Does decaf really contain zero caffeine? No, and no regulation requires it. A 470 mL cup measured in 2006 by a Florida team still contained 8.6 to 13.9 mg of caffeine, and from 3 to 32 mg depending on the brand. For comparison, an ordinary espresso supplies 60 to 80. It therefore takes about ten cups of decaf to approach a single coffee, which is reassuring in most cases and is not for someone extremely sensitive who drinks it all day.

Is it dangerous because of the solvents? The residue in the cup is tiny, for a simple reason: dichloromethane boils at 40 °C, roasting climbs above 200 °C. What would have survived the drying does not survive the drum. The American limit is 10 ppm in the roasted bean, that is, ten millionths, and the measurements recorded are commonly well below. The real debate is not in the cup but at the plant, where worker exposure is real: that is exactly the subject of the current quarrel, described above.

“Chemical-free”: what does that mean? Nothing, strictly speaking. Water is a chemical, and so is CO₂. Ethyl acetate sold as “natural” because it is drawn from sugarcane is the same molecule as synthetic ethyl acetate, and it is made in a plant. In practice the mention means the absence of a chlorinated solvent, which is useful information, but it says it badly.

Does decaf keep the health benefits of coffee? For a good part, yes, and it is one of the most solid results in the field: the favorable associations observed for the liver, type 2 diabetes and all-cause mortality are found in decaf drinkers, which suggests that the credit goes to polyphenols and not to caffeine. Effects that clearly depend on caffeine, such as alertness, disappear with it. See the caffeine plate for the organ-by-organ detail.

Why does my decaf taste burned? Because it was probably roasted too dark, deliberately, to mask the lack of aromatic matter, and because the bean starts out already brown, which fools the roaster. That is the subject of the section on roasting above.

How long does it keep? Less long. A more porous bean, oils that rise faster, faster oxidation. With decaf, buying small and often is not a merchant's advice, it is a necessity.

Wikipedia, Decaffeination (Florida study 2006); FDA, 21 CFR 173.255; see plate XII for the epidemiology