Guide · decaf
Brewing decaf: how it is made and how to brew it
Decaf starts as ordinary green coffee. Before roasting, a decaffeinator pulls the caffeine out with a solvent, with water and activated carbon, or with carbon dioxide. Here is what each method does, what US rules allow, how much caffeine is left in the cup, and what to change when you brew it.
What "decaf" means
No method removes all of the caffeine (Britannica). The usual US benchmark, which Britannica attributes to the FDA, is that at least 97% of the caffeine is removed. The FDA's own consumer page gives the result per cup: decaf "typically has 2 to 15 milligrams" in an 8-fl-oz cup.
| Measure | Figure | From |
|---|---|---|
| US benchmark | at least 97% of the caffeine removed | Britannica (attributed to FDA); Wikipedia |
| Brewed decaf, 8 fl oz | typically 2–15 mg | FDA consumer update |
| Decaf instant (EU label rule) | at most 0.3% caffeine in the coffee dry matter | Directive 1999/4/EC |
| Green arabica, one lab test | 0.98 → 0.02 g per 100 g | Toci et al. 2006 |
| Green robusta, same test | 2.15 → 0.07 g per 100 g | Toci et al. 2006 |
In the Toci, Farah and Trugo study, beans decaffeinated with dichloromethane (methylene chloride) kept about 2% of their original caffeine for arabica and about 3% for robusta (our arithmetic). Those levels met the Brazilian legal limit of 0.1%. In the cup, Wikipedia reports a 2006 study where decaf usually held 1–2% of the original caffeine, sometimes up to 20%, and a Florida State University test that found 8.6–13.9 mg in 16-oz decaf samples. For a side-by-side with regular coffee, see caffeine by brew method.
The four ways caffeine comes out
Every method works on green, unroasted beans (Britannica). The aim, Wikipedia says, is to leave the flavor precursors as close to their original state as possible. According to Fergus Clydesdale of UMass Amherst, writing in Scientific American, the main processes all run at about 70–100 °C (160–210 °F).
- Green beans. Caffeine is taken out before roasting.
- Caffeine removed at about 70–100 °C, whichever process is used (Clydesdale).
- Four routes: A, solvent rinses the beans; B, solvent cleans the soak water, not the beans; C, water and activated carbon with no organic solvent; D, carbon dioxide under high pressure.
- Roast. Decaf tends to roast faster, and its surface darkens (Roast magazine).
- Grind. Start from the usual setting for the method.
- Brew. Same tools; the adjustments are in the table below.
- Caffeine in green arabica before and after dichloromethane decaffeination, g per 100 g (Toci et al. 2006).
| Method | What touches the beans | Caffeine removed (Clydesdale) | US status |
|---|---|---|---|
| Direct solvent | Beans are steamed, rinsed repeatedly with methylene chloride or ethyl acetate, then steamed again | 96–97% with methylene chloride | Methylene chloride: residue up to 10 ppm (21 CFR 173.255). Ethyl acetate: allowed under good manufacturing practice (21 CFR 173.228) |
| Indirect solvent | Hot water; the solvent treats the water, which then goes back to the beans | not given separately | Same two rules |
| Water + activated carbon (Swiss Water Process) | Water and a caffeine-free green coffee extract; carbon filters trap the caffeine | 94–96% for water processing | No organic solvent used (Wikipedia) |
| Supercritical CO₂ | Carbon dioxide at high pressure | 96–98% | No organic solvent used |
- Solvent methods. The University of Queensland article describes the direct route as steaming, repeated solvent soaks, then more steaming to drive off leftover solvent. Wikipedia says the rinse is repeated 8 to 12 times and that the indirect version was first described in 1941. Britannica calls ethyl acetate the most common modern solvent and says methylene chloride is used to a lesser extent.
- Water and carbon. According to Wikipedia, the process was first developed in Switzerland in 1933 and commercialized by Coffex S.A. in 1980, with the Swiss Water company of Burnaby, British Columbia, introducing it in 1988. A batch takes 8 to 10 hours. Clydesdale notes that the charcoal is pretreated with sucrose so that it takes up caffeine and not flavor compounds.
- Carbon dioxide. Wikipedia credits the method to Kurt Zosel of the Max Planck Institute and gives about 300 atm and 65 °C. Clydesdale gives 250 to 300 times atmospheric pressure. Britannica says the method keeps carbohydrates and proteins, so the taste changes less, but it is costly.
The first commercial process came from Ludwig Roselius and co-workers in 1903 and was patented in 1906. It used benzene, a solvent later recognized as a carcinogen. The coffee was sold as Kaffee HAG and, in the US, later as Sanka (Wikipedia).
Methylene chloride: where the rules stand
Methylene chloride may remain in decaffeinated roasted coffee and instant coffee at up to 10 parts per million (0.001%), according to 21 CFR 173.255. In December 2023 a coalition led by the Environmental Defense Fund petitioned the FDA to remove it, and three other solvents, from the food additive rules (Daily Coffee News). The FDA first noticed the petition in January 2024. In a notice published May 28, 2026, it reopened comments and asked how manufacturers would phase out the uses if the petition were granted in whole or in part (Docket FDA-2023-F-5684). As of Barista Magazine's July 27, 2026 report, no decision had been announced. The National Coffee Association opposes a ban. It says about 26 million US adults drink decaf daily and that most decaf is made with the methylene chloride "European Method" (Daily Coffee News).
