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Bioseparation of Nutraceuticals Using Supercritical Carbon Dioxide
Abstract
Use of supercritical carbon dioxide (SC–CO2) for the extraction and fractionation of nutraceuticals offers numerous advantages, avoiding the use of organic solvents
and minimizing the degradation of bioactives. Optimal design of such processes requires fundamental knowledge of not only
the solubility behavior but also physical and transport properties of the SC–CO2 + nutraceutical mixture under high pressure. Determination of such fundamental data is challenging and requires specialized
equipment. Because of the nonpolar nature of SC–CO2, lipid-based nutraceuticals, including specialty oils and carotenoids, can be extracted with neat SC–CO2; however, recovery of phytochemicals like phenolics require the addition of a polar cosolvent. Ethanol is the cosolvent of
choice for nutraceutical applications. Extraction of nutraceuticals from a large number of plant materials has been studied
extensively for the optimization of various processing parameters. Further fractionation of the extracts or various other
mixtures is possible using fractional extraction, fractional separation, or column separation approaches to obtain bioactives
in concentrated form. Supercritical fluid technology offers the flexibility to extract and fractionate nutraceuticals by combining
different techniques and simplifying the overall process compared to conventional technologies, but feasibility of every application
needs to be evaluated on a case-by-case basis. Some applications such as the extraction of specialty oils and recovery of
tocopherols from deodorizer distillate have already reached commercialization level while numerous other promising applications
are under development around the world.
... Fractionation of anthocyanins as glucosides and the corresponding acetylated, coumaroylated, and caffeoylated derivatives Vidal et al., 2004a (Continued on the next page) with lower solvent consumption and lower working temperature (Temelli and Seifried, 2011;García-Salas et al., 2010;Pereira and Meireles, 2010). It is a form of liquid extraction where the usual liquid solvent phase has been replaced by a supercritical fluid; i.e., a substance that is above its critical point. ...
Anthocyanins are naturally occurring polyphenol compounds that impart orange, red, purple, and blue color to many fruits, vegetables, grains, flowers, and plants. In recent decades, interest in anthocyanin pigments has increased due to their possible utilization as natural food colorants and especially because their consumption has been linked to protection against many chronic diseases. It seems that anthocyanin posseses strong antioxidant properties leading to a variety of health benefits. Coupled to increasing consumer demand, food manufacturers have moved towards increased usage of approved natural colors. Despite the great potential in applications that anthocyanins represent for food, pharmaceutical, and cosmetic industries, their use has been limited because of their relative instability and low extraction percentage. Growing demands have been made on sample pretreatment, and over time some novel extraction techniques have been developed. Solid phase extraction, countercurrent chromatography, adsorption, pressurized liquid or fluid extraction, and microwave-assisted extraction are environmentally friendlier in terms of using smaller amount of solvents (often nontoxic) and reducing working time. The past few years have been characterized by wide interest in these techniques, and many contributions describing these methods have been published. The aim of this article is to review the literature available on the most important procedures proposed for the extraction of anthocyanins; the use of non-thermal technologies in the assisted extraction of anthocyanins will be covered in a separate report.
Carotenoids are used as natural food colourants in the food industry. As unstable natural pigments they need protection. This protection can involve the microencapsulation process. There are numerous techniques that can be used for carotenoid protection, but two of them -spray drying and supercritical micronization - are currently the most commonly used. The objective of this paper is to describe these two techniques for carotenoid microencapsulation.In this review information from articles from the last five years was taken into consideration. Pigments described in the review are all carotenoids. Short summary of carotenoids sources was presented. For the spray drying technique, a review of carrier material and process conditions was made. Moreover, a short description of some of the most suitable processes involving supercritical fluids for carotenoids (astaxanthin, β-carotene, lutein and lycopene) encapsulation was given. These include the Supercritical Antisolvent process (SAS), Particles from Gas-Saturated Solutions (PGSS), Supercritical Fluid Extraction From an Emulsion (SFEE) and Solution Enhanced Dispersion by Supercritical fluids (SEDS).In most cases the studies, independently of the described method, were conducted on the laboratory scale. In some a scale-up was also tested. In the review a critical assessment of the used methods was made.
Over the past three decades, there has been an incredible amount of research and commercialization activity for the supercritical carbon dioxide (SC-CO2) extraction of lipids, lipid-soluble components, as well as nutraceuticals from various matrices worldwide to generate ingredients for the functional food and nutraceutical product applications. This chapter provides an overview of the basic principles of supercritical fluid extraction and extraction equipment and operation at laboratory and industrial scales. In addition, a summary of the recent extraction studies is provided as well as current industrial applications worldwide. Indeed, thousands of studies have reported the extraction of various plant materials at the laboratory scale while few studies present data at the industrial scale. In addition to extraction, supercritical fluid technology offers numerous other possibilities in the inactivation of microorganisms in the food and beverage industry as well as delivery of bioactive components in the form of nano/micro-particles, which can be coupled with an extraction step.
