Decaffeinated coffee, chloroform

Methylene chloride (CH2C12) and chloroform (CHC13) are also good solvents for cleaning and degreasing work. Methylene chloride was once used to dissolve the caffeine from coffee beans to produce decaffeinated coffee. Concerns about the safety of coffee with residual traces of methylene chloride prompted coffee producers to use liquid carbon dioxide instead. Chloroform is more toxic and carcinogenic than methylene chloride it has been replaced by methylene chloride and other solvents in most industrial degreasers and paint removers. 

Figure 5. A gas chromatogram of the chloroform extract of cysteamine-treated decaffeinated coffee. Peak 1 = 2-methylthiazo-lidine, 2 = thiazolidine, S = internal standard, 3 = 2-acetyl-thiazolidine, 4 = 2-furfurylthiazolidine.

Figure 6. A gas chromatogram of the chloroform extract of cysteamine-untreated decaffeinated coffee.

Chloroform is a volatile, sweet-tasting liqnid that was nsed for many years as an anesthetic. However, because of its toxicity (it can severely damage the liver, kidneys, and heart) it has been replaced by other componnds. Carbon tetrachloride, also a toxic substance, serves as a cleaning liquid, for it removes grease stains from clothing. Methylene chloride is nsed as a solvent to decaffeinate coffee and as a paint remover. 

Solvent-assisted decaffeination of coffee can result in residues of solvent reaching the consumer.208 The use of chlorinated hydrocarbon solvents such as chloroform,209 methylene chloride, trichloroethylene,208 and difluoromonochloromethane (Freon),210 will probably be replaced by compounds already found in roasted coffee. The use of an ethyl acetate and 2-butanone mixture leaves a 26-ppm residue in green coffee, but zero residue in roasted coffee.211 Other solvent compounds used or suggested for coffee improvement or decaffeination include propane, butane,212 carbon dioxide,213 214 acetone215 dimethyl succinate,2161,1-dimethoxymethane, and 1,1-dimethoxyethane.217 Of all these, supercritical carbon dioxide, ethyl acetate, and methylene chloride are the solvents most used currently in decaffeination processes. 

Traditional coffee decaffeination was attained using liquid solvents such as benzene, chloroform, trichloroethylene and dichloromethane. However, evidence suggested that chlorinated solvents are carcinogenic and thus, their use was firmly reduced. Extraction of caffeine with water (a green solvent) requires a two-step process because many flavor and aroma substances are, as caffeine, very soluble in water. Ethyl acetate (obtained Ifom synthesis) is also employed in coffee decaffeination and is much more selective for caffeine and thus, extraction can be accomplished in a single-step contact process. 

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