Maillard reaction-based conjugation of hazelnut protein isolate with sodium alginate: structural and functional insights

This study aimed to enhance the techno-functional properties of hazelnut protein isolates (HPI) derived from cold-pressed meal by conjugating them with sodium alginate (SA) using a wet-heating method. Temperature, heating time, and protein ratio were evaluated as independent variables, and optimal conditions of 65 °C, 5 h, and 35 % protein content were identified by targeting maximum glycation degree, solubility, and emulsion capacity while minimizing hydroxymethylfurfural (HMF) content. Under optimal conditions, conjugation significantly improved solubility and emulsifying properties compared to native protein isolate (p < 0.05). Structural analysis revealed increases in β-sheet content, free SH groups, zeta potential, and surface hydrophobicity, alongside reductions in α-helix content. Rheological evaluation showed reduced viscosity and consistency coefficient in the conjugates, indicating weaker pseudoplastic behavior, while oscillatory tests confirmed an elastic structure (G' > G″). Temperature sweep revealed a viscous-to-elastic transition of the conjugates at lower temperatures, potentially beneficial in moderate-temperature food processing. This study demonstrates that controlled glycation can effectively enhance the functionality of hazelnut protein isolates, supporting their potential application in diverse food formulations.