Rice bran oil (RBO) is a good source of several commercially important bioactive phytochemicals, such as tocols (i.e. tocopherols and tocotrienols) and ferulic esters of sterols (i.e. gamma-oryzanol). The aims of the present study were to examine the effects of different pressure and temperature combinations on the fractional extraction of RBO using supercritical carbon dioxide (SC-CO2) and to assess the levels of tocols homologues and gamma-oryzanol components in the resulting oil fractions. Fractional extraction of rice bran oil was performed using SC-CO2 at either 27.6 or 41.4 MPa and either 40 or 60 degrees C. The effects of the four different pressure and temperature combinations on the levels of seven tocols homologues (alpha-, beta-, gamma- and delta-tocopherol and alpha-, gamma- and delta-tocotrienol) and the four major components of gamma-oryzanol in the resulting oil fractions were investigated. Superior extraction efficiency was obtained using the higher pressure of 41.4 MPa. The tocols (particularly a-tocopherol and alpha-tocotrienol) were recovered early in the extraction process, while the gamma-oryzanol compounds were obtained in the later stages. With regard to SC-CO2 extraction, tocols are more soluble than gamma-oryzanol components, alpha-tocopherol is the most soluble of the tocols and the four gamma-oryzanol components all have similar solubilities. Valuable data on solubilities of tocols homologues in SC-CO2 were provided from present study.
Anthocyanins are one of the many compound classes that belong to the polyphenolic flavonoid group. This group species of secondary metabolites are synthesized in almost all higher order plants, conferring the bright red, blue, and purple colors to berries and fruits. They have recently been the focus of significant beneficial health claims due to their antioxidant capacity. The interest of both consumers and academics in understanding the medicinal, therapeutical, and nutritional value provided by these naturally occurring phytochemical compounds is increasing. The development of analytical techniques to determine the identity and quantities of anthocyanins in natural products, as well as their effects in vivo and in vitro, is challenging. There is a need for extensive collection of information on the composition of natural colors and their recovery methods as a consequence of the increased demand for natural colors by industries. Numerous procedures have been used over the years for the sample treatment of phytochemicals. In this review special attention is paid to topics concerning with sampling and sample preparation methods, with the focus on anthocyanins; useful information is collected in tabular form.
Lipids were extracted from roasted pistachio nut particles by supercritical CO 2 (SC-CO 2 ) in an incomplete design at pressures of 20.7, 27.6, and 34.5 MPa and temperatures of 50, 60, and 70°C with ethanol (0, 5, and 10 wt%) as entrainer. Highest experimental extraction yield of 66% was obtained at 34.5 MPa and 60°C with 10 wt% ethanol. Data was analyzed by Response Surface Methodology. Temperature did not affect the extraction yield. Extraction yield increased linearly with pressure, while ethanol concentration had a curvilinear effect. The following equation adequately represented the experimental data (r 2 = 0.94): % Yield = 52.14 + 9.707 x P + 21.164 x EtOH - 11.049 x EtOH 2 , The solubility of pistachio oil in SC-CO 2 at 34.5 MPa and 60°C was 5 times higher in case of 10 wt% ethanol (1.29 wt%) compared to CO 2 alone (0.27 wt%). Difference between extracted and control pistachios in terms of texture was detected by puncture and compression tests as well as by sensory evaluation. Sensory evaluation showed a reduction in roasted pistachio flavor intensity following SC-CO 2 extraction.
Supercritical carbon dioxide (SC-CO2) extraction of β-carotene from apricot pomace obtained in apricot purée production process was investigated in the presence of an entrainer. Before response surface methodology (RSM) was applied, the effects of temperature, pressure, static extraction time, and type of entrainer on the amount of β-carotene extracted were studied. Ethanol was chosen as entrainer to obtain the best result. In the RSM, temperature, pressure and ethanol percentage (v/v) were critical components. RSM experiments were performed at the range of temperature 316–350K, pressure 13.3–47.3MPa, ethanol percentage 2–28% for three parameters. Optimum amount of β-carotene extracted was obtained as 100.4μg/g dry pomace with employing the following predicted optimum extraction conditions: temperature 342K, pressure 31.1MPa and ethanol percentage 27.4%. A verification experiment, conducted at these optimized conditions for maximum extraction of β-carotene, produced value for amount of β-carotene (98μg/g dry pomace) that was very close to predicted value, indicated the reliability of the empirical model.
A quantitative understanding of rate mechanisms such as diffusion is of considerable importance in the design of equipment for, and process development of, supercritical fluid (SCF) extraction. However, there is currently very little available fundamental diffusion data in the supercritical region. This is due, in part, to the sampling difficulties encountered in high pressure systems. The most reliable methods for obtaining diffusivity data in SCF systems have involved the use of non-obtrusive techniques such as solid dissolution, capillary peak broadening, photon correlation spectroscopy, and nuclear magnetic resonance spectroscopy. These techniques, together with the associated advantages and limitations, are discussed. The effects of various solute and solvent parameters on the diffusion coefficient, and the modelling aspects of diffusion behavior in SCFs are also analyzed.
When representative equations for the viscosity of carbon dioxide were published in 1990, it was recognized that, owing to inconsistencies among the available experimental liquid viscosity data which could not be resolved, new measurements were necessary. Since then, two new sets of measurements have been performed and it is appropriate to revise the published equations in order to improve their performance in the liquid region. In the previous work, the excess viscosity was represented by two separate equations, one for the gas phase and the other, a provisional one, for the liquid phase. Both equations were joined by a blending function. In the present work, the excess viscosity for the whole thermodynamic surface is represented by one equation. The resulting overall viscosity representation for carbon dioxide covers the temperature range 200 K⩽T⩽1500 K and densities up to 1400 kg m−3. In terms of pressure, the viscosity representation is valid up to 300 MPa for temperatures below 1000 K, whereas for higher temperatures and owing to the limitation of the equation of state used, the upper pressure limit is restricted to 30 MPa. The uncertainties associated with the proposed representation vary from ±0.3% for the viscosity of the dilute gas near room temperature to ±5.0% at the highest pressures. Tables of viscosity generated by the representative equations are included for easy reference and to assist validation of computer coding.
