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What is coffee roasting?
Roasting coffee is a method used to transform the
chemical and physical properties of green coffee beans
into roasted coffee beans.
This roasting process is essential to produce a savory
cup of coffee. When the green coffee beans are
roasted, the beans nearly double its original size,
thus changing in color and density. As the bean
absorbs heat, the color shifts to yellow and then to a
light "cinnamon" brown then to a dark and oily color.
During roasting oils appear on the surface of the
bean. The roast will continue to darken until it is
removed from the heat source.
When the beans are at lighter roasts, they will
exhibit more of its origin flavor which are the
flavors created in the bean by the soil and weather
conditions in the location of where it was grown.
Regions like Java, Kenya, Hawaiian Kona, and Jamaican
Blue Mountain roast their coffee beans lightly so
their signature characteristics dominate the flavor.
When the beans darken to a dark brown, the origin
flavors of the beans are overshadowed by the flavors
created by the roasting process itself. When the beans
are at darker roasts, it is hard to distinguish the
origin of the beans used in the roast because the
roast flavor is so dominant.
The coffee roasting process consists of cleaning,
roasting, cooling, grinding, and packing operations.
When larger operations are present, the bags of green
coffee beans are either hand or machine-opened, dumped
into a hopper, then screened to remove any debris.
After this process is done, the green coffee beans are
weighed then moved to a storage hopper by either a
belt or a pneumatic conveyor. Once the green beans are
in the storage hopper, the green beans are then
conveyed to the roaster. When the roasters are active,
they usually run at temperatures between 370F and
540F, and the beans usually roast from a few minutes
to about 30 minutes. The roasters that are used to
roast the coffee beans, are typically horizontal
rotating drums that tumble the green coffee beans in a
current of hot combustion gases. Some other type of
roasters use electricity or even heat from wood to
operate. The roasters can be operated in batches or in
a continuous mode and can be indirectly or directly
fired.
Indirectly fired roasters are roasters where the
coffee beans do not come in contact with the burner
flame, even though the combustion gases from the flame
do come in contact with the beans. For the directly
fired roasters, they are roasters where the coffee
beans do come in contact with both the burner flame
and the combustion gases. When the roasting cycle is
complete, water sprays are used to quench the beans.
Once the cycle is complete and the water is sprayed
onto the beans, the beans are then cooled and ran
through a destoner. In reference to destoners, they
are air classifiers that are used to remove stones,
metal fragments, and other waste that was not removed
from the initial screening of the beans. How the
destoners work, is that they pneumatically convey the
beans to a hopper, where the beans are stabilized and
dried leaving small amounts of water on the beans from
the quenching. This process of stabilization is called
the equilibration. After the stabilization process is
complete, the roasted beans are either grounded by
multi-stage grinders or packaged as whole beans.
Roasted whole beans are said to be fresh for up to,
but not exceeding 1 month. Once the coffee beans are
ground, they are good for up to 24 hours. Beans that
are unroasted boast all of coffee’s acids, protein,
and caffeine, but none of its taste. It takes heat to
spark the chemical reactions that turn carbohydrates
and fats into aromatic oils, burn off moisture and
carbon dioxide, and alternately break down and build
up acids, unlocking the characteristic coffee flavor.
Roasted coffee beans is like wine, there is no
substitute for your personal taste. Light roasted
coffees are also known as Cinnamon roast, half city,
and New England. These coffee beans are roasted for
about 7 minutes when the beans pop and double in size
and light roasting is achieved. The surface of light
roasted beans is dry and their flavor is light-bodied
and somewhat sour, grassy, and snappy.
Medium roasted coffee beans are also known as Full
City, American, regular, breakfast, and brown. These
coffee beans are roasted for 9 to 12 minutes to reach
medium. The surface of medium roasted beans is dry and
their flavor is a bit sweeter then light roast; full
body balanced by acid snap, aroma, and complexity.
Dark roasted coffee beans are also known as High,
Viennese, Italian Espresso, and Continental. These
coffee beans are roasted for 12 to 13 minutes when the
beans begin hissing and popping again, and oils rise
to the surface. The surface of dark roasted beans is
slightly shiny and their flavor is somewhat spicy;
complexity is traded for rich chocolate body, and the
aroma is exchanged for sweetness.
The darkest roasted coffee beans are also known as
French. These coffee beans are roasted for 14 minutes
or so when the beans grow quiet and begin to smoke.
Having caramelized, the bean sugars begin to
carbonize. The surface of these beans is very oily and
their flavor is smokey; tastes primarily of roasting,
not of the inherent flavor of the bean.
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