Method leveraging the ouzo effect to finely disperse natural resinous extracts in water

Abstract

Numerous studies have investigated the Ouzo effect in pure compounds, but its application to complex mixtures with practical potential remains largely unexplored. Many natural resinous substances are challenging to handle at low temperatures due to their water insolubility and unfavorable rheological properties, making emulsification difficult. We developed aqueous dispersions by first preparing a hydroalcoholic extract containing 2.5 to 20 wt% resin, then adding water to induce the Ouzo effect, forming micro- and submicron-sized resin-rich droplets. Gum Arabic stabilized the dispersion, while ethanol was removed at 35°C via reduced-pressure distillation, decreasing from approximately 0.15 bar in the initial stages to 0.06 bar. This process yielded dispersions containing 10 % resin and an equal amount of Gum Arabic. The higher polydispersity observed in our systems, compared to pure compounds reported in the literature, likely arises from the complex molecular composition of resins, leading to varying degrees of supersaturation with respect to the antisolvent and to different sizes. We demonstrate that this emulsification method is applicable to resins derived from propolis, poplar buds, and birch pitch. Dispersing these resinous substances in an aqueous phase could enhance their usability as final products with the aim of valorizing their antioxidant and bactericidal potential.