Roasting transforms green coffee beans into the aromatic brown beans we know and love. But what actually happens inside the roaster?
The Maillard Reaction
Starting around 150°C, amino acids and sugars react to create hundreds of flavour compounds. This is the same reaction that browns bread and sears steak. Its responsible for the caramel, chocolate, and nutty notes in your cup.
First Crack
At around 196°C, pressure builds inside the bean until it literally cracks — like popcorn. This is the point where most light roasts are pulled. The coffee is acidic, bright, and complex.
Development Time
The time between first crack and the end of the roast is crucial. Too short and the coffee will taste grassy and sour. Too long and it becomes flat and ashy. We typically aim for 15-20% development time ratio.
Second Crack
Continue roasting past first crack and youll reach second crack around 224°C. This produces dark, oily beans with smoky, bittersweet flavours. Most specialty roasters stop well before this point.
At Roastair, Alex profiles every origin individually, adjusting charge temperature, airflow, and drum speed to bring out the best in each bean.
Fascinating article. I always wondered what first crack meant. Now I understand why light roasts taste so different from dark roasts.