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In this work the fractionation of an ethanolic extract of Achillea millefolium L. (yarrow) using supercritical carbon dioxide anti-solvent technique was studied, with the target of increasing the concentration of phenolic compounds in the precipitated fraction. The effect of pressure on the selective precipitation was analyzed, together with the morphology and particle size distribution of the precipitates. In the range of pressures studied (10–20 MPa), up to a 3 fold increase of the total phenolic compound concentration was observed in the precipitates in comparison with the ethanolic yarrow extract. In addition, the selective fractionation of the main phenolic compounds identified in the extract (3,5-dicaffeoylquinic acid, a glycoside form of apigenin and luteolin, as well as the aglycones) was analyzed. Particle sizes around 250–330 μm were produced with a nozzle of 101.6 μm inner diameter, due to the formation of aggregates. In this respect, increasing pressure from 10 to 15 MPa resulted in smaller particles, while further pressure increasing had no significant effect on particle size decrease., The authors gratefully acknowledge the financial support from Ministerio de Economía y Competitividad of Spain (project AGL2013-48943-C2) and the Comunidad Autónoma de Madrid (ALIBIRD, project number S2013/ABI-2728).

Supercritical carbon dioxide (SCCO) extraction is an innovative and efficient method to recover valued substances from vegetal materials. The diffusion behavior of the extract in the supercritical solvent is an important parameter to understand the mass transfer behavior of the process. In this work, experimental data from the literature were utilized to analyze the diffusivity of lipophilic chemically similar solutes in SCCO. Substances with similar chemical structure, molecular weight and volatility, have also very similar diffusion coefficients, which are mainly determined by temperature, pressure and, in turn, by the corresponding physicochemical properties of the supercritical solvent (density and viscosity). Based on this premise, general correlations were derived to represent the diffusion coefficient of volatile oils, fatty acids and its esters, and fixed oils (triglycerides) in SCCO as a function solely of pressure and temperature. The diffusion coefficients obtained were satisfactory compared with those calculated with theoretical and semi-empirical models from the literature, which require pure component parameters., López-Padilla A thanks to COLCIENCIAS (568–2012) and Medellin Mayor's Office (Sapiencia/Enlaza Mundos Program, 2013) for the Ph.D. fellowship. This work was financed thanks ALIBIRD, S2013/ABI-2728 (Comunidad de Madrid) project.

This paper reports experimental data to analyze the effect of different green cosolvents, namely ethyl lactate, ethyl acetate and ethanol, on the supercritical carbon dioxide (SCCO) extraction of caffeine from green tea leaves. The experiments were carried out in a pilot-scale plant using two different approaches: a static procedure in which the cosolvent was introduced in the extraction cell soaking the vegetal material and then SCCO was pumped, and a dynamic assay in which the cosolvent was pumped and mixed with SCCO before introduction into the extraction cell. The overall caffeine recovery from plant matrix was determined for all experiments at the same extraction conditions (30 MPa and 343 K). Additionally, the overall extraction curves of the static experiments were determined at the same process conditions, and the mass transfer model of Sovová was utilized to adjust the kinetic data and to determine the mass transfer coefficients. The highest caffeine yield was obtained with ethyl lactate in both static and dynamic extractions (13.0 and 14.2 mg/g of tea, respectively), followed by ethanol (10.8 mg/g with the static method and 8.8 mg/g with the dynamic method). The yield obtained with ethyl acetate in both extraction approaches was lower than 7 mg/g. These data reinforce previous results obtained by the authors regarding the competence of ethyl lactate in the extraction of caffeine from natural materials., D. Villanueva acknowledges the predoctoral contract (JAE) given by the Consejo Superior de Investigaciones Científicas (CSIC) of Spain. This work was financed thanks ALIBIRD, S2013/ABI-2728 (Comunidad de Madrid) project.

