Abstract
Resveratrol is a phenolic compound with recognized antioxidant activity; however, its application is limited by its low stability and poor gastrointestinal bioavailability. This study investigated the functionalization of zein with resveratrol through a free radical-mediated grafting reaction using an ascorbic acid/hydrogen peroxide redox system and evaluated the effect of dialysis on the resulting conjugates. The materials were characterized by UV–Vis, FTIR, XPS, XRD, SEM, DSC, and TGA. Protein and total phenolic contents were determined using the Bradford and Folin–Ciocalteu assays, antioxidant activity was evaluated by ABTS and DPPH, and stability was assessed under simulated gastrointestinal digestion. Spectroscopic, structural, morphological, and thermal analyses indicated modifications in the zein matrix after functionalization, with dialysis producing a more homogeneous surface morphology. The functionalized materials exhibited significantly higher antioxidant activity than native zein, reaching ABTS and DPPH inhibition values of 87–93% and 84–86%, respectively, comparable to free resveratrol. During simulated gastrointestinal digestion, the conjugates maintained resveratrol contents between 885.9 and 1115.0 μmol GAE/g, although significant time-dependent variations were detected within each treatment (p < 0.05). Overall, free radical-mediated functionalization provided zein–resveratrol conjugates with improved physicochemical stability while preserving the antioxidant properties of resveratrol, supporting their potential application as protein-based delivery systems for phenolic bioactive compounds.