In specialty roasteries, a drum roast takes 12–20 minutes. Industrial hot-air roasting finishes in 2–7 minutes — usually at the expense of aroma development.

How Long Is Coffee Roasted?

In specialty roasteries, a drum roast takes 12–20 minutes. Industrial hot-air roasting finishes in 2–7 minutes — usually at the expense of aroma development.

Why that matters

Roast duration is directly tied to the roasting method and the desired result. Slow roasting gives heat time to penetrate the bean evenly. Fast roasting heats the outside intensely while the inside may remain underdeveloped — the result often tastes burnt and sour at the same time.

In drum roasting, the beans sit in a rotating, externally heated metal drum. Heat transfers through conduction (contact with hot metal) and convection (hot air). Over 12–20 minutes, the bean passes through all roast phases: drying (0–6 minutes), Maillard phase (6–10 minutes), and development phase (from First Crack onward). Each phase needs its time for aromas to develop fully.

Industrial hot-air roasters (fluid bed roasters) work with air temperatures of 400–600 °C and suspend the beans in a hot air stream. In 2–7 minutes the roast is done — but the bean barely had time to develop complex aromas. The outer cell layers are often overdeveloped while the inside remains underdeveloped. That explains why industrial coffee frequently tastes bitter and flat.

In the specialty scene, roast time is a deliberate tool. Lighter roasts are roasted shorter (12–14 minutes), darker ones longer (16–20 minutes). Development time after First Crack — typically 15–25 % of total roast time — determines the sweetness, acidity, and bitterness in the final cup.

At Green Wall Coffee

The coffees we serve at Sophienstraße 27 in Berlin-Lichtenberg are all drum-roasted — 12 to 18 minutes depending on the bean and target roast. At the counter I like to explain the difference: slow-roasted, the coffee tastes complex and sweet. Fast industrial roasting makes it bitter and one-dimensional. Roast time isn’t a technical detail — it’s the difference between good and mediocre coffee.

Related Questions

• At what temperature is coffee roasted?
• What is the difference between drum roasting and hot-air roasting?
• What is the difference between light, medium, and dark roast?

More depth on this topic in the article How to Make Perfect Espresso. Or stop by at Sophienstraße 27 — Mon–Fri 8am–5pm, Sat 10am–5pm.