Supercritical fluid chromatography (SFC) was employed to fractionate thyme (Thymus vulgaris L.) extracts, which were obtained by supercritical carbon dioxide extraction of thyme leaves. First, different supercritical extracts were produced at 313 K and at different pressures (15, 30 and 40 MPa). Thymol, a monocyclic terpenoid with recognized antiseptic, analgesic and anti-inflammatory properties, was identified and quantified in the different samples by GC-MS. Then, the supercritical extracts were fractionated by semi-preparative SFC, and different conditions such as pressure, temperature and amount of cosolvent (ethanol) employed were studied. Around a two fold increase of thymol was achieved at 15 MPa, 50 °C and 3% ethanol cosolvent, recovering 97% of the monocyclic terpenoid extracted. © 2010 Elsevier B.V. All rights reserved., The authors gratefully acknowledge the financial support from the Ministerio de Ciencia e Innovación (project 25506 FUN-C-FOOD) and Comunidad Autónoma de Madrid (ALIBIRD, project S-505/AGR-0153).

Chrastil (1982) [6] demonstrated that the solubility of a substance in a supercritical fluid (SCF) can be correlated with the density of the pure supercritical gas. Therefore, Chrastil's equation permits calculation of the supercritical phase composition of binary SCF + substance mixture based on the knowledge of the supercritical gas density and avoiding the use of equation of state based models. In this work, it is demonstrated that the supercritical fluid density also defines the liquid phase composition of binary systems; a density-dependent relationship is presented to calculate the solubility of supercritical gases in organic liquids. The isothermal solubility of several gases commonly employed in supercritical processing, such as carbon dioxide, methane, and ethane, in different organic liquids, including alkanes, alkenes, alcohols, acids, ketones, esters, terpenes and aromatic compounds, was successfully correlated as a function solely of the pure supercritical fluid density. As an application, pressure vs. composition phase diagrams of binary SCF + substance mixtures were obtained circumventing the use of equation of state models.

Prebiotic carbohydrates are defined as non-digestible carbohydrates that beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of bacteria in the colon. The present study is focused on two prebiotic ketosugars: tagatose and lactulose, which are currently obtained by alkaline isomerization of their respective aldoses—galactose and lactose. It is a part of a broader research devoted to examining the possibility of complex solid carbohydrate mixtures fractionation using supercritical carbon dioxide and alcohol-type cosolvents. We report new experimental solubility data of tagatose, galactose, lactulose and lactose in supercritical carbon dioxide with ethanol:water (95:5, v/v) used as a cosolvent at T = (60 and 100) °C, P = (10–30) MPa and cosolvent content from 6 to 21% (w/w). The solubility measured was in the range (0.02–1.09) mg g −1 . Additionally, the experimental data was correlated using the Soave–Redlich–Kwong cubic equation of state with the modified Huron-Vidal second order (MHV2) mixing rule. The latter employs the mS-UNIFAC, which introduces two new groups in the original UNIFAC parameter matrix to represent the sugar molecules.

This work explores the capabilities of UNIFAC-based models to predict the solubility of different solid solutes in subcritical water as a function of temperature. The original UNIFAC, its modified (Dortmund) version and the A-UNIFAC model, which explicitly includes association effects between groups, are applied to calculate the solubility of solid compounds in subcritical water in the temperature range 298–500 K. The comparison between the three models is carried out using polycyclic aromatic hydrocarbons (PAHs) as test substances and for which reliable physical properties and experimental solubility data are available in the literature. The results obtained indicate that modified UNIFAC (Dortmund) provides the best representation of the aromatic compounds’ solubility as a function of temperature. In addition, the application of the A-UNIFAC model confirms the hypothesis that a decrease in the level of association between the subcritical water molecules (in accordance with the dielectric constant decrease with temperature), greatly improves the solubility of hydrophobic organic compounds.

