Publication
Volatile substances are in high demand, especially in cosmetic and pharmaceutical applications. To prolong their shelf-life and prevent their degradation if exposed to air, these volatile substances are often encapsulated. Most frequently, matrix materials are composed of high-molecular-weight polymers because some of them can efficiently retain volatiles and meet the safety requirements these applications impose. However, these substances must be processed at high concentrations, resulting in viscous solutions that are difficult to spray or emulsify. To address this shortcoming, we employed a low-molecular-weight substance, succinic acid, as a matrix material to encapsulate a model volatile, vanillin. To facilitate the encapsulation of low-molecular-weight substances, such as volatiles, we produce these particles through surface acoustic wave (SAW)-based microfluidic spray-drying. This technique forms drops with diameters as small as 1-10 mu m that dry within a few hundred ms. Thereby, we can kinetically arrest or even suppress phase separations. We demonstrate that vanillin is most efficiently encapsulated and retained over a prolonged time if succinic acid is formulated from solutions initially containing succinic acid concentrations exceeding 10% of its saturation concentration. If appropriately formulated, these succinic acid based particles retain volatiles longer than the much more commonly employed high-molecular-weight dextrin. These results open up a new avenue to encapsulate volatiles in low-molecular-weight compounds that pack more densely than high-molecular-weight counterparts and therefore can retain volatiles for a prolonged time.