Air Roasting : Making Coffee Beans Dance via Hot Air
Imagine coffee beans suspended in a gentle whirlwind of hot air—that's air roasting in action! Unlike traditional drum roasting, which relies on direct contact with heat, air roasting uses hot air to surround and heat the beans from all sides. This unique method ensures a consistent roast and allows each bean to shine with its distinctive character.
Micken Coffee's 'Rolling Roaster' fluid-bed air roaster in operation.
Hot Air Roasting a.k.a Fluid-bed Roasting
The technology for fluid bed roasters has been around since the early 1970s, introduced by Michael Sivetz who was a chemical engineer.
Previously, these roasters were known as 'Sivetz Roasters', and were begun to be utilized in small numbers vs. traditional drum roasters.
Today, the trend continues with the majority of coffee roasters still operating drum-based roasting machines.
Convection vs. Conduction
Drum and fluid bed roasting differ in one major aspect. In a traditional drum roaster, the metal drum is heated (via gas or other means), which then transfers heat to the beans via conduction.
However, with a fluid bed roaster, the air is heated first and then blown through the roaster bed, eliminating the need for a heated drum. This means that the coffee beans are 'blown' via airflow from the bottom, keeping the beans in a constant rotation e.g. convection.
Therefore, the beans rarely touch the inner surface of the machine, as they 'dance' thanks to the fluid-bed of hot air and the pressure moving in the chamber, ergo they roast primarily via convection rather than conduction.
A simplified animation of Micken Coffee's fluid-bed air roasting operation.
Operating Micken Coffee's fluid-bed air roaster.
Benefits of Air Roasted Coffee Beans
Thanks to the principle of air roasting, every coffee bean gets roasted evenly. The hot air envelops them, ensuring an even roast throughout ensuring consistency.
As the hot air envelops the beans, they undergo a beautiful caramelization process. Sugars inside the beans develop and mingle, creating a symphony of flavors like caramel, nuts, and chocolate.
Air roasting occurs at a lower temperature and for a shorter time, the beans are not exposed to the high temperatures, eliminating smoky or burnt flavors.
Additionally, the process of air roasting uses less energy and emits fewer greenhouse gasses compared to drum roasting. Our roaster operates on electricity alone, negating the need of LPG/natural gas to heat up the air, contributing to a more sustainable world.
