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Old 11-01-2009, 03:29 AM   #1
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Default The effect of brewing water and grist composition on the pH of the mash

I'm pleased to announce that I finally finished my paper on “The effect of brewing water and grist composition on the pH of the mash”. To this point, this is my most detailed work and it represents data collected in experiments that I conducted during most of this year:


http://braukaiser.com/documents/effe...on_mash_pH.pdf


It all started with this discovery and blog post: http://braukaiser.com/lifetype2/inde...d=128&blogId=1
When I was writing a water spreadsheet, I noticed that chalk is not correctly considered for its alkalinity contribution in most of the water spread sheets that existed out there. 100 ppm CaCO3 is assumed to add only 50 ppm alkalinity as CaCO3. This didn't make sense to me and before I was going to tell others about this I thought I better run a few experiments to see what the actual alkalinity contributed by chalk would be. I ended up noticing an oddity in the mash pH resulting from water with undissolved and water with dissolved chalk that led me to do further investigation. But I didn't feel like stopping there and expanded the experiments to include the effects of various malts, calcium, magnesium, mash thickness and milling. The result is aforementioned paper.


But that paper is not intend to tell brewers how to build their water and calculate mash pH. At least not in understandable language. It makes a lot of assumptions of prior knowledge and unless you already have a good understanding of water chemistry in brewing it may not be of much practical use for you. In the following months I plan to write more practical and easier to understand articles which will be based on my findings during the experiments. I also want to update my water spreadsheet to include that data to allow for the estimation of the mash pH to a reasonable accuracy. Stay tuned for that.


Here are the new things that I found out.

  • The darker the lower the mash pH applies to most of the malts but there are a fair number of exceptions and the color → mash pH correlation is rather loose
  • cara type and base malts provide more acidity per unit of color than roasted malts. This is in direct contradiction to current knowledge but supported by titration and mash pH experiments.
  • Kolbach's work on pH in brewing has been misinterpreted to some extend. He was talking about the pH of the cast out wort while we are talking about the pH of the mash. I to didn't notice that until I reviewed his work more closely. In particular the pH change per ppm of CaCO3 residual alkalinity change is not 0.0017 pH but depends mainly on mash thickness. The thicker the mash the lower this number is (i.e. the less the pH changes with residual alkalinity changes)
  • the concept of residual alkalinity is a valid one but the neutralizing power of calcium and magnesium are not necessarily constant.
  • Chalk not dissolved by CO2 does a very poor job of raising pH. In particular above an addition rate of 9g for the 7.5 gal water used in 5 gal batches does little to change the pH and even below that it is not as effective as chalk dissolved by CO2. This may explain the recommendation not to exceed an RA of ~250 ppm as CaCO3 when building water.
  • Mash thickness effects how much effect the water has on mash pH

This may be a lot to digest right now and in the coming weeks and months I plan to revisit some of the water chemistry and mash pH discussions we had here and on the NB forum.


This comes in the shadow of being accused not to run my own experiments and arm-chair-quarterbacking by a prominent home brewing “celebrity”. What irony and now I can finally take care of that over there.


Acknowledgments go to A.J. DeLange who reviewed an early draft of the paper, gave valuable feedback and whose work on mash pH and water chemistry helped build the foundation for my understanding of the subject.


Prost (I just downed a celebratory half liter of Doppelbock),


Kai
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Old 11-01-2009, 05:07 AM   #2
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Thanks in advance for your work and testing, Kaiser. I'm looking forward to digesting your paper sometime when I haven't been into my stash of bourbon. I've a feeling this will require sharp wits,

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Old 11-01-2009, 05:13 AM   #3
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Kai, I haven't read the paper yet - but thanks for your posts and thoughts. I've learned a ton from you and it was cool to read your recent article in Zymurgy and think to myself - I know that guy! (well, in the interwebz way).

keep up the good work!

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Old 11-03-2009, 01:54 PM   #4
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I'll be taking a look, but not expecting to understand any of it. I'm still trying to understand basic brewing and water chemistry.

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Old 11-03-2009, 03:52 PM   #5
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Kai:

I'm taking down some notes as I read this, so please bear with me.

