The process of roasting is the heat induced released of the aromas of the coffee. It is the single most determining and important step in creating coffee
Mastering this process is essential because it can sublimate or destroy the quality of a coffee and an art form exercised by roasters.
The journey of a coffee seed
The coffee seed is grown and harvested at different levels of maturity that will influence the taste of the coffee you drink.
Once harvested, the seed is dried so that the skin that covers it is detached and releases the seed (dry) that will have to be peeled to obtain the green coffee.
We therefore switch from the coffee tree fruit:
Has a seed at different dryness levels:
Roasting, a delicate process
During roasting, the coffee seeds are heated intensely, or roasted, at varying levels . During roasting and depending on its duration, the grain progressively turns from green to black, depending on the desired result.
The lighter the roasting, the more acidic and light the coffee. The more it is roasted, the more the coffee will be black, full-bodied, caramelized and will become bitter. Here are the main nuances:
- Light : Blonde or New England (roasting mainly used in Scandinavian countries)
- Medium : Amber or American (the best way to roast vintage harvests to release all the aromas and generate only a slight bitterness)
- Moderately advanced : Golden or Light French (the most usual for roasting blends in France)
- Advanced : Brown or French (or Italian roast giving a very full-bodied coffee, ideal for preparing powerful ristretto)
- Very advanced : Very dark or Dark French (quite rare because it removes the majority of aromas, used most often with added sugar or butter to keep two components: a caramel aroma and a strong bitterness).
The different techniques
The operation takes place in a circular or cylindrical broiler, the roaster. The drum that surrounds the roaster is heated with electricity, woodfire or gas, and is constantly rotating (comparable to the principle of a washing machine).
There are different roasting techniques:
The traditional method (or old fashioned) lasts a little less than twenty minutes. It should be known that the seed loses 17 to 20% of its weight.
This technique involves bringing the green coffee beans into the roaster where they will be stirred inside the drum and caressed by the flames at a temperature around 200 ° C.
The coffee will lose its moisture and turn from its yellow color to a reddish color. The seeds start to crackle, losing the film of oil that has formed thanks to the heat, it is cafféolle. It is customary to say that the grains "crack". Imagine those millions of seeds crackling, the noise and the smell that emanate from them ...
Once it has reached its desired level of roasting, these same grains are cooled in the open air. Note that the speed of cooling directly impacts its efficiency because the grains continue to roast even though they are no longer in the roaster.
The quick method lasts only ten minutes. Powerful machines are used and there is a loss of weight of 12 - 13%. The coffee beans are kept in hot air at 800 ° C, before being cooled by air mixing or water bath. This method, which is more industrial, may correspond to productions intended for mass retailers.
The flash or flash method is only used for robusta coffees, regular blends and instant coffees. The grains undergo a temperature of 880 ° C during 90 seconds and a weight loss of 12 to 13%. Cooking is therefore uneven.
Home roasting performed until the beginning of 20stcentury at home, is possible even if it turns out to be restrictive.