The supercritical uid extraction (SFE) is considered an appropriate alternative for separation of biomolecules from food and pharmaceutical products. A major diiculty in utilizing the SFE for biomolecules has been the diiculty in measurement and prediction of their solubilities in supercritical solvents at various pressures and temperatures for process optimization. Lack of data for intermolecular energy parameters and=or critical properties, acentric factors, and molar refractions limits us to the use of the simple equations of state for prediction of their solubilities in supercritical solvents. In this report, six diierent cubic equations of state are used to predict the solubility of cholesterol and ÿ-carotene, as two representative biomolecules, in supercritical uids. They are the van der Waals, Redlich–Kwong, Mohsen-Nia–Moddaress–Mansoori (MMM), Peng–Robinson (PR) and Patel–Teja and modiÿed PR equations. It is shown that the two-parameter MMM equation is more accurate than ÿve of the other equations and comparable to the modiÿed PR equation in predicting the solubility of cholesterol and ÿ-carotene in supercritical uids. ?
In recent years, increasing demand for superior quality and safety of foods and medicines, as well as concern for environmental pollution during their commercial production, have triggered stringent regulations on the toxin levels in foods and medicines as well as on the discharge of pollutants to the environment. In addition, there has been increasing consumer preference for natural substances. All these factors have given strong impetus to development of cost-effective new technologies, such as the one for eco-friendly extraction from natural substances employing green and safe solvents. In recent years, supercritical fluid extraction (SCFE) has emerged as a highly promising environmentally benign technology for production of natural extracts, such as flavors, fragrances, spice oils, and oleoresins; natural antioxidants; natural colors; nutraceuticals; and biologically active principles. The state of a substance is called supercritical when both temperature and pressure exceed their critical point values. A supercritical fluid (SCF) combines the twin beneficial properties, namely high density (which imparts high solvent power) and high compressibility (which permits high selectivity due to large variability of solvent power by small changes in temperature and pressure). In addition, it offers very attractive extraction characteristics, owing to its favorable diffusivity, viscosity, surface tension, and other thermo-physical properties.
Extraction and fractionation of fish oils has become a major area of research over the last 30 years because of the potential application of these extracts and fractions in the pharmaceutical, nutraceutical, and cosmetic industries. The major constituents of fish oils are triacylglycerides (TAGs). Minor components include free fatty acids, squalene, tocopherols, cholesterol, wax esters, sterol esters, phospholipids, diacylglycerides, diacylglycerol ethers, pigments, and vitamins A, D, and E. Oils of marine origin are significantly more complex than those from plants and terrestrial animals. The fatty acids that constitute TAGs in fish oils vary considerably according to degree of unsaturation, variety of chain length, and number of isomeric compounds. TAGs are typically made up of straight-chain fatty acids containing from 12 to 24 or more carbons, with the degree of unsaturation varying from zero to six double bonds. Fish oils often contain more than 60 different fatty acids, including isomers, which differ according to the position of unsaturation within the carbon chain. The complex composition of fish oils makes them difficult to process to concentrate specific fatty acids. High levels of unsaturation make the use of high-temperature processing methods problematic because of the susceptibility of these compounds to oxidative and thermal degradation. The variability in fatty acid composition of fish oil is highly dependent on fish species, season, feeding habits, part of the fish used (e.g., liver or flesh), and catch location. Some fatty acid profiles of selected fish oils are shown in Table 5.1 [1], which shows that liver oil composition is usually less saturated than that of the flesh.
Conditions for maximum oil recovery from supercritical carbon dioxide (SC-CO2) extraction of raw sesame seeds were determined in an experimental region defined by three levels of temperature (50, 60, 70°C), pressure 20.7, 27.6, 34.5 MPa; (207, 276, 345 bar) and ethanol concentration (0, 5, 10 wt%). 27.6 MPa and 70°C and 34.5 MPa and 60°C in the presence of 10% ethanol gave maximum yield of 89.40 and 89.14%, respectively. Response surface methodology was used to analyze the data. The following equation represented the data adequately (R2=0.93) : % Yield = 45.02+17.74×P+1.36×T+30.35×EtOH+14.66×P×T. The analyses of the extracted samples showed minimal change in the fatty acid composition. Sesame oils extracted both with hexane and supercritical carbon dioxide were observed to be cloudy. The cloudiness seemed to be increasing with presence of ethanol in the supercritical solvent.
