EXTRACTION OF BETA-CAROTENE WITH SUPERCRITICAL FLUIDS - EXPERIMENTS AND MODELING

This work investigates extraction of p-carotene by supercritical carbo n dioxide and nitrous oxide from impregnated beds and from freeze-drie d carrots. Extraction rate was measured as a function of temperature, flow rate and particle size. Based on results from spiked beds, mathem atical models were proposed to analyze the dynamic behavior of extract ion from carrots. The validity of a diffusion model or a mass balance model was discussed through results on particle size. Although the dif fusion model and the experimental results were in good agreement, prov ided that two stages of diffusion were considered for larger particle size, we further analyzed all data regarding a differential mass balan ce model. This model, accounting for external mass transfer, diffusion within the matrix and dissolution at the solid/fluid interface, descr ibed the time-dependent process satisfactorily despite assumptions on the matrix description. Results showed that both external mass transfe r and desorption of solute from the matrix were the limiting steps. (C ) 1998 Elsevier Science B.V. All rights reserved.