Effect of different extraction and drying methods on walnut protein isolates: Systematic comparison of the functional properties, structural characteristics, and molecular dynamics simulation.

This study compared isoelectric precipitation (I) versus micellization (M) extraction, combined with freeze-drying (FD) or spray-drying (SD), on walnut protein isolates (WPI). Results showed extraction methods governed color and hydration: M produced lighter powders with higher oil-holding capacity (0.40 g/g), while I yielded darker isolates with superior water-holding capacity (0.34 g/g) and emulsion stability. Drying methods dictated structural properties: FD preserved higher α-helix content and larger particles, whereas SD induced unfolding, increased surface hydrophobicity, and reduced emulsion stability. Molecular dynamics simulation corroborated that SD caused greater conformational perturbation than FD. Overall, extraction methods determine color and hydration behavior, while drying methods control structural integrity and interfacial functionality, enabling tailored selection for specific food applications.