Supercritical carbon dioxide is a great solvent for apolar substances. Using a compressed water and carbon dioxide extraction system allows for the extraction of polar substances. The role of carbon dioxide is to permeate matrices, assisting water’s solvent action.
The Hightech Extraction System, when used to experiment with green coffee, allowed the complete decaffeination and the total recovery of caffeine from the separators. These new generation plants are different from traditional plants and require two high-pressure pumps working at the same pressure — one for CO2 the other for H2O.
Over the years, several studies have been conducted on the separation process using CO2 and/or the required phase equilibria data for the carbon dioxide + water + ethanol system at elevated pressures. The studies overwhelmingly suggest that the supercritical fluid extraction of ethanol from the aqueous solutions produced in biochemical processes has several advantages over conventional separation methods — including improved extract yield and quality.
Supercritical CO2 has been also used to extract components from hydro-alcoholic mixtures. On the other hand, ethanol aqueous solutions are used as solvents of different substrates in particle design using supercritical CO2. Mixtures of carbon dioxide and ethanol + water at 308.15 K show an increasingly exothermic behavior when the pressure is lowered from 8.5 to 7.5 MPa.
High-pressure extractions of polar compounds using supercritical CO2 followed by enhanced solvent extraction (ESE) with diverse CO2/ethanol/H2O solvent mixtures (0–90%, 0.5–100%, 0–95%, v/v/v), at 313 K and 21 MPa, shows that this ESE solvent mixtures have a substantial effect on extracts yield and composition.
Sub-sequential extraction, CO2 only followed by CO2 + EtOH and finally CO2 + H2O shows a different kind of fractionated extracts. Removing fat before performing CO2 + EtOH +H2O provides further improved results.