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3.2 A taste test (Water hardness and taste)




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This article is from the Water for coffee FAQ, by Jim Schulman with numerous contributions by others.

3.2 A taste test (Water hardness and taste)

These disputes call for a taste test. However, there's little
point doing the tests with brewed coffee. First, limescale is a
trivial problem in brewed coffee makers, so there's no reason to use
soft water when brewing coffee. Second, in good espresso, crema,
mouthfeel, and balance play a much larger role than in brewed coffee,
so results from a brewed test may not apply to espresso. The drawback
of an espresso test is that I can't do it side by side, since I need a
few minutes to switch waters in the tank and let my tastebuds recover.
I settled on tasting at fifteen minute intervals and relying on my
notes and taste memory for comparisons. I believe if I can't
distinguish the taste from different waters at this short an interval,
water quality isn't big deal. To keep myself undeluded, I blind tasted
by shuffling the water bottles.
I used four different waters. The first was boiled hard water,
at 100 hardness, 50 alkalinity. This is ideal for brewed coffee, and
will be the water one gets out of an espresso temperature boiler
whenever one runs anything harder through the machine. The second is
straight RO water with less than 10 hardness and alkalinity. The third
is RO water with charcoal filtered tap water added to get a 40
hardness, 25 alkalinity level. This approximates the composition of a
competent water treatment for commercial espresso machines. The fourth
is ion exchanged water with 100 alkalinity and less than 20 hardness,
this approximates the composition of water when using an ion excahnge
hose end or cartridge type softener. The hardness and alkalinity
figures are +/- 7.5 mg/l.

                          ESPRESSO TASTE TEST
------------------------------------------------------------
Water Hardness            RO     RO+Tap     IonEx     100/50
------------------------------------------------------------
Crema                      9       9          9          9
Body/Mouthfeel             4       7          8          9
Sweetness/Balance          3       8          9         10
Origin Flavors/Aroma      10       9          9          8
Roast Flavors              6       9          8          9
Finish                     3       7          8          9
------------------------------------------------------------
Total                     35      49         51         54
------------------------------------------------------------

The RO water didn't really produce an espresso, but rather an
unbalanced, overly bright shot of strong coffee with crema on top.
It's identity was painfully obvious. The proper mineral level espresso
was distinguished by a slight edge in the things I like in an
espresso, rich oily mouthfeel and sweetness, but I was using my own
blend which is formulated to really max these out at the expense of
complex origin flavors (50% total of Robusta, Brazil, Java, and
Uganda). Otherwise, the two boiler safe variations fared very well and
were nigh indistinguishable.

 

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