Pickering Emulsions Based on Gelatin/Tannic Acid/Hyaluronic Acid Nanocomplexes for Enhanced Emulsifying, Antioxidant, and Antimicrobial Properties

Several challenges, including the high hydrophilicity of proteins, oxidation of oils, bacterial contamination, and the chemical assembly of protein particles, have limited the application and development of Pickering emulsions (PEs) stabilized by protein particles in fields such as food and pharmaceuticals. In this study, we utilized a physical mixing strategy to combine tannic acid (TA), a natural polyphenol renowned for its outstanding antioxidant and antimicrobial capabilities, with gelatin (Gel) and negatively charged hyaluronic acid (HA) to form ternary nanocomplexes (TGH). Our research indicates that the assembly of TGH is likely mainly driven by noncovalent interactions, such as hydrogen bonding, hydrophobic interactions, and electrostatic interactions. These interactions alter the secondary structure of Gel, thereby enhancing its hydrophobicity. Compared with the binary nanocomplexes composed of TA and Gel (TG), TGH exhibits a significantly smaller particle size, superior stability, and a contact angle closer to 90°. Moreover, the antioxidant activity of TGH surpasses that of vitamin C, a commonly used antioxidant. TGH demonstrates the ability to stabilize herring oil and various vegetable oils. Particularly, at a concentration of 1% (wt %), TGH showed the potential to produce high internal phase PEs, which have the property of not flowing when inverted. Compared with TG, TGH shows enhanced emulsifying efficacy in stabilizing herring oil, as evidenced by the smaller droplet size, network structure formed by TGH on the surface of oil droplets, and more solid-like rheological characteristics revealed through micromorphological and rheological studies. Importantly, TGH-stabilized herring oil (TGH-PEs) effectively inhibited the growth of Escherichia coli and Staphylococcus aureus, demonstrating significant antibacterial activity. Moreover, TGH-PEs retarded the light-induced oxidation of active ingredient β-carotene embedded in them. Conclusively, TGH has great potential as a stabilizer for PEs and holds promise for applications in the food and pharmaceutical industries.