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Old 05-15-2011, 04:21 PM   #1
sdbrew1024
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Default Mash pH

I finally got a working pH meter and just took my first mash pH reading. However, I just realized that I completely forgot if I should care about the pH at mash temps or at room temp. My reading was a pH of 5.54 with a sample temperature of 115*, with the auto temp correction feature activated. With that information, do I have a good mash pH or not?

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Old 05-15-2011, 06:04 PM   #2
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I'm assuming the temp correction function works so I would say you have a good reading...a touch high from ideal but within the range of things being gtg.

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Old 05-15-2011, 06:17 PM   #3
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So I want a pH of 5.2-5.5 after temp correction, IE at room temp? Just double checking, I thought I had read somewhere that the pH difference of the same sample at room temp and at mash temps is about 0.3, so if I understood that correctly then my reading of 5.54 at room temp would mean that the mash is 0.3pH different from that one way or another. Is that correct, and if so which pH is the one I care about?

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Old 05-15-2011, 06:42 PM   #4
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Quote:
Originally Posted by sdbrew1024 View Post
I finally got a working pH meter and just took my first mash pH reading. However, I just realized that I completely forgot if I should care about the pH at mash temps or at room temp. My reading was a pH of 5.54 with a sample temperature of 115*, with the auto temp correction feature activated. With that information, do I have a good mash pH or not?
ATC corrects for the response of the probe to a given pH. Thus, properly calibrated with ATC on if you read 5.54 at 115 °F then the actual pH at 115 °F is very close to this.

Now the pH of most things changes with temperature. This effect is completely independent of the electrode response effect I mentioned above so that ATC does not compensate for it. As we control mash pH in order to control the performance of enzymes in the mash tun we would love to know what the pH is at mash temperature but this is not practical. You will have, for example, different pH's at dough in, protein rest, saccharification rest, dextrine rest and mashout temperaures. The pH will be different depending on grist and water composition. Dramatic temperature changes are hard on pH electrodes. In the days when pH was first measured in breweries the pH meter did not fit conveniently in your pocket - it took up a fair amount of space on a bench in the lab. For all these reasons, therefore, pH is measured at room (lab) temperature in most cases and you should assume that any pH you see listed in a textbook, magazine article or on the web refers to room temperature unless otherwise stated. You will sometimes be misled because people have published mash temp pH data without stating that it is mash temp. I think this is less likely the more recent the publication.

A change of 0.3 between mash and room temperature is often quoted without saying what mash and room temperature are. In my own experience I have found the change to be about 0.0054 pH/°C. The 0.3 shift thus corresponds to 55.6°C and if room/lab temp is 21 °C then mash temp would be 76.6 °C ~ 170 °F which is closer to mashout temperature than mash. Your reading at 115 °F ~ 46 °C would be (46 - 21)*0.0054 = 0.14 pH unit lower than at lab temp. The lab temp pH would then be 5.68 and this is what you would report and what you would be comparing to the 5.4 - 5.5 recommendation.

In the future cool the sample and measure at room temp. Your electrode will last longer and you will be comparing your apples to other peoples' apples.
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Old 05-15-2011, 08:32 PM   #5
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Thanks for the info!

So just to be 100% clear, I should cool my samples to room temp, then take the pH reading, and that reading is what I want to be between 5.4-5.5?

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Old 05-15-2011, 08:50 PM   #6
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That's it.

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Old 05-20-2011, 07:14 AM   #7
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murphy and sons in the uk who supply dwb and crs water treatments recomend ph levels of between 5.2-5.8

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Old 05-20-2011, 12:34 PM   #8
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murphy and sons in the uk who supply dwb and crs water treatments recomend ph levels of between 5.2-5.8
While that range works, its actually too broad to be truely useful. A more precise range is 5.3 to 5.5. Allowing the mash pH to fall into the 5.2 range or lower produces a noticeably tart beer. That can be a good thing for some styles. Allowing the mash pH to exceed about 5.6 can present a rougher and duller taste in the beer and I find that the mash efficiency falls also.
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Old 05-20-2011, 12:52 PM   #9
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Allowing the mash pH to fall into the 5.2 range or lower produces a noticeably tart beer.
I wonder if this is a case of correlation rather than causation. British brewers tend to strive for lower mash pH than German brewers (which makes the recommended upper limit of 5.8 by a UK company that sells acid seem strange) but it seems to me that what sets the beer pH (and hence the sensation of tartness) would be the pH that the yeast establish for themselves. Ale yeast like lower pH. Given that you pitch a sufficiency of healthy yeast into a wort that isn't ridiculously low or high WRT pH I would expect the yeast to be in charge of the fermentation and thus final beer pH. My experience seems to confirm that this is the case but is hardly the universe of brewing. ???


[EDIT] But I do note that Kolbach commented that a decrease in wort pH of 0.3 corresponded to a reduction of 0.1 pH in the beer. But also that research has shown that it is not pH that determines the impression of tartness so much as the total acidity.
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Old 06-27-2011, 04:44 PM   #10
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So given the 5.3 to 5.6 "optimal" range -- how does one target an appropriate pH for a given style? (Or is this not a good idea to link pH targets with styles -- except for maybe sours and pales? Do I want to target an a slightly less acidic mash as the SRM goes darker given the fact that the darker grains will -- in general -- decrease my pH?)

I brewed an Irish Red this weekend. Mash pH was on the low end (due to 8.75# grain bill with 3 oz. acid malt and a few grams each of gypsum and CaCl2). I ended up measuring 5.21 @ room temp 45 mins into the mash. Bru'n was telling me a pH of 5.3 based on my water and grain bill -- so I was a bit surprised to see it go to 5.2 midway through the mash after I'd pulled several earlier samples and cooled to see a 5.4 pH. But I assume this 5.2 is okay -- or at least within a fairly normal range. I do worry, however, if this is going to be tart -- but we'll see. I assume that my yeast will very much enjoy this particular brew given the pH.

Target SRM, I believe, was around 10 based on the grain bill.

Do I want to target slightly higher pH levels as the SRM increases? In other words, 5.2 for pales but maybe 5.5 for porters or stouts? ANd maybe I should aim for 5.3 for an Irish Red like this? Or is the idea (again, in general) to simply fall within the optimal range and avoid either extreme?

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