Precipitation of β-carotene and PHBV and co-precipitation from SEDS technique using supercritical CO2

The objective of this work was to investigate the application of the solution enhanced dispersion by supercritical fluids (SEDS) technique for the precipitation of pure β-carotene and copolymer poly(3-hydroxybutirate-co-hydroxyvalerate) (PHBV), as well as some encapsulation tests of the solute in the biopolymer. The following parameters were investigated in the precipitation of pure β-carotene: pressure (8.0 and 12.0 MPa), anti-solvent flow rate (20–40 mL/min) and concentration of β-carotene in an organic dichloromethane solution (4 and 8 mg/mL). For pure β-carotene, the results showed that the mean particle size varied from 3.8 to 246.8 μm, depending on the processing conditions. The morphology of β-carotene was modified from plate-like to leaf-like particles, as verified by micrographs of scanning electronic microscopy (SEM). For the PHBV precipitation, the SEM micrographs showed that for all experimental conditions the morphology of polymer was different from the unprocessed material. The precipitated polymer presented a quasi-spherical shape with interconnected particles in the sub-micrometric range (particle size in the range of 278–570 nm), while the unprocessed material was composed of films and large blocks. The co-precipitation tests showed that the best ratio of β-carotene to PHBV in solution was 1:3 (w/w), which resulted in approximately 80% of encapsulation. Fluid phase behavior of the ternary systems CO2 + dichloromethane + β-carotene and CO2 + dichloromethane + PHBV was also investigated with the aim of elucidating the region of the phase diagram in which the precipitation occurs. Phase equilibrium data were measured in the temperature range of 303–343 K, with CO2 compositions ranging from 40 to 90 wt% for β-carotene, and from 30 to 90 wt% for PHBV. Vapor–liquid and also solid–vapor–liquid phase transitions were observed in the phase equilibrium study. It was observed that the presence of β-carotene or PHBV in the ternary mixture had a little influence on the fluid phase behavior of the systems.