Coffee is a delicious and wholly natural product that
contains several hundred different chemicals and that help
to define its distinctive taste and aroma. Caffeine is just
one of these naturally occurring substances.
It is an extremely difficult process therefore to remove
only the caffeine and leave the other chemicals intact. To
all intents and purposes this is an impossible task and
even the best and most carefully produced decaffeinated
coffees will have its taste and aroma altered by the
decaffeinating process.
Coffee comes in two major varieties: Arabica coffees and
Robusta coffees. The Robustas typically contain twice the
amount of naturally occurring caffeine as the Arabicas.
So how do manufacturers go about removing the caffeine from
the bean?
There are several different methods in use today, all of
which treat the green or raw coffee bean before roasting.
A popular method is known as "Water Processing" that was
originally developed by the Swiss in the 1930's.
This process involves soaking the green coffee beans in hot
water to extract all the soluble and semi soluble compounds
(including the caffeine) into the solution. The first batch
of 'used' coffee beans are then removed and thrown away.
The solution containing all the coffee compounds is then
treated to remove the caffeine by passing through carbon
filters in solution. These carbon filters are designed to
only remove the caffeine molecules and to allow the other
compounds in solution to pass through.
A new batch of raw coffee beans is now introduced into the
'filtered solution' which has been kept at the same
temperature throughout the process. The 'clever' part of
this process is that since the hot water solution has
reached equilibrium and already has the maximum amount of
coffee compounds suspended in solution, then when the new
beans are introduced only the caffeine is dissolved out
from the new beans and the other compounds remain in the
bean as they are unable to be extracted by the hot solution
that already contains them from the original batch!
The beans are then removed, dried and sent away for
roasting.
This process is repeated many times using the original
solution, which is continually treated to remove the
caffeine.
Other processes used to remove caffeine rely on similar
principles as water processing but use different ways to
soak the beans and different ways to extract the caffeine.
For example some processes use steam instead of soaking the
beans and use solvents to remove the caffeine. Others use
carbon dioxide and oxygen gases to achieve a similar thing.
It should be noted that there are different criteria for
labelling coffee as decaffeinated: The International
Standard demands 97% of the caffeine to have been removed
from the beans and the European EU Standard of having 99.9%
of the caffeine removed by mass.
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For more information about coffee and coffee making
equipment visit http://www.cafebar.co.uk and view our
Coffee School Section
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