Encapsulation of Menthol in Bimodal Mesoporous Silica via Normal-Temperature and Alcohol-Thermal Loading Methods for Achieving Sustained Releasing Performances

Background: Menthol is a naturally occurring volatile terpene alcohol, widely used in food, pharmaceutical, and tobacco products; however, its high volatility leads to significant flavor loss during storage and handling. Methods: Herein, bimodal mesoporous silica materials (BMMs) were employed as carriers to encapsulate menthol, the loading and release behaviors were systematically compared using normal-temperature and alcohol-thermal loading methods. Results: Comprehensive characterizations (XRD and SAXS patterns, FT-IR spectra, SEM images, and N2-sorption isotherms) confirmed that menthol incorporation did not disrupt the hierarchical mesoporous channels of BMMs. The alcohol-thermal loading method achieved a superior menthol loading capacity of 87%, significantly outperforming the normal-temperature loading (58%). Release performances revealed a transition in the dominant release mechanism, from diffusion-controlled behavior at low loading levels to concentration gradient-driven desorption at high loadings. Molecular dynamics simulations further demonstrated that alcohol-thermal loading enabled faster molecular diffusion and a more uniform distribution of menthol within the mesopores due to weaker interfacial interactions, whereas normal-temperature loading induced localized multilayer adsorption, resulting in mesopore blockage and hindered diffusion. In addition, long-term atmospheric release tests assessed sustained menthol retention over 30 days. Conclusions: Overall, this work establishes alcohol-thermal loading as an effective approach for regulating adsorption and release in mesoporous carriers, providing a foundation for developing volatile compound encapsulation strategies.