Nowadays consumers hold high standards for the foods they consume and they also demand for products that can provide added healthful benefits; two of these products with an observed prebiotic activity, tagatose and lactulose, are the core of our study. These two carbohydrates are ketoses and have important biological activities, such as the stimulation of the growth of beneficial microorganisms in the colon. They are currently produced by alkaline isomerization of the corresponding aldose, followed by several purification steps to remove carbohydrate by-products and the unreacted aldose (around 30%). In this work, the possibility of using supercritical fluid extraction (SFE) technology to fractionate complex carbohydrate mixtures is analyzed. The study is based on previous results obtained for the fractionation of solid binary carbohydrate mixtures such as lactulose–lactose and tagatose–galactose. The appropriate selection of the co-solvent employed, together with the most suitable extraction conditions (including temperature, pressure and co-solvent flow rate) allows the selective extraction of the prebiotic ketose with high selectivity and recovery. The fractionation by SFE of a complex commercial carbohydrate mixture, containing around 74 wt.% of lactulose and 24 wt.% of different aldose carbohydrates, was carried out at the optimal extraction conditions attained in the study of binary mixtures. The selective extraction of the ketosugar lactulose was also observed in this case, obtaining an extract with 81 wt.% lactulose and around 67% yield.

This work presents the main results attained by our research group merging chemical reaction, supercritical fluid extraction, thermodynamic phase equilibrium modeling and chemical analysis to study alternative supercritical extraction processes related with oil-type materials. Different fatty oil raw materials were fractionated in a countercurrent packed column using supercritical carbon dioxide and following different process targets, such as the deacidification of lampante olive oil and the recovery of minor lipid compounds (squalene, tocopherols and phytosterols) from industrial byproducts and wastes. If necessary, in order to facilitate the concentration of the preferred minor lipids in the raffinate product, the raw material employed was previously esterified. The GC-EoS model was used as the thermodynamic tool to represent phase equilibria behavior of the multicomponent oil-type material + CO2 mixture, and was employed to guide experiments so as to simulate and optimize the supercritical extraction processes. The coupling of thermodynamic modeling with experimental work has offered an efficient low-time consuming tool to analyze the viability of supercritical extraction processes.

The purification of squalene from residues of the olive oil deodorization process using countercurrent supercritical carbon dioxide extraction was studied. The raw material employed is a by-product obtained after distillation and ethylation of olive oil deodorizer distillates. This by-product contains mainly squalene and fatty acid esters. The Group Contribution Equation of State was employed to simulate the separation process and to design the experimental extractions, which were carried out in an isothermal countercurrent column, without reflux, at 343 K, pressures ranging from 150 to 230 bar and a solvent-to-feed ratio around 13. Satisfactory agreement was found between experimental and calculated yields and phase compositions, obtaining a raffinate product with a squalene concentration up to 90 wt.%. Finally, the thermodynamic model was employed to find out optimal process conditions to enhance squalene recovery, including partial reflux of the extract product and recirculation of the supercritical solvent in a continuous countercurrent extraction column.

Specially designed chromatographic columns were evaluated for antioxidant compounds separation by supercritical fluid chromatography (SFC) with pure CO2. Columns studied involved the use of commercial octadecylsilica particles (ODS) and silica particles coated with a stationary phase commonly used in gas chromatography, such as CW20M (polyethylene glycol) of high polarity. In order to select the appropriate chromatographic conditions to elute antioxidant compounds of phenolic structure, carnosic acid was selected as a model molecule and a theoretical study of the solubility of carnosic acid was performed. Carnosic acid was eluted using CO2 as mobile phase (without modifiers) with a pressure programming up to 37 MPa (and at different temperatures) but only when coated particles were used. No elution was possible when ODS particles were tested, probably due to the strong interactions of the acid group of the molecule with the active sites remaining in the column. A separation of a complex mixture of a rosemary antioxidant extract (obtained by supercritical fluid extraction) using the columns designed in the present work is shown.

The present study is devoted to the experimental measurement and thermodynamic modeling of solid carnosic acid solubility in supercritical CO 2 + ethanol as a co-solvent. Measurements were carried out at temperatures in the range of 313.15 and 333.15 K, pressures ranging from 280 to 400 bar, and at different content of the modifier ethanol (from 0.7 to 10%). The Group Contribution Associating Equation of State (GCA-EoS) [H.P. Gros, S.B. Bottini, E.A. Brignole, High pressure phase equilibrium modeling of mixtures containing associating compounds and gases, Fluid Phase Equilibria 139 (1997) 75–87] was applied in this work to represent the experimental solubility data obtained. Due to the lack of information in the literature about pure carnosic acid parameters, its solid volume, critical properties, and sublimation pressures were estimated in this work. The key step in the thermodynamic modeling proved to be the introduction of a solute hard-sphere parameter in the Carnahan–Starling repulsive term of the model, which depends on both temperature and pressure.

