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People often buy coffee from a particular
place where they have enjoyed an excellent cup. They take the coffee home,
brew it correctly and wonder why it doesn't taste the same. As a cup of
coffee is more than 98 per cent water, the condition and taste of the
water are at least as important as the coffee used, and only water from
the same source will recreate an exact taste. Coffee experts tend to agree
that the best water for brewing coffee is slightly hard; a few minerals
will enhance the coffee flavor, hence the old custom of adding a pinch of
salt to "bring out the flavor". If the brewing water is very hard,
however, the calcium and magnesium ions can actually get between the water
molecules and the coffee particles, interfering with the extraction
process, and the resulting brew will have little flavor.
When considering the effect of soft water in brewing coffee, it is
interesting to examine the softest water possible, which is distilled or
de-ionized; as water it has virtually no taste, and no one would dream of
making coffee with it. It could therefore be assumed that coffee made with
distilled water would also be tasteless and would need a "pinch of salt to
bring out the flavor". Wrong! Because it contains nothing to interfere
with the extraction, coffee brewed with tasteless, distilled water has a
very strong coffee flavor, which in the course of normal brewing,
especially with a cheap blend, could easily be far too strong. Very soft
water requires less coffee per brew, or a slightly coarser grind, or less
contact time - any of which work to ensure that over-extraction does not
occur. The old wives' habit of adding a pinch of salt may have worked not
in "bringing out the flavor", but rather in toning it down, modifying the
flavor for the better, if the original water was very soft.
Chlorinated or other chemically treated water, or water polluted by old
pipes, rust or other tastes can affect the flavor of coffee. Filtering
devices, which remove objectionable tastes, are available both in jug
(carafe) form and in more permanent systems that attach to the kitchen
main water pipe.
Generally, experts agree that fresh, cold water, which presumably has a
higher oxygen content, makes the best coffee. Somewhat confusingly,
however, it is oxygen that causes ground coffee to go stale, and it is
from oxygen that vacuum flasks protect liquid coffee. Thus the need to
have oxygen in the brewing water seems surprising, especially as
convincing scientific explanations are rather scarce. (This calls for the
challenge of a taste test: try brewing the same coffee with stale, warm
water and with fresh, cold water and observe the difference.) Remember
that most electric coffee-makers are equipped with thermostats which
expect to start with cold water, and may not function very well if hot
water is used.
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