Vegetable oils can be extracted from crushed seeds with liquid or supercritical carbon dioxide. The yields obtained depend upon the pressure and the temperature employed during extraction as well as the size and shape of the seed particles. Oil fractions differing in color, taste, and odor can be recovered at various pressures and temperatures. Parameters influencing the extraction and fractionation of soybean, sunflower seed, and rapeseed oils are described.
A new method of microextraction with supercritical gases involving direct coupling with thin-layer chromatography enables the solubility behavior of a large number of natural products to be investigated in pressure gradients of up to 400 bar. The results are summarized in general rules that enable the extractability to be predicted on the basis of the chemical structure. The substances that can be satisfactorily extracted in supercritical carbon dioxide and nitrous oxide are preferably lipophilic. The extracting capacity of the two gases was compared using alkaloids. In the case of polar compounds such as sugars and amino acids the solubility is so low even at pressures of 2500bar (less than lOpg/Nl) that application is not practicable. Quantitative tests of the solubility behavior of model substances in supercritical gases provide a basis for the technical application of the method.
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