Matt Perger's water recipe for coffee - Is it ok/safe for espresso machines? What do you think? - Page 6

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
jdsuz

#51: Post by jdsuz »

Awesome discussion

Im looking at using a dosing pump that injects a concentrate into RO water... but dont want to have to shake the concentrate every time it gets used. Could there be some way of fully dissolving the minerals so that they don't precipitate over the course of weeks/months?

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homeburrero
Team HB

#52: Post by homeburrero »

jdsuz wrote:Could there be some way of fully dissolving the minerals so that they don't precipitate over the course of weeks/months?
If your concentrate has just sodium and potassium carbonates (no Mg or Ca) there would be no worry. For concentrates that include either Ca or Mg along with carbonates, some folks who mix at home acidify with a CO2 spritzer which helps keep the carbonates in solution. I don't think that would be very practical and would probably not work if you're using a strong concentrate solution.

To inject both hardness minerals and carbonates I think you'll need separate bottles and injectors. That appears to be the method used by commercial systems, like the gcwater AB formulator. With separate injection/blending valves you would be able to control hardness and alkalinity independently, which is good. Downside is that the system will require that the hardness source be non-carbonate salts like sulfate or chloride which could be undesirable if the final blend's hardness is set high and the alkalinity is set low.
Pat
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BobStern

#53: Post by BobStern »

@rpavlis recommended a completely different approach that I believe merits discussion and experimentation. (See links at end of this post.)

Potassium bicarbonate (KHCO3) is the only additive he recommends for purified water. I've tried it and like it! It produces lots of tasty crema and reduces sourness (i.e., permits reducing the extraction temperature).

In contrast, I do not get extra crema from the more commonly recommended sodium bicarb. (I have not tried epsom salt, which he says promotes scale if the water includes calcium.)

My purified water is simply tap water run through an activated carbon filter (General Ecology "Seagull"). I add 1/4 teaspoon of KHCO3 to one liter of water. KHCO3 is sold cheaply on amazon, etc because it is used in winemaking.

I'll attempt to summarize rpavlis's key points:

For espresso, you should ignore advice derived from brewed coffee experiments because the ratio of beans to water is dramatically different.

Coffee beans already have huge amounts of potassium (K), so adding K to the water does not alter the true espresso flavor because it has negligible effect on the amount of K in the espresso.

pH: KHCO3 acts a pH buffer. He believes stabilizing the pH, especially with lighter roasted beans, is the only benefit of adding chemicals to purified water.

Sodium: Coffee beans have almost zero sodium (Na). Adding sodium bicarb or any other sodium compound adds a salty flavor. Some people like this but he does not. That's why he prefers potassium bicarb over sodium bicarb.

Hardness: Contrary to the standard advice that water hardness (Ca & Mg) is important to espresso flavor, coffee beans already have vastly more of these elements than even the hardest water, so there's no reason to believe adjusting their concentration in water will affect flavor.

Corrosion: For copper boilers, KHCO3 forms a protective oxide layer to prevent corrosion, eliminating the need to increase water hardness for this purpose.

Scale: Do not add calcium-containing compounds because they precipitate scale.

Epsom salt (magnesium sulfate MgSO4): Sulfate compounds exacerbate the precipitation of calcium.

Chlorine compounds (including table salt NaCl): Briny flavor is unpleasant. Corrosive.

Stale water is a myth. Heating water to espresso extraction temperature rapidly degasses it.

References — 3 threads between Oct 2015 and Aug 2016 from which I extracted the recommendations of @rpavlis:

Purified vs spring water and espresso quality?

Water quality?

Boiler-safe level of chlorides (and other compounds) in water

—Bob

ben8jam

#54: Post by ben8jam »

Oh man I could use some help digesting this thread. I'm doing the basic 25g Epsom Salts, 8.6g Baking Soda (though I seem to also have a similar recipe that calls for 12.9g), plus 500g DI water. Add 2ml of this to 1000ml of DI water. Achieve 70-90 TDS.

But is the Epsom salts really corroding my boiler? There seems to be a lot of discussion but I'm lost what the answer is?

Interesting last post above - is the trick to moving to KHCO3? $8 for a 1lbs bag would last a lifetime...

BUT before that - is my boiler eating itself alive?

BobStern

#55: Post by BobStern »

ben8jam wrote:But is the Epsom salts really corroding my boiler?
He said epsom salts and other sulfates exacerbate scaling, not corrosion. So you'd have to de-scale more often.

ben8jam

#56: Post by ben8jam » replying to BobStern »

Huh I guess I totally misread that somewhere.

