Continuous production of dilute to dense food grade emulsions via vapor condensation on films

Hypothesis: Scalable formation of high dispersed-phase fraction (ϕ) emulsions without mechanical agitation is a critical challenge in colloid and interface science. Conventional high-energy routes rely on cavitation and shear induced breakup, leading to uncontrolled temperature rise and degradation of bioactives, whereas low-energy methods offer gentle operation but limited throughput. We hypothesize that vapor-phase condensation on surfactant solutions can bypass shear-driven breakup entirely, enabling thermally gentle, energy-efficient and continuous formation of dense emulsions by nucleating and stabilizing droplets at the interface before coalescence can occur.

Experiments: Building on earlier studies of Emulsions by Vapor Condensation (EVC) on deep stagnant pools, we developed a continuous Emulsions by Vapor Condensation on Thin Film (EVC-F) process incorporating a custom-designed Dispenser-Spreader-Sweeper (DSS) arm. The arm uniformly spreads a surfactant-laden oil film on a cooled substrate and cyclically sweeps away condensate formed emulsions, enabling continuous operation. Using food grade Surfactants (polyglycerol polyricinoleate and soy lecithin), we systematically investigated how variations in film thickness, residence time (DSS rotation speed), and condensation rate modulate interfacial nucleation kinetics and droplet evolution, thereby controlling ϕ and emulsion stability, as supported by morphological and rheological analyses.

Findings: The EVC-F process produced submicron droplets (100 to 800 nm) with tunable ϕ up to about 25%, surpassing previous EVC systems that produced less than 1%. PGPR yielded highly stable emulsions with monomodal, narrow droplet size distributions and near-Newtonian like rheology, whereas lecithin produced larger and more polydisperse droplets. Mixed systems exhibited composition dependent stability, with PGPR rich blends remaining stable for more than 30 days. The improved stability of EVC-F emulsions relative to ultrasonication suggests that condensation-driven interfacial nucleation mitigates coalescence and dispersed phase loss typically observed under shear-dominated, non-isothermal conditions. These results establish EVC-F as a thermally gentle, energy-efficient, and scalable route for producing dilute to dense food-grade emulsions relevant to soft-matter, colloidal, and interfacial science.

Condensation; Continuous synthesis; Dense emulsions; Dispersed fraction; Emulsions.