A "Standard Candle" by which to confirm Kolbach's mineral pH shift in the mash

[Silver_Is_Money]

In astronomy things such as magnitudes and distances are measured via the assistance of association with what are referred to as "Standard Candles".

With AJ deLange having stated that in his opinion the downward shift in pH within the mash is only on the order of 50-60% of what Kolbach had determined, and with Braukaiser (Kai Troester) in general agreement with AJ on this (albeit to a lesser degree than 50-60%), but with others (Martin Brungard and I believe DM Riffe also) accepting Kolbach at full value a "Standard Candle" is needed whereby to determine the correct answer.

I may have found one. Within Charles W. Bamforth's peer reviewed document titled "pH in Brewing: An Overview" such a standard candle may be found within the statement that "Taylor reports a lowering of pH in wort from 5.51 to 5.1 by increasing the level of calcium from 50 to 350 ppm." Bamforth's reference for this indicates that D.G. Taylor made this statement in 1990 within a document titled "The importance of pH control during brewing. MBAA Tech. Quart. 27: 131-136". This presumably independently derived observation of measured pH drop under the influence of increased calcium can be seen as a "Standard Candle" by which to test Kolbach.

But first, there is a catch. The problem with pH drop in association with ppm's of calcium within mash water is such that a mash thickness value and mash water volume must be assigned to it, as for example a 12 Lb. Grist mashed in 4.5 gallons of water (a mash thickness of 1.50 quarts per pound, or ~3.13 Liters per KG) at 50 or 350 ppm respective calcium would exhibit only 25 or 175 ppm calcium respectively if the same grist was to be 'no-sparge' mashed within 9 gallons of water. PPM is thereby a highly faulty means by which to approach the problem, and mEq's of calcium (and magnesium) are the solution to counter this weakness, as mEq's are independent of mash water volume. Now back to the story...

It turns out that for a mash in the mash thickness ballpark of roughly 1.5 quarts per pound (roughly 3 Liters per Kg.), and with buffering such that a composite grist that has an initial DI_pH of 5.58 falls to a pH of 5.51 when in the presence of 50 ppm of added calcium, will subsequently only exhibit a drop from 5.51 to ~5.1 (and thereby agree with D.G. Taylor) if Kolbach's calculated pH drop formula is taken at full 100% face value within the mash.

There are a lot of if's and presumptions being made here with respect to Taylor's observation, and there is also the possibility that Taylor merely used Kolbach's formula rather than independently measuring a drop from 5.51 pH to 5.10 pH when calcium was increased from an initial 50 ppm to a final 350 ppm, and we don't know the buffering nature of Taylor's grist or his chosen mash thickness, but if the general presumptions which I've made here stand and Taylor observed this fully independent of Kolbach, then Kolbach's observed pH drops which were measured downstream at "knock-out" are also fully valid for computing pH drop within the mash as well. And therefore so is Kolbach's formula derived to math-model the same.

I had formerly sided with only 50% of Kolbach in my most recent 'version 8.01' series release of 'Mash Made Easy', but with the D.G. Taylor "Standard Candle" to go by I will correct this to 100% in the soon to be released MME version 8.10.

 

[Silver_Is_Money]

The above should just about put a fork into water profiles based upon ppm (mg/L) of minerals, and perhaps particularly more so with respect to calcium and magnesium. As stated above, if one is to both mash and sparge in 4.5 gallons each of water, and a certain mEq value of calcium is added such that the mash water has 50 ppm of calcium, then another person reading the same water profile advice, but no-sparging in 9 gallons of water will have to add twice as many mEq's of Calcium to their water such as to also comply with 50 ppm. And twice as many mEq's of extant calcium will lower the mash pH noticeably more than for the sparging case accordingly.

It appears that the only honest way to express water profiles is based upon mineral mEq's. PPM (mg/L) is seriously flawed in this application. And to go even further in the right direction, the mEq's added should be in referenced lock step to the weight of the grist.

