First crack is the audible popping sound coffee beans make during roasting, a bit like popcorn. It happens when the beans reach around 196°C (385°F), and it tells the roaster that the coffee is roasted enough to drink. Most light roasts are finished shortly after first crack, and it's one of the most important moments in roasting.
What causes first crack?
Green coffee beans contain a small amount of water. As they heat up in the roaster, that water turns to steam, and gases such as carbon dioxide build up inside the bean. Eventually the pressure becomes too much and the bean's structure cracks open with an audible pop. At the same time, the bean expands, gets lighter and changes colour.
What happens before first crack?
Roasting follows a few broad stages:
- Drying: the green beans turn yellow and smell grassy, like hay, as they lose moisture.
- Browning: sugars and amino acids start to react in what's called the Maillard reaction, the same process that browns toast and bread crusts. The beans turn tan, then brown, and start to smell like coffee.
- First crack: the beans pop, and the coffee is now drinkable. From here, every extra second changes the flavour.
Why first crack matters
The time between the start of first crack and the end of the roast is often called development time. Roasters watch it closely:
- Light roasts are stopped soon after first crack. They keep more of the coffee's origin flavours, like fruit and florals, and taste brighter.
- Medium roasts go a little longer, for more sweetness, body and caramel notes.
- Dark roasts carry on to second crack, at around 224°C (435°F), when the beans pop again more quietly and oils appear on the surface. They taste bolder, smokier and more bitter, and less of the original character comes through.
How roasters judge the roast
Every coffee is different, so there's no single recipe. Roasters create a roast profile for each coffee, and they judge its progress by temperature, time, colour, smell and sound. First crack is one of the clearest signals they have, because you can hear it.
That skill is why we work with the UK's independent speciality roasters. Each one roasts every coffee to bring out its best, so it arrives fresh and tasting just as it should.
Want to know more? Follow the journey of the coffee bean from plant to cup.
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