Encapsulation of curcumin by hetero-protein aggregates of whey protein isolate and lysozyme

Curcumin (CUR) is a bioactive polyphenol with significant health potential; however, its use in food systems is limited by poor aqueous solubility. Hetero-protein aggregation offers a promising encapsulation strategy; however, its performance is highly dependent on formulation conditions. Here, an experimental screening approach was used to evaluate the effects of pH (4–10), whey protein isolate (WPI): lysozyme (LYS) ratio (3:1–1:3), and CUR concentration (905–54 μM) on the formation and encapsulation performance of WPI–LYS hetero-protein aggregates. The screening identified pH, protein ratio, and CUR loading as interdependent drivers of aggregation behaviour, surface charge, particle size, crystallinity, and encapsulation efficiency. Maximum encapsulation efficiency (97.56 ± 0.50%) was achieved at pH 7, 494 μM, and a WPI: LYS ratio of 1:1.5; however, structural analyses revealed that high CUR loadings resulted in residual crystallinity despite the high apparent encapsulation efficiency. In contrast, lower CUR loading (106 μM; 1:50 CUR: protein) produced amorphous hetero-protein aggregates with high encapsulation efficiency and improved structural homogeneity. Spectroscopic evidence indicates that, in the ternary WPI–CUR–LYS system, CUR is stabilised within a reorganised protein network through localised hydrophobic interactions and hydrogen bonding. In contrast, single-protein systems rely on less restrictive associations. Overall, WPI–LYS hetero-protein aggregates outperformed single-protein systems, demonstrating that reliable CUR encapsulation cannot be inferred from encapsulation efficiency alone. This work highlights the critical role of systematic screening in establishing formulation-dependent design rules for hetero-protein-based delivery systems in food applications. • WPI–LYS hetero-protein aggregates enhanced curcumin encapsulation vs single proteins • Maximum encapsulation efficiency achieved at pH 7 and WPI:LYS ratio of 1:1.5 • Curcumin modulated protein–protein interactions, reducing aggregation and particle size • XRD and SEM revealed amorphous curcumin at ≤106 μM and saturation above 494 μM • FTIR showed α-helix/β-sheet increase correlates with higher curcumin encapsulation