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Old 07-21-2009, 01:30 AM   #1
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Default low mash pH results in "sour" taste?

After reading a response in an earlier post (http://www.homebrewtalk.com/f128/wha...ash-ph-128855/), I may have figured something out that was bothering me. I'm hoping someone can let me know if I'm on the right track.

A stout I entered into a homebrew competition fared pretty well, but the judges detected a sour/tart flavor that detracted from the overall brew. I have not been able to figure out where this may have come from (and must admit, my palate does not seem refined enough to really taste it).

I recently received my water report and discovered that my residual alkalinity is quite low (12-15 ppm) and, overall, my water is more suited, as is, to pilsners than to stouts.

So, this is what I am thinking: When I did my partial mash, my residual alkalinity was not enough to counteract the acidity of the dark grains, resulting in a low mash pH. The low mash pH resulted in a more acidic-than-desired beer, so the beer turned out sour enough to be noticed by a panel of beer judges.

This was only a partial mash, with a partial boil, but do you think I'm on to something?

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Old 07-21-2009, 02:02 AM   #2
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This was only a partial mash, with a partial boil, but do you think I'm on to something?
With the caveat that I never brewed extract or partial mash beers, yes I think you're on to something. It was either that or you had a mild infection. What was the pH of your water (liquor)?
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Old 07-21-2009, 02:28 AM   #3
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With the caveat that I never brewed extract or partial mash beers, yes I think you're on to something. It was either that or you had a mild infection. What was the pH of your water (liquor)?
Good question, but, unfortunately, I have no idea. I only recently began thinking about the consequences of my water chemistry. I'll be checking it in future batches.

BTW, does the pH typically change from liquor to wort to beer? What is a typical pH for a finished beer (still in the 5.2-5.6 range?)

I don't think I had an infection - I'm still drinking the stout 6 months later and I don't perceive any problem.
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Old 07-21-2009, 01:08 PM   #4
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The average beer pH is in the low 4.Xs. The pH of the solution, from liquor to beer reduces throughout the process. You'll see it stated on here that the pH of the brewing liquor doesn't matter, that it's only mash pH that matters. This is an overstatement at best. The pH of the liquor does matter, especially if it is in an extreme range. For example, if your water pH was already 5.5, and you brewed with dark grains, the pH would likely go lower than than the optimum range, resulting in increased enzyme activity that breaks down insoluble protein and decreased enzyme activity that would have broken down starches, resulting in a hazy beer with lowered foam stability and increased sourness due to the lower final beer pH.

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Old 07-21-2009, 03:50 PM   #5
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The average beer pH is in the low 4.Xs. The pH of the solution, from liquor to beer reduces throughout the process. You'll see it stated on here that the pH of the brewing liquor doesn't matter, that it's only mash pH that matters. This is an overstatement at best. The pH of the liquor does matter, especially if it is in an extreme range. For example, if your water pH was already 5.5, and you brewed with dark grains, the pH would likely go lower than than the optimum range, resulting in increased enzyme activity that breaks down insoluble protein and decreased enzyme activity that would have broken down starches, resulting in a hazy beer with lowered foam stability and increased sourness due to the lower final beer pH.
OK. So, if I take the pH of my beer that has been sitting in a bottle for a few months, at what pH would I expect to get a sour/tart flavor? <4? Also, wouldn't the amount of carbonation affect the pH?
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Old 07-21-2009, 04:12 PM   #6
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For example, if your water pH was already 5.5, and you brewed with dark grains, the pH would likely go lower than than the optimum range,
It's still the buffering capacity of the water (alkalinity in most cases) that matters. If your water pH is low, then the alkalinity is likely to be low as well. You can have soft water that has a pH of 5.5 (you'll have to add some acid to it as it will not be there naturally) and when you add malt to it the malt may even pull it towards 5.7. This would be the case with Pilsner malt for example.

I think that pH of the brewing water matters very little if the alkalinity (not bicarbonate) is known as it is a direct measure of how much acid it takes to lower the water's pH to 4.3 (or any other reference point that the lab set for alkalinity testing). The pH of the water factors into the alkalinity but only to a small amount. Distilled water with a pH of 7 has an alkalinity of 2.5 ppm CaCO2 just because it takes 2.5 ppm CaCO3 acid equivalents to lower the pH to 4.3 in this unbuffered system.

But yes, the dark grains and the soft water are likely the culprit in your case.

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Old 07-21-2009, 04:13 PM   #7
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OK. So, if I take the pH of my beer that has been sitting in a bottle for a few months, at what pH would I expect to get a sour/tart flavor? <4? Also, wouldn't the amount of carbonation affect the pH?
I'm not 100% sure at which pH sourness starts to be noticeable. You're probably right in presuming <4.0.

As for carbonation, I would think the more carbonated a beer is, the more acidic it would be due to increased carbonic acid, but this effect may be lower than the other factors that affect final beer pH. In other words, taking the same average pH beer (say 4.2 prior to carbonation) at 2.0 volumes CO2 and at 3.0 volumes CO2, how much more acidic would the latter be? It might not be that dramatic. But when you're taking a beer that already has a relatively low pH, the effect of carbonic acid could exacerbate sourness. Just thinking out loud here.
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Old 07-21-2009, 04:24 PM   #8
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You can have soft water that has a pH of 5.5 (you'll have to add some acid to it as it will not be there naturally) and when you add malt to it the malt may even pull it towards 5.7. This would be the case with Pilsner malt for example.
I don't disagree with anything you said, but that naturally soft water can't have a pH as low as 5.5. My well water is very soft and has a pH of 5.7 (according to Ward Labs). It doesn't seem like a stretch to think that soft water can have a lower pH than that.

But, that being said, I definitely have more to learn about brewing water chemistry.
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Old 07-22-2009, 11:41 AM   #9
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I'm not 100% sure at which pH sourness starts to be noticeable. You're probably right in presuming <4.0.
yes, I played once with witbier, lactic acid and pH-meter, and the lactic tang was noticeable when pH was about 3.9
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Old 07-22-2009, 01:48 PM   #10
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I don't disagree with anything you said, but that naturally soft water can't have a pH as low as 5.5. My well water is very soft and has a pH of 5.7 (according to Ward Labs). It doesn't seem like a stretch to think that soft water can have a lower pH than that.
agreed. I didn't have data for what I said. It was based on intuition.

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