Interfacial Stabilization of Green and Food-Safe Emulsions through Complexation of Tannic Acid and Nanochitins

Nanochitins exhibit unique structural attributes that confer distinct physical properties to multiphase systems. Amphiphilic tannic acid (TA) serves as an excellent candidate for interfacial modification via electrostatic adsorption and complexation with nanochitin. In this study, we developed green and food-safe strategies to enhance the stabilizing and functional performance of complexes formed through the coassembly of chitin nanofibers (ChNF) and TA. Their interactions were systematically investigated using spectroscopy, rheological measurements, and molecular simulations, all confirming strong interfacial binding primarily through hydrogen bonding. X-ray diffraction analysis further revealed TA-induced changes in ChNF crystallinity. The resulting ChNF-TA complexes effectively stabilized high internal phase Pickering emulsions (HIPPEs), which exhibited long-term stability and were successfully applied in direct ink writing. The exceptional stability of the HIPPEs was attributed to the synergistic effects of electrostatic charge neutralization and interfacial tension reduction. Quartz crystal microgravimetry demonstrated rapid complexation, with TA binding to ChNF thin films at a level of approximately 450 ng/cm2. The resulting HIPPEs remained stable for at least two months and readily formed cryogels upon freeze-drying. Owing to their enhanced stability and viscoelastic properties, HIPPEs stabilized with ChNF-TA complexes offer a promising platform for the development of sustainable emulsions, with the potential for customization in personalized food and related fields.