5.4.2. Extraction with other liquefied gas solvents

A disadvantage in the use of liquid carbon dioxide is the comparatively high pressure required producing liquefaction. This difficulty can be obviated by the use of a fluid such as 1,1,1,2-tetrafluoroethane (R134a) with a normal boiling point of -26.2 °C and a vapour pressure of 6.6 bar at 25°C (the dipole moment is 2.66 Debye). This was originally developed as an ozone friendly non-toxic refrigerant fluid, but an extracting technology is being developed with it (Wilde, 1994). Very encouraging results are claimed for the extraction of flavour and aroma essences using the solvent as a compressed liquid at near ambient temperatures probable extraction conditions are shown at point 6 on the figure.