 

[Silver_Is_Money]

Could you imagine two people reading the very same water profile for the very same recipe and discovering thereby that a robust Porter or Stout recipe which has caught their interest is best mashed in 150 ppm alkalinity water, with the case being that one of the people sparges and one no-sparges? In keeping with 4.5 gallons and 9 gallons respectively, the person mashing in 9 gallons is going to experience a much higher mash pH than the person mashing in 4.5 gallons, because there is twice as much alkalinity in 9 gallons at 150 ppm vs. 4.5 gallons at 150 ppm. It's precisely the same situation as for the above calcium addition scenario, only in pH effect reverse. Both people think they are explicitly following the magic ppm water profile, yet one makes a good beer while the other makes a potential tosser. Magic PPM based water profiles must go, or alternately be constrained within highly specific mash parameters, whereby anyone deviating from the explicitly strict parameters must fully understand how to compensate accordingly and alter the water profile.

 

[mabrungard]

I have to wonder if the high 'degree of modification' in modern malts has an effect on this pH change. Back in Kolbach's day, the degree of modification was almost certainly lower and that could explain why the shift took longer.

 

[Silver_Is_Money]

I have to wonder if the high 'degree of modification' in modern malts has an effect on this pH change. Back in Kolbach's day, the degree of modification was almost certainly lower and that could explain why the shift took longer.

Since we have no indication from Kolbach that he ever measured the mineral induced pH drop within the mash, we will never know. Since in 1990 Taylor came very close to pegging Kolbach's results (and did so within the mash), my guess is that if Kolbach had taken his pH measurements somewhere within the middle to end of his mash cycles, the pH drop he quantified would likely have been found to already be present within the mash. But I can only guess here.

 

[eric19312]

I’m really trying to follow this analysis but lost on the terms. I guess the no sparge brewer is mashing with double the total number of ions from his salt additions vs the sparging brewer and so may end mash at closer to desired pH (pre boil kettle pH) but the sparge brewer is either going to add the other half of his salts to the sparge water or direct to the kettle. In the end going to have pretty similar ion concentrations in the kettle and so long as the mash was carried out in the rather widely acceptable mash pH range aren’t the brewers going to end up with pretty similar beers?

Another question...if point of this is to get to most accurate model for prediction of mash pH ... which version is working best for you? Model vs measurements? Why do we need to look Int decades old textbooks to puzzle this out seems simple test tube measurements should be able to answer the question directly.

 

[Silver_Is_Money]

It turns out to be the case that specifically for the criteria of a "Congress Mash" the only way to get Kolbach's formula for the depression of pH via the presence of Ca and Mg ions to fully comply with D.G.Taylor's presumed direct observation is to multiply Kolbach's 1950's era formula by a factor of ~0.80. I tentatively believe that Kai Troester (Braukaiser) observed much the same 0.8 factor (or ~20% less pH drop in mash) roughly a decade and a half ago. A careful read of Kolbach's dissertation shows that he was measuring the pH drop caused by adding calcium and magnesium to the mash water only at "knock-out" (which occurs well downstream of the mash). Potentially not all of the mineral induced drop occurs within the mash, and some additional drop in pH due to added minerals carries on through lautering and even perhaps the boil, such that it's full impact (as measured by Kolbach, and as present within his formula) can not be measured purely in the mash, but rather is measured only at knock-out.

The specific criteria of a "Congress Mash", as should be used by all knowledgeable beer process scientists so as to be as well as possible on the same page, is to mash 50 grams of malt(s) in 200 mL of water. Thus the established criteria indicates a mash thickness of 4 Liters per Kg. of grist (as opposed to the mash thickness guesses I had made earlier, as can be seen above).

I'm currently modifying Mash Made Easy to apply the ~0.8 x correction factor to Kolbach such that Taylor's observation of a 4L per Kg. thickness Congress Mash with 50 ppm Ca which mashes at a measured pH 5.51 will subsequently mash at a measured pH 5.10 when the Ca is bumped up to 350 ppm. If mEq measure is applied to mineral additions (as opposed to ppm measure), then the observed outcome as to mineral induced pH drop remains consistent across any mash thickness. I'm of course making the presumption here that both Taylor and Kolbach indeed performed "Congress Mashes" by which to perform their tests. Stay tuned for MME version 8.45.