Impacts of Single and Sequential Enzymatic Extraction on the Functional Properties of Khao Dawk Mali 105 Rice Bran Proteins at Two Maturity Stages

Proteins from the bran of Khao Dawk Mali 105 rice at two maturity stages, green (GB) and fully ripe (RB), were extracted using single and sequential enzyme-assisted processes. Non-enzymatic extraction (control), α-amylase (AA), protease (PT), and two sequential treatments (AA-PT and PT-AA) were applied to defatted bran to evaluate their effects on protein yield, structural attributes, and functional properties. Protease-based extractions, particularly PT, produced the highest protein contents (28% in GB and 23% in RB) and significantly improved solubility, water- and oil-holding capacities, and foaming performance. GB extracts consistently outperformed RB across all functional and antioxidant measurements, indicating greater extractability and bioactive potential in green rice bran. Enzymatic hydrolysis also enhanced phenolic and flavonoid release, leading to markedly higher DPPH and FRAP activities. SDS-PAGE profiles demonstrated reduced band complexity and lower-molecular-weight protein in enzymatically treated samples, while FTIR spectra confirmed secondary structural modifications associated with hydrolysis. Overall, protease and sequential assisted extractions provide an efficient and sustainable approach to improving rice bran protein recovery and functionality. These findings highlight green rice bran as a promising source of high-value plant proteins for food and nutraceutical applications.