Foundational
Caffeine content and decaffeination, explained
Why caffeine content varies so much between drinks, and how decaffeination actually works.
Why caffeine content varies
Caffeine content depends on species (robusta generally contains more than arabica), dose, brew method and contact time — far more than on roast level, despite the common belief that darker roasts contain more caffeine. A large, weakly brewed filter coffee can easily contain more caffeine than a single espresso shot.
How decaffeination works
Several industrial decaffeination processes exist, generally involving a solvent (chemical, carbon dioxide under pressure, or a water-based process) applied to green coffee before roasting to remove most caffeine while retaining as much flavour-relevant compound as possible.
Decaf is not caffeine-free
Regulatory decaffeination thresholds typically require removal of at least 97% of original caffeine, not 100%. Decaf coffee still contains a small residual amount of caffeine, generally a few milligrams per cup.
Related
Sources
- FoodData Central caffeine content entries — U.S. Department of Agriculture (USDA)
- FDA consumer guidance on caffeine — U.S. Food and Drug Administration (FDA)