Browsing by Author "Zetzl, C"

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    Extraction of boldo (Peumus boldus M.) leaves with supercritical CO2 and hot pressurized water
    (ELSEVIER, 2005) del Valle, JM; Rogalinski, T; Zetzl, C; Brunner, G
    High-activity fractions in boldo leaves were extracted with supercritical CO2 (SC-CO2) and hot pressurized water (HPW). Total yield after 3 h of extraction (0.6-3.5%) in low-pressure SC-CO2 experiments increased with process pressure (60-150 bar) and decreased with temperature (30-60 degreesC), as expected. The extract obtained with SC-CO2 at 50 degreesC and 90 bar contained approximately 50% of essential oil components. In higher pressure experiments with solvent mixtures. the yield increased with pressure (300-450 bar) and modifier concentration (2-10% ethanol), ranging 0.14-1.95 ppm for the alkaloid boldine and 1.8-4.81%. for total solids following 1.5 h treatment at 50 degreesC. Boldine recovery was solubility-controlled, reaching 7.4 ppm after 7-h extraction at 450 bar and 50 degreesC using an ethanol-SC-CO2 mixture (5% co-solvent). Boldine solubility and yield decreased when using pure CO2 at higher pressure (600 bar, 50 degreesC). The extract yield after 3 h batch-wise HPW extraction increased from 36.9% at 100 degreesC to 53.2% at 125 degreesC. and then decreased as temperature was increased to 175 degreesC. Boldine yield decreased from 26.8 ppm at 100 degreesC to 0-7 ppm at 125 degreesC. and was negligible at greater than or equal to 150 degreesC. The essential oil yield increased to a maximum at 110 degreesC and was negligible at greater than or equal to 150 degreesC also. The ranking of antioxidant potency of various extracts was as follows: HPW at 110 degreesC > methanol (soxhlet extraction) much greater than high-pressure SC-CO2 with or without polar co-solvent > low-pressure SC-CO2. (C) 2004 Elsevier Ltd. All rights reserved.
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    Microstructural effects on internal mass transfer of lipids in prepressed and flaked vegetable substrates
    (ELSEVIER, 2006) del Valle, JM; Germain, JC; Uquiche, E; Zetzl, C; Brunner, G
    Predictive models that describe supercritical fluid extraction (SCFE) processes would be welcomed to support its industrial application, particularly for the supercritical carbon dioxide (SC-CO2) extraction of vegetable oil from seeds subjected to common high-shear pretreatments. This work explores the application of microstructure-extractability relationships for modeling the SCFE of lipids from vegetable substrates. We measured the extraction kinetics of prepressed rapeseeds, olive husks, and flaked rosehip seeds, with SC-CO2 at 313 K and 30 MPa, and simulated the extractions using a shrinking-core model. Model parameters included the oil solubility and film mass transfer coefficient from literature correlations, and an effective diffusivity (D-e) inside the porous particles. We determined that D, could be calculated as D-12 x F, where D-12 is the diffusivity of oil in CO2, and F is a microstructural correction factor, estimated as the ratio between the final porosity (epsilon(p) from Hg porosimetry) and pore-network tortuosity (tau, from fractal-texture analysis of binary light-microscopy irnages) of the substrates. Simulations adjusted the experimental data reasonably well (5.4% < mean percent error < 15%). Additionally, best-fit estimates of D, were obtained for literature data on SC-CO2 extraction of lipids from prepressed and flaked seeds. Resulting values of F did not depend on particle size and spanned a narrow range - one order of magnitude (0.030-0.29) - as it would be expected when comparing similar systems. Although further work will be required to refine the relationship between tau and fractal parameters, or between tau and the hysteresis of Hg infiltration, this work demonstrates that is possible to develop predictive models for SCFE of solid substrates subjected to high-shear pretreatments. (c) 2005 Published by Elsevier B.V.