Grape seeds extracts have shown a broad range of pharmacological activities including, among others, antiulcer and antioxidant properties, which are mainly attributed to the phenolic compounds present. To date, the most abundant phenolic compounds isolated from grape seeds are catechins and their derivatives, e.g. quercetin. The present study is devoted to the experimental measurement and thermodynamic modelling of the solubility of quercetin in supercritical CO 2 + ethanol as a co-solvent. The solubility of quercetin was measured at 313.15 K, pressures ranging from 80 to 120 bar, and at different content of the modifier ethanol—from 5 to 30%. Two types of thermodynamic models were applied to model the solubility of quercetin—the group contribution equation of state (GC-EoS), developed by Skjold–Jogensen, and the Soave–Redlich–Kwong (SRK) EoS.

This contribution reports new experimental data on the fluid phase behavior of binary mixtures of carbon dioxide and three saturated, low-molecular weight triglycerides: tributyrin, tricaproin and tricaprylin. The objective of this work is to analyze the effect of the triglyceride molecular weight on the phase behavior of mixtures with carbon dioxide. The experimental work covers a temperature range between 276 and 368 K and pressures up to 15 MPa. All mixtures show liquid-liquid immiscibility near the critical point of pure carbon dioxide. From the analysis of the experimental data, it became apparent that the CO2-systems with tricaproin and tricaprylin have both type-IV fluid phase behavior in the classification of Van Konynenburg and Scott. The fluid phase behavior of these systems was modeled with the group contribution equation of state GC-EoS. The equation was able to describe vapor-liquid, liquid-liquid and vapor-liquid-liquid equilibria, with a single set of group interaction parameters. Fil: Florusse, L.J.. Delft University of Technology; Países Bajos Fil: Fornari Reali, Tiziana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina Fil: Bottini, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina Fil: Peters, C.J.. Delft University of Technology; Países Bajos

The Group Contribution Equation of State (GC-EOS) is applied to model high-pressure phase equilibria in mixtures of fatty oils and acid alkyl esters with supercritical fluids. The fatty oil is represented by a pseudo-triacylglyceride with the same molecular weight and degree of unsaturation of the natural oil. The critical hard sphere diameter of the oil, i.e. the size-related parameter, is determined from the correlation of infinite dilution activity coefficients of n -alkanes in high molecular weight triacylglicerides and hydrocarbons. Good predictions of vapor–liquid, liquid–liquid and vapor–liquid–liquid equilibria in mixtures of supercritical solvents (propane, ethane and CO 2 ) with pure triacylglycerides, natural vegetable oils and fatty acid alkyl esters are obtained. These results show the capability of the GC-EOS model to describe the phase equilibria of size-asymmetric mixtures and its potential for modeling supercritical processes involving oils and derivatives.

This contribution reports new experimental data on the phase behavior of the binary system dimethylether (DME)+tripalmitin (PPP). The experimental work covers a temperature region between 275 and 450 K and pressures up to 12 MPa were applied. Near the critical point of pure DME a three-phase region liquid–liquid–vapor (l1l2g) was established. Although only an upper critical endpoint of this three-phase equilibrium could be determined experimentally, it is most likely that the system DME+PPP belongs to type-V fluid phase behavior in the classification of Van Konynenburg and Scott. Besides the fluid phase behavior of the system, also phase equilibria in the presence of solid PPP were measured. From earlier work it became apparent that a Group Contribution Equation of State is capable to model the vapor–liquid and liquid–liquid equilibria in related systems. Therefore, this equation also was chosen to model the fluid phase behavior of the system DME+PPP.