Lipids were extracted from roasted pistachio nut particles by supercritical CO2 (SC-CO2) in an incomplete design at pressures of 20.7, 27.6, and 34.5 MPa and temperatures of 50, 60, and 70°C with ethanol (0, 5, and 10 wt%) as entrainer. Highest experimental extraction yield of 66% was obtained at 34.5 MPa and 60°C with 10 wt% ethanol Data was analyzed by Response Surface Methodology. Temperature did not affect the extraction yield. Extraction yield increased linearly with pressure, while ethanol concentration had a curvilinear effect. The following equation adequately represented the experimental data (r2 = 0.94): % Yield = 52.14 + 9.707 x P + 21.164 x EtOH - 11.049 x EtOH2. The solubility of pistachio oil in SC-CO2 at 34.5 MPa and 60°C was 5 times higher in case of 10 wt% ethanol (1.29 wt%) compared to CO2 alone (0.27 wt%). Difference between extracted and control pistachios in terms of texture was detected by puncture and compression tests as well as by sensory evaluation. Sensory evaluation showed a reduction in roasted pistachio flavor intensity following SC-CO2 extraction.
The solubilities of three organic solids were measured in carbon dioxide, ethane, fluoroform, and chlorotrifluoromethane. The solutes were selected so that each contained a single organic functional group affixed to a parent bi- or tricyclic aromatic ring. The solvents were chosen on the basis of their chemical dissimilarities yet nearly equal critical temperatures. It was found that the choice of solvent gas can significantly affect the equilibrium solubility of a particular solute species in that gas, and different solvents either enhance or depress solubility in conjunction with the particular functionality of the solute molecule. Acid-base and solvent-solute association effects appear to play a role in some specific cases. The experimental data were correlated with a single adjustable parameter Peng-Robinson equation, and regressed binary interaction coefficients (k//i//j's) are tabulated for all of the systems studied. In addition, a new empirical correlation of the experimental data is proposed which models the solid-fluid solubility isotherms well.
The knowledge of the solubility behavior of different Lipid classes in supercritical carbon dioxide (SCCO2) is of great importance in the design of SCCO2 fractionation, extraction, and reaction processes. Solubility data from the literature for binary mixtures of SCCO2 and pure lipids (fatty acids, mono-, di-, and triglycerides, and fatty acid esters) were correlated using Chrastil's equation to determine the effect of compound properties (molecular weight and polarity) and operating conditions (density of CO2, pressure, and temperature) on the solubility behavior. The physical state of the lipid solute had a significant effect on model parameters and, hence, the solubility behavior. An isothermal increase in the pressure and a temperature increase at constant CO2 density led to an increase in solubility for all the compounds studied. Retrograde solubility behavior was observed for liquid solutes, whereas the solid solutes were in the nonretrograde region under the examined conditions. In a homologous series, solubility decreased with an increase in the molecular weight and polarity. The effect of solute proper ties on solubility was observed to be dependent on operating conditions. The solubility behaviors of pure lipid classes outlined in this study are intended to provide the basis for further study of complex multicomponent lipid mixtures in supercritical processes.
The studies conducted by Smigelskas and Kirkendall showed that during diffusion in alpha brass zinc moves significantly faster than copper. The force acting on a particle in a potential field is the negative gradient of its potential energy. A chemical analysis is employed to determine the diffusivity, which is compared with the diffusivity obtained from the isotope tracer technique. The major isotope or mixture is regarded as component one and the tracer isotope as component two. The properties of the isotope tracer is assumed to be identical with those of the major isotope or isotopes, except for the slight difference in mass, thus it follows that the drift velocity under unit force is essentially the same for the two. W.A. Johnson conducted experiments in which diffusivity D for the gold-silver system near the composition N 1 = N2 = 0.5 is determined in usual manner and the diffusivity of radio-active gold and silver isotopes in the alloy is also measured.
The separation of oil from wheat germ by extracting with supercritical carbon dioxide (C02) is described. The solubility of wheat germ oil in supercritical C02 at 200 atm and 40°C was about 0.35 weight%. The effect of pressure on the extraction process with liquid or supercritical C02 was of great significance. On the other hand, the effect of temperature on the extraction process was small. Oil extracted with supercritical C02 was lighter in color and contained less phosphorus than that extracted with hexane. The contents of α- and β-tocopherol in the oil extracted with supercritical CO2. were comparable to those in the hexane-extracted oil
As a continuation of an earlier review, a compilation of systems for which high-pressure phase equilibrium data have been published between 1994 and 1999 is given. Vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), vapor–liquid–liquid equilibria (VLLE), solid–liquid equilibria, solid–vapor equilibria, solid–vapor–liquid equilibria, critical points, the solubility of high-boiling substances in supercritical fluids and the solubility of gases in liquids (GLE) are included. For the systems investigated, the reference, the temperature and pressure range of the data, and the experimental method used for the measurements is given in 39 tables. Most of experimental data in the literature has been given for binary systems. Of the 824 binary systems, 350 have carbon dioxide as one of the components. Information on 135 pure components, 337 ternary systems and 120 multicomponent systems is given. Experimental methods for the investigation of high-pressure phase equilibria are classified and described.
Various factors affecting SC-CO//2 peanut oil extraction were examined. Pressure, temperature, particle size, moisture, and flow rate effects in a vertical extractor were evaluated using a half-factorial design. the effect of temperature and pressure was studied further for temperatures of 25 to 95 degree C and pressures of 140 to 550 bar. At 25 degree C and 550 bar, the particle size dependence of both the initial extraction rate and the overall oil yield was studied for particle size of 0. 864 to 4. 75 mm.
