High internal phase Pickering emulsions stabilized by tannic acid-ovalbumin complexes: Interfacial property and stability

Abstract

While protein-stabilized high internal phase Pickering emulsions (HIPEs) have demonstrated promising potential for various applications in food, their poor interfacial stability remains as a major challenge to overcome. In this work, tannic acid (TA) was used to increase the stability of ovalbumin (OVA)-stabilized HIPEs. The binding clusters between OVA and TA were hypothesized by the molecular docking simulation, and the interfacial properties of OVA and TA complexes (OVA-TA) were investigated by interfacial tension and three-phase contact angle. The characteristics of HIPEs under different pHs were studied by static light scattering and confocal laser scanning microscopy (CLSM), as well as rheology. The results showed that there were some specific clusters in OVA and TA which may form hydrogen bonds and hydrophobic interactions. The wettability of OVA was significantly improved by TA, resulting in greater interfacial stability at the oil-water interface. Compared with OVA-stabilized HIPEs (O-HIPEs), OVA-TA-stabilized HIPEs (OT-HIPEs) had narrower size distribution, more compact droplet structure and denser gel network to resist droplet aggregation. Especially at pH 4.0, OT-HIPEs exhibited stronger gel network and higher viscosity than at other pH values, because of smaller electrostatic repulsion between OVA and TA, and easier crosslinking on the oil-water interface. In addition, the viscosity of OT-HIPEs was increased after 24 h incubation, indicating the formation of more hydrogen bonds. Meanwhile, OT-HIPEs showed good storage and freeze-thaw stability. Our research findings from this study are expected to provide novel insight on protein-based particles stabilized HIPEs from an interfacial perspective.