The Effect Of Ultrasonic Pretreatment On Emulsifying Property Of Phosphorylation Whey Isolate Protein

Whey protein has many properties such as water holding capacity and foaming capacity which make it become an important part of many baked goods formula. With the rapid development of the food industry, we will add some good functional properties of the protein to foods, which can not increase food nutrition but improve the taste. Therefore, improving their different functional properties of the existing protein is very important for the development of the food industry. In this paper, whey isolate protein(WPI) was used as materials, we studied the effect of phosphorylation, ultrasonic treatment and ultrasonic treatment phosphorylation on emulsifying property of WPI. The following is the results of the study:In this study sodium tripolyphosphate(STP)was used as the modification reagent, technological parameters of phosphorylation were determined by response surface methodology, effects of addition of WPI, addition of STP, reaction p H, reaction time, reaction temperature on emulsifying property had been analysed. The optimal extraction conditions by phosphorylation were as following: the addition of WPI 5.47%, the addition of STP 9%, the reaction p H value 7.94, the reaction time 1.81 h, and the reaction temperature 44℃. The effect order of five factors was: reaction temperature, reaction p H, addition of STP, concentration of WPI, reaction time.The properties of WPI were affected by phosphorylation modification condition. With the change of phosphorylation condition, the emulsifying property, emulsion stability and solubility was increasing first then decreasing. Compared with the WPI, the emulsifying property, emulsion stability and solubility of P-WPI were improved, and the emulsify stability was rarely changed.The functional properties of WPI were affected by ultrasonic treatment. The emulsifying property, emulsion stability and surface property of U-WPI improves significantly. When the ultrasonic time was 10 min, emulsifying property and surface property of WPI were best; but when the ultrasonic time was more than 10 min, with the increasing of ultrasonic time, emulsifying property and surface property of WPI was decreasing.The functional properties of WPI were affected by ultrasonic pretreatment phosphorylation. After ultrasonic pretreatment phosphorylation, emulsifying property, emulsion stability, solubility and surface hydrophobicity of WPI improves significantly. When the ultrasonic time was 10 min, emulsifying property, emulsion stability, solubility and surface hydrophobicity of WPI were best; But when the ultrasonic time was more than 10 min, with the increasing of ultrasonic time, emulsifying property, emulsion stability, solubility and surface hydrophobicity of WPI were decreasing.The surface property, emulsifying property and structure of WPI were affected by three different modification methods. Compared with P-WPI, the emulsifying property and surface property of UP-WPI increased in different degrees, but the solubility was rarely changed. The emulsifying property, emulsion stability, solubility and surface hydrophobicity of UP-WPI were the highest in three modification methods. The emulsifying property of UP-WPI increased by 115.41% than WPI and the emulsion stability of UP-WPI increased by 78.58%; the emulsion stability of U-WPI is slightly larger than P-WPI; the solubility of UP-WPI increased by 91.23% than WPI; the surface hydrophobicity of UP-WPI increased by 60.49% than WPI. Compared with UP-WPI, the surface hydrophobicity of U-WPI is increased by 39.12% than P-WPI. Through the infrared absorption spectrum, it shows that three modification methods cause the change of secondary structure of whey protein isolate; through the SDS-PAGE, it shows that the primary structure of whey protein isolated does not change.