Preparation of mint oil microcapsules by microfluidics with high efficiency and controllability in release properties

Mint oil is a complex mixture of comparatively volatile and labile components, making it challenging to be efficiently encapsulated and retained in microcapsules using traditional approaches. Microencapsulation, by encapsulating the substance with certain shells, can effectively reduce the diffusion, evaporation and the reactions of the inside actives with the external environment. The microencapsulation of mint oil and other aromatic actives have been a prevailing method to improve the stability, prolong the storage time, and enhance the controllability of the actives. Monodisperse core–shell microcapsules based on double emulsions prepared by microfluidic technology with controllable structure, pH-responsive ability, and adjustable release properties are successfully developed. Different flow rates, glutaraldehyde concentration, solidification time and pH have been used to adjust the core sizes, the shell thickness, the crosslinking density and the shrinkage degree of the shell. By monitoring their mint oil sustained release ability through an ultraviolet spectrophotometer, appropriate conditions to form the mint oil microcapsules with high encapsulation efficiency and controllability in release properties are achieved, building the foundation for better mint oil storage, transportation, and their applications.