How decaf beans differ before they reach your grinder
- Chemistry. Toci and colleagues measured green beans before and after methylene chloride decaffeination. Arabica lost about 60% of its sucrose and robusta about 20%. Total chlorogenic acids fell about 16% and 11%, and arabica's trigonelline fell 13%. Lipids and total carbohydrates changed comparatively little. The authors say the effects on taste still need study.
- Structure and roast. Roast magazine summarizes a ZHAW study run with Swiss Water: decaf green coffee is denser, has collapsed cell chambers, and darkens on the surface during decaffeination. It roasts faster, its first crack is quieter, and ground colour is a more reliable roast indicator than whole-bean colour. The same article cites James Hoffmann's 2024 Decaf Project, which suggested roasting has the largest effect on decaf flavor.
- Taste. Caffeine adds bitterness, so decaf is often less bitter, and some aromatic compounds may leave with the caffeine, depending on the method (University of Queensland).
Brewing adjustments
The SCA's Golden Cup guidance has no separate decaf target: 55 g/L ± 10% (≈1:18) and water at 200 °F ± 5° (93.0 °C ± 3°). Swiss Water's own brew guide uses the same temperature. It suggests "a little bit more coffee than when brewing regular, or a slightly finer grind," sometimes both, to make up for decaf's slightly different composition. Its starting recipes:
| Method | Grind | Coffee : water | ≈ g/L | ≈ ratio |
|---|---|---|---|---|
| Pour over | Medium coarse | 22 g : 330 ml | 67 | 1:15 |
| Chemex | Medium coarse | 47 g : 700 ml | 67 | 1:15 |
| French press | Coarse | 61 g : 850 ml | 72 | 1:14 |
| AeroPress | Medium fine | 15 g : 200 ml | 75 | 1:13 |
| Auto drip | Medium | 40 g : 850 ml | 47 | 1:21 |
Four of the five recipes are stronger than the SCA's 55 g/L, in line with "a little more coffee". The auto-drip recipe is weaker. Treat them as one company's starting points, not a standard. Ratios for any batch size are on the coffee-to-water ratio page, and temperature by altitude is on the water temperature page.
Dialing in a decaf, step by step
- Weigh the dose. Start at your usual ratio, or one step stronger (for example 1:16 instead of 1:17).
- Keep the water at 200 °F ± 5° (SCA; Swiss Water).
- Taste. Sour or thin: go one step finer on the grind chart. Bitter or drying: go coarser. Swiss Water's guide links sour with under-extraction and bitter with over-extraction.
- Judge roast level from the roaster's label or the ground coffee, not whole-bean colour, which runs darker on decaf (Roast). How roast level changes a recipe is covered under coffee roast levels.
- Change one variable per brew and write it down.
Checklist: reading a decaf bag
- Process named? Swiss Water and CO₂ use no organic solvent. Ethyl acetate and methylene chloride are solvent methods.
- Roast level from the roaster, not from how dark the beans look.
- Decaf still contains caffeine: typically 2–15 mg per 8 fl oz (FDA).
- If you are pregnant, trying to become pregnant or breastfeeding, the FDA says to talk with a health care provider about whether to limit caffeine.
A given bag of decaf can differ from these figures. Weigh, taste and change one thing at a time.
Sources
- eCFR — 21 CFR 173.255 Methylene chloride (residue not to exceed 10 parts per million, 0.001 percent, in decaffeinated roasted coffee and decaffeinated soluble coffee extract)
- eCFR — 21 CFR 173.228 Ethyl acetate (permitted under good manufacturing practice as a solvent in the decaffeination of coffee and tea)
- U.S. FDA — Food additive petition from Environmental Defense Fund et al.; reopening of the comment period, Docket FDA-2023-F-5684 (Federal Register, scheduled for publication May 28, 2026)
- Daily Coffee News (Nick Brown, June 30, 2026) — FDA weighs next steps on decaf solvent rules following new comments
- Barista Magazine (Bhavi Patel, July 27, 2026) — Will the FDA ban methylene chloride in decaf coffee? The industry is awaiting a decision
- U.S. FDA — Spilling the Beans: How Much Caffeine Is Too Much? (decaf typically 2–15 mg per 8 fl oz; content current as of 08/28/2024)
- Encyclopaedia Britannica — Decaffeination (FDA requires at least 97 percent of the caffeine removed; methods and solvents)
- Wikipedia — Decaffeination (secondary: history, Swiss Water and CO2 process details, measured caffeine in decaf)
- Scientific American — How is caffeine removed to produce decaffeinated coffee? (answer by Fergus Clydesdale, University of Massachusetts Amherst)
- University of Queensland School of Public Health — How is decaf coffee made? And is it really caffeine-free? (Lauren Ball, Emily Burch, 1 November 2023, from The Conversation)
- Toci A., Farah A., Trugo L.C. (2006) Effect of decaffeination using dichloromethane on the chemical composition of Arabica and Robusta raw and roasted coffees. Química Nova 29(5): 965–971
- Roast Magazine — Decaf Reconsidered: Insights for Better Roasting (ZHAW study with Swiss Water: density, colour, roast speed, first crack)
- Directive 1999/4/EC on coffee extracts and chicory extracts, Article 2(b) (“decaffeinated” only if anhydrous caffeine does not exceed 0.3% of coffee-based dry matter)
- Specialty Coffee Association — Protocols & Best Practices (Golden Cup: 55 g/L ± 10%; water 200 °F ± 5°, 93.0 °C ± 3°)
- Swiss Water Decaffeinated Coffee — The Art of Brewing Decaf (decaffeinator's brew guide: a little more coffee or a slightly finer grind; 200 °F ± 5; recipe table)