Wednesday, April 12, 2017
Roasting is a process of exposing the green beans to a heating process that is rapid enough to drive off the free and bound moistures and later the dry bean is heated above 180 °C to a moisture level of 2 to 2.5 %. The amount of time that the beans remain in the roaster determines the strength and flavor of the brewed coffee in the cup.
Actual contact roasting is no longer importance because heat transfer is uneven and the roasting times required are long (20-40 min).
In the contact convection roasting process (roasting time 6-15 min), efforts are made to increase the convection component as much as possible by suitable process management. Centrifugal roasters, revolving tube roasters, fluid-bed roasters etc. are used either batch or continuously.
In the new short-time roasting process (roasting time 2 to 5 min), the heating–up phase is significantly shortened by improved heat transfer.
To cater to different tastes, five different roasts have been developed. It is a rundown from very light to very dark.
Temperature and time length for coffee roasting process