Coffee roasting is the art and science of roasting green coffee beans at approximately 400 degrees. Although sounding simple, roasting and blending are two of the most important aspects of creating a great gourmet coffee.
The roasting process caramelises the sugars and carbohydrates in the beans creating an oil-like substance which gives the coffee its flavor and aroma. The longer the coffee is roasted, the darker and more oily its appearance becomes.
Drum machines roast the coffee as it is tumbled in a rotating drum.
Hot air machines, also known as fluid bed roasters, roast the coffee as it tumbles on a current of hot air.
Both machines keep the coffee moving to maintain a consistent and even roast.
The Roasting Process
The First 9 Minutes:
The First Pop:
Around 10 minutes, gasses build up in the beans causing them to swell to about double their original size and then rupture. This rupture releases the gas and can be heard in the roaster, kind of like popcorn.
The swelling smoothes out the surface of the bean and then it begins to even out in colour to a very light brown. This is the lightest roast and is referred to as 'cinnamon roast'.
The Second Pop:
After about 11 minutes the colour changes to a darker brown, known as 'full city'. At around 12 minutes the colour and aroma of the coffee begin to change very rapidly. Just as in the first pop, the gasses build up and burst creating a second pop.
Article by Jason www.2basnob.com
The Dark Roasts:
At around 15 minutes the coffee beans now look very dark. A little bit more and we finally come to the darkest roast, the 'French roast'. It is important to note that this has nothing to do with where the beans come from, just how much the beans are roasted. In Europe, this is sometimes known as the Italian or Espresso roast.
At whatever stage the roast master decides to stop, the beans are poured out onto a cooling vat. This stirs the beans, quickly cooling them in order to stop the cooking.
After the beans are roasted, they begin to give off vapours for about a day or two. When this is complete the coffee will be at its optimal flavor. Quality roasters will package the freshly roasted coffee in special bags that are air tight and have one-way valves to let the vapors escape.
It is important to note that the freshness of roasted coffee depends on when it was roasted, not when it was harvested. If not kept in air tight containers, the flavour deteriorates rapidly.