The paper contains new, representative equations for the viscosity and thermal conductivity of carbon dioxide. The equations are based in part upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the low‐density thermal conductivity at high temperatures, all available data are shown to be inconsistent with theoretical expectation and have therefore been abandoned in favor of a theoretical prediction. Similarly, the liquid‐phase thermal conductivity has been predicted owing to the small extent and poor quality of the experimental information. In the same phase the inconsistencies between the various literature reports of viscosity measurements cannot be resolved and new measurements are necessary. In the critical region the experimentally observed enhancements of both transport properties are well represented by theoretically based equations containing just one adjustable parameter. The complete correlations cover the temperature range 200 K≤T<1500 K for viscosity and 200 K≤T≤1000 K for thermal conductivity, and pressures up to 100 MPa. The uncertainties associated with the correlation vary according to the thermodynamic state from ±0.3% for the viscosity of the dilute gas near room temperature to ±5% for the thermal conductivity in the liquid phase. Tables of the viscosity and thermal conductivity generated by the representative equations are provided to assist with the confirmation of computer implementations of the calculation procedure.
This work reports the countercurrent extraction and fractionation of a range of crude fish oils using supercritical carbon dioxide and carbon dioxide+ethanol mixtures. Vitamin A palmitate was extracted from model Cod liver oil/vitamin mixtures using pure CO2. The separation factor was low, due to similar solubilities of the vitamin ester and the oil. Vitamin A was also recovered from Cod liver oil ethyl esters\vitamin A mixtures. The separation factor was substantially improved over the non-esterified oil, due to large differences in the solubilities of the esters and vitamin A in supercritical CO2. Solubilities of fish oils and squalene are reported using CO2+ethanol mixtures at 333 K, ethanol concentrations from 0 to 12% by mass and pressures from 200–300 bar. Solubilities of all oils and squalene increased exponentially with linear increases in the ethanol concentration. The solubility of polar components increased more rapidly than non-polar components. Pilot scale removal of fatty acids from Orange Roughy oil and squalene from deep sea shark liver oil was carried out using CO2+ethanol as the solvent. The extent of fatty acid removal from Orange Roughy oil was superior to pure CO2, whereas the degree of separation of squalene from shark liver oil was inferior. Throughput was substantially increased relative to pure CO2 in both cases. Mass transfer behaviour and product purity results are also presented for the demonstration scale production of squalene and diacyglycerylether fractions from deep sea shark liver oil using pure CO2. Fractionation results are compared with previous experimental results obtained at a laboratory and pilot scale to obtain the height of a transfer unit (HTU) and packed height required as a function of scale. Modelling of flooding at supercritical conditions was carried out to enable optimal design of the packed column. A liquid–liquid flooding model gave reasonable correlation of literature flooding data, obtained at a laboratory and pilot scale.
An equation proposed by Darken, including the thermodynamic factor and tracer diffusion coefficients of solvent and solute, was adopted to correlate the diffusion coefficients for naphthalene and dimethylnaphthalene (DMN) isomers in supercritical carbon dioxide and the correlated results were compared with the experimental data. IML equation of state with mixing rules and combining rules containing two adjustable interaction parameters were used for calculation of the thermodynamic factor. By using the interaction parameters adjusted to the solubility data, the concentration dependence of diffusion coefficients and their anomaly near the critical point of carbon dioxide can be quantitatively represented. In order to improve the reliability of experimental results, some re-measured diffusion coefficient data for naphthalene, 2,6- and 2,7-DMN at 308.2 K, and new data for naphthalene at 318.2 K and for 2,3-DMN at 308.2 K are presented.
Experimental methods for the investigation of high-pressure phase equilibria are classified and described. A review of systems for which high-pressure phase-equilibrium data have been published between 1988 and 1993 is given. Vapor-liquid equilibria (VLE), liquid-liquid equilibria (LLE), vapor-liquid-liquid equilibria (VLLE), the solubility of high-boiling substances in supercritical fluids and the solubility of gases in liquids are included. For the systems investigated, the reference, the temperature and pressure range of the data, and the experimental method used for the measurements is given in 28 tables.
The phase behaviour of fluid mixtures at high pressure has received great attention over the past decade. This upsurge of interest has been occasioned by the importance that high pressure fluid phase equilibria has now assumed in some industrial areas.This work reviews and classifies recently developed experimental methods for investigating high pressure fluid phase equilibria. A review of the systems studied in the last 10 years is also given.
The viscosities and densities of supercritical mixtures of methanol, ethanol, n-propanol, isopropanol, n-pentane, n-hexane, n-heptane, and acetone in carbon dioxide, at concentrations between 1 and 5 mol %, were determined using a falling weight viscometer at pressures up to 240 bar and at temperatures between 313 and 328 K. The effects of pressure, temperature, cosolvent concentration, and the physical properties of the cosolvents on the mixture viscosity and density were examined. The viscosities and the densities of the mixtures were found to increase with the size, polarity, and concentration of the cosolvent molecule. The mixture viscosity was correlated with several empirical dense gas viscosity correlations. The best correlation was the Ely and Hanley technique modified with a density-dependent noncorrespondence factor. The Peng-Robinson equation of state was used to correlate the mixture densities.
A table is given of the compounds of low volatility, whose experimental solubilities in supercritical carbon dioxide have been published up to the end of 1989, with the temperature and pressure ranges of the experimental measurements, the experimental method, and references to the source of data. The data for pure compounds, which were presented in tabular form in the original publications, are shown in a series of figures along with correlation lines for each isotherm. The method of correlation was to fit the experimental data for each isotherm, in the form of the natural logarithm of the product of mole fraction and pressure, to a linear function of density above a pressure of 100 bars. The constants obtained from the fitting procedures are given in a table. Procedures for estimating, from these constants, the solubilities of the compounds at temperatures and pressures different from those of the experimental data are suggested.
