Browsing by Author "de la Fuente, JC"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Extraction kinetics of pre-pelletized Jalapeno peppers with supercritical CO2
    (ELSEVIER SCIENCE BV, 2003) del Valle, JM; Jimenez, M; de la Fuente, JC
    The aim of this work was to assess and model supercritical carbon dioxide (ScCO2) extraction kinetics of pre-pelletized Jalapeno peppers (Capsicum annuum L.). Pepper flakes were conditioned to low moisture, ground finely and pelletized at high pressure, and pellets were subsequently ground and size classified. The effects of average sample particle size (D-p = 0.28-3.19 mm) and superficial solvent velocity (U-s = 0.14-2.62 mm s(-1)) were evaluated at 40 degreesC and 120 or 320 bar. Extraction rate increased as a result of a decrease in D-p. It also increased as a result of an increase in US at 120 bar, but the effect was almost negligible at 320 bar. Integral extraction yields of capsicum oleoresin and capsaicinoids were approximate to0.102 g g(-1) and approximate to240 mg kg(-1), respectively, independent of extraction conditions. External mass transfer coefficients (kr) increased with U-s, but this effect was less pronounced than commonly reported in the literature. Values of kr increased as D-p or process pressure decreased, due respectively to increments in specific area and improvements in transport properties. Internal mass transfer coefficients, on the other hand, were 5.3 x 10(-8) m s(-1) at 40 degreesC and 120 bar, and 34.7 x 10(-8) m s(-1) at 40 degreesC and 320 bar. Solutes were effectively liberated from the original matrix with our multistage pretreatment, so that the fraction of free solute did not depend on D-p (alpha = 0.46). Pseudosolubilities for capsicum oleoresin in ScCO2 ( approximate to 2100 mg l(-1) at 40 degreesC and 120 bar; approximate to13,700 mg l(-1) solute/CO2 at 40 C and 320 bar) were of the same order of magnitude as corresponding true solubilities of capsaicin (5600 and 11,800 mg l(-1) respectively). Estimated true solubilities of chlorophyll-a in ScCO2 (2 mg l(-1) at 40 degreesC and 120 bar; 18 mg l(-1) at 40 degreesC and 320 bar), on the other hand, were orders of magnitude smaller, which justifies a much slower extraction rate for green pigments than pungent compounds. Thus, oleoresin obtained after 4 h at 40 degreesC and 120 bar had a very attractive light yellow tinge. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Thumbnail Image
    Item
    Natural convection retards supercritical CO(2) extraction of essential oils and lipids from vegetable substrates
    (AMER CHEMICAL SOC, 2005) Germain, JC; del Valle, JM; de la Fuente, JC
    External mass-transfer coefficients (k(f)) during supercritical fluid extraction (SCFE) of high-solubility solutes, under solvent upflow conditions and low superficial velocities, can be small because of the negative influence of natural convection phenomena. A shrinking-core model for mass transfer was used to estimate best-fit values of k(f) for data on SCFE of lipids from prepressed rapeseeds. Values of k(f) at a high Reynolds number (Re = 14.1) were similar when using solvent upflow or downflow, but k(f) at lower Re (1.57) was 3.6 times smaller when using solvent upflow than that predicted from a literature correlation for downflow conditions. These k(f)'s are consistent with values estimated by fitting literature data, or gathered from various sources under similar, nonadequate conditions (solvent upflow under low Re) for the extraction of both fatty and essential oils. Care is advisable when employing best-fit values of k(f) from laboratory data for process design purposes, especially when sizing of the solvent pumps for the experiments is questionable.
  • Thumbnail Image
    Item
    Solubility of boldo leaf antioxidant components (Boldine) in high-pressure carbon dioxide
    (ELSEVIER, 2005) de la Fuente, JC; Quezada, N; del Valle, JM
    This work contributes to the development of an enrichment process for antioxidant compounds in aqueous alcoholic extracts of boldo (Peumus boldus M.) leaves by using high-pressure CO2 as the solvent. Specifically we measured the high-pressure solubility (y(2), molar fraction) of a selected bioactive compound in boldo leaves (boldine) in CO, as a function of system temperature (298 K <= T <= 333 K) and pressure (8 MPa <= P <= 40 MPa). Experimental data was correlated by using a density-based model which is valid for solvent densities > 607 kg/m(3). Predicted solubility values are low (4 x 10(-7) <= y(2) <= 6 x 10(-5)) but comparable with those of nitrogen-containing organic compounds with similar molecular weight (327.4 Da) and solubility parameter (28.3 MPa (0.5) at 313 K) as boldine. (c) 2005 Elsevier B.V. All rights reserved.