coffee transforms the chemical and physical properties
of green coffee beans into deliciously caramelized and
aromatic roasted coffee products.
process is integral to producing a savory cup of coffee.
When roasted, the green coffee bean expands to nearly
double its original size, 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. At lighter roasts, the bean
more of its
- the flavors created in the bean by the soil and weather
conditions in the location where it was grown. Coffee
beans from famous regions like
Kenya, Hawaiian Kona, and Jamaican Blue Mountain are
usually roasted lightly so their signature characteristics
dominate the flavor.
As the beans
darken to a deep brown, the origin flavors of the bean are
eclipsed by the flavors created by the roasting process
itself. At darker roasts, the "roast flavor" is so
dominant that it can be difficult to distinguish the
origin of the beans used in the roast. These roasts are
sold by the degree of roast, ranging from "Light Cinnamon
Roast" through "Vienna Roast" to "French Roast" and
beyond. Many consider that a "full city" roast is a great
roast because it is "not too light" and "not too dark".
In the 19th
century coffee was usually bought in the form of green
beans and roasted in a frying pan. This form of roasting
requires much skill to do well, and fell out of favor when
vacuum sealing of pre-roasted coffee became possible.
Unfortunately, because coffee emits
CO2 for days after roasting, the coffee
must be allowed to get slightly stale before it can be
vacuum sealed. For this reason two technologies have been
employed: pressurized canisters and bags featuring
built-in pressure relief valves.
roasting is becoming popular again. Computerized drum
roasters are available which simplify home roasting, and
some home roasters simply roast in an oven or in air
roasted, coffee loses its flavor quickly. Although some
prefer to wait 24 hours after roasting to brew the first
cup, all agree that it begins to get off-flavors and
bitterness about 1-2 weeks after roasting even under ideal
conditions like being stored in an airtight container or
de-gassing valve bag.
Professional Coffee Roasting
roasting process consists essentially of cleaning,
roasting, cooling, grinding, and packaging operations.
Bags of green coffee beans are hand or machine-opened,
dumped into a
hopper, and screened to remove debris. The green beans
are then weighed and transferred by belt or
pneumatic conveyor to storage hoppers. From the
storage hoppers, the green beans are conveyed to the
roaster. Roasters typically operate at temperatures
between 370 and 540
°F (188 and 282
°C), and the beans are
roasted for a period of time ranging from a few
minutes to about 30 minutes.
Roasters are typically horizontal rotating drums that
tumble the green coffee beans in a current of hot
combustion gases; the roasters operate in either batch
or continuous modes and can be indirect- or direct-fired.
Indirect-fired roasters are roasters in which the burner
flame does not contact the coffee beans, although the
combustion gases from the burner do contact the beans.
Direct-fired roasters contact the beans with the burner
flame and the combustion gases. At the end of the roasting
cycle, water sprays are used to "quench" the beans.
Following roasting, the beans are cooled and run through a
"destoner". Destoners are air classifiers that remove
stones, metal fragments, and other waste not removed
during initial screening from the beans. The destoners
pneumatically convey the beans to a hopper, where the
beans are stabilized and dried (small amounts of water
from quenching exist on the surface of the beans). This
stabilization process is called equilibration. Following
equilibration, the roasted beans
are either ground by multi-stage grinders or packaged as
whole beans. Roasted whole beans can be considered fresh
for up to, but not exceeding one month. Once coffee is
ground it is only good for about 24 hours. Unroasted beans
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
Cinnamon roast, half city,
After about seven minutes
the beans “pop” and double in size, and light roasting
is achieved. American mass-market roasters typically
Light-bodied and somewhat
sour, grassy, and snappy
Full city, American,
regular, breakfast, brown
At nine to eleven minutes
the beans reach this roast, which U.S. specialty
sellers tend to prefer.
A bit sweeter than light
roast; full body balanced by acid snap, aroma, and
High, Viennese, Italian
After 12 to 13 minutes the
beans begin hissing and popping again, and oils rise
to the surface. Roasters from the U.S. Northwest
generally remove the beans at this point.