Production of omega-3 (ω3) fatty acid concentrates continues to be a topic of interest for both the pharmaceutical and health food industries. Since the early studies on long-chain ω3-polyunsaturated fatty acids (PUFA) in 1929 by Burr and Burr (J. Biol. Chem., 1929, 82, 345–367), the health benefits of consumption of this class of compounds have been thoroughly investigated. With the growing public awareness of the nutritional benefits of seafoods and their ω3-PUFA, the market for such products is expected to grow in the future. This overview provides a discussion of nutritional aspects and methodologies used for producing ω3 concentrates from source materials.
The safety of the consumption of spices – turmeric, red pepper and black pepper and their respective active principles was established in animal studies by observing the influence on growth, organ weights, nitrogen balance and blood constituents upon feeding at levels close to human intake as well as upto 100-times the normal human intake. Exhaustive animal studies documented the beneficial influence of turmeric/curcumin, red pepper/capsaicin, and garlic on lipid metabolism, especially anti-hypercholesterolemic effect of the three spices and anti-lithogenic effect of curcumin and capsaicin. The anti-diabetic effects of turmeric/curcumin, onion and cumin seeds were also evidenced with particular ameliorative influence of curcumin and onion on diabetic nephropathy. The antioxidant effects of curcumin (of turmeric), capsaicin (of red pepper) and eugenol (of clove) were evidenced both in in vitro and in vivo systems and the consequential health beneficial anti-inflammatory influence in experimentally induced arthritis was documented. The mechanism of digestive stimulant action of common spices examined in experimental animals revealed to be mediated through phenomenal stimulation of bile secretion with an enhanced bile acid concentration (ingredients essential for fat digestion and absorption) and an appropriate stimulation of the activities of digestive enzymes of pancreas and small intestine. The protective influence of hypolipidemic spices – curcumin, capsaicin and garlic on the altered fluidity of erythrocytes under hypercholesterolemic situation was evidenced in experimental animal models. Antioxidant spices were also shown to greatly reduce LDL-oxidation and also modulate the synthesis of prostaglandins and leukotrienes. Several spices or their extracts were also found to beneficially inhibit platelet aggregation. All these observations strongly indicate that many spices and their active principles are excellent nutraceuticals.
Tomato skins and their mixtures with seeds were submitted to supercritical CO2 extraction using a flow apparatus at pressures of 250 and 300 bar and temperatures of 60 and 80 °C. Two different mean particle sizes (80 and 345 μm) were used at two solvent flow rates (0.792 and 1.35 kg/h). The yields of lipids, lycopene, and β-carotene obtained by supercritical fluid extraction were compared with those obtained by conventional organic solvent extraction. Supercritical fluid extraction from tomato skins at 300 bar and 80 °C allowed the recovery of 80% of the lycopene and 88% of the β-carotene, using about 130 g of CO2 per gram of matrix at the lower flow rate of CO2.
Density and viscosity of the coexisting phases and interfacial tension of the following binary systems were measured: pelargonic acid, linoleic acid, oleic acid or stearic acid as subcritical and carbon dioxide as superecritical components. Also the corresponding phase equilibria were investigated at pressures ranging from 2 to 20 MPa and temperatures from 313 K to 393 K. With increasing pressure the concentration of the supercritical component in the liquid phase increases and viscosity and liquid interfacial tension decreases. At greater activities of the dense gases the interfacial tension decreases dramatically to values less than 2 mN/m. If the pressure exceeds a certain limit, a falling film disintegrates into small droplets. The surface excess passes through a maximum at these conditions. At first appearance of instabilities on a falling film, the logarithm of the Reynolds number is a linear function of the logarithm of the film number. Independent of the type of the investigated packings, the number of theoretical stages per meter versus Hodenstein number fall all on the same curve when an extraction is carried out in the droplet regime. Also the logarithm of the capacity of a column al the flooding point versus the logarithm of the density difference between the coexisting phases is a linear function when an extraction is carried out in the droplet regime.
Development and state of the art of counter-current separation, in particular for liquids, with supercritical fluids, is reviewed, covering principles, early development, actual and possible applications, and counter-current separation as published in the Journal of Supercritical Fluids. A description of processes (continuous counter-current flow, mixer-settler principle, the role of co-solvents), necessary fundamentals, design procedure (including gas cycles), a summary of the methodical knowledge, and cost calculation are covered. A discussion and a comparison to competitive processes and an outlook on future perspectives conclude the review.
Micronization processes using the unique properties of supercritical fluids (SCF) have reached a state, where they are entering industrial application. Results from almost 3 decades of basic research concerning thermodynamics and mass transfer during solidification in presence of SCF have been applied to develop a multitude of process ideas. Selected processes from the anti-solvent- and PGSS-type have been scaled up and are successfully operated. The key to success was not only to develop the technologies and to demonstrate their technical and economical feasibility but also to generate new concepts for applications in the food area. Selected examples will be presented and the achievements and challenges still to be met are summarized.