So perhaps just use the lower baking soda amount recipe (8.6). Though given I have found two recipes that call for differing amounts of soda, I guess I could use any amount

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homeburrero
Team HB

#57: Post by homeburrero »

BobStern wrote:@rpavlis recommended a completely different approach that I believe merits discussion and experimentation. (See links at end of this post.)
I agree with that. Professor Pavlis' approach (bicarbonate salt only, don't bother adding hardness) is corrosion-safe, scale-free, easy, and straightforward. Is a good idea to try it and taste it before concluding you really need to mess with adding hardness minerals.
BobStern wrote:I add 1/4 teaspoon of KHCO3 to one liter of water.
That's a ton of bicarbonate - maybe a typo there? Prof Pavlis recommends a 0.5 to 1.0 milliMolar solution. A quarter teaspoon would be a little over a gram, and if you add a gram of KHCO3 to a liter of water you would have a 10 milliMolar solution.
ben8jam wrote:But is the Epsom salts really corroding my boiler? There seems to be a lot of discussion but I'm lost what the answer is?
At high levels, and at low alkalinity/pH, sulfate can be a corrosion concern. Professor Pavlis points out that in the presence of calcium it can also be a problem because of creating calcium sulfate (aka calcium sulphate) scale, which can't be removed by typical descaling. In a machine like a dual-element Pavoni, which hisses off a lot of steam and therefore tends to concentrate the water in the boiler this can be a special problem. (Use the search tool - author rpavlis, keyword sulphate for more info.)

Your recipe:
ben8jam wrote:...25g Epsom Salts, 8.6g Baking Soda plus 500g DI water. Add 2ml of this to 1000ml of DI water.
Only has about 0.4 millimol/L of sulfate (about 34 mg/L) and has no calcium. You needn't worry.

If you want to use the same recipe approach and get rpavlis' recommended water, simply add 25g of potassium bicarbonate to 500 g of DI water for your concentrate. Then add 2 ml of that concentrate to each 1000ml of DI water. That gives you the 1.0 milliMolar solution. (alkalinity = 50 mg/l as CaCO3, hardness = 0). The professor says that he sometimes uses half this strength if it tastes better, so you could try that by just adding 1 ml of your concentrate.
Pat
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BobStern

#58: Post by BobStern »

BobStern wrote:I add 1/4 teaspoon of KHCO3 to one liter of water.
homeburrero wrote:That's a ton of bicarbonate - maybe a typo there? Prof Pavlis recommends a 0.5 to 1.0 milliMolar solution. A quarter teaspoon would be a little over a gram, and if you add a gram of KHCO3 to a liter of water you would have a 10 milliMolar solution.
No, not a typo!

I'm pretty ignorant regarding chemistry, but Prof Pavlis describes the KHCO3 as functioning as a pH buffer, not a base. Would that remain true even at the 10x higher concentration of KHCO3 I'm using? If so, do you anticipate any harm in my solution?

The higher concentration of KHCO3 is what I found to increase the crema.

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hankbates

#59: Post by hankbates »

homeburrero wrote: In a machine like a dual-element Pavoni, which hisses off a lot of steam and therefore tends to concentrate the water in the boiler this can be a special problem.
Even greater solids build up occurs in any HX or dual boiler machine if the boiler is only used for steaming.
Every shot in a Pavoni (or other similar lever machine) takes water out of the boiler, and an equilibrium (at a higher concentration than the feed) is reached.
There is essentially no limit to the concentration of solids in the other machines unless one removes water periodically.

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homeburrero
Team HB

#60: Post by homeburrero »

hankbates wrote:Even greater solids build up occurs in any HX or dual boiler machine if the boiler is only used for steaming.
Good point!
BobStern wrote:Prof Pavlis describes the KHCO3 as functioning as a pH buffer, not a base. Would that remain true even at the 10x higher concentration of KHCO3 I'm using? If so, do you anticipate any harm in my solution?
No harm should come from your 10x strength solution. Carbonates are an acid-base buffer, but water high in bicarbonate will act as a base when interacting with the acidic coffee, and might be expected to reduce the acidity of the final brew. High bicarbonate should also tend to decrease the flow rate, and, as you say, tend to increase the crema.*

* An up-to-date reference for this is an article from researchers at Illy published in the journal, Food Chemistry: L. Navarini, D. Rivetti, "Water Quality for Espresso Coffee", Food Chemistry 122 (2010) 424-428. ( https://doi.org/10.1016/j.foodchem.2009.04.019 ) Unfortunately that article isn't freely available on the internet. With respect to bicarb and crema, in the conclusion the authors report: "The foam layer, extremely important in assessing the Espresso coffee quality, is not merely related to the presence of carbon dioxide in the roasted coffee. Bicarbonate ions naturally present in the water ingredient represent a source of ''extra" carbon dioxide available for foaming. Unfortunately, the abundant initial foam ensured by bicarbonate rich waters corresponds to a very poor foam persistency and to an unacceptable foam texture."
Pat
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