Why Does Coffee Need to Be Roasted?
Green coffee is undrinkable — grassy, sour, with no coffee aroma. Only roasting at 180–230 °C creates over 800 aromatic compounds through the Maillard reaction and caramelisation.
Why that is
Green coffee contains around 250 chemical precursors that taste nothing pleasant on their own: chlorogenic acid (bitter and sour), proteins, sugars, and lipids. Chewing a raw bean yields grass, acidity, and an astringent coating in the mouth. Nothing resembling what we know as "coffee" is there yet.
Roasting transforms the bean fundamentally. Two main chemical reactions drive this transformation. First, the Maillard reaction: from around 150 °C, amino acids react with sugars and form hundreds of new compounds — brown colour pigments (melanoidins), caramel-like aromas, nutty and chocolatey notes. Second, caramelisation: sugars in the bean caramelise and produce sweetness and roast flavours.
Dozens of additional reactions run in parallel: chlorogenic acid breaks down (the bean becomes less sour), CO₂ forms and inflates the bean, lipids are released and carry aromas, volatile organic compounds evaporate. The result: from 250 precursors, over 800 identified aromatic compounds emerge. Few other foods develop comparable complexity during roasting.
The art of roasting lies in control: temperature, airflow, duration, and energy input determine which aromas form and which are destroyed. Roasted too short, the coffee stays grassy and overly sour. Roasted too long, the delicate aromas burn off and bitterness dominates. The roaster balances between both extremes — making hundreds of decisions per batch.
In practice at Green Wall Coffee
At our café on Sophienstraße 27 in Berlin-Lichtenberg, we work with specialty roasteries based in Berlin. When guests ask why specialty coffee tastes different from supermarket coffee, I often start with the roast: the same bean, roasted differently, yields a completely different coffee. Roasting is the moment when raw material becomes pleasure.
Stop by Sophienstraße 27 in Berlin-Lichtenberg — Mon–Fri 8am–5pm, Sat 10am–5pm.
Further reading
Related questions:
- How Long Is Coffee Roasted?
- At What Temperature Is Coffee Roasted?
- What Is First Crack and Second Crack?
Also relevant:
- How many aroma compounds does coffee have? — Flavor, Sensory & Aromas
- What Is Green Coffee and What Does It Look Like? — Harvesting & Processing
All questions in this topic: Roasting & Roast Levels