Design and characterization of starch/solid lipids hybrid microcapsules and their thermal stability with menthol

A hybrid microcapsule with modified starch shell and solid lipids core was designed to enhance the thermal stability of menthol with high loading. The hybrid microcapsule was prepared by high-pressure homogenization of the lipid and water phase, and spray drying of the modified starch stabilized emulsion. Menthol was incorporated with the oil phase into the modified starch shell. The crystalline structure of menthol in solid lipids and the hybrid microcapsules was investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis. The encapsulation efficiency, surface menthol content, loading amount, and thermal stability were optimized. A hybrid microcapsule with a high encapsulation efficiency (99.78%), low surface oil content (3.02%), high loading amount (31.18%) and superb thermal stability was obtained. The microstructure of the hybrid microcapsule was studied by scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). The mechanism of superb thermal stability and high loading was discussed, both of the amorphous form of menthol and the dense modified starch shell are important. Finally, the shelf storage stability for 300 days was evaluated. In general, a simple and general method was provided to stabilize menthol at high temperatures. And the microencapsulation concept proposed in this manuscript may provide a potential idea for other crystalline active ingredients used in food, cosmetic and pharmaceutical area.