Decaffeinated Coffee: Introduction
Technology is always trying to give us back the
garden without the snake. So you like coffee and not caffeine?
Well, then, we will take out the caffeine and leave you your pleasure,
Decaffeinated coffee is indeed without venom.
It contains, at most, one fortieth of the amount of caffeine in
untreated beans. Nor should the removal of caffeine alter the
taste of coffee. Isolated, caffeine is a crystalline substance
lacking aroma and possessing only the slightest bitter taste.
Its flavor is lost in the heady perfumes of fresh coffee. So if
you hear people say, "Coffee doesn't taste like coffee without
the caffeine," they are wrong. The only real problem is how
to take out the caffeine without ruining the rest of what does
influence coffee flavor. But technology has triumphed, more or
less. The best decaffeinated coffee, freshly roasted and ground
and carefully brewed, can taste so nearly the equal of a similar
untreated coffee that only a tasting involving direct comparison
reveals the difference.
Unfortunately, fine decaffeinated coffees are
the exception rather than the norm. Decaffeinated beans are notoriously
difficult to roast, so even the best decaffeinated beans may produce
a thin-bodied, half-burned cup once they are roasted. Still, for
the coffee devotee even listless decaffeinated coffee is better
than mint tea, and you can always compromise and spruce up a caffeine-free
coffee by adding a little full-bodied caffeinated coffee before
grinding it, or by creating your own low-caffeine blend.
Most caffeine-free coffee sold in specialty stores
is shipped from the growing countries to decaffeinating plants
in Europe or Canada, treated to remove the caffeine, then re-dried
and shipped to the United States.
Coffee is decaffeinated in its green state, before
the delicate oils are developed through roasting. Hundreds of
patents exist for decaffeination processes, but only a few are
actually used. They divide roughly into those that use a solvent
to dissolve the caffeine, those that use water and charcoal filters,
and those that use a special form of carbon dioxide.
The direct solvent method is the oldest and most
common decaffeination process. On coffee signs and bags it is
typically not identified at all, or called by various euphemisms
like European or traditional process. The beans are first steamed
to open their pores, then soaked in an organic solvent that selectively
unites with the caffeine. The beans are then steamed again to
remove the solvent residues, dried, and roasted like any other
A more recently developed process called the indirect
solvent method starts by soaking green beans in near-boiling water
for several hours. The water is transferred to another tank, where
it is combined with a solvent that selectively absorbs most of
the caffeine. The caffeine-laden solvent is then skimmed from
the water, with which it has never really mixed. The water, now
free of both caffeine and solvent, still contains oils and other
materials important to flavor. In order to return these substances
to the beans, the water is returned to the first tank, where the
beans reabsorb the flavor-bearing substances from the water.
What About the Solvents? The joker in the process
is still the solvent. People concerned about the effects of coffee
on their health obviously are not going to feel comfortable purchasing
a product containing even minute traces of solvent. In 1975 one
of the most widely used solvents, trichloroethylene, was named
a probable cause of cancer in a "Cancer Alert" issued
in 1975 by the National Cancer Institute.
Also, no one knows how much of the solvent residue
-- if any -- is retained in the brewing process and ends up in
the cup. Given the volatility of the solvent and the relatively
minuscule amount left in the bean after roasting, it is most likely
that none whatsoever ends up in the coffee we ultimately consume.
A New and Better Solvent: Methylene Chloride.
Nevertheless, the news that the caffeine that some feared caused
heart disease was being replaced by a solvent that actually did
cause cancer provoked understandable consternation among health-conscious
The coffee industry promptly responded by replacing
trichloroethylene with methylene chloride, a solvent not implicated
in the National Cancer Institute study. So far tests of methylene
chloride have not linked it to any known disease, and given its
volatility (it vaporizes at 104° F; coffee is roasted at over
400° F for at least 15 minutes, then brewed at 200° F) it seems
hardly possible that any of the 1 part per million occasionally
found in the green beans could end up in the consumer's cup or
An Even Newer and Better Solvent. A second solvent
is now in use in some European decaffeination plants: ethyl acetate.
Like methylene chloride, ethyl acetate has not been implicated
in any diseases, and environmentalists consider it more benign
than methylene chloride. Because ethyl acetate is derived from
fruit, some publicists and brochure writers have taken to calling
coffees decaffeinated using ethyl acetate "naturally decaffeinated,"
and you may see them so advertised.
Swiss Water Process
In the 1980s the Swiss firm Coffex S.A. developed
a commercially viable decaffeination process using water only
-- no solvents whatsoever. As in the indirect solvent or solvent/water
process described earlier, the various chemical constituents of
the green coffee, including the caffeine, are first removed by
soaking the beans in very hot water.
In the Swiss Water Process, however, the water
is stripped of its caffeine, not by a solvent, but by percolation
through activated charcoal. (It really ought to be called the
Swiss Charcoal Process.) The beans are returned to the hot water,
where they reabsorb the remaining, caffeine-free flavor constituents
from the water.
This process is more costly than the solvent process
because the separated caffeine cannot be recovered from the charcoal
and sold separately, as it is with the two solvent methods. It
is also controversial in terms of flavor. Many coffee professionals
contend that the Swiss Water Process blurs flavor more than the
competing solvent processes. However, the management of the Canadian
plant that currently produces all of the Swiss Water Decaffeinated
coffees sold in North America continues to make determined efforts
to refine and improve the process.
Carbon Dioxide Methods
Decaffeination processes using carbon dioxide
(CO2) differ in their details. All take advantage of the fact
that carbon dioxide, when compressed, behaves partly like a gas
and partly like a liquid, and has the property of combining selectively
with caffeine. In the most widely used CO2 process the steamed
beans are bathed in the compressed carbon dioxide and the caffeine
is removed from the carbon dioxide through charcoal filtering,
just as it is in the water-only process. However, the flavor components
remain in the bean throughout the process, rather than being soaked
out and then put back in again, as they are in both the Swiss
Water and the indirect solvent processes.
Since carbon dioxide is the same ubiquitous and
undisputably "natural" substance that plants absorb
and humans produce, and since, in most versions of the CO2 method,
the flavor components remain safely in the bean throughout the
process rather than being removed and put back in again as they
are in the Swiss Water process, carbon dioxide methods would seem
to be the decaffeinating wave of the future. However, coffees
decaffeinated by the CO2 method have been slow to come onto the
specialty market, and reviews have been mixed.
Decaffeination Methods and Flavor
Which decaffeination method produces better tasting
coffees? It is difficult to say for certain for two reasons. First,
it is virtually impossible to turn up the identical coffee decaffeinated
by a range of different methods, and the quality of the original
coffee obviously influences the quality of the final cup. Second,
decaffeinated coffees are difficult to roast properly, and subtle
differences in decaffeination method may be overwhelmed by differences
in the quality of the roast.
Nevertheless, my own experience clearly and consistently
indicates that the Swiss Water Process tends to emphasize body,
de-emphasize acidity and high notes, and occasionally (but not
always) alter or blur flavor, whereas the European or solvent
method tends to preserve acidity, nuance, and high notes, but
may reduce body and dimension. As for coffees processed using
the CO2 method, I have tasted some excellent samples, but not
enough of them to generalize.