® Andy White (andy@...)
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 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 (or 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, resources and recipes, visit
http://www.coudycoffee.com.