Precipitation of lutein and co-precipitation of lutein and poly-lactic acid with the supercritical anti-solvent process

The supercritical anti-solvent (SAS) process has been used to re-crystallize lutein from ethyl acetate solutions. The influence of several process parameters (pressure, temperature, initial concentration, CO2 and solution flowrates) on the particle size and morphology have been studied. The results have been compared to these obtained with other carotenoids (β-carotene and lycopene) with similar operating conditions, and have been interpreted with the aid of a phase equilibrium model based on the perturbed hard sphere chain equation of state. Large differences in particle size have been observed between the experiments performed in the two-phase and the single-phase regions of the vapor–liquid phase diagram. A change in the particle morphology, from agglomerated microparticles to polygonal crystals, has been observed when the CO2/solution flow ratio was increased or the initial concentration was decreased. As a result of the precipitation, the purity of the lutein has been increased from 75% to over 90%. The co-precipitation of lutein with poly-lactic acid (PLA) has also been studied. A reduction in the particle size with the polymer/drug ratio has been observed, down to a minimum diameter of 1–5 μm.