Quick take: Decaf coffee starts as regular green coffee. Most of the caffeine is removed before roasting, but decaf does not automatically mean zero caffeine.
Decaf starts as green coffee
Decaffeination happens before roasting. Producers begin with green coffee beans and use a process designed to remove most of the caffeine while preserving as much flavour potential as possible.
After decaffeination, the coffee is dried and stabilized, then roasted and brewed much like other coffee.
What methods are used?
Commercial decaffeination can use water-based systems, solvent-based systems or carbon-dioxide processes. The details differ, but the goal is the same: separate caffeine from the green bean before roasting.
Process names can sound dramatic when reduced to one word. What matters is the complete method, the controls used and the quality of the green coffee going into the process.
Does decaf still contain caffeine?
Yes, usually a small amount. Health Canada lists an average of about 3 mg of caffeine in a 237 mL serving of roasted-and-ground decaf coffee. That is far below regular brewed coffee, but it is not necessarily absolute zero.
Does the process ruin the flavour?
Not automatically. Green-coffee quality, storage, roasting and brewing still matter. A carefully handled decaf can be far more interesting than an old or poorly roasted regular coffee.
For more on freshness and roasting, see Why Freshly Roasted Coffee Tastes Different.
The useful takeaway
Decaf is still coffee. The caffeine has been substantially reduced before roasting, while the rest of the coffee journey continues as usual.
For context on regular coffee, visit How Much Caffeine Is in Coffee?.
Sources
Health Canada: Caffeine in Foods
Shop Urban Calm Specialty Coffee, roasted in Calgary from Colombian Arabica.
