A new study explores a promising, sustainable solvent system, offering new possibilities for the absorption of aromas and volatile organic compounds (VOCs). Scientists have successfully characterized a supramolecular deep eutectic solvent (SUPRADES) composed of β-cyclodextrin (β-CD) and lactic acid (LA). This solvent exhibits unique structural properties and an impressive ability to capture aromas such as trans-anethole.
This study presents the first detailed structural analysis of this specific SUPRADES, combining β-CD and LA at a 1:30 molar ratio. Through molecular dynamics simulations and X-ray scattering, the team found that the system is remarkably well-dispersed. Instead of clumping together, the individual β-CD molecules are effectively separated and stabilized by sheaths of LA molecules. This is achieved through a delicate balance of optimized hydrogen bonding and dispersive interactions that prevent the β-CD from coalescing. The study revealed that approximately 35 LA molecules surround each β-CD, which aligns with the chosen molar ratio to create a stable mixture.
Beyond Structure: Performance in Aroma Absorption
This unique microstructure provides significant functional advantages. The β-CD:LA SUPRADES has a strong capacity to solubilize and retain trans-anethole. Although direct encapsulation of trans-anethole by β-CD within the SUPRADES was limited in terms of the complex formation constant (Kf = 57 M⁻¹), 2D ROESY NMR experiments unequivocally confirmed the formation of inclusion complexes. This is a key finding because it shows that β-CD retains its host capabilities even when it is a major component of the solvent.
The study also investigated how water content influences the properties of SUPRADES. As water was added, the density and dynamic viscosity of the mixtures decreased exponentially. Conversely, surface tension increased with higher water content. Notably, pure SUPRADES showed trans-anethole absorption efficacy up to 300 times greater than pure water, with significant absorption was maintained even at 10 wt% and 25 wt% water content.
Implications for Green Chemistry
This study highlights the potential of β-CD and LA-based SUPRADESs as eco-friendly and sustainable alternatives to conventional solvents. Both components are naturally derived and biodegradable. The findings offer valuable insights into designing new green solvents, especially for applications requiring the capture and stabilization of volatile compounds in fields such as food, cosmetics, and pharmaceuticals. The researchers suggest that the intricate interplay between hydrogen bonding and dispersive interactions is fundamental to the stability and functionality of such systems.
This research paves the way for the development of new, sustainable media for a wide range of encapsulation applications.
Emanuela Mangiacapre, Alessandro Triolo, Miriana Kfoury, Steven Ruellan, Fabrizio Lo Celso, Daniel J.M. Irving, Sophie Fourmentin, Olga Russina, Sustainable aroma absorption: exploring the potentiality of a β-cyclodextrin and lactic acid supramolecular eutectic solvent, Carbohydrate Polymers, 366, 123819, 2025.
https://doi.org/10.1016/j.carbpol.2025.123819