Bru N Water profile for an APA using 100% distilled water - Sparge question

[copper2hopper]

Why is it that I ALWAYS end up with a negative RA when formulating a water profile. I primarily do IPA and APA recipes and always have to pump in lactic acid to knock my ph to within range. How much is too much lactic acid and is a negative RA something to be concerned about? Also with my ending water profile my cations and anions are far apart from one another. I thought they are wanted to be as close to equal to eachother as possible. And yes I know I'm plugging stuff in correctly. I also always build up from distilled water.

 

[ajdelange]

Why is it that I ALWAYS end up with a negative RA when formulating a water profile. I primarily do IPA and APA recipes and always have to pump in lactic acid to knock my ph to within range. How much is too much lactic acid and is a negative RA something to be concerned about?

The concept of RA was first advanced by Paul Kohlbach in 1941. The original paper was lost as a consequence of the war and so he revisited the subject in another paper in 1953. Discussion of it was found in textbooks thereafter but it didn't really go public until a talk I gave in 2002 at the Craft Brewer's Conference in which I presented that chart that you'll find in Bru'n water and elsewhere. John Palmer, ever looking for a way to make the brewer's life easier jumped on it and really wanted to make it the basis of his Water book which he more or less did. The interesting thing about RA is that it cannot be the basis for water treatment but it is a very important part of it.

The basis for brewing water treatment is that the sum of the proton deficits (the amount of acid you must add to a given mash component to get it to a desired mash pH) must be 0. This means that some of them must be less than 0 and added acids or acidic malts (sauermalz, dark malts) do indeed have negative proton deficits with respect to desirable mash pH's. So using the letter D to represent a proton deficit we need

Dm1 + Dm2 + Dm3.... + Da + Db + Dw + Dphos = 0

m1 means malt1 etc
a means an acid you add (Da < 0)
b means a base you add
w means the water. Dw is about 90% of the reported alkalinity of the water at pH 5.4
phos designates the reaction between malt phosphate and calcium ions. Dphos < 0

Dphos = -([Ca++] + [Mg++]/2)/3.5

in which the values in brackets are the concentrations of the two ions in mEq/L. Dphos added to the alkalinity of the water gives the residual alkalinity

RA = Dw + Dphos = Dw -([Ca++] + [Mg++]/2)/3.5

so our balance condition now becomes

Dm1 + Dm2 + Dm3.... + Da + Db + RA = 0

It's easy to see how we design a beer from this. Compute Dm1, Dm2 etc, add on the RA and if the sum is > 0 add acids (with their negative Da's) or more or a new dark malt (with their positive Da's until the sum is 0. If the sum is negative then we add a base (Db > 0) or more malt with Dm > 0 or remove malt with Dm < 9. With a properly designed spreadsheet you can whip out recipes really quickly while gaining great insight as to what the roles of the individual components are.

The problem you are seeing isn't really a problem. The RA the popular spreadsheets and calculators display is actually (as far as I can tell) Da + Db + Dw + Dphos , IOW Kohlbach's RA plus the proton deficits of the added acids and bases. That sort of makes sense as it is the RA of the treated water if you add all the acids and bases to the water or the treated water as added to the mash if you add acids or bases to the mash tun.

As most beers require that you add some acid with it's negative proton deficit it should be clear that the sum of the water's actual RA and the acid's negative deficit is going to be smaller than the actual RA and, if acid in quantity greater than the RA is used, the sum can easily be negative. That's what you are seeing. Given that the RA as presented is not useful information without the malt components just ignore it.

I think most users of these programs are smart enough to know that in synthesizing a mineral profile they should not try to chase the bicarbonate. What many may not know is that lots of the profiles use calcium carbonate and lime as sources of calcium and sodium bicarbonate as a source of sodium. If that is done acid will have to be added to neutralize the alkalinity of those salts to mash pH at which pH 90% of the alkalinity attributable to them has been removed. This leaves calcium and magnesium at elevated levels with no compensating alkalinity (that was the intention) and, consequently, a more negative RA. It also requires more acid to the point that you may wind up with more than you want. My advice is to not use any of the alkaline salts. The neutral one's will usually get you reasonably close to the targets.

Also with my ending water profile my cations and anions are far apart from one another. I thought they are wanted to be as close to equal to eachother as possible.

I pointed this out and was told that you have to have the paid version for the cation and anion fields to be correct. But don't worry. As water is balanced and any salt you can buy is balanced mixing them together results is a balanced combination.

 

[copper2hopper]

Great! So keeping it simple, cuz I went a little cross eyed reading that, and also after reading palmers water book,....don't worry about negative RA and cations and anions being far apart.

Then how much lactic acid is too much? My last batch only required 4ml. My next one (from a different water source I want to try) will require 8ml. My usual starting volume is 8 gallons of water.

 

[ajdelange]

Then how much lactic acid is too much?

That's a tough one to answer because it is really a matter of your personal taste. If you like the flavor of lactic acid you might well accept more of it than people that don't like it. But then a Pils that tastes like a Gueze isn't really a pils.

I think most people would agree that a 3% sauermalz content in a grist is well below the level of objectionability and certainly most of the German beers you drink are going to have been acidulated to about that level because that's how much it takes to get a Pilsner malt to a mash pH of 5.4 or so given that you have dealt with any alkalinity in the water. That amount of sauermalz corresponds to about 4 mL of lactic acid in a typical batch.

My last batch only required 4ml.

Should not have been a problem.

On Weyermanns web site someone asks about using sauermalz to make Berliner Weiße. The response inludes:

"To reach the “sourish” character 8% of Acidulated malt are a perfect rate." From which I think we can take it that 8% is going to be too much unless you want "sourish" character and that we ought to be pretty cautious at above, say, 6% (double the amount discussed above). Six percent sauermalz corresponds to about 8 mL of lactic acid in a 5 gal batch.

My next one (from a different water source I want to try) will require 8ml. My usual starting volume is 8 gallons of water.

That puts you right on the edge of the "be careful" zone. Lots of posters here look at someone's water and say "neutralize the alkalinity with acid" leaving out the caveat that every mEq of alkalinity that is removed in this way is replaced by a mEq of the anion of the acid used. I always suggest that people remove alkalinity by other means (dilution with RO water is the simplest conceptually) to the point that the acid required to remove alkalinity from the water is less than the amount required for the grains.

Probably the best thing for you to do is to add some lactic acid to a finished beer and figure out how much you can tolerate before you notice it or it becomes objectionable.

 

[copper2hopper]

Thank you AJ. I brewed last night and sacrificed my PH a little and cut back the called for 8ml of acid to 5 ml. It got my PH to 5.6-5.7 when measured at 90 degrees according to my Milwaukee ph56 meter. So we will see how it turns out.