Supercritical CO2 extraction

Supercritical CO2 extraction has potential for the removal of cholesterol. Careful manipulation of process conditions is necessary to obtain efficient removal of cholesterol. When supercritical CO2 extraction is used to fractionate milk fat, the liquid fraction is enriched in cholesterol while that of the solid fraction is reduced (Arul et al., 1988b). 

The efficiency of supercritical CO2 for removing cholesterol is temperature- and pressure-dependent. Removal of about 90% cholesterol from milk fat was achieved using bench-scale supercritical CO2 extraction using an ascending pressure profile (Bradley, 1989). With multistage supercritical CO2 extraction, more than 90% cholesterol can be removed from milk fat (Anon, 1989). 

The use of adsorbents in conjunction with appropriate conditions for supercritical CO2 extraction enhances the efficiency of cholesterol extraction. Selective removal of 97% of cholesterol has been achieved with the use of silica gel as an in-line adsorbent (Huber et ah, 1996). Removal of 96% of cholesterol in milk fat fractions can be achieved by a combined supercritical C02 extraction and an alumina adsorption process (Mohamed et al., 1998). 

In terms of CO2 as a reaction medium, a novel one-step process involving supercritical CO2 and enzymahc hydrolysis of cellulose has been shown to produce a 100% glucose yield [47]. However, to maintain the high pressure and temperature (160 bar and 50 °C) means the technology may have limited viability for industrial production, but it is an ideal technology for specialty products and possibly for other applications. For example, butyl butyrate can be synthesized via enzymatic esterification and transesterification using a lipase, Novozym 435, under supercritical CO2 conditions. Butyl butyrate is a component of pineapple flavor used by 

Hops were first extracted with carbon dioxide under supercritical conditions in the 1950s and results were reported from the Soviet Union [16] and Japan [18]. The quality of the extracts obtained was poor, comparing unfavourably with solvent extracts then available and discouraging the pursuit of carbon dioxide for hop extraction. It has been suggested that these early products were contaminated with iron owing to the use of unsuitable grades of steel in the plants concerned. 

By 1981, hops were being successfully extracted in Germany with supercritical CO2. A second plant was built shortly afterwards and both have been succeeded by units of greatly increased capacity during the 1980s. The combined capacity of these plants now exceeds 10 000 tonnes per annum. Perceived consumer reaction against the use of chemical solvents like methylene chloride has ensured a strong demand for CO2 extracts at the expense of the technically popular methylene chloride. 

The capital cost of a supercritical extractor of given capacity is very much dependent on the width of the top and bottom closures. The use of baskets necessitates full-width openings and these will require expensive and massive closures. Nevertheless, it can be desirable to incur this expense even if baskets are not employed as it can otherwise prove very difficult to unload the spent 

The technique for changing round extractors on a supercritical system is somewhat different from that used on a liquid plant since the concept of liquid transfer between spent and fresh extractors is not applicable, though the principal objective of transferring as much CO2 as possible to the fresh extractor at no energy cost still applies. There is also less incentive to install gas recovery systems since the amount of residual gas left in the extractor, once equilibrated to the work tank pressure, is much less because of the higher temperature and the consequent avoidance of spent hops that are wet with CO2. 

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Solvent extraction removes chlorophyll and other pigments to give a light-colored product but increases processing costs. Furthermore, solvent extraction removes p-carotene and reduces vitamin A activity (89) (see Terpenoids Vitamins). Supercritical CO2 extraction at 30 and 70 MPa (4,350 and 10,150 psi) and 40°C removed 90 and 70% carotene and lutein, respectively, from alfalfa LPC (96). This process avoids organic solvent residues and recovers valuable by-products. 

Low cholesterol egg products are formed by extraction of cholesterol from the egg. Attempts have been made to extract cholesterol by using hexane or by supercritical CO2 extraction methods (24,25). A whole egg product in which 80% of the cholesterol is removed by a process using beta-cyclodextrin, a starch derivative, added to egg yolks has been introduced. The cyclodextrin binds up to 80% of the cholesterol, the mixture is centrifuged, and the Hquid separated. The cholesterol-reduced yolk is then blended with egg white, pasteurized, and packed in asceptic containers to give a Hquid whole egg product having a shelf Hfe of 60 days under refrigeration (see Eood packaging). 

