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Old 11-15-2009, 02:59 AM   #1
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Default Mash pH and Full Volume / No Sparge Mash

I wasn't sure where to put this post. I can see it here or brewing science .

I've been taking notes the last few brew sessions. I'm curious about some things that people caution me about with Full Volume / No Sparge Mash (Brew in a Bag). I don't ever adjust my grain bill to compensate for this mashing technique.

The results of this session is the same as the last 3 sessions. I check my pH after putting grain in the water and mixing well. The pH is 5.3 minutes into the mash. I haven't treated the water with anything. I've only carbon filtered the water. 30 minutes in to the mash I checked the pH again expecting maybe the pH might have risen. It never does. I get the same readings throughout the mash.

I've been doing iodine test also and usually after 30 minutes I have a negative iodine test (no color change I hope I used the term “negative iodine test”correctly).

Is my pH consistent because the grain keeps it that way. It seems to adjusts itself to 5.3 each mash. I've read and many have told if the liquor to grist ratio creates too thin of a mash it would increase pH. As a result it would extract more tannins. I'm using anywhere from 2.75 quarts per pound to 3 quarts per pound.

Does the grain just seek to have a pH it needs to do the conversion?

The Mash for this batch:
Heated 7.5 gallons strike water to 66C and dumped in grain. Grain temp settled in at 63C. Mashed 40 minutes 63C, 20 minutes 70C, and 10 minutes 77C. The other 2 batches I've done have had 20 min 63C rest and 40 min 70C rests.

Tonight's recipe:
Pre-boil gravity is 1.052 (predicted 1.051 with 75% efficiency)
Post boil gravity 1.061 (predicted 1.060 with 75% efficiency)

3 lb. 2-row
5 lb. Wheat malt
1 lb. crystal 120L
2 oz. chocolate
2 lb. Munich
1 lb. Belgian aromatic

2 previous batches recipes:
2 of my my grain bills have been
9 lbs American 2 Row
1 lb. American crystal 40L



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Old 11-15-2009, 05:22 AM   #2
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Are you asking how the grain will lower the pH? That's a good question that I also would like to know the answer to. However, the concept of a thinner mash yielding a higher pH is intuitive because whatever acid compounds are being released, their concentration is being decreased by the increased amount of water which would yield a more unchanged (higher) pH. Also: 3 quarts per pound seems a little high, don't you think? I've been using around 1.5 quarts per pound.



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Old 11-15-2009, 06:20 AM   #3
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The thing about pH is, it's a logarithmic scale. pH is defined as the negative logarithm of the hydrogen ion concentration:

pH = -log [H+]

in other words, at pH 5.2 there are around 6.3 X10^-6 mol/l (e.g. 10^-5.2) of hydrogen ions floating around.

To simplify, let's say that the hydrogen ions all come from the grain, and the water has no buffering capacity. What happens if you go from a typical mash at 1.5 qts/lb (forgive my mixed units) to a thin one with 3 qts/lb of water? The concentration of hydrogen ions would be halved to 3.15 X 10^-6 mol/l.

So, what's that pH?

- log (3.15 X 10^-6) = 5.50.

So, doubling the amount of water would (in this simplified and theoretical condition) lead to an increase in mash pH, from 5.2 to 5.5. In other words, doubling the amount of water leads to only a shift of about 0.3 pH. Now, combine that with the effects of the buffering capacity of "real" water (not to mention the use of buffers like Five Star's pH5.2) and the actual effect seems, at least to me, to be essentially negligible for the home brewer.

Kaiser did some nice real-world experiments on this exact issue -- his results are at http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdf

3 qts / lb is not anywhere near too thin a mash for a no-sparge brewing process.

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Old 11-15-2009, 03:42 PM   #4
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amercuric I was asking if the mash will naturally seek a pH of 5.2 (or somewhere around that pH with all other mash parameters equal). Meaning if I my water had a pH of 14 and someone else had a pH of 8 would the mash to achieve 5.2 in both cases.

jds.. wow thanks for that. I've been "trying" to read Kia's research. A bit over my head, but I'm trying to understand. I've read through it a couple of times.

I found this post http://www.homebrewtalk.com/f36/mash-thickness-fermentability-135838/ has a link to a brewing science pdf http://rapidshare.com/files/107178743/Brewing_Science_and_Practice__2004_.pdf. Section 4.3.6 and 4.3.7 have some good material about mash thickness. The thread is similar to what I'm talking about but the OP is talking about thickening the mash. The sections above cover wort that is highly fermentable or one that is less fermentable by varying times and temps. I made some educated guesses on my times/temps for my mash. I think I have them pegged. If I want a highly fermentable wort for a wit or wheat beer I keep the lower mash temps longer and vice versa for one that I want some malt backbone and more mouth feel. Its really like a single infusion mash when they hold a temp in the lower 150's for something that needs a low FG and in the high 150's for something with more body.

3 qts/lbs is about as high as I will be on the liquor to grist ratio. I can see it being a bit higher on a session beer though. That ratio would be 4.6/1. So -log(2.1 X (10^(-6))) = 5.68. I think that is correct. I took your equation and plugged in 2.1 which is 1/3 of 6.3. I figured a ratio of 4.6/lbs (6.5 lbs grain in 30 qts water). It worked nicely that session beer ratio was 3 times the amount at roughly 4.5 (3 X 1.5).

At some point in the near future I'll be giving a talk at my brew club meeting about Full Volume / No sparge mashing (I think people are more receptive to that term as opposed BIAB). Trying to get my arguments prepared for the "it won't work" crowd who have never even considered trying it.

