During roasting, the characteristic coffee taste aroma components are formed, along with the typical brown colour of the beans. More than 1000 different aroma components of coffee are known. By variation of the roasting conditions it is possible to achieve the specific flavor profile of the final coffee according to the preferences of the consumer. Green coffee beans are heated to between 180ºC and 240ºC for 1.5 to 20 minutes. Stronger roasting will generate darker colour and more intense aroma and flavour.
Coffee is typically roasted in horizontal rotating drums that are heated from below or fluidized bed roast chambers where the coffee is heated and moved by hot air. On an industrial scale, the burners are typically heated with gas or oil. Following roasting, the beans are cooled down to room temperature. They may then be packaged as whole beans ready from sale.
If required, the roasted coffee beans may be ground. This is done in a coffee grinder. Grind size needs to be adapted for each intended use (espresso machine, filter brew, instant coffee) as it will also influence the taste in the cup.