Lipids supercritical fluid extraction

Eggers, R., Supercritical fluid extraction (SFE) of oilseeds/lipids in natural products, in Supercritical Fluid Technology in Oil and Lipid Chemistry, King, J.W. and List, G.R., Eds., AOCS Press, Champaign, IL. 1996, 35. 

High performance liquid chromatography (HPLC) has been by far the most important method for separating chlorophylls. Open column chromatography and thin layer chromatography are still used for clean-up procedures to isolate and separate carotenoids and other lipids from chlorophylls and for preparative applications, but both are losing importance for analytical purposes due to their low resolution and have been replaced by more effective techniques like solid phase, supercritical fluid extraction and counter current chromatography. The whole analysis should be as brief as possible, since each additional step is a potential source of epimers and allomers. 

Supercritical fluid extraction (SFE) is a technique in which a supercritical fluid [formed when the critical temperature Tf) and critical pressure Pf) for the fluid are exceeded simultaneously] is used as an extraction solvent instead of an organic solvent. By far the most common choice of a supercritical fluid is carbon dioxide (CO2) because CO2 has a low critical temperature (re = 31.1 °C), is inexpensive, and is safe." SFE has the advantage of lower viscosity and improved diffusion coefficients relative to traditional organic solvents. Also, if supercritical CO2 is used as the extraction solvent, the solvent (CO2) can easily be removed by bringing the extract to atmospheric pressure. Supercritical CO2 itself is a very nonpolar solvent that may not have broad applicability as an extraction solvent. To overcome this problem, modifiers such as methanol can be used to increase the polarity of the SFE extraction solvent. Another problem associated with SFE using CO2 is the co-extraction of lipids and other nonpolar interferents. To overcome this problem, a combination of SFE with SPE can be used. Stolker et al." provided a review of several SFE/SPE methods described in the literature. 

Bernardo-Gil MG, Grenha J, Santos J and Cardoso P. 2002. Supercritical fluid extraction and characterization of oil from hazelnut. Eur J Lipid Sci Technol 104(7) 402-409. 

Ruiz del Castillo ML, Gomez-Prieto MS, Herraiz M and Santa-Maria G. 2003. Lipid composition in tomato skin supercritical fluid extracts with high lycopene content. J Am Oil Chem Soc 80(3) 271-274. 

Supercritical Fluid Extraction of Muscle Food Lipids for Improved Quality... 

Another processing procediue that could involve supercritical fluid extraction with CO2 is the preparation of flavor concentrates from meat lipids for use in mixtures of other natural precursors for the preparation of tynthetic meat flavor additives that serve bofii as antioxidants that prevent warmed-over flavor (WOF) in cooked meat diuing storage and enhance the flavor of the natural products. 

BAILEY ET AL. Supercritical Fluid Extraction ofMusde Food Lipids 131... 

Extraction of fat by supercritical carbon dioxide was investigated as an important option for minimizing the expanded use of frequently flammable and carcinogenic solvents in food analysis. Unfortunately, the presence of moisture in foods has an adverse effect on the quantitative extraction of fat by supercritical fluid extraction (SEE). Hence, samples have to be lyophilized first. The total fat content of freeze-dried meat and oilseed samples was found to be comparable to values derived from Soxhlet-extracted samples (26). Besides, only small amounts of residual lipids could be recovered by an additional extraction of the SFE-extracted matrix by the Bligh and Dyer solvent extraction procedure. As far as the minor constituents are concerned, it was found that the extraction recovery ranged from 99% for PC to 88% for PA. Hence, Snyder et al. concluded that SFE can be used as a rapid, automated method to obtain total fat, including total phospholipids, from foods (26). 

JM Snyder, JW King, MA Jackson. Analytical supercritical fluid extraction with lipase catalysis conversion of different lipids to methyl esters and effect of moisture. J Am Oil Chem Soc 74 585-588, 1997. 

Methods of extracting the fat-soluble vitamin from food matrices include alkaline hydrolysis, enzymatic hydrolysis, alcoholysis, direct solvent extraction, and supercritical fluid extraction of the total lipid component. 

Bjorklund, E., L. Mathiasson, P. Persson, et al. 2001. Collection capacity of a solid phase trap in supercritical fluid extraction for the extraction of lipids from a model fat sample. J. liquid Chromatogr. Rel. Technol. 24 2133-2143. 

Other extraction methods used in the lipid extraction include supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE). With SEE, good extraction yields have been obtained for nonpolar lipids including ester-ified fatty acids, acylglycerols, and unsaponifiable matter. However, complex polar lipids are only sparingly soluble in supercritical carbon dioxide alone and polar modifiers, such as methanol, ethanol, or even water is required to improve the extraction of polar lipids (10). SFE has been used for the extraction of lipids especially from various food matrices, such as different nuts, edible oils, and seeds (11). The recoveries of lipids in SFE were on the same levels than with conventional solvent extraction methods (12,13), no significant differences between the fatty acids extracted were observed. PLE has also been used in lipid extraction, although only in very few applications (14). The elevated temperatures used in PLE can cause alteration of the lipid composition. 

Astaire, J.C., Ward, R., German, J.B., Jimenez-Flores, R. 2003. Concentration of polar MFGM lipids from buttermilk by microfiltration and supercritical fluid extraction../ Dairy Sci. 86, 2297-2307. 

Methods are available to remove cholesterol from animal fats (23), and a line of low cholesterol edible lipids, termed Appetize, was marketed in the United States in the 1990s (24). The product consisted of 70-90% tallow whose cholesterol had been reduced by steam distillation to only 8 mg/100 g. Despite the fine rationale underlying its production, however, high production costs resulted in the withdrawal of the Appetize line from the market. Supercritical fluid extraction can also be used to reduce the cholesterol content of animal fats (25), although to this author s knowledge, this approach has not been commercially implemented. 

Ion Exchange Adsorption Process. Supercritical fluid extracts of Crotalaria spectabilis contain monocrotaline, a basic alkaloid, and non-polar lipid material. In the separation of caffeine from coffee, Zosel (3) recommended separation of the caffeine from the fluid phase by either adsorption onto activated carbon or absorption into liquid water. Activated carbon adsorption would be undesirable in the present case because the lipids would also be adsorbed and because desorption from activated carbon is quite difficult. Liquid water would absorb... 

Because tocopherols and tocotrienols and their esters are lipid-soluble compounds, they are soluble in organic solvents and can be extracted with them. Simple extraction of vitamers from cereal products and other foods containing high amounts of fiber and other polysaccharides may be less effective because of the complex matrix. Inclusion of the vitamers in the matrix by various interactions may hinder the penetration of the solvent into the sample, thus lowering its extraction power. To improve the extraction of lipids from cereals, dynamic extraction with hot solvents (Balz et al., 1992 Zhou et al., 1999), and modem techniques such as supercritical fluid extraction, may be used. 

After the initial euphoria of the late 1980s and early 1990s, supercritical fluid extraction (SFE) has consolidated as a powerful tool for the preparation of environmental, pharmaceutical, and polymer samples and, especially, food samples (particularly for extracting fat, and lipids in general) (1). 

Nilsson WB. Supercritical fluid extraction and fractionation of fish oils. In King JW, List GR, eds. Supercritical Fluid Technology in Oil and Lipid. Champaign, IL AOCS Press, 1996 180-212. 

Liescheski, P.B. 1996. Supercritical fluid extraction coupled directly to infrared spectroscopy for the analysis of lipids in food. Seminars in Food Analysis, 1, 85. 

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