A New Supercritical CO2 Defatting—pH Multistage Regulation Extraction Method of Walnut Protein Isolate With Excellent Functional Properties

In this paper, we proposed a new supercritical CO 2 defatting—pH multistage regulation extraction method (SD-PMRE) of high water soluble walnut protein isolate (HWPI), by investigating the effects of PMRE, three defatting methods, and walnut seed coat on the functional properties of HWPI. The results showed that HWPI had high yield of 48.56% and high protein content of 87.58%. More importantly, it had a solubility of 91.58%, significantly higher than walnut protein isolate (WPI) with the highest solubility. Meanwhile, other functional properties of HWPI were greatly improved, with emulsification capacity and stability of 118.07 m 2 /g and 91.03%, and foaming capacity and stability of 129.17% and 89.29%, respectively. Through the SD-PMRE, the problem of WPI’s poor functional properties such as solubility was solved, avoiding the shortcomings brought by modification methods and expanding the application of walnut protein in the fields of food and medicine.