The traditional categories of coffee roasts are Espresso/Italian roast, Dark French, Viennese/Light French and the lightest roast of all, the American roast.
There are three kinds of roasting: drum rolling, hot air and rolling bed roasting.
The drum rolling method involves roasting the beans in a rotating drum above
a heat source. The hot air method involves putting the beans in a chamber that
is heated with hot air which is forced into the chamber by fan/blower means.
High volume commercial roasters use the rolling bed method of roasting almost
exclusively. This process involves putting the beans onto a conveyor belt that
runs through heating chambers. This process is also known as flash roasting
because the beans are roasted in a quarter of the time compared to the other
methods.
As the beans roast, rapid chemical changes called pyrolyses take place. These changes affect the aroma, taste and colour of the beans. Once the desired colour is reached, the process is stopped abruptly.. the beans are sometimes cooled with water, called quenching, or by exposure to cool air.
Roasting will cause the beans to lose between 14 to 24% of their weight, depending on how long they roast. For example, according to International Coffee Organization guidelines, an average weight loss of 16% for a North American roast style will result in 116 kilograms of green coffee becoming approximately 100 kilograms of roasted coffee.
The longer a bean has been roasted, the less caffeine remains in the bean. Darker roasts are lower in caffeine and lighter roasts have a lighter concentration of caffeine.
All coffee beans have oil in them and when the beans have been roasted for a certain time period these oils are released. Darker roasts of coffee tend to be oilier, as in a Dark French roast.
We flavour our beans using the finest concentrated
essence, added soon after roasting, so the beans will absorb all the flavour
and aroma.