First, if you can't tell the difference between a Panamanian and
Papua New Guinean coffee, put off the espresso and get to know good
coffee first. Buy a freshly roasted half pound each from Central
America, Africa, South America, and Indonesia, and learn to appreciate
their differences. Those who buy the green coffees for espresso, those
who roast and blend them, and those who pull the best shots have one
thing in common: they know their coffee well. In any case, espresso is
coffee intensified; if there are coffees you dislike brewed, you really
want to avoid them in espresso.
Second, go into a coffee store and look for "espresso roast." What
you'll almost always find is dark brown to black beans shining in oil.
Starbucks' success has reinforced the impression that espresso is any
coffee roasted very dark. This is wrong on almost all counts. Coffee
blends destined for espresso come in a variety of roasts, ranging from a
milk chocolate colored dry bean, to a dark chocolate colored slightly
oil-sheened bean, to a black and very oily bean. The very lightest
roasts for regular brewing (cinnamon or tan colored) cannot be used for
espresso, but otherwise any roast level will work.
Instead, espresso is almost always a blend of beans; the Italian
word for blend is miscela. There is
fairly wide latitude in blending, but there are also some general
rules. The most basic rule of espresso blending is that espresso must
have subdued acidity, be heavy bodied, and be sweet enough to balance
the bitter and acidic flavors in the blend.
At the Coffee Plantation
A large proportion of the blend will consist of "natural" or
"pulped-natural" processed beans from Brasil, Indonesia, Ethiopia, or
Yemen. Natural or "dry processed" means the coffee cherry is air dried
on the tree or on terraces prior to removing the skin and fruit from the
pit (the actual coffee bean). Pulped-natural or "semi-wet processed"
means the skin is removed, but the fruit remains on the bean while it is
drying. These techniques create the more heavy bodied, sweet, and
subdued acidity coffees required by espresso brewing. Such coffees also
develop more crema. Single origin, unblended espresso is almost always
derived from a bean of this type. The drawback of these techniques, even
when carefully done, is they create a few fermented beans with
off-flavors that slightly muddy the aroma and taste.
The alternative, known as wet processing, washes the skin and fruit
off the bean prior to drying. This process produces less sweet, more
acidic coffees, which generally would be unsuitable for espresso if used
pure. However, since these beans often have beautifully clean and
powerful floral and fruity aromas and tastes, they are used in smaller
proportions in more expensive blends to enhance the more subdued taste
of dry processed beans. When these beans are used, the coffee is usually
roasted at the lighter end of the espresso spectrum, since dark roasting
destroys their aromatics.
Finally, some espresso blends use Robusta coffees, which derive from
a different species of coffee tree found at lower altitudes and having
higher yields. These coffees are generally less expensive than the
Arabicas discussed above. Low grade Robustas can add body, sweetness,
and above all, very strong crema to an espresso. But they do so at the
expense of having an unpleasant, burnt rubber smell. High grade Robustas
do not have this offensive odor, but will usually muffle the other
aromatics. Their use is controversial. Many very gifted espresso
professionals use Robustas, while many others would never touch them.
At the Roaster
Different roasters have different blending strategies. Some use only
two to four different coffees; these blends can have very distinct
tastes and will vary a lot year to year. Other roasters will try to keep
the blend's taste the same year in, year out. They will do this by using
seven to twelve different coffees, many from different plantations in
the same country and region, so as to average out the annual variations
of coffees from any one plantation.
As with all coffee, espresso blends are always best when used within
two weeks of roasting. Unlike regular brewing, the carbon dioxide in the
beans in the first day or two after roasting can sometimes interfere
with the espresso extraction, so many cafés allow the coffee to
rest 48 hours prior to use.
My main advice is to first find several good local roasters. Try many
different espresso blends, varying in roast levels, use of Robusta (or
not), level of acidity, or use of wet processed coffees, and then decide
for yourself which styles you like most. Ask the roasters about what's
in the blend; the exact recipes are usually proprietary, but they will
be happy to give you general information so you can develop an informed
preference. If you home roast, try various dry or semi-wet processed
Brasils, Indonesians, Ethiopian and Yemen coffees, and create a blending
base from your favorites among these. Then add small amounts of your
favorite wet processed, high grown Arabica to give it some
distinctiveness. If this later coffee is exceptionally sweet and low
acid, more than the usual 10% to 20% can be used.
Single Origin Espresso
As mentioned earlier, most washed, high grown coffees are unsuitable
for espresso either straight or in high proportions in a blend. In my
opinion, this shows that espresso technology requires further
development. It would be absurd if you tried to buy a coffee and were
told it was too strong to be prepared in a presspot.
However, espresso technology has advanced far enough so that some
high-grown, washed coffees can make interesting and sometimes
spectacular shots. These usually don't have the balance of conventional
blends, but can have far more interesting aromas and tastes. Low toned,
sweet coffees, even those from regions usually not regarded as suitable
for espresso, are always worth trying as single origin shots. The
research that could adapt espresso equipment to the full range of
coffees won't happen until more people try these, develop an
appreciation for them, and form a market for roasters, cafés, and
manufacturers pushing the envelope.
Water for Espresso
Finally, a note about water, the other constituent of good coffee and
espresso. Water for coffee should be pure and odor free. Charcoal
filtering to remove chlorine and sediments from municipal water is a
good idea. Further filtering is required if the water is from a well
having iron, sulfur, heavy metals, or organic contaminants.
Alternatively, consider bottled water.
Note that "pure water" in this case does not mean distilled or free
of all minerals. Natural water contains calcium carbonate and some
magnesium carbonate; these constitute the water's hardness. Overly soft
(low mineral) water will create a light bodied, metallic and excessively
bright tasting shot. Overly hard (high mineral) water will scale the
machine, while the chalkiness of the calcium carbonates precipitating as
the water heats will interfere with proper extraction. The best coffee
water has about 5 grains (90 mg/L) hardness and 150 mg/L total mineral
content. For espresso machines, water at about 3 grains (50 mg/L) and 90
mg/L total mineral content is used to reduce descaling costs. This is a
compromise on the ideal water for espresso, but the 90 mg/L shots are
almost indistinguishable from shots with the higher 150 mg/L mineral
content. If your tap water is excessively hard or soft, look into
bottled water or water treatment options, many of which are not
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