THE PROCESS IN MOTION

What leaves the bean, and what does not come back

Count what remains in the cell: the caffeine leaves, but not alone. The loss that matters shows at the last stage, in the drum. Start the scene or choose a step.

▶ Play the process01The green bean, before02Swell, leach: not only the caffeine03Re-dry: a brown, fragile bean04In the drum: what does not form

The green bean, before

The green bean carries its caffeine, its chlorogenic acids, which in roasting become lactones and phenols, a good part of the fine bitterness and of the length in the mouth, and the aroma precursors, the raw material of the Maillard reaction.

Read the stages without animation

1. The green bean, beforeThe green bean carries its caffeine, its chlorogenic acids, which in roasting become lactones and phenols, a good part of the fine bitterness and of the length in the mouth, and the aroma precursors, the raw material of the Maillard reaction.
2. Swell, leach: not only the caffeineSwelling and leaching carry off the caffeine, and with it some of the aroma precursors. The chlorogenic acids drop, a little.
3. Re-dry: a brown, fragile beanThe cellulose of the wall is partly ordered, partly amorphous; it is the amorphous zones that absorb water and reorganize when the bean is swollen and then dried. It comes out more fragile, a little less dense, and brown or dull olive before having seen any fire: color no longer says anything.
4. In the drum: what does not formAfter roasting, 3 to 9% less chlorogenic acids are measured in water-decaffeinated arabicas, and up to 58% less 3-ethyl-2,5-dimethylpyrazine. Pyrazines, the molecules of roasted and hazelnut notes, are not removed: they do not form at the same level, for lack of precursors.

To remember: The main loss does not occur at the decaffeination plant: it occurs later, in the drum, for lack of raw material.

In history: The bad decaf of collective memory was made with the worst beans available.

Read the full article and its sources ↓

“Decaf has no taste” is one of those sentences that everyone repeats and almost nobody has checked. It is false in its absolute form and true in one precise detail. Here is what has been measured.

The chlorogenic acids drop, a little. They are what, in roasting, turn into lactones and phenols, that is, a good part of the fine bitterness and of the length in the mouth. Measurements comparing water-decaffeinated arabicas with their untreated equivalents find, after roasting, 3 to 9% less chlorogenic acids. That is little. It is enough to be noticed in the cup, not enough to explain a flat coffee.

A family of roasting aromas collapses. Here, the figure is quite different: after roasting, a decaffeinated coffee can contain 58% less 3-ethyl-2,5-dimethylpyrazine than its control. Pyrazines are the molecules of roasted and hazelnut notes, those that give coffee its coffee smell. They are not removed by the solvent, they do not form at the same level, because the Maillard reaction starts from precursors that swelling and leaching have partly carried off.

In other words: the main loss does not occur at the decaffeination plant, it occurs later, in the roaster's drum, for lack of raw material to make it.

Farah et al., Chlorogenic acids and lactones in regular and water-decaffeinated arabica coffees, J. Agric. Food Chem. (2006); literature on the pyrazines of decaffeinated coffee

The structure of the cell is damaged. The cellulose of the wall is partly crystalline, ordered like a regular stack, and partly amorphous, disordered. It is the amorphous zones that absorb water and reorganize when the bean is swollen and then dried. A decaffeinated bean is therefore more fragile, a little less dense, and it breaks differently in the grinder: the distribution of particles changes, which is enough to shift an extraction without the coffee having anything to do with it.

Color lies. A decaffeinated green bean is not green. It is brown, or dull olive, before having seen any fire. The practical consequence is brutal for the roaster: color, which is the roaster's main reference point, no longer says anything. Sweet Maria's sums up the rule in one sentence: decaf is not judged by color.

Sweet Maria's, Roasting decaf coffee and Understanding Swiss Water process decaf, accessed on 09/18/2026; Al-Shemmeri, on the effect of decaffeination on roasting and grinding

What to retain comes down to two propositions that do not contradict each other. A well-handled decaf, on a good starting bean, holds up perfectly in the cup, and blind tasting competitions show it regularly. And a decaf remains a coffee from which part of its aroma precursors has been removed, which leaves the roaster a narrower margin for maneuver and forgives mistakes less.

The bad decaf of collective memory was not bad because it was decaffeinated: it was made with the worst beans available, on the principle that nobody would pay attention.