Mild-temperature conjugation of pea protein isolate with oxidized sodium alginate: structural, interfacial, and emulsion properties.

Pea protein isolate (PPI) has limited food applications because of poor aqueous solubility and emulsifying performance. Here, sodium alginate (SA) was oxidized to generate reactive aldehyde groups, enabling Schiff-base-mediated conjugation with PPI under mild conditions (40 °C, 90 min). By varying reaction parameters, conjugates with grafting degrees (GD) of 10.67-22.87% were obtained. Increasing GD was accompanied by increased β-sheet content (32.81-41.52%), tertiary structural reorganization, enhanced surface charge, a water contact angle of up to 79.35°, and a > 50% reduction in oil-water interfacial tension. The conjugates, particularly at GD >18%, stabilized high-internal-phase emulsions containing 75% oil at 4% protein, with good stability during heating, exposure to NaCl up to 200 mM, and 15 d storage. High-GD emulsions retained >85% of curcumin during storage, showed lower gastric curcumin release, and increased final bioaccessibility to >68% in the present in vitro digestion model. These findings demonstrate a mild, tunable strategy for improving PPI functionality and developing plant-protein-based delivery systems.