2018-01-28

Coffee with bottled water

Project history

  1. old posting: 'roast only' on the Bonaverde - Aldo Parducci
  2. current posting
  3. next posting: 'roast only' on the Bonaverde - Familia Alfaro


Before

Up to now I have used tap water with a filter for my coffee experiments.
According to the water plant the water should be very hard but be only slightly above Ph neutral.
I always had the issue of always having an acidic taste.
Some coffee cups had a very balanced acidic taste, some where so strong as to be undinkable.
Especially freshly roasted coffe that was not given any time to release trapped CO2.

After

Now I experimented with using cheap bottled water insted.
DAMN, WHAT A DIFFECENCE.
Absolutely no sour taste anymore. Roasted the day before and even freshly roasted (with all the CO2 still in there and ALYWAYS tasting distinctly sour before) it tasted like a good cup of coffee.

Sadly it contains 500mg Ca/l+64mg Mg/l=>84,86dH and thus will just about kill the machine with scale if used often.

Why?

 Let's have a look...
The bottled water was from REWE "Aqua Mia Still" from the Alwa Spring in Sersheim.

There is a nice comparison of German bottled waters here. It has pH values (the content only lets you calculate hardness)

Chlorine

The water plant says, we have 23.1mg/l.
The bottled water says, we have 29.0mg/l
The 
0mg/l is perfect
effect: in high temperature/pressure this creates hydroloric acid thatg eats away on metal.
There is nothing I can do anything about this except maybe carbon filtration.
But I don't care enough about this minor effect to do that.

 pH 

The water plant says, we have 7.57pH.
The bottled water says: nothing
Water #2 says: nothing

7.0pH is perfect,
6.5-7.5pH is acceptable
effect: abovr 7.5pH this causes excess scale


Next steps: I ordered a digital pH and TPS meters from China for less then 2eur.

Hardness (Calcium only)

The water plant says, we have 75,8mg/l of Calcium
and a total hardness (considering not just the Calcium) of 12.5°dH or 2.19mmol/l
The bottled water says, we have 500mg Ca/l+64mg Mg/l=84,86dH

7°dGH/68mg/l is perfect
17-85mg/l is acceptable (first source).
8-12 °dH is acceptable (second source).
3-7 °dH is acceptable (third source).
effect:
Above 85°C this forms scale.
High hardness makes coffee go bitter quickly.
Low hardness supresses the taste of the coffee.

Here is a nice calculator between °dH, mg/l of Calcium-Oxide and ppm CaCO3,...
Or you calculate °dH = 0.1402*[Ca in mg/l ] + 0.2307*[Mg in mg/l ]
Or mmol/l= [Ca in mg/l] / 40 + [Mg in mg/l] / 24,3 .

Sodium (DE: Natrium)

The water plant says, we have 10.2mg/l.  But ADD what the water filter releases.
The bottled water says, we have 18.0mg/l

10mg/l is perfect.
Anything near that level is acceptable.

The problem may of cause also be that the water filter with my very hard water (12.5°dH or 2.19mmol/l) releases enough sodium (DE: Natrium) to exceed 10mg/l.
The original water already has 10.2mg/l and is thus at the brink of the acceptable level.
Above 50mg/l this seems to cause a sour flavor. (Very low sodium levels seem to cause sweet flavors. That sounds very interesting as it's a taste I generally like.)

TDS=total dissolved solids

The water plant says, we have 75.8mg/l of Calcium + 7.3mg/l Magnesium + 10.2mg/l Natrium+1.7mg/l potassium (DE: Kalium)
= 95mg/l  I'm not sure I did this calculation correctly and am not missing anything.
The bottled water says, we have 500+29.0+64.0+18.0+5.0=616mg/l

150mg/l is perfect
75-250mg/l is acceptable.
effect:
low=overextraction, tannic taste (DE: Gerbsäure), dry mouth
high=mineral taste, overextraction

Total alkalinity

The water plant says, we have TODO
The bottled water says: 1130mg/l of Sulfate + 414.0mg/l of Bicarbionate (DE: Hydrogencarbonat)
TODO: I need to refresh my chemistry on this topic.

40mg/l is perfect.
Anything near that level is acceptable.
effect: high=gum up outher layer of coffee and cause uneven extraction. Also scale buildup.

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