Coffee roasting: techniques and evolution

At the beginning, coffee roasting was made using artisanal or handmade methods: roasting tools were iron pots with pierced bottom or little empty metal cylinders with very long handles and sharpened top to insert in the chimney firedogs and rotate on the fire.

During Industrial revolution, born the first big machineries to roast coffee in specific factories: the roasting coffee industries. These machineries, only marginally modified so far, consist essentially in very big cylinders where raw coffee beans were roasted with furnaces powered by natural gas, wood or coal.

Roasting by gas is the most recent method to cook coffee beans and is faster than the other ones, however it tends to cook coffee beans on the outside, creating a final product with some tasting anomalies. In addition, when gas is mixed with air, is affected by atmospheric conditions, so the cooking time must be continuously adapted. Moreover, the high temperature accentuates bitter and acid notes of coffee, reducing its texture and structure.

Coffee roasting by coal implicates a slow roasting cycle that enable aromatic oils contained in beans to give a more complex texture to the drink.

However, this method has a very difficult temperature regulation, and the strong smoke smell can modify the final taste.

Finally, the wood-fired roasting technique is the more ecological compared to the other ones, using renewable energy sources.

It guarantees an easier heating regulation and implicate a slow roasting cycle, giving a round and intense texture to the coffee, with mild notes of smoked and seasoned wood.

Wood used for this technique is named “strong wood”, that burns slowly and for a long time, such as elm, oat, holm oat and ash woods, and can be used without distinction for the final result. The main issue is that wood logs must be well-seasoned and stored correctly, to remove humidity and have similar calorific power.

There are also homemade roasting methods, rarely utilized, such as the use of pan, electric or gas oven, special equipment for popcorn or coffee beans and also the microwave oven.