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Bioseparation of Nutraceuticals Using Supercritical Carbon Dioxide

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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.

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... 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 It is a form of liquid extraction where the usual liquid solvent phase has been replaced by a supercritical fluid; i.e., a substance that is above its critical point. ...
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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.
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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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.