LEAVING THE DARK SIDE
The Forgotten Art of Light Roasting
by Joachim Eichner
A GOOD ROASTER, in my view, is a master at roasting both light
and dark coffees, and knows how to match a good roast profile to
a given batch of green coffee.
Light roasting does justice to the subtle flavors
in many excellent green coffees, flavors which are completely lost when a roast
is too dark. Light roasting demonstrates a roaster’s true skill in bringing
out the best in a good green coffee. And yet, I see more and more roasters
roasting their coffees on the dark side.
It is a trend that began on the West Coast, and now coffee roasters across the
country are jumping on board. It seems the adjectives “dark roast” and “good,
strong coffee” have become synonymous. This is simply not true. Some
coffees, of course, do taste great when roasted dark. However, a large part
of the dark roast trend is simply that: a trend. Of course there are other
reasons why dark roasts are appearing everywhere. Some are untrue beliefs based
on perception; for example, the belief that darker coffees are stronger and
contain more caffeine. In fact, the opposite is true.
Some genuine reasons also play a role in the increase
in dark roasting. Light-roasted coffees can have an unpleasantly acidic taste
character or can lack body and strength. In an attempt to overcome these shortcomings,
we sometimes roast coffee to a darker finish. While this is a quick fix that
helps in producing a fuller body and less acidic taste, the solution seems to
me to be a bit extreme. Dark roasting, when used indiscriminately, buries the
true flavor of coffee in an ill-informed attempt to suppress undesirable effects.
It is time to reconsider the forgotten art of light roasting. It is an essential
skill any good roaster needs to have, and a few light roasts should be a part
of any roaster’s line of coffee offerings.
Who Should Join the Light Side?
If you are a specialty roaster who places a lot of value on quality and a
unique product, light roasting will give you a wide spectrum of flavor possibilities.
This will help set you apart from and provide alternatives to the darker roasts
offered by many of the well-established commercial roasters.
Light roasting isn’t just for small roasters.
Large-scale commercial roasters can also benefit from roasting light. Not only
does a light roast preserve the delicate flavors of a coffee, it also helps decrease
the amount of bean shrinkage. Light-roasted beans typically show eight to 10
percent less shrinkage than dark-roasted beans, translating into potential financial
savings.
For small and larger roasters then, light roasting
offers distinct advantages and benefits.
What Is Light Roasting?
With the advantages in mind, what exactly is light roasting? What’s
so great about it? Oren Bloostein, owner of Oren’s Daily Roast in New
York, says, “Light roasting, light enough so there is no oil on the
bean surface, or perhaps just a hint of oil after a day or so, is suitable
for coffees that have a more delicate character. A great Ethiopia Yirgacheffe
comes to mind. The light roast complements and supports the brilliant citrus
notes, the flowery aroma, the sincerely delicate flavor that so subtly covers
the palate.”
 Other roasters define light roasting slightly differently. Todd Curtis, master
roaster at Green Mountain Coffee Roasters, believes that “light roasting
is a manipulation between green coffee character, cupping, air flow
to the burner chamber, time, burner temperature, batch size and thermo
couplers. It is truly an art, like mixing colors. It depends on mixing
all of the above in various ways for each individual green origin to achieve
the full potential taste profile a roaster is looking for.”
This description might sound intimidating, but it really isn’t.
There are a variety of resources available to help roasters gain a better understanding
of light roasts. A good place to begin is to use the SCAA/Agtron Roast
Color Classification System as a guide in your light roasting and blending.
As you may have gleaned, the distinction between light roasts and medium
roasts is a very fine line. “Not all roasted coffees should be treated
the same,” says Curtis. “The end result is in the cup. Most
companies use an Agtron reading around 55.00. This may be great for a Central
American but not an Indonesian. But to really bring out the full taste
profile for a light roast, tools like Agtron and color disks are only tools
of the trade. The palate should make the final decision.”
