Processes · 4

The four words on the bag

Swiss Water, sugarcane EA, CO₂ and Mountain Water cover basically every decaf you will meet in Europe. What each one does to the bean, where it happens, and how much of the caffeine it takes out.

Process	Solvent	Removed	In the cup
Swiss Water ProcessTrademarked · Swiss Water, CA	No solvent	99.9% (supplier guarantee)	Trade consensus, not laboratory finding, is that it has the least impact on origin character. Typically clean, chocolate and caramel leaning, with some loss of the most volatile aromatics.
Sugarcane EAGeneric · Descafecol, CO	Ethyl acetate	minimum 97%	Balanced, chocolatey and sweet is well supported. A corpus analysis of UK EA decafs found caramel and chocolate dominating, with citrus in about a third. A faint sweet-fruity character has an actual mechanism behind it: ethyl acetate is itself a fruity-smelling ester.
CO₂ processGeneric · CR3, Germany	Carbon dioxide	97–99%	Best in class for body, lipids and mouthfeel. Reported to fare less well on very bright light roasts, where Swiss Water gives more vivid acidity.
Mountain Water ProcessTrademarked · Descamex, MX	No solvent	above 97% (plant's own claim)	Roasters report tobacco, malt and caramel, with the honest caveat that this depends heavily on origin and roast profile.

Illustration: a row of tall activated-carbon filtration columns linked by pipework.

Swiss Water Process

A water-only process run at a single plant in British Columbia, using coffee extract already saturated with everything except caffeine. The best known name in decaf, and the most misunderstood. It is a company guarantee, not a certification.

Also sold as: Swiss Water · SWP · water process decaf

Illustration: cut sugarcane stalks in the foreground, a small copper still behind them.

Sugarcane EA

Ethyl acetate fermented from sugarcane molasses, used as an extraction solvent in Colombia. The sweetest-cupping process and the one whose marketing is furthest from its chemistry.

Also sold as: EA · ethyl acetate · sugarcane process · natural process decaf · EA decaf

Illustration: a bolted steel pressure vessel with two analogue gauges.

CO₂ process

Caffeine dissolved out under pressure by carbon dioxide above its critical point. The most selective process and the best for body and mouthfeel, and the most expensive to run, which is why you see so little of it.

Also sold as: CO2 · carbon dioxide process · supercritical CO2 · liquid CO2 · subcritical CO2

Illustration: a snow-capped volcanic cone above a braided meltwater channel.

Mountain Water Process

A water process run in Veracruz using glacier-fed watershed water. Mechanically a close cousin of Swiss Water, and the process most often described with a number its own plant does not claim.

Also sold as: MWP · Mountain Water · agua de montaña

A fifth thing on the bag, and not a process

Low-caf is not decaf

Laurina and Aramosa are arabica varieties that make less caffeine on the plant. Nothing is removed from them, so no process above applies. They are worth trying and they are not a substitute if you are avoiding caffeine for medical reasons.

0.6%
Laurina: 0.8%
Aramosa: 1.2%
Standard arabica

Does the process decide the cup?

Less than the bag implies

No published head-to-head sensory comparison of the four processes exists. The tendencies are real. EA cups sweeter, water processes finish longer. But the green coffee and the roast matter more than the process, and anyone telling you otherwise is quoting trade consensus, not a study.