Pellicle-retained roasting enables endogenous polyphenol-mediated covalent remodeling of walnut protein for enhanced gelation and curcumin delivery.

Pellicle-retained roasting was investigated for modifying walnut protein (WP) through endogenous polyphenol release and subsequent reactions during alkaline extraction. WPs from untreated pellicle-removed (K), roasted pellicle-removed (RK), pellicle-retained roasted (RK-P), and in-shell roasted (RK-P-S) kernels were compared. K and RK showed polyphenol grafting contents of 6.41 and 10.13 mg GAE/g and solubilities of 17.54% and 21.42%, whereas RK-P reached 181.46 mg GAE/g and 56.53%, respectively. Hydrophobic interactions and disulfide bonds contributed substantially to RK-P gel stabilization, with hardness reaching 155 g versus 28.4 g for K and 58.8 g for RK. RK-P achieved a curcumin retention efficiency (RE) of 81.02% and cumulative intestinal release of 32.73%, versus 50.87% and 8.27% for K and 59.04% and 11.45% for RK, while limiting gastric release to 2.19%. RK-P-S showed intermediate performance. These results indicate that pellicle retention promotes WP remodeling and gelation and enhances curcumin retention and intestinal-phase release under the tested conditions.