Stabilizing L-Menthol by Cocrystallization: Supramolecular Cavities Succeeded in Retaining the Volatile Flavor

L-menthol is one of the most important flavoring additives with abundant plant sources. The distinctive odor, cooling characteristic, and diversified biological activities attribute to its widespread application, especially on confections, oral-care commodities, over-the-counter drugs, and tobacco flavors. However, the manufacturing and storage of L-menthol face challenges due to its high volatility and low melting point. In this work, cocrystallization provides a new strategy to manage the stability problem of this important ingredient. Coformers of dietary sources were chosen based on a supramolecular synthon design, and six cocrystals of L-menthol were synthesized by either a solvent-mediated or solvent-free approach. These new solid forms could significantly increase the melting point and reduce the vapor pressure up to 1/45 of the pure L-menthol. Moreover, cocrystals present a high retention rate under storage conditions. The superior stability can be ascribed to diversified supramolecular cavities assembled by coformers, to which L-menthol molecules are restricted by hydrogen bonds.