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/effect_of_water_and_grist_on_mash_pH.pdf


It all started with this discovery and blog post: http://braukaiser.com/lifetype2/index.php?op=ViewArticle&articleId=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

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,

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!

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.

Kai:

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

On page 6, you state:

It can be argued that an exponential function the the data for
the pilsner malt grist better than a linear function.

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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.

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.

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 ?

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.

craigevo said:

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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You may consider using food grade acid to lower your mash pH

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 ?

craigevo said:

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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It depends. Some people do use acid in their sparge water. Another option would be to use RO or distilled water for the sparge.

Acid can be useful but just like anything else, too much is not a good thing. Overdoing it with lactic acid will impact your beer flavor.

Kaiser,

Your website, braukaiser.com, is quickly becoming my greatest resource for brewing. You taught me how to decoction mash. And, I recently read your article about using CO2 to dissolve chalk, and I am amazed! I used your water profile spreadsheet and everything was perfect!

Tomorrow I'm brewing a maibock with a bit of help from your maibock page, and for the first time I doubt I'll need ph buffer. I plan to do the enhanced double decoction.

If your ever in LA drop by for a brew. And if you want a place to host your website, I can carve out some free space for you on my VPS. PM me if your interested.

Thanks for all your great work!

hollywoodbrew said:

Kaiser,

Your website, braukaiser.com, is quickly becoming my greatest resource for brewing. You taught me how to decoction mash. And, I recently read your article about using CO2 to dissolve chalk, and I am amazed! I used your water profile spreadsheet and everything was perfect!

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Thanks.

The idea of dissolving the chalk is one of those things where we can argue about tangible benefits, but it’s also were we brewers can express our inner geek when it comes to water treatment

…, and for the first time I doubt I'll need ph buffer.

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I like that

Thanks for the offer to host. I’m pretty happy with my hosting provider though.

Kai

Kaiser said:

[*]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.

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I didn't notice that when I translated his paper! But if we assume (probably a shaky assumption) a more or less constant drop in kettle pH we're probably still OK using this for rough calculation - it's the slope that is really of value (i.e. how much pH falls as caclium hardness increases) not the absolute drop. The shakiness of the assumption of constant drop is probably swamped by the shakiness of the assumption that the slope is 0.00168 pH/ppm. In the limited measurements I've done the slope has been all over the map to the point that I question my technique.

Kaiser said:

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)

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That only makes sense - the change should depend on the buffering strength.

Kaiser said:

[*]the concept of residual alkalinity is a valid one but the neutralizing power of calcium and magnesium are not necessarily constant.

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I guess I feel that RA should be used for what it was intended: comparing water supplies. This includes, of course, water that has been treated. Where water is decarbonated RA will change. When calcium salts, other than carbonate are added, RA decreases. Where brewers get into trouble is when they add carbonate to water without dissolving it properly. This is the problem with the popular spreadsheets - they assume that chalk is just like any other salt. It isn't.

Kaiser said:

[*]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.

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The problem is that the rate at which acid can dissolve chalk and convert carbonate to bicarbonate appears to change with pH. It becomes very slow as pH rises above 5. It takes hours for the acid to do it's job. Of course if you put in more chalk than there is acid available to dissolve it you will never see its full effect but even if you add a reasonable amount it may take several hours for you to see the full effect. Note: conclusion based on simple experiment with chalk and hydrochloric acid. It's more complex with actual mash where phosphate drops chalk releasing hydrogen ions and lowering pH - thus nullifying the effect of the chalk to some extent.

Kaiser said:

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

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Well you are to be congratulated on doing a lot of hard work! To further indicate my support I believe I will also go down a quantity of Dopplebock. [/QUOTE]

ajdelange said:

I didn't notice that when I translated his paper!

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I didn’t pick up on that at first either. Maybe because I never questioned that the 0.03 pH drop for every 1 dH alkalinity change refers to mash pH. I have to check at home, but it is my recollection that he (Kolbach) never mentions mash pH and only talks about cast-out pH. It seems that the cast-out wort pH has mattered to German brewers more than or as much as the mash pH. The ultimate goal seems to be a beer pH close to 4.0. The cast out wort pH is affected not only by the mash but also by the minerals in the sparge water and the pH drop in the kettle. He also talks about wort buffers and how they affect pH drop during fermentation. This, however, is a different topic.

The shakiness of the assumption of constant drop is probably swamped by the shakiness of the assumption that the slope is 0.00168 pH/ppm. In the limited measurements I've done the slope has been all over the map to the point that I question my technique.

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I have measured this slope a few times as well and I’m convinced that it is best expressed as mEq/(kg*pH). I.e. calcium hardness per unit of grain weight and pH change. This takes the mash thickness out of the picture which seems to make sense since the buffer in the mash is the grain and what’s changing this buffer’s pH are the minerals, acid and basses that are added to the grain or that react with the grain.

I guess I feel that RA should be used for what it was intended: comparing water supplies. This includes, of course, water that has been treated. Where water is decarbonated RA will change. When calcium salts, other than carbonate are added, RA decreases.

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I agree and I started to move away from using RA to estimate mash pH. However, I have not yet made these updates to my water spreadsheet. In the end the difference is mainly the treatment of Ca and Mg and how much their presence changes the pH.

The problem is that the rate at which acid can dissolve chalk and convert carbonate to bicarbonate appears to change with pH. It becomes very slow as pH rises above 5. It takes hours for the acid to do it's job. Of course if you put in more chalk than there is acid available to dissolve it you will never see its full effect but even if you add a reasonable amount it may take several hours for you to see the full effect. Note: conclusion based on simple experiment with chalk and hydrochloric acid. It's more complex with actual mash where phosphate drops chalk releasing hydrogen ions and lowering pH - thus nullifying the effect of the chalk to some extent.

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I think that this might be a key observation and I hope we can design and run more experiments to support this. It also means that chalk only relases as much calcium into the mash as it contributes alkalinity to a pH rise. In order words, if the addition of chalk only adds 50% of its alkalinity potential, then only half of the chalk’s calcium is added to the mash/beer. This is something that water spreadsheets, that tolerate undissolved chalk, don’t do.

Well you are to be congratulated on doing a lot of hard work! To further indicate my support I believe I will also go down a quantity of Dopplebock.

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Yes, that was a nice one. Another batch is currently fermenting.

Kai