Tailoring purple rice bran protein via multi-modal modifications: Chemical, physical, and enzymatic strategies for...

Purple rice bran protein (PRBP) is a high-quality resource, but its application remains limited due to poor solubility. This study systematically investigated how selected physical (ultra-high pressure and microwave treatments), chemical (phosphorylation and glycosylation), and enzymatic (alkaline protease and papain) treatments altered the structure and thereby influence the functionality of PRBP. Structural analysis revealed that these modifications reduced the β-sheet content, particle size, and thermal stability of PRBP, while concurrently altering its surface morphology. Consequently, these structural changes led to a notable improvement in functional properties. Both the emulsifying activity index and foaming stability were improved, with the ultra-high pressure treatment showing the highest increase in emulsifying activity index, and the alkaline protease treatment achieving the greatest enhancement in foaming stability. Meanwhile, enzymatic modification improved oil absorption capacity, while physical modification enhanced water absorption capacity. These findings indicated that different modification methods exert distinct yet beneficial effects on the structure-function relationship of PRBP, providing a basis for targeted functionality enhancement and broader application in food systems.