Preparation and characterization of protein-antioxidant complex pickering particles for high internal phase emulsions

Herein, novel Pickering particles were fabricated by integrating tannic acid (TA) into Spirulina protein isolates (SPI) to enhance the oxidative stability of Pickering high internal phase emulsions (Pickering-HIPEs). The interactions between SPI and TA were examined using molecular docking simulation, attenuated total reflection Fourier-transform infrared (ATR-FTIR), and isothermal titration calorimetry (ITC). The interfacial properties of SPI-TA (ST) complex particles with different ratios of SPI to TA were characterized, and their emulsifying performances were also investigated with different oil volume fractions. The results revealed that hydrogen bonds may play a key role in the formation of ST complex particles. The presence of TA improved the wettability of SPI, and the resultant ST complex particles displayed a better emulsifying capacity, with the ability to emulsify up to 85  vol % of oil. Especially, ST complex particles stabilized Pickering-HIPEs exhibited a narrower size distribution, a stronger gel network, better stability upon long-term storage and UV exposure. Additionally, the oxidative stability of embedded oil and lipophilic bioactive compounds in Pickering-HIPEs was significantly improved regardless of exposure to room temperature or UV irradiation. Our research findings are expected to provide novel antioxidant Pickering particles for food-grade Pickering-HIPEs.