Swiss water process
The Swiss Water Process is a method of decaffeinating coffee beans that was developed by the Swiss Water Decaffeinated Coffee Company. To decaffeinate the coffee bean by the Swiss Water method, a batch of green (unroasted) beans is soaked in hot water, releasing caffeine. This process is done until all the caffeine and coffee solids are released into the water. These beans are then discarded. Next, the water passes through a carbon filter which traps the caffeine molecules but allows the water and the coffee solids to pass through. The caffeine-free water which comes through, known as "flavor-charged" water by the company, is then put in a similar filtration device, and new coffee beans are added. However, since the flavor-charged water cannot remove any of the coffee solids from the new beans, only the caffeine is released. The process repeats, filtering out all the caffeine until the beans are 99.9% caffeine free. These beans are removed and dried, and thus retain most if not all of their flavour and smell.
In the direct method the coffee beans are first steamed for 30 minutes and then repeatedly rinsed with either methylene chloride or ethyl acetate for about 10 hours. The solvent is then drained away and the beans steamed for an additional 10 hours to remove any residual solvent. Sometimes coffees which are decaffeinated using ethyl acetate are referred to as naturally processed because ethyl acetate can be derived from various fruits or vegetables. However, for the purpose of decaffeination, it is not generally possible to create such a large quantity of ethyl acetate, thus the chemical is synthetically derived.
In the indirect method beans are first soaked in hot water for several hours, essentially making a strong pot of coffee. Then the beans are removed and either methylene chloride or ethyl acetate is used to extract the caffeine from the water—as in other methods, the caffeine can then be separated from the organic solvent by simple evaporation. The same water is recycled through this two-step process with new batches of beans. An equilibrium is reached after several cycles, where the water and the beans have a similar composition except for the caffeine. After this point, the caffeine is the only material removed from the beans, so no coffee strength or other flavorings are lost. Because water is used in the initial phase of this process, sometimes indirect method decaffeination is referred to as "water processed" even though chemicals are used.
This process is technically known as supercritical fluid extraction. With the CO2 process, pre-steamed beans are soaked in a liquid bath of carbon dioxide at 73 to 300 atmospheres. After a thorough soaking, the pressure is reduced allowing the CO2 to evaporate, or the pressurized CO2 is run through either water or charcoal filters to remove the caffeine. The carbon dioxide is then used on another batch of beans. This same process can also be done with oxygen (O2). These liquids work better than water because they are kept in supercritical state near the transition from liquid to gas so that they have the high diffusion of gas and the high density of a liquid. This process has the advantage that it avoids the use of potentially toxic solvents.
Green coffee beans are soaked in a hot water/coffee solution to draw the caffeine to the surface of the beans. Next, the beans are transferred to another container and immersed in coffee oils that were obtained from spent coffee grounds.
After several hours of high temperatures, the triglycerides in the oils remove the caffeine - but not the flavor elements - from the beans. The beans are separated from the oils and dried. The caffeine is removed from the oils, which are reused to decaffeinate another batch of beans. This is a direct contact method of decaffeination.