How Coffee Gets Roasted: A Look Inside the Process

Green coffee beans smell like grass and taste like nothing. They’re dense, hard, and pale — closer to a dried pea than the dark aromatic thing you grind every morning. Roasting is the alchemy in between.

What happens inside the drum

A coffee roaster is essentially a rotating drum with a heat source. Green beans go in, heat is applied, and a series of chemical changes transform them.

Drying phase (0–5 min): The beans lose moisture. They start turning from green to yellow, and the grassy smell gives way to something more like bread or toast.

Maillard reaction (5–8 min): The same browning process that happens when you sear a steak. Sugars and amino acids interact to create hundreds of flavour compounds. The colour shifts from yellow through tan to light brown.

First crack (~8–10 min): The signature sound — a crack, like popcorn — as expanding gases and steam rupture the bean’s structure. This is the minimum threshold for drinkable coffee. Light roasts are pulled just after or just during first crack.

Development phase (first crack onwards): This is where the roaster’s skill shows. Pull it early (one to two minutes after first crack) and you preserve brightness, acidity, and fruit character. Let it go longer and you develop more body, sweetness, and — eventually — bitterness.

Second crack (optional): A second, quieter crackle. Dark roasts push through to here and beyond. Most specialty coffee doesn’t go this far — the origin character has already been roasted away.

What makes two roasters different

The drum temperature, the airflow, the rate at which heat is applied at each phase — all of these variables produce different flavour profiles from the same green beans. This is why roasting is equal parts science and feel. The best roasters taste their work constantly and adjust.

See it live in Amman

The Amman Coffee Festival’s Coffee Roasting Experience lets you watch and smell the transformation in real time, during “The Picnic” (20–23 August, Balsam Grounds). You’ll hear first crack, smell the development, and see the colour change happen in front of you.

Entry 5 JOD, free drink included. See roasting live at amman.coffeefestival.me · @acoffeefestival.