For a long time, the chemical Dichloromethane was used to decaffeinate coffee. There were health and environmental concerns about this chemical. Then ethyl acetate was used. Health concerns were also raised about it. Now two major methods are used. In one, carbon dioxide (which we breathe out and is in the atmosphere around us right now) is used. High heat and pressure cause carbon dioxide to enter a "supercritical fluid" state in which it is a bit like gas and a bit like a liquid. I learned about this at the following website:

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The Swiss Water Process is another method. Water is used to extract the caffeine and flavor compounds from unroasted coffee, then these beans are discarded. They then remove the caffeine from the solution using filters. Now the coffee they want to decaffeinate is put in the solution. Caffeine will enter the solution due to diffusion but the flavors won't leave the coffee because the solution is full of the flavor compounds already. They repeat this several times before roasting the beans. Several sites describe this method. Here's one: click here

If you haven't covered diffusion yet, look into it. It is one of the big concepts in biology. You might look into the health effects of coffee while you're on the Internet. What are the possible problems and benefits? Does it make a difference whether there's caffeine in the coffee?

Thanks for your question. As you probably know, coffee is a huge product these days. I actually just read that over 400 billion cups are consumed each year! In addition decaffeinated coffee has become ever more popular. For instance, in 1962 decaf accounted for only 3% of coffee sales and today it claims more than 20%. So, your question is an important one - is our decaffeinated coffee safe? First,let's just say what caffeine is. Caffeine is a mild stimulant that affects our central nervous system (our brain for example). A normal 6 oz cup of coffee contains about 50 to 75 milligrams of caffeine, whereas most decaf brands contain less than 10 milligrams. So, how do the makers get the caffeine out and is it a safe process? In fact the methods are proven to be quite safe and a great deal of work has been done to perfect the process. Now, let's describe the techniques that are commonly used to actually remove the caffeine. There are basically two methods of decaffeination: direct and indirect contact.

In the first the beans come directly in contact with the decaffeinating agents. In the latter method, a water/coffee solution is normally used to draw off the caffeine. For both methods green or roasted coffee beans are first moistened with water, so as to make the caffeine easier to draw out. In the direct method various decaffeinating "solvents" are used. These solvents basically pull the caffeine out of the bean. The solvents are then simply removed leaving behind a decaffeinated bean. Some of these solvents have actually been shown to be dangerous, and this is why you might have heard that decaffeinated coffee is unhealthy. In truth, though, the solvents are completely removed so that there is no harm to the decaf coffee drinker.

In the indirect contact method, sometimes referred to as the "water process", the green beans soak for several hours in a water/coffee solution at almost boiling temperature. Gradually the solution draws out the caffeine, as well as other flavor elements and oils, from the beans. The caffeine/water mixture is drained away and treated with a solvent, which absorbs the caffeine. The resulting mixture is then heated to evaporate the solvent and caffeine. Next, the mixture is reunited with the beans, allowing them to regain most of the coffee oils and flavor elements. The solvent never touches the beans.

I hope this helps to answer your question. In summary, any danger that would come from decaffeination would do so from the solvents used. But, since these are removed in the final product it's a guarantee that decaffeinated coffee won't do you any harm.

Thanks again for sending in your question.