Ultrasonic engineering of bovine serum albumin nanoparticles for high internal phase Pickering emulsions: Interfacial behavior, microstructural evolution and stabilization enhancement

This study investigated the influence of ultrasonic treatment on the physicochemical properties of bovine serum albumin (BSA) and its applicability in stabilizing high internal phase Pickering emulsions (HIPPEs). Under optimized sonication conditions (250 W, 12 min), stable ultrasonically modified BSA (UBSA) particles were generated, exhibiting a small particle size (41.39 nm), a polydispersity index < 0.17, a higher absolute zeta potential (> 20 mV), and favorable wettability (three-phase contact angle: 78.71°), accompanied by reduced surface hydrophobicity. Intrinsic fluorescence spectra and circular dichroism (CD) analysis confirmed that ultrasonication altered the secondary structure of BSA, leading to the exposure of hydrophobic groups. Dynamic interfacial tension and adsorption kinetics analyses revealed that UBSA particles exhibited lower interfacial tension and significantly higher diffusion coefficient (K_diff) and penetration coefficient (K_p) than native BSA, indicating enhanced diffusion and adsorption capabilities of UBSA at the oil-water interface. Rheological analyses demonstrated that UBSA-stabilized HIPPEs possessed higher viscosity and larger storage (G') and loss (G″) moduli. Optical and confocal laser scanning microscopy confirmed the successful formation of HIPPEs at UBSA concentrations ≥ 1.0 % (w/v). UBSA-stabilized HIPPEs displayed a reduced droplet size (10.59 µm) and a more densely packed droplet structure, which conferred enhanced resistance against droplet coalescence compared to emulsions stabilized by native BSA. Moreover, stability assessments indicated that the centrifugal, freeze-thaw and storage stability of the prepared HIPPEs were significantly improved. Importantly, UBSA-based HIPPEs serving as a delivery vehicle also effectively enhanced the thermal processing stability of β-carotene. The findings demonstrate the potential of ultrasound-modified BSA nanoparticles as effective stabilizers for HIPPEs, providing valuable insights for the development of healthy and safe food-grade emulsion systems.