Microfluidics-engineered ovalbumin-carvacrol nanoparticles for ultrasonically fabricated pickering emulsion coatings: a sonochemical strategy for fruit preservation.

Postharvest spoilage of fresh fruits causes substantial global food loss and exacerbates environmental burdens associated with conventional plastic packaging, driving the urgent need for sustainable and effective preservation alternatives. Herein, we address this challenge through a microfluidics-ultrasound route that fabricates edible chitosan coatings reinforced with ovalbumin (OVA) Pickering emulsions for passion fruit preservation. Microfluidic precision synthesis enabled the production of uniform OVA-carvacrol (Car) nanoparticles with narrow size distribution and excellent batch-to-batch reproducibility-advantages not achievable by conventional bulk mixing. Subsequently, ultrasonic emulsification (20 kHz, 100-400 W, 2-8 min) was applied, and the acoustic cavitation effects were systematically exploited to refine emulsion droplet dimensions, reinforce the interfacial adsorption of OVA-Car nanoparticles, and tailor the viscoelastic properties of the Pickering emulsion network. The optimally ultrasonicated emulsion (300 W, 6 min) exhibited significantly enhanced rheological performance and sustained release behavior. When compounded with chitosan to form edible coatings, the composite film delivered potent synergistic antioxidant and antimicrobial activities, with DPPH and ABTS radical scavenging rates of 66.92 % ± 1.48 % and 91.40 % ± 0.29 %, respectively, and ≥ 75 % inhibition against S. aureus, E. coli, and A. niger. Coating application restricted passion fruit weight loss to 10.2 % (vs. 17.4 % in uncoated controls) and extended shelf life to 7 days at ambient temperature. This work demonstrates that the integration of microfluidic nanoparticle engineering with ultrasonic cavitation modulation offers a scalable, clean-label sonochemical strategy to supplant synthetic preservatives and petroleum-derived packaging in postharvest fruit preservation.