11.84% ,the foaming is 10.56% ,the foam stability is 82.79% ,and the foam stability of walnut protein decreases continuously with the extension of sitting time.
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