Enhancing the stability of astaxanthin by encapsulation in poly (l-lactic acid) microspheres using a supercritical anti-solvent process

Abstract To improve the physicochemical properties of astaxanthin, it was encapsulated in poly (l-lactic acid) (PLLA) using a supercritical anti-solvent (SAS) process with dichloromethane/acetone mixture as the solvent, and supercritical CO 2 as the anti-solvent. The effects of altering five SAS operating conditions, solvent ratio, temperature, pressure, concentration of carrier, and flow rate, on the microstructure of particles were investigated using an orthogonal experimental design. Under the optimal conditions, astaxanthin/PLLA particles were produced with an encapsulation efficiency of 91.5% and a mean particle size of 954.6 nm. SEM images showed that most astaxanthin/PLLA particles were uniform microspheres. FT-IR spectra showed that the chemical structure of astaxanthin was unchanged by the SAS process. The results of chromatic difference, X-ray diffraction, thermogravimetric, and differential scanning calorimetry analyses showed that astaxanthin had been encapsulated in the PLLA matrix in an amorphous state. Overall, astaxanthin/PLLA microspheres greatly enhanced the stability of astaxanthin during storage, and the levels of residual solvents were far lower than the ICH limits. This means that astaxanthin/PLLA microspheres prepared using SAS show great potential for use in many food, cosmetic, and pharmaceutical formulations.