A third motivation for studying gas solubilities in ILs is the potential to use compressed gases or supercritical fluids to separate species from an IL mixture. As an example, we have shown that it is possible to recover a wide variety of solutes from ILs by supercritical CO2 extraction [9]. An advantage of this technology is that the solutes can be removed quantitatively without any cross-contamination of the CO2 with the IL. Such separations should be possible with a wide variety of other compressed gases, such as C2LL6, C2LL4, and SF. Clearly, the phase behavior of the gas in question with the IL is important for this application. 

Vasapollo G, Longo L, Rescio L and Ciurlia L 2004. Innovative supercritical CO2 extraction of lycopene from tomato in the presence of vegetable oil as co-solvent. J Supercrit Fluids 29(1-2) 87-96. 

Lipids that contain polyunsaturated fatty acids (PUFA) have therapeutic value. Supercritical CO2 extraction was chosen as an alternative method to recover these valuable compounds from the lower fungus, Pythium irregu-lare (Walker et al., 1999). 

In their test system, the researchers used the ionic liquid l-butyl-3-methylimidazol-ium hexafluorophosphate (bmim)(PF6), which is stable in the presence of oxygen and water, with naphthalene as a low-volatility model solute. Spectroscopic analysis revealed quantitative recovery of the solute in the supercritical CO2 extract with no contamination from the ionic liquid. They found that CO2 is highly soluble in (bmim)(PF6) reaching a mole fraction of 0.6 at 8 MPa, yet the two phases are not completely miscible. The phase behavior of the ionic liquid-C02 system resembles that of a cross-linked polymer-solvent system (Moerkerke et al., 1998), even though... 

Four aspects of research involving the use of SFE for the improvement of quality of muscle food products are briefly discussed. These include supercritical CO2 extraction of lipids fi om fresh ground beef and from dried muscle foods the extraction and separation of lipid and cholesterol from beef tallow supercritical CO2 extraction of flavor volatiles from beef and pork lipids for use as additives in synthetic meat flavors and identification and quantitation of flavor volatiles extracted with SC-CO2. 

The main volatile components isolated from bacuri shells using various isolation methods, such as steam distillation and supercritical CO2 extractions were (Z)-linalool oxide, ( )-linalool oxide, 2-pentanone, 2-nonanone, ds-hexenyl acetate, methyl dodecacanoate, and several hydrocarbons, including bisabolene [46]. 

The supercritical CO2 extraction of Capsicum annuum var. Scotch Bonnet gave 16.4% of extract, and it contained 3.2 and 0.5% capsaicin and dihydrocapsaicin, respectively, per dry weight of the raw material. Organic solvents (hexane, CHC13, and methanol) were used... 

Chao, R.R., Mirlvaney, S.J., Sanson, D.R., Hsieh, F., and Tempesta, M.S. 1991. Supercritical CO2 extraction of anatto (Bixa orellana) pigments and some characteristics of the color extracts. J. Food Sci. 56 80-83. 

Favati, F., King, J.W., Friedrich, J.P., and Eskins, K. 1988. Supercritical CO2 extraction of carotene and lutein from leaf protein concentrates. J. Food Sci. 53 1532-1536. 

Spanos, G.A., Chen, H., and Schwartz, S.J. 1993. Supercritical CO2 extraction of (3-carotene from sweet potatoes. J. Food Sci. 58 817-820. 

Figure 6. Plot of recoveries (log scale) for supercritical CO2 extractions at a density of 0.70 g/ml vs. the inverse of the extraction temperature for methoxychlor, pyrene, perylene, benzo[ghi]perylene, and coronene.

Supercritical CO2 extraction may be used in batch or continuous systems to fractionate anhydrous milk fat into fractions with specific properties in order to enhance its utilization (Arul et al., 1987 Bhaskar et al., 1993). Supercritical fluid extraction using CO2 provides an alternative to the use of... 

The fractions obtained by supercritical CO2 extraction are different from those by dry fractionation. There are differences in the fatty acid and triacylglycerol compositions and melting profiles (Table 8.1). As the characteristics of the fractions depend on the conditions of the processes and the number of fractions obtained, any comparison between fractions should take into account not only the type of processes employed but also the specific process conditions. 