On page 6, you state:

Quote:
It can be argued that an exponential function the the data for
the pilsner malt grist better than a linear function.
I assume you mean the data for pilsner malt is better fit by an exponential function rather than a linear one. It's just a typo.

I've only read through the paper once so far, and one of the key things I take away from it is the difference in mash acidity for roasted vs. crystal-type malts. That suggests to me that when estimating salt additions via Palmer's methods, greater emphasis should be placed on the relative proportions of of crystal or roasted malt, rather than simply the estimated color of the wort. Any comments on whether the ranges of RA Palmer recommends for a given mash correlate with your acidity data?

Your work appears to provide a framework for more closely estimating mash pH via the summation of each grain's contribution to mash acidity, rather than by relying on the color alone. However, what doesn't seem clear to me yet is whether that increased accuracy represents a real improvement for the home brewer, or if Palmer's approximations are good enough.

I can sense a lot more math coming up ahead of my next brew. Guess I need a new probe for my pH meter, too.
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Old 11-04-2009, 02:01 AM   #6
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Sorry for the long post.

Kia this topic is very interesting to me, but a little over my head at this point as you mentioned it would be in your post. I've read posts on this board you have replied to theorizing about why thin mashes work. I also enjoyed the the pod cast with James Spencer recently. I can't tell you how many times I've listened to it.

I do full volume - no sparge mash (Brew in a Bag). Every beer I've brought to brew club meetings has been BIAB and I've got great reviews on them. We number our homebrew beers and have anonymous comment sheets for them so people can be honest without having to embarrass the brewer in front of a crowd.

I've been raked over the coals at club meetings with people telling me why BIAB won't work. They tell me I'll extract tannins, get poor efficiency, and make wort that will attenuate too much. I tend to do a 2 step mash with a rest at around 63C for 15-20 minutes, and another at 70C for 40-45 minutes for an APA (many compliments about character) and for a wit or hefe-wiessen I'll rest at 63 longer and 70 shorter. I did the steps like this as I thought it would be better to allow the grain to spend more time at the temps specifically for beta and alpha amylase, rather than try and split the difference at 67-68. I started to do this because I could (direct fired mash) and thought it would be interesting to see if it made a difference. I think it does.

The other thing I hear is using a lot more grain, but I don't. I run my recipe through StrangeBrew and use 75% as my expected efficiency and I usually pass that up and end up at 80% consistantly. The last few brews I've started to predict efficiency at 80% when entering my recipes.

Did I stumble across a nice tempurature combination to compensate for the highly fermetable wort with my rests? My attenuation is never higher than what I expect from the yeast. I also like the malt character my brews exhibit. I crush my grain quite fine because I can.

Am I just lucky with the last 11 beers I've brewed? I don't think so, but I can't explain to them why it works.

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Old 10-01-2010, 06:16 AM   #7
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Kai - if my mash finishes at say PH 5.8 with a ratio of 3L/Kg and I then double the volume of water to get 6L/Kg and vorlauf and drain - will this mean I am going to get astringency due to the PH having gone up above 6 due to the doubling of the ratio ? Could I add 5.2 to stop the second water addition causing the PH increase ?

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Old 10-01-2010, 12:02 PM   #8
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I don't think Kai posts here much anymore. You can contact him through his website though.

I will say that Kai was one of the several people who did experiments with 5.2 and a pH meter and found it to work very poorly.

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Old 10-01-2010, 02:55 PM   #9
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Quote:
Originally Posted by craigevo View Post
Kai - if my mash finishes at say PH 5.8 with a ratio of 3L/Kg and I then double the volume of water to get 6L/Kg and vorlauf and drain - will this mean I am going to get astringency due to the PH having gone up above 6 due to the doubling of the ratio ? Could I add 5.2 to stop the second water addition causing the PH increase ?
You may consider using food grade acid to lower your mash pH
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Old 10-05-2010, 04:04 AM   #10
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Thanks Maida, would I need to add acid if my sparge water is very soft ? or would the mash already contain enough buffering power to lower the high alkaline sparge water by itself ?

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