I started my coffee roasting career as a home roaster. Getting
started was easier than I thought. And as I did so, it occured
to me how a relatively simple concept, roasting coffee beans,
has been made to appear to be an arcane art, with a variety of
roast types held out as arcane knowledge. How many different
names have you run across for different types of coffee roasts?
Light, Medium, Dark? Espresso? Continental? Vienna, French,
Italian, Spanish? City? Full-City? C’mon, who’s thinking up
these things?
Well, the dark secret (pardon the pun) of the coffee industry is
that, well, there really isn’t full agreement on which roast is
which. So basically, we all pretty much get to hunt around, try
different coffees from different sources and pick the one(s) we
like. In this article, I’ll try to use the standard
nomenclature, and map it to a process of observing the color and
texture anyone can judge for himself.
The roasting adventure begins with green coffee beans. These are
stored at room temperatures, at 12-15% moisture content.
Roasting is done at temperatures of up to 450+ degrees F.
Duration and temperature determine the roast.
A coffee bean will take on heat until the internal temperature
of the bean reaches approximately 212-240 deg F. At this point,
the outer layer of the bean(s) will discolor, turning a nice
cinnamon color. Here, steam will start being released from the
bean.
As the bean heats up further (approx 250-300 degrees F, again
depending on the variety), the external membrane of the bean
will dry up and start separating from the bean itself. At
approximately 350 degrees F, the continuing heating of the bean
forces a ‘first crack.’ This cracking occurs as moisture within
is released through the existing seam in the bean. This
essentially blows this small crack open, forcing the separation
of the remaining bean ‘chaff’.
Coffee at this stage is a light brown color; entering the ‘light
City Roast’ stage. City Roast is usually achieved at a slightly
higher temperature (above 370 deg F), where the sugars within
the bean start melting or ‘carmelizing’. This gives the
distinctive ‘coffee brown’ color. City Roasts are usually
stopped around 400 deg. or so. At this point, the sugars are not
fully carmelized, and flavor of the beans at this stage are very
much determined by their origin; not by the degree of roast. The
‘Full City Roast’ stage occurs at higher temperatures, just as
the bean reaches the ’second crack’ stage. This stage happens at
different temperatures for different beans based on variety. The
second crack comes as the temperatures of the bean reach the
point where the cellular composition of the bean starts breaking
down. To obtain the Full City roast, roasting is stopped just at
the point where this second crack starts (approx 425-435 deg F.)
At this point the bean is darker brown, but ‘dry’ looking, as
the oils of the bean have not started to emerge through the
molecular breakdown of the bean.
Going into the second crack, we reach the Vienna, Continental,
French and/or Italian roast stages. These are sometimes also
referred to as “Espresso Roast”, although strictly speaking,
there’s no such thing. Italian espresso blends actually vary -
northern blends are typically roasted to the ‘Vienna’ stage,
well into the second crack, where the sugars within the bean are
almost fully carmelized and many beans within the roast will
appear dark brown with hints of fissures. Espresso blends in
southern Italy are usually roasted into the “French Roast”
stage, where almost all of the beans will be about one shade
removed from black and oils will start emerging from some beans.
Beyond this point, beans will start releasing oils and their
soluble compounds - mainly as a lot of smoke; but the beans will
be left quite dark with a very oily sheen. Assuming they have
not fully burnt yet, this can be specified as “Italian Roast”.
I’ve observed different temperatures (within the roaster) for
all of these stages depending on the bean variety - so as my
roasts reach the second crack, I tend to trust my eyes and ears
more than I trust my probe thermometer.
One interesting note of coffee roasting is that as beans reach
into the second crack, they tend to lose any distinctive
varietal flavors. Is this a bad thing? Well, for some,
perhaps… I for one will mutter a bit if my Ethiopian
Yirgacheffe goes past Full City and I lose the distinctive
flavor notes; and in my early roasting career I almost cried as
a batch of prized Puerto Rican select went unheeded into the
Italian Roast realm before I managed to get back to it. But…
some varieties do better at the distinctive French Roast stage.
De gustibus non disputandum est - it just doesn’t pay to dispute
the results in the cup!
And that is coffee roasting. I have seen a fair amount of
advertising of ’slow-roasted’ or ‘deep-roasted’ coffee, which
always gets me to wondering. I suppose if you roast a huge
amount of beans in a low-temperature environment… why, yes,
that would in fact be a slow process! Certainly for a roaster to
get beans to a certain roast point and no further, it does pay
to be precise and not rapidly incinerate his product. But I
can’t say I’d want to purposely take any longer than necessary
to do so.
As for ‘deep’ roasting? Hmm. Can’t say as I’ve ever heard of
’shallow’ roasting; but whatever it is, ‘deep roast’ must be the
opposite! Seriously, the only ‘trick of the trade’ that I can
think of runs counter to the notion of holding beans at any
given temperature… and that is, once a batch reaches the
desired point, get it out of the roaster and cool it down FAST!
As described above, the quality of a roast depends on those
sugars and soluble materials within the bean getting ‘cooked’
very specifically. Keeping the beans near additional heat (yes,
even other beans nearby, releasing their own heat energy) will
continue to cook them.
To some extent this is unavoidable, so the experienced roaster
will compensate for this by knowing his roasting environment;
and ideally provide a cooling location where beans can cool as
rapidly as possible by the flow of cool (i.e., room temperature)
air over the freshly-roasted beans. This allows them to ‘coast’
into their final characteristic color and taste.
© Andy White, Roastmaster for Coudy Coffee. For more coffee and
espresso information and resources, visit
http://www.coudycoffee.com
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