Browsing by Author "Uquiche, Edgar"

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    Matrix effects in supercritical CO2 extraction of essential oils from plant material
    (ELSEVIER SCI LTD, 2009) Araus, Karina; Uquiche, Edgar; del Valle, Jose M.
    In this work, we reviewed the effect of the solid matrix in the supercritical CO2 (SC-CO2) extraction of essentials oils from plant material. A diffusional model was adopted that assumed the substrate is as an homogeneous solid and the partition of essential oils between the solid substrate and the SC-CO2 phases is constant. The model was fitted to literature data from several plant materials (relevant solute identified between parenthesis): chamomile flowers (alpha-bisabolol), lavender flowers (camphor), oregano bracts (thymol), pennyroyal leaves and flowers (menthol), and sage leaves (1,8-cineole). Based on values of binary diffusion coefficient of the solute in the solvent (D-12) from a literature correlation, and the best-fit values of effective diffusivity of the Solute in the solid matrix (D-e) we estimated the value of the so-called microstructural factor (MF), which is defined as the ratio between D-12 and D-e which ranged from 420 for pennyroyal to 25,000 for oregano. MF encompasses several factors, mainly related with to the microstructure of the substrate, that affect the extraction rate of a solid substrate with a solvent. (c) 2009 Elsevier Ltd. All rights reserved
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    Quantification of the Browning Kinetic on Pita Bread Using Fractal Method
    (2018) Quevedo, Roberto; Rojas, Richard; Pedreschi Plasencia, Franco; Bastías, José Miguel; Siché, Raúl; Uquiche, Edgar; Silva, David; Díaz, Oscar
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    Time Fractionation of Minor Lipids from Cold-Pressed Rapeseed Cake Using Supercritical CO2
    (WILEY, 2012) Uquiche, Edgar; Fica, Ximena; Salazar, Katherine; del Valle, Jose M.
    This work explored the possibility of using supercritical carbon dioxide (SC-CO2) to achieve fractionation of pre-pressed rapeseed (Brassica napus) cake oil at 30-50 MPa, at 40 or 80 degrees C, and increase the concentration of minor lipids (sterols, tocopherols, carotenoids) in the oil. Minor lipids are partially responsible for desirable antioxidant effects that protect against degradation and impart functional value to the oil. The weight and concentration of minor lipids in oil fractions collected during the first 60 min were analyzed. Cumulative oil yield increased with pressure, and with temperature at >= 40 MPa, but was lower at 80 degrees C than at 40 degrees C when working at pressure <= 35 MPa. Differences in solubility between the oil and minor lipids explained fractionation effects that were small for tocopherols. Unlike tocopherols, which are more soluble in SC-CO2 than the oil, sterols and carotenoids are less soluble than the oil, and their concentration increased in the later stages of extraction, particularly at >= 40 MPa, when there was not enough oil to saturate the CO2 phase. Because of the fractionating effects on rapeseed oil composition, there was an increase in the antioxidant activity of the oil in the second half as compared to the first half of the extraction. Consequently, this study suggests that SC-CO2 extraction could be used to isolate vegetable oil fractions with increased functional value.