Selective recovery of aroma-active menthol from peppermint hydrosol by wrinkled graphene oxide-based surface...

Menthol is the key aroma-active constituent of peppermint essential oil and an important cooling ingredient in food-related applications. During industrial steam distillation, large amounts of peppermint hydrosol are generated as by-products, and appreciable menthol remains in this aqueous stream. However, selective menthol recovery from this complex aqueous matrix is difficult because structurally related compounds with similar polarity coexist with the target molecule. In this study, a surface molecularly imprinted polymer based on micro-wrinkled graphene oxide (WGO) was developed for the selective enrichment and pH-responsive release of menthol from authentic peppermint hydrosol. 3-Aminophenylboronic acid was selected as the functional monomer by molecular docking, which also suggested a stable ternary pre-assembly with menthol and phenyltriethoxysilane. Compared with the flat graphene oxide-imprinted counterpart, the WGO-based material showed superior performance, with a maximum adsorption capacity of 226 mg g^-1 and a specific surface area of 141.72 m² g^-1. In authentic peppermint hydrosol, it achieved an equilibrium menthol uptake of 36.28 mg g^-1, a distribution coefficient of 14.28 L g^-1, and an imprinting factor of 2.21. The material also exhibited clear pH-responsive release, with cumulative release approaching 90% under acidic conditions, while maintaining relatively stable performance over five adsorption-desorption cycles. These results demonstrate that interfacial morphology regulation is an effective strategy for selective menthol recovery and for valorizing peppermint hydrosol by-products in food-related processing.