Somewhat spicy; complexity
is traded for rich chocolaty body, aroma is exchanged
After 14 minutes or so the
beans grow quiet and begin to smoke. Having carmelized,
the bean sugars begin to carbonize.
Smokey; tastes primarily
of roasting, not of the inherent flavor of the bean
Coffee at Home
Up until the
20th century, it was more common for at-home coffee
drinkers to roast their coffee in their residence than it
was to buy pre-roasted coffee. During the 20th century,
roasting coffee in the home faded in popularity with the
rise of the commercial coffee roasting companies. In
recent years home roasting of coffee has seen a revival,
and while there may be economic advantage, primarily it is
a means for connoisseurs to achieve finer control over the
quality and characteristics of their coffee.
roasting is the process of buying green coffee beans and
roasting them in your own home. Roasting coffee in the
home is something that has been practiced for centuries,
and has included methods such as heating over fire coals,
roasting in cast iron
pans, and rotating iron drums over a fire or coal bed. The
majority of coffee roasters will agree that once coffee is
roasted, it is only good for a maximum of one month.
process is about as varied as the latte orders you might
hear in line every morning. There are easily half a dozen
different methods for how to roast coffee beans, each of
them with their own merits. Before we get to the methods,
there are a few basic requirements for roasting coffee.
Coffee Roasting Requirements
the beans are roasted at very high temperatures, between
460F and 530F.
- The beans
must move around! This is to avoid uneven roasting or
worse, burnt beans. Air, stirring and tumbling are
common ways to keep the beans on the move.
- When the
roasting is done, the beans must be cooled promptly.
How to Roast Coffee - With a Coffee Roaster
There are two
types of roasters for home use: fluid bed and drum
roasters. Each machine roasts the beans and makes sure
they are cooled properly.
Because of the quick heating times of the fluid bed
roasters, coffee roasted with this method tends to be more
acidic, while drum roasted coffee is often fuller in body.
Personal preference will help you choose.
The best home
coffee roasters today, using one of these two methods can
reproduce and surpass many professionally roasted beans on
Roasters: The drum roaster is a method that relies on
the constant movement of the coffee beans. These machines
are fairly simple to operate. Often it is simply a matter
of loading your fresh beans into the roaster and setting a
time. With some experimentation, you'll decide how long
you want your beans roasted. Obviously less time for a
light roast and longer for dark roast coffee.
Fluid bed roasting utilizes air flow instead of bean
movement, allowing for substantially faster heating times
(hence the acidity). However, the ability to adjust fluid
levels, airflow, and time spent in the roaster make fluid
bed roasting slightly more adjustable for the home coffee
How to Roast Coffee - Without a Coffee Roaster
I do not
recommend the following methods but wanted to mention
them. Espresso uses a very dark roast and if you cross
that line, the beans will burn and possibly catch fire.
These methods also produce smoke and the smell can radiate
through the whole house for days! Never leave roasting
beans unattended! If you try these methods, you are on
Poppers: A popcorn popper will provide the even air
flow and high temperatures needed for a nice clean roast.
And it’s fairly simple, merely tossing your green coffee
beans into a popcorn popper and keeping a close eye on
them. Because this technique uses air to roast, the chaff
(outer skin of coffee bean) will come flying out of the
popper. You may want to roast outside, if possible. This
one can get messy!
Roasting: Another simple method is the use of an oven.
Ovens offer ample space, easily controlled temperatures,
and efficient venting when experimenting with how to roast
coffee. While this method requires patience and careful
attention, properly oven roasted coffee beans can have a
quality of taste that very few other beans carry. To cool
the beans, dump into a metal colander and stir. The chaff
of the bean will come off so either stir over a sink or
Pan: How about the frying pan method? If done properly,
a frying pan can give you perfectly roasted beans. Because
the temperature is never quite as high with stove top
pan-frying, you will need to constantly move the beans,
never setting the pan down or walking away. To cool the
beans, dump into a metal colander and stir. The chaff of
the bean will come off so either stir over a sink or
learning how to roast coffee, there are multiple options,
from the oldest in the book – pan frying – to the best
home coffee roasters on the market. No matter what you
decide though, you’ll be getting coffee that’s fresh and
roasted to exactly how you like it.