Succinic Acid Based Particles as Carriers of Volatile Substances

Abstract

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 lowmolecular-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 μm 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.

Controlling the crystal structure of succinic acid via microfluidic spray-drying

“…This solution is injected into a poly(dimethyl siloxane) (PDMS)-based channel that guides it onto a SAW-based spray-drier at a rate of 1.5 ml h −1 . The SAW device breaks the solution into airborne drops that dry within a few hundred ms. 29,30 The resulting spray dried particles are spherical, independent of the initial solute concentration, as shown in the scanning electron microscopy (SEM) images in Fig. 3A and B, and well in agreement with what we previously reported.…”

“…3A and B, and well in agreement with what we previously reported. 29 Because each drop forms exactly one particle, 30,38 the size of these particles scales with the initial solute concentration: particles produced from solutions containing 10 mM succinic acid have an average diameter of 150 nm whereas those produced from solutions containing 100 mM succinic acid have an average diameter of 250 nm, 29 as exemplied in Fig. 3.…”

“…The SAW-based spray drier forms small drops with diameters between 10 and 100 mm. 29,30 The evaporation rate scales with the surface to volume ratio of the drop. Due to the very small size of these drops, they dry within a few hundred milliseconds, 31 thereby giving access to length and time scales for materials synthesis and formulations that cannot be reached using traditional macroscopic spray-drying processes.…”

Hydrolysis of lignocellulose to succinic acid: a review of treatment methods and succinic acid applications

“…Due to the great potential of SA and its derivatives, they have been widely explored by researchers in recent years. Okur et al [ 92 ] used SA as a matrix material to encapsulate model volatile vanillin, which can be retained for a longer period of time, as low molecular weight compounds are denser than high molecular weight compounds, which opens a new way to encapsulate volatiles in low molecular weight compounds. Succinate esters are promising environmentally friendly plasticizers for PVC that can replace toxic phthalate plasticizers.…”