Understanding roast profiles — light vs. dark explained

What actually happens to a bean during roasting, and why it matters far more than the colour of the finished roast.

Most coffee drinkers have an opinion on light versus dark. Light drinkers prize clarity, brightness, and origin character. Dark drinkers want body, bittersweet depth, and the familiar roasty warmth of an Italian bar. Both are valid — but the choice is rarely as simple as the colour of the bean suggests.

What roasting actually does

When green coffee enters a drum roaster, a sequence of chemical changes begins. Moisture evaporates. Sugars caramelise. The Maillard reaction between amino acids and reducing sugars produces hundreds of aromatic compounds. The bean doubles in size and loses 15–22% of its mass as water and CO₂.

A light roast ends this process early — around 196–205°C — preserving the fruit acids and floral aromatics that the terroir and processing imprinted on the bean. A dark roast pushes past 220°C, breaking down those delicate compounds into more uniform, bitter-tasting chemicals. The origin becomes harder to detect.

The roast curve matters more than the colour

At Kyiv Roasters we define our roasts not by colour but by development time ratio — the percentage of total roast time spent after first crack. A skilful light roast uses 20–23% DTR to develop sweetness while keeping acidity lively. A rushed light roast at the same colour can taste grassy, sharp, and underdeveloped.