Contribution of sequential pretreatments and enzyme-assisted extraction to rice bran protein yield improvement

Alcalase is commonly used in enzyme-assisted extraction of rice bran protein. However, broad handling of rice bran can affect proteins before proteolysis. Various pretreatments, including thermal stabilization, washing, defatting, alkaline extraction, and enzymatic cellulosic degradation, and combinations were identified regarding the present and possible handling processes of rice bran protein extraction to investigate their effects on the proteolysis of the protein afterward. Then, the protein extraction yield and proteolytic abilities were compared. The thermal stabilization of the rice bran strongly affects enzymatic protein extraction, which more elaborate extraction protocols can mitigate. Rice bran oil can be extracted earlier without seriously affecting the protein extraction. Washing removes native protease inhibitors and hence speeds up the protein extraction. Alkaline extraction is highly efficient but can cause protein denaturation, generating a challenging protein separation from the gel-like structure. The protein extraction with enzymatic (Ultimase) pretreatment is an efficient method that allows high hydrolysis of intact rice bran protein during the protein extraction step.