Dichloromethane (or Methylene chloride) is an organic solvent used extensively for decaffeinating green coffee and tea. During the decaffeination process the coffee beans come into direct contact with the solvent, which is then removed through vaporisation. Dichloromethane has a boiling point of 40°C, and therefore it is easy to remove at the end of the process, leaving only insignificant levels of the solvent on the roasted coffee.
The dichloromethane used for decaffeination is food grade, and its purity is certified by both its manufacturer and Demus, with periodic testing and monitoring to ensure it complies with European Directive 2009/32/EC of 23 April 2009 and Italian Ministerial Decree No. 390 of 20 July 1987. Its use is governed in Europe and in the United States under the following regulations:
- Europe: European Directive 2009/32/EC of 23 April 2009, Annex I, Part II, which fixes a maximum limit of 2 parts per million (mg/kg) in roasted coffee;
- United States: F.D.A. Code of Federal Regulations, Title 21, Chapter 1, Subch. B, Part 173, Sec. 173.255 - "Methylene chloride may be present: ...in coffee as a residue from its use as a solvent... at a level not to exceed 10 parts per million (0.001 percent) in decaffeinated roasted coffee and in decaffeinated soluble coffee extract (instant coffee)".
These maximum levels of dichloromethane residue were set to prevent any risk to human health. The solvent content in green coffee after processing at Demus is far below these levels. After roasting, which occurs at temperatures exceeding 200°C, the dichloromethane residue is generally imperceptible. There are therefore absolutely no grounds for concern about the product's toxicity. It is also important to remember that the pharmaceutical industry uses dichloromethane in certain manufacturing processes, and it is listed amongst the excipients on some drug labels, even though it is only present at low concentrations.
Another curious fact is that the toxicity of dichloromethane expressed as a lethal dose (LD50) is about eight times lower than that of caffeine (dichloromethane has an LD50 of approximately 2000 mg per kilogram of body mass, compared to roughly 250 mg for caffeine).
All this means that there is no reason to consider coffee which has been decaffeinated with dichloromethane as dangerous for human consumption. On the contrary, it offers various advantages compared to other decaffeination techniques - it removes waxes (Nβ-Alkanoyl-5-hydroxytryptamine) which cause irritation to the gastric mucosa and Ochratoxin A, a carcinogenic fungal metabolite (European legislation restricts its levels to 5 parts per billion in roasted coffee and 10 parts per billion for soluble coffee), as well as eliminating several negative flavours such as trichloroanisole and geosmin. The removal of Ochratoxin A and the negative flavours has been patented (see the patent section) by Demus.
Finally, it should be stressed that the highly selective nature of dichloromethane makes the decaffeination process more energy efficient than other techniques, and the recovery and re-use of almost all of the solvent implies a low environmental impact.