Whey protein-tannic acid conjugate stabilized high internal phase Pickering emulsions: Interfacial stability based on covalent crosslinking

Protein-stabilized high internal phase Pickering emulsions (HIPEs) have potential usage in food and cosmetic fields. However, the poor interfacial activity of proteins in HIPEs is still a key bottleneck. In this work, whey protein (WP)-tannic acid (TA) conjugates by covalent crosslinking were used to fabricate HIPEs, and then the emulsifying ability and stability of HIPEs were also studied. The result indicated that covalent bonds formed between WP and TA. WP-TA conjugates had better oil-water interfacial activities and more suitable wettabilities than free WP. WP-TA conjugate stabilized HIPEs had a narrower size distribution, a more compact droplet structure and a denser gel network compared with free WP stabilized HIPEs, especially at high TA mass ratios and alkaline conditions. At the same time, the conjugates stabilized HIPEs exhibited better stability against heat treatment and centrifugation. Covalent crosslinking in WP-TA conjugates formed network based on TA molecules as bridges among emulsion droplets and played an important role in stabilizing HIPEs. This study expects to provide a new perspective for investigating the stabilizing mechanism of protein-polyphenol conjugate stabilized HIPEs.