Co-precipitation of carotenoids and bio-polymers with the supercritical anti-solvent process

• Published in: The Journal of supercritical fluids 2007-05, Vol.41 (1), p.138-147
• Main Authors: Martín, A., Mattea, F., Gutiérrez, L., Miguel, F., Cocero, M.J.
• Format: Article
• Language: English
• Subjects: Lutein; PEG; Perturbed hard-sphere-chain equation of state; Supercritical carbon dioxide; β-Carotene
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2006.08.009

Carotenoids are widely used as natural colorants in food or pharmaceutical industries. In some industrial formulations, these carotenoids are mixed with bio-polymers, to improve the stability of the carotenoid, its dissolution rate in water, and to make the dosage and the handling of the product easier. The supercritical anti-solvent (SAS) process is specially suitable for the production of fine powders of these mixtures, as it yields solvent-free products with a reduced thermal degradation or oxidation of the carotenoids. In this work, the application of the SAS process to the precipitation of β-carotene or lutein with poly-ethylene glycol (PEG) has been studied. The influence of different process parameters, including the operating pressure and temperature, the polymer/carotenoid concentration ratio, and the CO 2 flowrate have been studied experimentally. Additionally, a phase equilibrium model of these systems based in the perturbed hard-sphere-chain equation of state (PHSC EoS) has been developed. This model is helpful for the analysis of the experimental results. In particular, this model predicts the apparition of a liquid–liquid immiscibility region at moderate temperatures due to the co-solvent effect of CO 2 on PEG. This explains the difficulties found in the precipitation experiments performed at these conditions. The existence of this phase behavior has been corroborated by performing batch gas anti-solvent (GAS) precipitation experiments in a windowed vessel.