Chemistry of Roasting Determines Flavor
Roasting is a chemical process that yields different flavors at different
stages. Given the complexity of coffee chemistry, we should be aware that a)
one type of roasting (such as dark roasting) is not an adequate way to fully
exploit coffee flavor potential and b) light roasts preserve some excellent
compounds in coffee that are desirable.
Coffee flavor is the result of a large group of
complex heat-activated reactions that occur during roasting. One main group of
reactants is known as volatile aromatic compounds. These are the most researched
group of compounds. We know more about how this group of compounds plays a role
in development of taste than any other group of chemicals found in coffee.
Within this group, researchers have identified
approximately 850 volatile aromatic compounds in roasted coffee so far. This
number is more than in any other material used as food or drink, including red
wine! Fortunately, it is likely that only a handful or so of these compounds
are present above their respective odor detection thresholds. Those aromatics
are known as aroma impact compounds. Unfortunately, this does not mean that the
others play no role whatsoever. The influence of these sub-threshold chemicals
on the overall fate of reactions will become clear soon.
Obviously, the aroma chemistry of coffee is highly complex, even before one
considers that aroma is not due simply to an additive effect of the volatiles.
Not only do individual compound concentrations markedly affect that compound’s
perceived odor, different volatiles also complement or antagonize each other,
whether their odor is perceptible or not. Moreover, some volatiles increase
significantly when roasting is prolonged, while others decrease. Strong compounds
that are formed during the later stages of roasting may overpower other compounds.
Some of the acids and bitter agents present in coffee play at least as large
a role in flavor generation as these compounds, but relatively little is
known about these agents and their specific influence. By the time you cup
a batch of roasted coffee, a Trojan war of chemical compounds has just concluded.
Although the chemical pathways have not yet been
mapped out completely, we know that roasting conditions have a major impact on
the physical and chemical properties of roasted coffee beans. Different time-temperature
histories lead to distinct aroma compound profiles. A dedicated specialty roaster
who continually strives to optimize the flavor and quality of his roasted coffee
should work on creating specific bean temperature profiles for every bean variety
he uses. Profiles that provide optimal flavor development can be determined through
cupping roasted coffees produced by means of different candidate profiles.
I usually advise roasters to try roasting their
beans for a slightly longer or shorter time and to play around with higher or
lower temperatures during the early and later stages of roasting. Ensure that
your own experiments are not a waste of your time by documenting everything you
do, including seemingly innocuous parameters such as barometric pressure, room
temperature and humidity. If you are using a control system, make sure it is
responsive to your profile adjustments immediately in real time and that it is
not just logging data. In all stages, use cupping as a guide to help you develop
your roast profile. All this applies to dark roasts, too.
Table 2. on page 44 details the main compounds
and reactions that occur in light roasting.
Knowledge and Tools Get You There
Roasters always ask me how to change their roast profile to underline the
flavors of the coffees while avoiding the pitfalls of light roasting. Well,
simply dropping the end temperature will not do it.
Once a roaster has settled on a profile for a specific
type of bean, close control of the time-temperature curve is needed to obtain
consistently the required aroma quality. Achieving consistent quality of every
batch is now easier through automation and profile roast systems that help a
roaster to create and then exactly reproduce a desired flavor profile. 
In the 19th ASIC colloquium, Stefan Schenker of Nestlé, Switzerland
notes, “Roasting technology cannot make up for poor quality of coffee
beans. However, for a given type of a green coffee bean blend, roasting is
the main flavor (odor and taste) determinant. The time-temperature conditions
during roasting influence the bean core temperature, dehydration and pressure,
which, in turn, determine the specific conditions for aroma formation reactions.
They are the major factors impinging on the potential of green coffee beans,
leading to the formation of the distinct and desirable profile of aroma compounds.”
I would extend his argument further: excellent
beans deserve to be appreciated in their complex subtlety, and light roasting
with extreme care is the best complement to superb green coffees.
Roasters I work with are always excited to discover
just how valuable tools such as chemistry and automation can be to taste development.