One of the big arguments is high mash pH. So I thought I'd start to documents my mash pH and perform iodine tests. The other is the beer will be too dry for many styles, and while it may be a good technique for a light and dry beer its not a good option for a beer with a higher FG and some sweetness left. In other words it will attenuate too much. I have all my FG readings that tend to be on the high side of the attenuation percentage, but I also got this with “normal” mashing.

I get predictable mashes with this technique and a predictable fermentation also. With the ability to control the mash parameters by direct firing if needed and I can perform multi-step mashes. Which the pdf above seems to indicate will result in a better conversion over all even with “highly modified malts”. Which is another thing that seems to bother people. Why a multi-step mash? You don't need to do that. They're right, but I can and I think it makes a difference. You don't need to do a starter either, but it helps.

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Old 11-15-2009, 06:18 PM   #5
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Quote:
amercuric I was asking if the mash will naturally seek a pH of 5.2 (or somewhere around that pH with all other mash parameters equal). Meaning if I my water had a pH of 14 and someone else had a pH of 8 would the mash to achieve 5.2 in both cases.
Starting with relatively neutral water (~pH 7) without too many minerals, the mash will end up around pH 5.2.

High mineral concentrations and acidic or alkaline water will not.
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Old 11-15-2009, 06:36 PM   #6
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Originally Posted by david_42 View Post
Starting with relatively neutral water (~pH 7) without too many minerals, the mash will end up around pH 5.2.

High mineral concentrations and acidic or alkaline water will not.
I guess this would depend on how high the malt was kilned?
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Old 11-15-2009, 06:54 PM   #7
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Quote:
Originally Posted by jds View Post
The thing about pH is, it's a logarithmic scale. pH is defined as the negative logarithm of the hydrogen ion concentration:

pH = -log [H+]

in other words, at pH 5.2 there are around 6.3 X10^-6 mol/l (e.g. 10^-5.2) of hydrogen ions floating around.

To simplify, let's say that the hydrogen ions all come from the grain, and the water has no buffering capacity. What happens if you go from a typical mash at 1.5 qts/lb (forgive my mixed units) to a thin one with 3 qts/lb of water? The concentration of hydrogen ions would be halved to 3.15 X 10^-6 mol/l.

So, what's that pH?

- log (3.15 X 10^-6) = 5.50.

So, doubling the amount of water would (in this simplified and theoretical condition) lead to an increase in mash pH, from 5.2 to 5.5. In other words, doubling the amount of water leads to only a shift of about 0.3 pH. Now, combine that with the effects of the buffering capacity of "real" water (not to mention the use of buffers like Five Star's pH5.2) and the actual effect seems, at least to me, to be essentially negligible for the home brewer.

Kaiser did some nice real-world experiments on this exact issue -- his results are at http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdf

3 qts / lb is not anywhere near too thin a mash for a no-sparge brewing process.
Thanks for clearing this up. It seems I need to take Qualitative Analysis to sharpen up on my water chemistry. You can never learn too much!
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Old 11-16-2009, 01:13 AM   #8
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Quote:
Originally Posted by bigjoe View Post
3 qts/lbs is about as high as I will be on the liquor to grist ratio. I can see it being a bit higher on a session beer though. That ratio would be 4.6/1. So -log(2.1 X (10^(-6))) = 5.68. I think that is correct. I took your equation and plugged in 2.1 which is 1/3 of 6.3. I figured a ratio of 4.6/lbs (6.5 lbs grain in 30 qts water). It worked nicely that session beer ratio was 3 times the amount at roughly 4.5 (3 X 1.5).
Whoah!

The numbers I gave you were meaningless, back-of-the-envelope calculations. The actual pH of any given mash will depend on a complicated relationship between the specific grains you choose, the specific parameters of your water supply, and any adjustments you make. All I was trying to do was illustrate how little a big change in mash thickness affects mash pH. There are a lot of other factors at play too, so please don't try to do anything useful with my vastly oversimplified example.

The whole point I was trying to make is this: At a given mash thickness and pH, doubling the amount of water would only increase the mash pH by about 0.3, all other things being equal.

In reality, all other things are NOT equal, but as far as I can see, those inequalities tend to buffer the mash more than they tend to move the pH out of optimum ranges.
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Old 11-16-2009, 01:55 AM   #9
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Looking at Kia's paper. It does indicate a rise in pH with thinner mashes. Its pretty much in line with the "theoretical condition" mentioned above. There is a rise in pH, but its not much.

I think we are saying the same thing. If I mash thick or thin, the only parameter is the tickness of the mash. So with the same grain bill, and water supply, one with thin and one with thick, the increase is minimal. I'm not going to get a wildly high pH mashing thin. I may do an experiment of my own to see how much the ph rises with a REALLY thin mash compared to a "normal" 1.5qt/lb.

I get that it will vary with the grains used and the quantities of each in the grist.

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Old 11-19-2009, 04:26 AM   #10
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I've continued to look at the information in the Brewing Science and Practice pdf above.

Page 117 Table 4.14 has a chart with mash thicknesses various percntages listed. The extract ratio for what they are calling a thin mash 2:1 liquor/grist is only slightly less than the the 4:1 ratio. The 4:1 ratio also beats the the thin mash by slight margin in most of the categories. In the categoreis that the thin mash does better is an extremely small margin.

I think Kia's research article does demonstrate that a thinner mash indeed raises the pH, but in the ratios I'm working with (mostly 3:1) the increase is minumal and if needed I could adjust the mash water pH to overcome it. The pdf also examines pH and water/grist ratios with similar results.

As I mentioned in a previous post I'm working on a presentation for my homebrew club. So far everything I've read has support my anecdotal experiences.



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