Fatty acid ethyl esters from fish oil (FAEE) were continuously fractionated with supercritical carbon dioxide (SCCO2). A pilot plant countercurrent extraction column with an inner diameter of 68mm and an effective height of 12m packed with Sulzer CY wire mesh packing was used for the experiments. The operating conditions varied in the temperature range of T=40–80°C and the pressure range of p=6.5–19.5MPa.All experiments focused on a separation between the low-molecular-weight components (LMC), with carbon numbers from C14 to C18, and the high-molecular-weight components (HMC), C20 and C22. This separation represents a possible first step in an enriching process for the commercial interesting components EPA and DHA. HMC concentrations greater than 95wt% at a yield greater than 95% were achieved with this set-up.The pilot plant was equipped with a sampling system to measure the concentration profile along the column. These experiments allow the height of a theoretical plate to be calculated. Previously published phase equilibrium data [V. Riha, G. Brunner, Phase equilibrium of fish oil ethyl esters with supercritical carbon dioxide, J. Supercrit. Fluids 15 (1999) 33–50] are employed as base information for these calculations. The methods of McCabe-Thiele and Ponchon-Savarit (R.E. Treybal, Mass-transfer Operations. Classic Textbook Reissue, 3rd edition, McGraw-Hill, New York, 1987) and a multi-component simulation with the flowsheeting program Aspen+ are used to compute the theoretical number of plates for each experimental run. All methods yield similar results. A height of approximately 0.3m can be assumed for a theoretical plate with this set-up.
Solubilities of synthetic trans-β-carotene in supercritical carbon dioxide and ethane were measured, at temperatures from 35 to 60°C and pressures up to 300bar, using a single-pass flow apparatus. The compound showed a low solubility in both solvents, but in ethane, its value was about an order of magnitude higher. The solubility measurements were compared with those published by other workers, which used different methods for the determination of the concentration of β-carotene in supercritical fluids. Moreover, the solubility data were correlated using the Peng–Robinson equation of state.
Carbon-dioxide SCF extraction from herbaceous substrates produces nearly solid extracts because of simultaneous solubilization of essential oil components and cuticular waxes. Fractionation of the extract is required to isolate the essential oil.A mechanism is proposed to explain coextraction of essential oil and leaf and cuticular waxes, based on different mass transfer mechanisms for the two compound families. Cuticular waxes are hypothesized as mainly solubilized by leaching, while essential oil extraction is supposed dependent on complex diffusion phenomena.If extraction mechanisms operate as modeled, fractional separation of supercritical solution can be realized in a series of separators, taking advantage of the different solubilities of the two compound families and of their different concentrations in the solution.Marjoram leaf (Origanum Majorana L.) essential oil isolation by SCF has been studied as an application of fractional separation procedure. A nearly complete fractionation has been realized and a high quality essential is oil produced.
This contribution provides basic data for developing an extraction process for carotenoid compounds in terrestrial and marine plants with supercritical CO2 (SC-CO2). Specifically, the solubility (y2, molar fraction) of lycopene and astaxanthin was measured in SC-CO2 as a function of temperature (313K≤T≤333K) and pressure (10MPa≤P≤42MPa). Experimental data were correlated using a density-based model valid for a solvent density above 330kg/m3. Based on this model and the best-fit model parameters, the solubility of lycopene in SC-CO2 at 313K and 30MPa (y2=0.40×10−6) was within a wide range of experimental values for the solubility of β-carotene in CO2 under same conditions (0.20×10−6≤y2≤0.50×10−6). The interpolated solubility of astaxanthin in SC-CO2 at 313K and 30MPa was slightly smaller (y2=0.19×10−6) than the one of lycopene, as expected for a slightly heavier and more polar solute. There was a larger increase in solubility of both lycopene and astaxanthin by increasing the temperature from 313 to 333K at a constant pressure of 30MPa (2.8–5.1 times) than by increasing the pressure from 30 to 50MPa at a constant temperature of 313K (1.3–1.6 times), which was consistent with the trend in literature for the solubility of β-carotene in SC-CO2.
The methods for obtaining reliable data on diffusion coefficients at high pressure have received great attention over the last 15 years. This interest has been due to the importance that supercritical fluids have assumed in some industrial areas, mainly in emerging separative operations based on mass transfer mechanisms. This review includes all the available data of diffusion coefficients in supercritical fluids at infinite dilution. Revised literature includes references until 1998. Frequent types of graphical correlation were analyzed.
The objective of this paper is to propose a predictive method for the estimation of the change in the solubility of a solid in a supercritical solvent when another solute (entrainer) or a cosolvent is added to the system. To achieve this goal, the solubility equations were coupled with the Kirkwood–Buff (KB) theory of dilute ternary solutions. In this manner, the solubility of a solid in a supercritical fluid (SCF) in the presence of an entrainer or a cosolvent could be expressed in terms of only binary data. The obtained predictive method was applied to six ternary SCF–solute–cosolute and two SCF–solute–cosolvent systems. In the former case, the agreement with experiment was very good, whereas in the latter, the agreement was only satisfactory, because the data were not for the very dilute systems for which the present approach is valid.
The solubility of components of low volatility having the same vapour pressures at 70 °C - hexadecanol, octadecane and salicylic acid phenyl ester - in various gases and entrainers have been determined. The gases dissolve the low volatile components in different quantities, yet separation factors are modest in general. Entrainers enhance the solvent power of the gas phase and in some cases also enhance the separation factor.
