Supercritical fluids: technology and application to food processing

Supercritical fluids (SCFs) are substances at pressures and temperatures above their critical values. It is characteristic that properties of SCFs can be changed in a wide range. Their solvent power is the highest for non-polar or slightly polar components and decreases with increasing molecular weight. They can easily be removed from the solutes by mere expansion to ambient pressure. Carbon dioxide (CO2) is particularly advantageous for processing food materials. SCFs are used for batch extractions of solids, for multi-stage counter-current separation (fractionation) of liquids, and for adsorptive and chromatographic separations. State of the art design for commercial plants is available, and a number of installed plants are working. Special applications to food processing include decaffeination of green coffee beans, production of hops extracts, recovery of aromas and flavours from herbs and spices, extraction and fractionation of edible oils, and removal of contaminants, among others. The application of SCFs is now extended to new areas like formulation or specific chemical reactions. Costs of SCF extraction (SCFE) processes are competitive. In certain cases SCFE processing is the only way to meet product specifications. (C) 2004 Published by Elsevier Ltd.