The preparation of peppermint oil/2-hydroxypropyl-β-cyclodextrin/chitosan composite microcapsule and their prolonged retaining ability

In this paper, the peppermint oil/HP-beta-CD (2-hydroxypropyl-beta-cyclodextrin)/chitosan composite microcapsules were prepared. The release ability of these microcapsules was improved for peppermint oil through the combination of molecular encapsulation by HP-beta-CD and physical encapsulation by chitosan shell. First, stable peppermint oil/HP-beta-CD pre-emulsion was prepared by stirring, based on which the optimal conditions were determined for producing the pre-emulsions with the highest encapsulation efficiency. Then, the pre-emulsion was moved into the flow-focusing microfluidic device as the inner phase and was cut into droplets by chitosan aqueous solution as the middle phase and the octanol as the outer phase to obtain templated emulsions. They were collected using a Petri dish with n-octane coagulation bath containing glutaraldehyde and 2 wt% span80 to be cured into microcapsules. The crosslinking time and the ratio of HP-beta-CD in the templated emulsions were adjusted to investigate their impact on the microcapsule structures and correspondingly the capability of the microcapsules to retain peppermint. It was found out that the extended crosslinking time and the addition of HP-beta-CD can improve the capability of the composite microcapsules to retain peppermint oil. It provides a straightforward method to produce composite microcapsules. Besides, the microcapsules with improved retaining ability were obtained by combing molecular and physical encapsulation, thus laying a foundation for the exquisite, efficient and polylaminate protection of the volatile perfume or other physically or chemically active components.