Dense gas extraction followed by thin-layer chromatography (DGE-TLC) gives a first fast survey of various parameters influencing this separation technique. As an example, the effect of pressure on the extraction of castor beans is illustrated. Applying the coupling procedure to steroids allows to establish relations between the structure of such compounds and their solubility. The quantitative determination of solubility is described and the behaviour of soybean oil up to 2600 bar is discussed. The solubilities of limonene and eugenol in the subcritical pressure range serve to demonstrate that the recovery of volatile compounds requires carefully chosen separation parameters. The detoxification of wormwood leaves on a preparative scale is described.
This work describes the influence of some operative parameters of supercritical carbon dioxide extraction employed for the isolation of lycopene and β-carotene from the pulp and skins of ripe tomatoes. The extractions were conducted at pressures and temperatures ranging from 2500 to 4000 psi and 40 to 80°C, respectively. The extracted product at 4000 psi and 80°C contained about 65% of lycopene and 35% of β-carotene. Lycopene and β-carotene showed a different solubility in the supercritical fluid depending on process parameters. With a proper choice of operative parameters, it has been possible to obtain a product that contained 87% lycopene and 13% β-carotene.
Hiprose seed oil has been extracted by supercritical CO2 operating at pressures of 1500, 3000, 6000 and 10000 psi, temperatures of 40, 50 and 70°C, CO2 flow rates of 1, 2, 4 and 6g/min using mean particle sizes of 0.42, 0.79 and 1.03mm. The obtained oil yield data has been used to validate a mathematical model of the extraction process, based in part on the information obtained from the microscopic structure of the hiprose seed particles. The differential mass balances forming the model have been numerically integrated. The best fit between model curves and data has been obtained when a linearly variable internal mass transfer coefficient was adopted, with an initial value of 1.9×10−5m/s.
The viscosity of carbon dioxide has been measured with a transpiration method at temperatures between 0° and 75°C at pressures up to 2000 atmospheres. Previous measurements described earlier revealed an unexpected increase of the thermal conductivity of argon round the critical density. Therefore special attention has been given to the critical region although the transpiration method is not particular suitable for this region.
The viscosity of CO2 above 40°C shows the normal trend with pressure, but deviates considerably from Enskog's theory. In the critical region the viscosity shows a similar abnormal behaviour as found for the heat conductivity of argon. Viscosity measurements of argon did not show this effect but in this case the temperatures relative to the critical temperature were higher than in the present measurements of CO2. The results are compared with those of other authors.
Most of the models proposed in literature for binary diffusion coefficients of solids in supercritical fluids are restricted to infinite dilution; this can be explained by the fact that most of experimental data are performed in the dilute range. However some industrial processes, such as supercritical fluid separation, operate at finite concentration for complex mixtures. In this case, the concentration dependence of diffusion coefficients must be considered, especially near the upper critical endpoint (UCEP) where a strong decrease of diffusion coefficients was experimentally observed. In order to represent this slowing down, a modified version of the Darken equation was proposed in literature for naphthalene in supercritical carbon dioxide. In this paper, the conditions of application of such a modelling are investigated. In particular, we focus on the order of magnitude of the solubility of the solid and on the vicinity of the critical endpoint. Various equations proposed in literature for the modelling of the infinite dilution diffusion coefficients of the solutes are also compared. Ten binary mixtures of solids with supercritical carbon dioxide were considered for this purpose.
The paper contains the results of a new determination of the viscosity of carbon dioxide in the single-phase region surrounding the critical dome. The determination was performed in a modified oscillating-disk viscometer used earlier for the determination of the viscosity of several noble gases and steam.The results show that the anomalies in the dynamic viscosity of carbon dioxide are rather mild, and several orders of magnitude lower than those reported by A. Michels, A. Botzen and W. Schuurman. The kinematic viscosity, however, exhibits a region of very rapid change with pressure at constant temperature.At attempt was made to provide a very crude estimate of the effect of density stratification in the terrestrial gravitational field in the neighborhood of the critical dome.
The hydrodynamic behavior, i.e., flooding, liquid holdup, and pressure drop of countercurrent columns with two random packings, Raschig rings and Berl saddles, and two gauze packings, Sulzer CY and Sulzer EX, is scrutinized at temperatures between 313 and 373 K and pressures between 8 and 30 MPa using carbon dioxide as the supercritical solvent and water and olive oil deodorizer distillate as liquid phases. Two models are employed to correlate the experimental data: a sophisticated mechanistic approach;based on the liquid holdup and a well-known empirical approach for the flooding point. The experimental data for the dry pressure drop and the liquid holdup below the loading point are successfully correlated using modified models from normal pressure operation. The flooding points can be correlated with good accuracy as well.
The goal of this paper is to develop a predictive method for the solubility of a solid in a supercritical fluid containing an entrainer at any concentration. The main difficulty consists in the derivation of an expression for the fugacity coefficient of the solid solute in the binary solvent. A method based on the Kirkwood–Buff formalism was employed and expressions for the derivatives of the fugacity coefficient of the solute in a ternary mixture with respect to the mole fractions were obtained. On the basis of these expressions an algebraic equation was derived, which allowed one to predict the solubility of a solid solute in terms of its solubilities in the supercritical fluid and in the entrainer. The equation was compared with the experimental results available in the literature regarding the solubility in a mixture of supercritical fluids and good agreement was obtained.