When it comes to light roasts, roasters can experiment with different time/temperature
conditions and learn where to tweak their roast temperatures. For example, roasters
need to meet the challenge of maximizing fine acidity, but avoiding undesirable
acid notes. Nearly 30 percent of consumers intensely dislike the taste produced
by malic acid in roasted coffee.
The Tyranny of One Perfect Roast
There can be an optimum range of good roasting for any given green coffee
batch, but there is no such a thing as a “perfect” roast across
all green coffees. The roaster needs to know what flavor profiles best suit
any given coffee, and what flavor profiles his customers like, and balance
these two considerations.
My aim here is not to demonize dark coffees. In
many areas of the United States, consumers show a distinct preference for darker
coffees. Developing the distinctive flavor characteristics of dark coffees is
an art in itself, requiring much more than simply extending the time of roast
or raising roast temperatures. The roaster has to keep close control of the roasting
process. A good espresso coffee, for example, should have a nice, smooth character,
which should not be overpowered by strongly acidic notes. If the espresso shot
is to be used in a latte or other mixed-coffee drink in which milk is used, however,
the coffee should be given a stronger flavor profile in order to be a complement
to the milky taste.
All this is to show that a variety of roast profiles
and the means to consistently achieve them constitute the skills and tools of
a good roaster. And especially for light roasts.
Light roasting appeals directly to the core philosophy
of the specialty coffee industry, which has built its reputation on the high
quality and sophisticated taste of their coffees. Much emphasis is placed on
the characteristics of coffee, such as origin and cup profile. Over the last
decade, specialty coffee roasters have succeeded in teaching coffee drinkers
to enjoy a cup of coffee and appreciate various aesthetic, geographic and even
philanthropic aspects of the cup. When we have gone so far in creating space
for the subtleties and individualities of various coffees, must we not maintain
them in the cup by ensuring that they are not lost due to aggressively dark roasting?
Blend In for Outstanding Results
According to Oren, “The darker a person roasts, the narrower the available
flavor spectrum that is available to taste. If the coffee is truly a premium
type that has all the interesting characteristics of its origin—the quirks,
the subtle differences that separate the Sumatra from the Celebes, the Antigua
from Huehue or Fraijanes—these would be lost in the dark roast.”
Now you are in a bind: you need to please your customers’ dark desires
but not compromise the full range of possible flavor.
Blending offers an ideal solution for the specialty roaster who is aware of
his customers’ preferences for dark roasts, but nevertheless seeks
to incorporate subtlety and complexity to his roast. Blends of dark and light
roasts can contribute to an overall feeling of strength in coffee. They provide
not only an expanded palate experience, but also a balance. This is accomplished
by preserving the subtle and delicate flavor notes that are optimized in
lighter roasts and by adding the improved body and bitter notes of a carefully
crafted dark roast.
Seeing the Light
A roaster’s passion is to roast his green beans the best way possible.
The perfect light roast will allow a roaster to develop the flavor characteristics
and subtle notes contained in his green beans to perfection—this requires
skill, close control of the roast process, educating the customer and cupping,
cupping, cupping. The challenge of light roasting is not an excuse to hide
in the dark.
Joachim Eichner is the chief engineer
of Praxis International Inc.,
a process control and automation
technology company for
coffee roasters and food processing companies.
He can be reached via e-mail at joachim@praxisinc.biz.
Further Reading
Clarke, R.J. and Macrae, R. (Eds.), Coffee.
Vol. 1: Chemistry,
1985: London.
Flament, I. and Bessière-Thomas, Y., Coffee
Flavor Chemistry,
2002: Chichester.
Schenker, S. et al. Impact of Roasting Temperature
Profiles on Chemical Reaction Conditions in Coffee Beans, Proceedings
of the 19th Colloquium of the Association Scientifique Internationale
du Café (ASIC), 2001: Trieste.
Resources
Specialty Coffee Association of America/Agtron Roast Color Classification
System (R400100)—this can be ordered directly from the
SCAA.
Lingle, Ted R., The Coffee Cuppers’ Handbook: A Systematic
Guide to the Sensory Evaluation of Coffee’s Flavor, 1992:
Washington D.C.
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