Supercritical plant extraction

A method of extracting caffeine from coffee, oil from hops and other high-value plant ingredients for use in medicinal and cosmetic products, is to be exploited by startup company Express Separations, a University of Leeds spin-off. The move should boost Britain’s emergent biotechnology industry. It is the first company in the UK to provide manufacturers […]

A method of extracting caffeine from coffee, oil from hops and other high-value plant ingredients for use in medicinal and cosmetic products, is to be exploited by startup company Express Separations, a University of Leeds spin-off.

The move should boost Britain’s emergent biotechnology industry. It is the first company in the UK to provide manufacturers with a complete range of plant extraction facilities from laboratory trials to full scale production.

Initially working with plants, the process could be extended to industrial applications making metal powders and dyes, or in chromatography used to separate complex mixtures.

Tony Clifford, professor of chemical technology at the university and the company’s technical director, pioneered the supercritical fluid extraction process in which plant extracts are removed under pressure using a form of gas as a solvent.

Instead of steam or organic compounds which can be harmful to some processes, Clifford and his colleagues are working with carbon dioxide.

For co2 gas to work as an effective solvent it must be held at a temperature above the critical temperature for the gas – hence supercritical – when the compound is neither gas nor liquid.

Because it is gas-like, says Clifford, one benefit is that everything happens more quickly. But the main benefit of co2 is that it does not contaminate the product or cause environmental problems associated with volatile organic solvents. That is important when producing health food additives or medicine ingredients.

Co2 extraction is a relatively low temperature process of around 40 degrees C, so plants and their extracts are not damaged.

The co2 used by Express Separations has been recovered as a byproduct of other industrial processes such as fermentation, thus helping to reduce the greenhouse effect.