I have been brewing over the last 14 years with a herms system. I usually grab a small sample of wort from the top of the mash (10 minutes into the mash) and measure my mash pH. Today I was helping my son brew a batch of pale ale. He was doing a no-sparge mash in a cooler. Water to grain ratio was 2.48. He does not recirculate the mash. At 10 minutes, I pulled a sample from the top of the mash and was shocked to measure a pH of 4.89. Bru'nwater predicted a pH of 5.28. I obtained another sample 10 minutes later and obtained a similar result. I checked a preboil pH in the BK and it was 5.39. Was this low mash pH from the thin mash and/or lack of mixing? In non-recirculating systems, should one vorlauf prior to obtaining mash pH sample?
mash pH in thin mash (no sparge)
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Yes definitely. This is what finally pushed me to get a RIMS tube.
You will lose a bunch of heat in the vorlauf or stirring the mash.
You will have to add it back somehow.
You could try reserving some water from the mash, boil it and add it to the mash after stirring or vorlauf and drawing your sample.
I found stirring to be inadequate. Not only for pH during mash, but for gravity after sparge as well.
I’ve given up on stirring.
Even a march pump wide open, drawing off the bottom and returning on a tangental port 2/3 of the way up the wort for 15 minutes doesn’t do it.
You will lose a bunch of heat in the vorlauf or stirring the mash.
You will have to add it back somehow.
You could try reserving some water from the mash, boil it and add it to the mash after stirring or vorlauf and drawing your sample.
I found stirring to be inadequate. Not only for pH during mash, but for gravity after sparge as well.
I’ve given up on stirring.
Even a march pump wide open, drawing off the bottom and returning on a tangental port 2/3 of the way up the wort for 15 minutes doesn’t do it.
Silver_Is_Money
Larry Sayre, Developer of 'Mash Made Easy'
Pale malts are "effectively" basic with respect to typical mash pH targets. There is clearly no mechanism aside from acid addition or acid malt addition which could conceivably result in such a false low pH reading. I presume this might likely be a case whereby the requisite and pre-determined acid addition was made directly to the mash, and not to the mash water pre the mash, whereby it could receive adequate mixing to uniformly disperse it. Or a case of inadequate stirring during the mash. Or both. It is assuredly a case of premature sampling, which inevitably will yield a false low pH reading to begin with (whereby the solution to this delema is to never sample until at least 30 minutes have gone by in the mash, and to stir, stir, stir). If the pre-boil pH was 5.39, this reading is a much better reflection of the actual mash pH conditions. My preferred time to sample mash pH is at the 60 minute mark of the mashing step, but others agree that 30 minutes is the earliest sampling point with any level of validity.
Other reasons for a false low pH reading include:
1) Stirring the sample with the pH probe and taking the pH reading while stirring
2) Not allowing the pH probe to sit in an undisturbed sample for up to several minutes to fully stabilize
3) Reading pH on a sample that is above room temperature, and incorrectly presuming that ATC will correct for this.
Other reasons for a false low pH reading include:
1) Stirring the sample with the pH probe and taking the pH reading while stirring
2) Not allowing the pH probe to sit in an undisturbed sample for up to several minutes to fully stabilize
3) Reading pH on a sample that is above room temperature, and incorrectly presuming that ATC will correct for this.
Could happen (and frequently does, at least at first) where acid is added to the strike water. Especially in a case like this where the acidified water is not well mixed with the grist. It doesn't react with the alkali in the malt and stays acid.
Thanks for your replies. Phosphoric acid, calcium sulfate and calcium chloride were added to the strike water prior to heating. Mash was stirred when we mashed in and at 10 and 20 minutes into the mash (prior to obtaining the two samples). We mashed 60 min and then recirculated for 5 min with a pump prior to transfer to the BK. I am confident in my pH reading. I do not think it was falsely low. My current theory is the low mash pH resulted from inadequate mixing and the very thin mash, but I am certainly willing to entertain other ideas.
Again, a thin mash increases dilution and hence raises PH...
As for inadequate mixing, grains release acids which will lower PH. I don't see how inadequate mixing would give you a lower PH value which will then rise later as the mash is mixed? To achieve that the grains would have to somehow reabsorb some of the protons which is absurd.
As for inadequate mixing, grains release acids which will lower PH. I don't see how inadequate mixing would give you a lower PH value which will then rise later as the mash is mixed? To achieve that the grains would have to somehow reabsorb some of the protons which is absurd.
This is true if the water is alkaline but it is not the dilution that causes the pH to increase. It is the increased alkalinity. If RO water is being used the alkalinity is so small (even pure water has some alkalinity) that the increase in volume has a very small effect on pH.
The high kilned malts do but with the base malts it is just the opposite. They absorb protons.
As that is exactly what happens (except that there is no reabsorption as no protons were ever given off) it is hardly absurd. If, for example, you add 2 mL of 88% lactic acid to 10 gal RO water you will have water at pH 3.6. If you now dump in 30 lbs Crisp Maris Otter (which has a DI mash pH of 5.69) it clearly isn't going to pass protons to water at pH 3.6. It's the other way round. It will absorb protons from the water whose pH, as a consequence, will rise. But over time as the water is mixed with and penetrates the grist particles. Thus the pH of the liquid increases over a half hour or so until it reaches pH 5.65 at which point the system is near equilibrium.
Silver_Is_Money
Larry Sayre, Developer of 'Mash Made Easy'
Sampling too early in acidified water (which is partially wort and partially acid/water at this juncture) combined with inadequate mixing and incomplete grain level absorption (directly related to sampling too early and inadequate mixing) is the only mechanism I can imagine which could result in a pH of 4.89 for a pale ale.
When all of the initial acid/water/mineral mix has fully permeated every last vestige of a hideout within the grains, only then can pH equilibrium be achieved, and therefore only then should a mash pH sample be taken. The environment here is a continually rising mash pH environment, until equilibrium is achieved. That is why pre-boil it measured pH 5.39. And why the true mash pH was also 5.39, but only for the specific case whereby this mash was undertaken as a no-sparge process.
When all of the initial acid/water/mineral mix has fully permeated every last vestige of a hideout within the grains, only then can pH equilibrium be achieved, and therefore only then should a mash pH sample be taken. The environment here is a continually rising mash pH environment, until equilibrium is achieved. That is why pre-boil it measured pH 5.39. And why the true mash pH was also 5.39, but only for the specific case whereby this mash was undertaken as a no-sparge process.
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I am guessing that this commonly occurs in thin mashes that are not recirculated (no-sparge and BIAB). I think it would be much less pronounced in a more traditional 1.25-1.75 qt/lb mash.
It's quite common in mashes of normal thickness too. I'm sure not circulating exacerbates this though.
For my recipes, the mash thickness using a RIMS BIAB system is always between 2.0 to 2.5 qt/lb. I also recirculate the mash the entire time and take a pH reading at 30 minutes. Preparing my brewing water the night before or the morning of brewday I've never experienced what the OP describes. If the mash was thoroughly doughed into consistency I'm not sure why the readings would vary by such a wide range.
