The secrets of
roasted coffee were not discovered until the thirteenth century. Unlike fragrant
wine grapes or scented tea leaves, raw coffee beans conceal their flavor and it
is only with roasting that flavors and aromas are liberated.
Roasting coffee beans is a blending of
science and art. A professional roast master must determine both the length of
time and temperature to bring out a roast’s best qualities and to achieve
the desired flavor. Before roasting, coffee beans are green; during the
process they progress from light to dark in colour. At 400 degrees Fahrenheit,
the chemistry of the bean changes and true roasting begins. As the heat
increased, acidity is lost and the beans acquire more body and a heavier
texture. At higher temperatures the natural oils rise to the surface of the
beans. Too long at a high heat, though, and the beans become burnt and lose
their taste together.
After the beans have reached the desired
roast, they are quickly cooled to avoid over-cooking. Air jets are used for
higher-quality beans. This is referred to as dry roast. In contrast,
large-scale commercial roasters frequently cool their beans with water jets,
which tend to swell the beans with unwanted moisture. This method is referred
to as wet roast.
Roasting Stages
Light or pale roast: the beans have a dry,
cinnamon-coloured surface and are often brewed as a morning coffee and served
with milk.
Medium roast: the beans are medium brown in
colour, and their surface is dry. Although this brew may have acidic
qualities, its flavor tends to be flat.
Full, high roast: the beans are chestnut
brown in colour and show patches of oil. It is the favorite of many
specialty-coffee stores because the taste strikes a balance between sweetness
and sharpness.
Espresso: the almost-black beans have a
shiny, oily surface. All acidic qualities and specific coffee flavors are
gone, but it contains less caffeine than any other roast.
