The Art and Science
of Transforming Green Beans into Coffee
During
roasting the beans trasnform from a light to
deep brown color.
Roasting is what transforms the
green beans into dark, fragrant coffee with its
tantalizing aroma and flavor. It is the most critical
stage in coffee production and at illycaffè,
it is highly automated, and heavily monitored by
both instrumental quality control checks and people
with vast amounts of experience and skill.
Coffee roasting is performed in
enormous roasting machines: large drums holding
the coffee beans rotate over a flame, enveloping
the coffee in a flow of hot air. The roasting process
can be divided into three stages: a drying phase
during which moisture is eliminated, a roasting
phase where a number of complex chemical reactions
take place, transforming the precursors into the
aromatic flavor components of roasted coffee, and
finally a cooling phase where the freshly roasted
coffee is brought back to room temperature.
Drying
During the drying stage of roasting,
the beans lose their residual moisture through
evaporation, causing the beans to lose 20% of their
weight and to take on a yellowish color. This phase
takes about half of the total roasting time. The
more homogeneous the green coffee beans, the more
uniform and better the drying process. Indeed the
1500 substances responsible for the flavor and
aroma of coffee are formed in this crucial quarter
of an hour, when the beans lose about 18% of their
weight and gain 60% of their volume.
Roasting
The greatest transformation occurs
during the roasting phase where the coffee is heated
to a temperature of 428°F (220°C). During
this phase the beans puff up, doubling in size
due to internal pressure exerted by carbon dioxide.
The beans also become a light tan color, but as
the roasting temperature continues to rise, the
color deepens and the beans lose weight and become
more brittle. The last moments of the roasting
phase heavily modify the chemical composition of
the beans: sugars carmelize in what is known as
a Maillard reaction; more than 700 new compounds
are created, including key volatile aroma compounds
responsible for the characteristic coffee flavor;
and carbon dioxide is released. illycaffè has
two roasts: a lighter, roast with a smooth, rich
flavor and a dark roast which is more robust and
intense.
Cooling
The final step is to cool the freshly
roasted beans, which can be accomplished by either
the use of water showers, or by streams of cool
air. illycaffè treats its beans delicately,
employing only the cool air method which is slower
and more expensive, but which leaves the precious
aromas intact and protects the coffee from humidity.
At this point, the beans are gently transported
to the packaging area on a current of air.
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