Day 405

What better way to start mid-term week than with a 90-minute Brewing Calculations mid-term at 8:30 am on a Monday.

Erk.

…followed by a one-hour lecture on predicting residual alkalinity and pH of the mash.

Erk Erk.

So here’s the thing. Water hardness–the amount of calcium and magnesium in the water–is desirable. Water softness or alkalinity (an overabundance of free CO32- ions, aka carbonates) is not, since it will not only raise the pH of the mash, but also acts as a pH buffer, resisting the efforts of the brewer to lower the pH. Since low pH is good for enzymes, good for yeast, limits extraction of phenols from malt husks, improves the quality of hop bitterness, improves filterability of the mash, and improves coagulation of proteins in the kettle, a low pH is very desirable.

Being able to predict when our mash pH is going to be too high before we even start brewing is better than discovering that our mash pH is too high in mid-brew and trying to correct it after the fact.

Both hardness and alkalinity can be characterized by the presence of calcium carbonate (CaCO3), since it contains both hardness in the form of calcium (Ca2+) and alkalinity in the form of carbonate (CO32-). So if we take all the calcium and magnesium ions in brewing water and convert them to equivalent amounts of CaCO3, and then take all the carbonates and bicarbonates present and also express them as an equivalent amount of CaCO3, we will then be able to see what the total hardness and alkalinity of the water is as expressed by the presence of CaCO3, calculate how this will affect our mash pH, and then make suitable adjustments to the brewing water.

The first step is to convert the calcium and magnesium into equivalent units (called milli-Equivalents or mEq). The conversion formula is

milliEquivalents (mEq) = amount of ion (in ppm) ÷ equivalent weight (calculated as molecular weight of ion/absolute valence of ion)

For instance, water here at Niagara-on-the-Lake has 34.8 ppm of calcium (Ca2+, valence of 2, molecular weight of 40) and 8.7 ppm of magnesium (Mg2+, molecular weight of 23.4 and valence of 2). First of all, the equivalent weight of calcium would be (molecular weight of 40/valence of 2) = 20. The equivalent weight of magnesium would be (molecular weight of 24.3/valence of 2) = 12.2. The millEquivalents of both of them would be

(34.8 ppm Ca ÷ 20) + (8.7 ppm Mg ÷ 12.2)

= 1.74 + 0.71 = 2.45 mEq

The next step is to convert this value to an equivalent amount of CaCO3 in parts per million, which is done by multiplying the mEq by the molecular weight of CaCO3 (which happens to be 50). Therefore, 2.45 mEq x 50 = an equivalent value of 122.5 ppm of CaCO3 in the local water.

So what, you say? We’re not done yet, I reply.

A German researcher discovered that 3.5 equivalents of calcium or 7 equivalents of magnesium would offset the pH raising effects of 1 equivalent of carbonate. Therefore, if we simply subtract the equivalent of calcium (divided by 3.5) and the equivalent of magnesium (divided by 7) from the carbonate equivalent, we can see how much Residual Alkalinity is left in the water–that amount of alkalinity that will resist any attempted lowering of pH.

First, we can quickly calculate the mEq of CaCO3, using the same formula we used above. The concentration of CaCO3 in our local water is 85.9 ppm, and its molecular weight is 50, so

mEq of CaCO3 = 85.9/50 = 1.72

Since

RA = (mEq of CaCO3) – [(mEq of calcium/3.5) + (mEq of magnesium/7)]

then

RANiagara-on-the-Lake = 1.7 – [(1.74/3.5) + (0.71/7)]

 = 1.72 – (0.50 + 0.10) = 1.12  mEq

If we then convert this back into CaCO3 (1.12 mEq x equivalent weight of 50), we get a Residual Alkalinity of 55.95 ppm. This is right on the edge of being too alkaline for brewing.

But wait, we’re not done yet. The same German researcher discovered that one degree of Residual Hardness as measured in units called German Hardness Units or °dHa in a 12°P mash will increase the pH of the mash by 0.03. (No, I am not making this up!) So now that we know the Residual Alkalinity of our water, we can calculate its effect on the pH of the mash. First we can look on the malt analysis sheet provided by the maltster to discover the pH rating of the grain we are using (which is calculated in a lab by making a “congress” mash using distilled water). We can then convert our RA to German Hardness Units by dividing the RA by ppm per °dHa of CaCO3, which happens to be 17.85:

55.95/17.85 = 3.13°dHa

So if our grain has a malt pH rating of 5.8, then

Predicted pH of mash = malt pH rating  + (RA as  °dHa x 0.03)

= 5.8 + (3.13°dHa x 0.03) = 5.8 + 0.09 = 5.9

(If you are using multiple grains, then you would use the above forumla for each grain multiplied by the percentage of that grain in the mash. Add the weighted pH’s together and you get a prediction of the eventual mash pH.)

But wait, there’s more…

Alas, my brain had melted by this time, so my notes are meaningless scribbles highlighted by phrases like “acidulated malts” and “acid additions”. Some day this will all make sense.

As if this wasn’t enough for one day, it was also the first day of class presentations in History of Beer. Yours truly was the third presenter, speaking for 12 minutes on Russian Imperial Stout: Being a moft excellent and entertaining Recital of the Hiftory of the Exportation of Strong Beers from London to Russia with divers scholarly Addenda and learned Afides by the Author.

This was actually a very educational topic from my point of view. I had previously understood that Russian Imperial Stout was so named because it was made by English brewers for the court of Catherine the Great, and that it was stronger and hoppier than normal so that it wouldn’t freeze as it was being shipped across the icy Baltic Sea. What I discovered was that trade in strong porter had started six decades before Catherine the Great, during the reign of Tsar Peter (also “the Great”), who discovered English beer on a trip to London in 1698. He liked dark London porter so much that, during his visit, he became a prodigious party animal who had to be wheeled back to his lodgings in a wheelbarrow each night. Upon his return to Russia, he ordered a shipload of the stuff to be sent to his new court at St. Petersburg. Alas, the 4-month voyage proved too much for the low-gravity English beer, and brewers were forced to increase the bitterness and strength not so that it wouldn’t freeze, but so that it would arrive in Russia in a drinkable state. The export of strong stout continued for the next 300 years, until the First World War and the Russian Revolution put an end to the beer export market. However, the name “Russian Imperial Stout” actually wasn’t given to the stuff until 1934–twenty years afterwards–as a marketing gimmick to attract English drinkers.

But wait! There was more. Bill White then gave a one-hour lecture on technology and its effect on beer, from the water canal and the steam engine to the microscope.

Finally, the end of a long day. But hark! I sense another mid-term…

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3 Comments on “Day 405”

  1. Eric Ross Says:

    Well, I hope you at least get your modterms done before the break, so you can have some time off. Are you attending the OCB conference this Friday?

  2. Canageek Says:

    ……You can do that calculation far, far more easily if you just convert everything to moles. Once it is in moles you don’t have to worry about equivalence factors, and the pH change will fall out naturally. I can loan you my 2nd year Analytical Chemistry textbook and notes if you want.

    Oh wait, that is 2nd year analytical, I um, don’t think I took any notes.

  3. Richard Says:

    Thanks for this. Best explaination I have come across that I actually understand. Bonus that my water is the same source.


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