Huber, W., Molero, A., Pereyra, C., Martinez de la Ossa, E. 1996. Dynamic supercritical CO2 extraction for removal of cholesterol from anhydrous milk fat. Int. J. Food Sci. Technol. 31, 143-151. 

In another method, developed by Jacobucd and co-workers (9), alcohol is removed by supercritical CO2 extraction in a semi-continuous system. 

Piantino, C.R. Aquino, F.W.B. Follegatti-Romero, L.A. Cahral, F.A. 2008. Supercritical CO2 extraction of phenolic compounds from Bacharis dracunculifolia. J. Supercrit. Fluids 47 209-214. 

Baysal, T. Ersus, S. Starmans, D.A. J. 2000. Supercritical CO2 extraction of 3-carotene and lycopene from tomato paste waste. J. Agric. Food Chem. 48 5507-5511. 

Supercritical CO2 extraction methods were evaluated for a number of oilseeds in the 1980s. Corn germ extraction by supercritical CO2 was evaluated by ARS researchers in Peoria, IL. Methods for corn germ extraction using 100% supercritical CO2 were developed (10, 17) and patented (18). Others have demonstrated that addition of ethanol modifier (0 -10%) to supercritical CO2 can decrease the extraction time and improve the functionality of germ proteins (19). Although there are no technical barriers, extraction of com germ with supercritical CO2 is more costly than conventional extraction methods. 

Supercritical CO2 extraction also has been used to selectively extract phosphatidylcholine from de-oiled soybean lecithin (197). The effects of temperature, pressure, and amount of ethanol on phosphatidylcholine extraction were examined, and a high-purity product could be produced with optimized conditions. 

Sarrade SJ, Rios GM, and Carles M. Supercritical CO2 extraction coupled with nanoflltration separation Applications to natural... 

There are many publications showing the applications of SFE to the determination of polymer additives. Antioxidants such as Irganox 2246, BHT and others, as well as UV stabilizers such as Tinuvin P, have been effectively extracted with supercritical CO2. Extraction conditions varied from 15 to 25 MPa at 60°C and with a total time of 30 min [1], If microwaves are applied to extract these compounds, a mixture of sol-... 

Yang, Y. Gharaibeh, A. Hawthorne, B. Miller, J.D. Combined temperature/modifier effects on supercritical CO2 extractions efficiencies of polycyclic aromatic hydrocarbons from environmental samples. Anal. Chem. 1995, 67, 641-646. 

Reverchon, E. Porta, G.D. Senatore, F. Supercritical CO2 extraction and fractionation of lavender essential oil and waxes. J. Agric. Food Chem. 1995, 43 (6), 1654-1658. 

Emulsion Drying. Supercritical CO2 extracts the water and organic solvent (a heavy alcohol or ketone) and the same recycle system as proposed for the antisolvent process is applicable. The dilference is that, much lower fluid/substrate ratios, of the order of magnitude of 10 -10 are required, with the resulting savings in the recycle loop. 

The low distribution coefficients, the attendant requirement of recycling CO2 containing very little ethanol in order to achieve a high recovery of ethanol from the feed stream, and the inability to achieve the separation of ethanol from the extract stream by pressure letdown required the development of this SCF extraction-distillation process. The diagram shown in figure 8.14 pictorially summarizes that an old distillation technique can be combined with new supercritical CO2 extraction to solve the separation problem supercritical CO2 can extract the ethanol from the feed stream, distillation can separate and regenerate the solvent for recycle, and vapor compression can achieve energy efficiency. 

Zosel explains in the prior art section that foam formation during supercritical CO2 extraction of coffee liquor is a problem the invention eliminates the foaming problem. The improvement in a countercurrent contacting of coffee liquor is to form a thin film of the liquor in the extractor rather than to contact coffee liquor on a sieve tray. The film can be formed in a number of ways, e.g., on packing or in a thin film evaporator. 

Friedrich, J.P., Supercritical CO2 extraction of lipids from lipid-containing materials, U.S. 4,466,923 (August 21, 1984). 

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