Roasting
Roasting coffee is another important step in bringing out the flavours and aroma of a coffee bean, and is one that takes a long time to master. Every batch of beans is different from another, therefore requiring an expert eye to determine the roasting time and temperature for the beans.What happens to the coffee during roasting?
Coffee is placed in a rotating roasting drum and heated at over 200-2400C. The physical changes are obvious and many; the green beans get approximately 3 times bigger than normal, turn a golden brown colour, and lose weight from the evaporation of moisture.
But the most important effect of roasting is the development of the flavour of coffee that we all experience. During this process, a series of chemical reactions occur. The basic cellular structure of the beans is broken down causing the beans to ‘pop’ like popcorn. Proteins are broken down into peptides and emerge through the surface of the beans in the form of oils, also known as pyrolysis. It is this oil, created by over 2000 complex chemical changes in the coffee beans, that allows for the wonderful aromas and flavours of the coffee bean.
Types of Roast :
The degrees of roast are generally classified as Light Roast, Medium Roast, and Dark Roast, although the most widely used are probably medium and dark.
Light Roast : the beans change from a green colour to a light golden brown. This type of roast leaves a highly acidic taste that is light to the palate, like wine. This type of roasting does not release caffeoil, which is the volatile, oily substance usually released when green beans are heated.
Medium Roast : the beans change from a green colour to a light brown colour. The acidic taste will not be as prominent as in a light roast, but will still be present. There will be more body and the beans will start to release the aromatic ‘caffeoil’ onto the surface of the bean.
Dark Roast : the beans change from a green colour to a dark brown to an almost black colour, with a coating of caffeoil on its surface, giving it the slick-to oily appearance. This type of roast contains considerably less acid and somewhat less caffeine than lighter roasts, as these substances evaporate, and gives more body to the coffee. Also known as French Roast, Italian Roast or Espresso.
