As coffee roasters in Bristol, we import coffee as green beans, which are dried, hard and tasteless seeds from the berries of the coffea plant. Roasting them at a high temperature brings out all of those hidden flavours and aromas.
When the beans enter the roaster they have a quite high moisture content, during the roasting process, the beans slowly release that moisture which breaks down the cells of the bean releasing the sugars, proteins and acids within.
For the first part of the roast, the process is endothermic so the beans are absorbing heat. This slowly decreases until the ‘first crack’, where almost like popcorn, the beans cells are breaking down and you get a cracking sound.
After this point, the process becomes exothermic so the beans start giving off heat. As coffee roasters, the trick is to time it perfectly at this point to get the best out of the bean