Coffee Roasting is essentially a cooking process that takes the raw green coffee bean, applies heat in a complex and controlled way, to produce the delightful and aromatic beans that we all love.
Firstly the Roaster is heated up to the desired temperature, and allowed to stabilise so that all of the roaster components are a uniform temperature. The green bean (the charge) is then introduced to the roaster and the beans begin to heat up.
During this initial process the beans are absorbing heat (endothermic) and expelling moisture and carbon dioxide. When the beans are heated up enough, they start to go through different stages that will greatly affect the flavour of the beans. Firstly, they go through the Maillard Reaction (a reaction that occurs by heating any food type that contains protein and sugars), then the caramelisation process, and then finally first crack.
The Maillard Reaction is first indicated when the beans begin to brown. This browning is where a lot of the coffee flavours we know are developed, especially the savoury notes. Next is the caramelisation stage, and here is where the (you guessed it) caramel flavours are developed. Throughout these stages there are literally hundreds of reactions occurring as a result of the breakdown of amino acids and sugar molecules.
These reactions occur at different times in different individual beans depending on where they are in the roaster, their size relative to their neighbouring beans, their individual moisture content and make up and how they are absorbing and reacting to the application of heat. This is where paying attention to the look and smell of the beans relative to heat and time will give an indication of how the roast is developing.
By understanding these processes and anticipating the first crack, the roaster can have better control over trying to create a particular flavour profile.
First crack is that amazing audible cracking sound that is heard indicating that your beans have gone through all of the required reaction states and are now entering the drinkable state. We now have COFFEE!!!
From here we can vary the time after first crack to bring different roast levels and therefor flavours to our beans. We then scale and blend according to our recipes to bring you your daily cup of Bliss.