Stabilization of allyl isothiocyanate by β-cyclodextrin : thermal robustness and potent antimicrobial activity

Abstract

Allyl isothiocyanate (AITC) is a potent natural antimicrobial agent; however, its practical application is severely hindered by its extreme volatility and pungent, irritating odor. In this study, AITC inclusion complexes (AITC@β-CD) were successfully fabricated via a co-precipitation strategy using β-cyclodextrin (β-CD) as the host matrix. Physicochemical characterizations, including FTIR, SEM, and XRD, confirmed the successful integration of AITC into the β-CD framework, inducing a crystalline phase transition from a cage-type to a channel-type structure. TGA demonstrated a substantial enhancement in thermal stability, with the maximum decomposition temperature shifting to 330 °C. This indicates that the spatial confinement within the channel-type lattice acts as a robust molecular shield that minimizes premature volatilization. Notably, water contact angle measurements revealed that the complexes attained a modulated surface wettability (89.0°), attributed to the structural rearrangement of surface hydroxyl groups. This modification ensures that the material remains compatible with aqueous food matrices while notably masking the unpleasant sensory attributes of pure AITC. Antibacterial assays against the standard indicator strain Escherichia coli (E. coli) confirmed that the encapsulation process preserved the intrinsic bioactivity of the guest, exhibiting comparable inhibitory zones to free AITC. Furthermore, the complexes maintained high inhibitory efficacy against indigenous microbial populations from spoiled fruits. These findings suggest that β-CD encapsulation effectively stabilizes AITC through guest-induced co-crystallization and enhances its consumer acceptability, providing a versatile and efficient strategy for sustainable food preservation.