Decaffeination is the extraction of caffeine from coffee beans, mate, cocoa, tea leaves or any other product containing caffeine. This industrial process may involve:
- a water extraction.
- extraction by a supercritical fluid (carbon dioxide or CO2 );
- an extraction by an organic solvent;
The first method, which has been used for years, tends to be replaced by the second for reasons of health (residual traces of solvents), environmental impact, cost and flavor. The last one is the least effective and can distort the taste. These three processes are described below in the case of decaffeination of coffee.
Water extraction
Coffee beans are soaked in water, which absorbs not only the caffeine but also many other nutrients. compounds which contribute to the taste of the coffee, and then passed through activated charcoal, which retains the caffeine. The water can then be reinjected with the beans and evaporated, leaving a decaffeinated coffee with a good aroma.
Manufacturers recover the caffeine and resell it for use in sodas or over-the-counter caffeine tablets.
Supercritical carbon dioxide extraction CO2
Supercritical fluid carbon dioxide is an excellent nonpolar solvent for caffeine and is also healthier than organic solvents. The extraction process is simple: CO2 is forced through coffee beans at temperatures above 31.1 °C and pressures above 73 atm . Under these conditions, CO 2 , which is in a supercritical state , has specific properties, on the one hand those of a gas, which allows it to penetrate deep into the coffee beans, but also those of a liquid that dissolves 97-99% of the caffeine. The CO 2 loaded with caffeine then passes through a high-pressure water jet to remove the caffeine. The caffeine can finally be isolated by adsorption on activated carbon , by distillation, recrystallization or reverse osmosis.
Extraction by organic solvents
This is the classic process which is based on the solubility differential (partition coefficient) of caffeine. Caffeine from coffee is dissolved in the organic solvent, usually a chlorinated solvent (chloroform, trichloroethylene And dichloromethane), which is then removed by distillation. The use of dichloromethane is regulated in Europe and the United States, through the following standards:
- Europe: European Directive 2009/32/EC of 23 April 2009, Annex I, Part II, which establishes a maximum limit of 2 parts per million (mg/kg) in roasted coffee;
- UNITED STATES : FDA Code of Federal Regulations, title 21 , Chapter 1 , Subchapter B, part. 173 , sec. 173.255 – “Methylene chloride may be present: […] in coffee, in residual quantities, resulting from its use as a solvent […] In quantities not exceeding 10 parts per million (0.001%) in roasted decaffeinated coffee and in decaffeinated soluble coffee extract.”
Organic solvents such as ethyl acetate pose much less risk to health and the environment than the aromatic and chlorinated solvents used in the past. Another method is to use the triglyceride oils obtained during milling coffee.
Source: Wikipedia