Supercritical Fluid Extraction triglycerides

The promise shown by supercritical fluid extraction led to the development of the Solexol process for the purification and separation of vegetable and fish oils. This process concentrated the polyunsaturated triglycerides in vegetable oils and the so-called vitamin A values from fish oils using propane as a selective solvent [5]. 

Montanari, L., Sensidoni, A. and Kikic, I. (1997) Supercritical fluid extraction of mixtures containing triglycerides and sterols, in E. Reverchon (ed.), Proceedings of the 4th Italian Conference on Supercritical Fluids and Their Applications, Capri, Italy, pp. 89-95. 

Some modifications were proposed by Chuang and Brunner in this supercritical fluid extraction process to contour the low selectivity that they have previously observed [63]. The authors utilized a process of transesterification of palm oil and subsequently after the three-step extraction obtains a product 200-fold concentrated in carotenoids but virtually absent of esters, fatty acids, and triglycerides. Nevertheless, the temperature used (60 °C) and the presence of O2 in supercritical CO2, conditions that lead to carotenoid degradation, require addition of antioxidants (such as butylated hydroxytoluene) to the process [64]. 

After hydrolysis of triglycerides, denaturation (ethanol) and extraction (hexane) of milk samples are similar to those procedures used in preparation of plasma samples. EHie to high concentrations of coextracted lipophilic compounds, a semipreparative HPLC cleanup step often is used in these preparations. Indyk et al. (92) and Lambert et al. (99) used adsorption HPLC and hexane/isopropanol mixtures for cleanup and a reversed-phase HPLC for detection, whereas Isshiki et al. (94) used a Cig reversed-phase system with a methanol/acetonitrile mixture for cleanup and a C2 or C3 reversed phase for detection. Canfield et al. (95,96) worked with two open-column chromatography systems (silica) to isolate vitamin K compounds prior to HPLC detection, whereas Schneiderman et al. (98) introduced a completely different method for isolation of these compounds. They used supercritical fluid extraction (SFE) with CO2 as solvent to determine VKl in powdered infant formulas. Details of this particular method will be discussed later in this chapter. 

Previous studies have shown that fatty acids are quite soluble in supercritical carbon dioxide. Solubility levels of 1 to 10% are easily obtained for fatty acids, triglycerides, and esters in CO2. In addition, several previous patents exist for the extraction of fatty materials using supercritical fluids. Therefore, a process which uses supercritical CO2 for the extraction of fatty acids from spent nickel catalyst should be successful. 

In the food industry, commercial plants with supercritical fluids have so far only been used with supercritical CO2 as solvent. The first plant was opened in 1981 in Bremen (Germany) for decaffeination of coffee, by a process invented in the 1970s by Zosel (1973). Plants for the production of hop extract and for the decaffeination of tea are today also in operation, for example, in Germany, England, and Australia (Voeste et al., 1997). Supercritical hydrocarbons such as propane are also used, for example, for deasphalting of heavy oils or for the removal of triglycerides from fish oils. 

Above its critical point, carbon dioxide forms a supercritical fluid (SCF), which is widely used in the food industry because of its nontoxic nature, for example in ultra-clean processes employed to decaffeinate coffee and to extract cholesterol and triglycerides from eggs. Similarly, SCFs promise to be an environmentally responsible replacement for the organic solvents cvurently used in polymerizations and many other industrial applications. SANS has been used [24] to elucidate the thermodynamics of COi-soluble polymers (e.g. fluoropolymers and siloxanes) and the technique is particularly suited to studying the structure of matter under pressure, due to the well-known high neutron transmission of many of the materials used in the construction of pressure vessels. 

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