The roasting processes

Learn more here about the different roasting methods for coffee and espresso – and how they affect the aroma and preparation.

Roasting processes at a glance

Unimaginably large quantities of coffee are consumed worldwide. Not only cultivation, but also roasting methods have changed dramatically over time, evolving into a true art form. While coffee was once roasted in clay pots, today there are essentially two main methods: the drum roasting process and the Hot air roasting process.

The traditional drum roasting process

Drum roasting is primarily used in smaller, traditional roasteries. Drum roasters are available in a wide variety of sizes – now even for home use.
In this process, the raw coffee beans are placed in a rotating drum that is heated from the outside. The direct contact with the hot surface ensures that the heat is transferred evenly to the beans.

This gentle method allows the aromas to develop particularly well. Due to the relatively long roasting time of 15 to 20 minutes at 180 to 230 °C Many acids are broken down or significantly reduced.

Through a small opening, the roast master regularly takes samples during the process to determine the roast level based on the color and to end the roasting at the right moment. This requires a good eye, a lot of experience, and a fine sense of touch – only in this way can perfectly roasted beans with a consistent flavor be produced.

To prevent the heat contained in the beans from unintentionally continuing the roasting process, the coffee must be cooled quickly afterward. In drum roasting, this is achieved by pouring the beans directly from the drum onto a sieve. Cold air flows through the openings in the sieve and is evenly distributed by a stirring mechanism. This gently cools the beans to approximately... 30 °C and below.

The hot air roasting method

Since coffee is more popular than ever before, faster roasting methods had to be developed for industrial production. Large roasteries can particularly benefit from hot air roasting. Save time and money.

These machines, mostly designed as continuous roasters, consist of a large, perforated drum equipped with an internal screw conveyor. They operate at temperatures of up to... 700 °C will the beans in it only one to five minutes roasted and then cooled with water.

While this method allows for quick and inexpensive roasting, the quality often suffers. Because the different bean varieties are not roasted separately, it can happen that larger beans are not fully roasted inside, while smaller ones are already too dark and over-roasted.

The extremely short roasting time also leaves less time to break down the harmful chlorogenic acids. Furthermore, the subsequent cooling with water distorts both the weight and the aroma of the coffee.

Conclusion

Truly excellent roasts come from the drum roaster. We at Espresso International also place the utmost importance on quality – therefore, all our coffees are gently refined using the drum roasting method.