Preparation of Peppermint Oil/β-CD Inclusion by High-speed Shearing with Process Optimization Using ResponseSurface Methodology

Objective: To investigate the optimal process for preparing peppermint essential oil/β-cyclodextrin (β-CD) inclusion complex using high-speed shearing combined with freeze-drying. Methods: The effects of freeze-drying and vacuum drying, high-speed shearing, and stirring on the encapsulation process were compared. Based on single-factor experiments, the ratio of β-CD to essential oil, encapsulation temperature, and mass fraction of β-CD were considered as influencing factors. The comprehensive score of oil content and encapsulation efficiency was used as an evaluation index to investigate the Box-Behnken response surface method for optimizing the encapsulation process. The content of pulegone in the inclusion complex was measured by high-performance liquid chromatography (HPLC). Fourier transform infrared spectroscopy (FTIR) was used to characterize the inclusion complex. Results: The yield of inclusion complex prepared by freeze-drying was higher, with an average yield of 97.6%. The oil content and encapsulation efficiency by the high-speed shearing method were relatively high, being about 3% and 19% higher than those by the stirring method, respectively. The optimized conditions were as follows: The weight ratio of β-CD to volatile oil was 9:1 (g/mL), the encapsulation temperature was 55 ℃, and the mass fraction of β-CD was 17%. Under these conditions, the essential oil content was 10.9%, the encapsulation efficiency was 97.6%, the comprehensive score was 99.7, the RSD value was 1.59%, and the optimized process was stable and feasible. The content of pulegone in the inclusion complex was found to be 2.465 mg/g by HPLC. The formation of the peppermint oil/β-CD inclusion complex was confirmed by analysis using FTIR. Conclusion: The combination of high-speed shearing and freeze-drying for the preparation of peppermint essential oil inclusion complex had the advantages of high efficiency, simple process, and it improved theyield, would provide guidance for the production process.