A solvent-based method for washing the caffeineAn alkaloidal compound that has a physiological effect on humans, and a bittering taste. It is found throughout the coffee plant but is more concentrated in the seed... out of coffee. Called MC decaf for short: The Methylene Chloride decaf method is a solvent-based process for washing the caffeine out of coffee. Called MC decaf for short. MC decafs have been shown to leave insignificant trace amounts of solvent that are fully dispatched in the roast process.