low mash pH results in "sour" taste?

After reading a response in an earlier post (https://www.homebrewtalk.com/f128/what-happens-when-you-undershoot-your-mash-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?

JLem said:

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

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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)?

menschmaschine said:

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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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.

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.

menschmaschine said:

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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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?

menschmaschine said:

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,

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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.

Kai

JLem said:

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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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.

Kaiser said:

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.

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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.

But, that being said, I definitely have more to learn about brewing water chemistry.

menschmaschine said:

I'm not 100% sure at which pH sourness starts to be noticeable. You're probably right in presuming <4.0.

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yes, I played once with witbier, lactic acid and pH-meter, and the lactic tang was noticeable when pH was about 3.9

menschmaschine said:

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.

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agreed. I didn't have data for what I said. It was based on intuition.

Kai

menschmaschine said:

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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I realize this an older thread, but I've been wondering the same thing. For most of this season, I've been targeting a mash pH at room temp of 5.2 to 5.3. It dawned on me several weeks ago that perhaps this is too low -- that maybe I should be aiming for a mash pH of 5.4-5.5 at room temp in order to (maybe) have slightly rounder, fuller flavors.

The finished pH (out of the fermenter at bottling time) is always around 4.01 to 4.4 (4.4 for higher alcohol styles -- Scotch Ales, Winter Warmers, etc.). I ferment cool -- Safale 05 @ 60F or 62F for 7 days, then a slow ramp to 70F for 1-2 weeks. (I understand that cool fermentations can also drop the finished pH.)

Out of the fermenter -- at bottling time -- the beers taste fine -- no off tastes, no sourness. I add the normal amount of priming sugar at bottling -- and out of the bottle after a week (not enough to carbonate fully, I realize) they taste pretty good -- round, good malt, nice hop character, etc.

However, after about 4-5 weeks -- essentially at the month mark -- when I know the bottles are fully conditioned, the taste is still pretty good but in each of my 5.2-5.3 mash pH batches, I taste a very light -- very faint -- but distinct sourness. Hard to explain: it's not *quite* citric tart, and it's not an "off" sourness -- it's more like a direction that the malt has taken (hops still pop for the styles in which I expect the hops to pop). I don't think it's oxidation -- no cardboard tastes, no band-aid tastes, etc. In other words, the beers are still pretty good. Folks who drink them say they're great -- so I at least know other folks aren't thinking "sour" when they drink them. So far, no one who has had one has said, "This is sour." But I detect the taste -- and it's distinct across all styles.

It's not infection -- no bottle bombs, no green apple sourness -- and the beers themselves look wonderful: crystal clear, not at all cloudy, bright as any off the shelf beer.

I've got several batches of the same beers in various stages of fermentation where I've increased the mash pH to 5.4 to 5.5 (I use a pH meter I calibrate a few minutes before I start brewing for the day each day. The meter itself is new -- less then three months old -- and is always stored in solution, etc. etc.) so I'm hoping to be able to tell a difference between these new batches and the old batches.

At any rate, the thing that I'm wondering about is the carbonic acid -- if it can increase the sourness perceptibly when the pH is already low. (These are all ales, BTW -- in the brown/amber/black range -- not that color makes a difference, but I tend to like malty beers with a distinct but not overpowering hop presence.)

Finally, the beers are not at all over-carbonated. I pop the caps off beers conditioning for 1 month or so -- stored in my basement -- and i get a normal amount of fizz with a solid pour --a good, solid, tight head of bubbles -- maybe an inch or so -- in a glass. No gushers, no slowly creeping carbonation out of the bottles (signs I've seen previously with infected beers). Carbonation head atop the beer thins as I drink, but it's still there (albeit very thin) as I drink the last sips.

Is it worth decreasing the priming sugar slightly? Increasing the mash pH as I've done?

I know I have to experiment -- and I am -- but I'm looking for any additional comments on the effect of carbonic acid and taste perception on finished beers.

I've noted a similar performance for young beer that is not fully carbonated (I force carbonate) and fully carbonated (and even more so for overcarbonated) beer. Carbonation and the carbonic acid definitely has an effect of increasing the tartness.

That being said, I think that your approach where you've increased your mashing pH target is going to do the trick. I've brewed several beers where the mash pH dropped into the 5.2 range and they were definitely too tart. In addition, it mutes the malt flavor because worts mashed at that lower pH tend to be more attenuative and finish dryer, using up some of that malt flavor perception. Aim for that 5.4 to 5.5 range and you'll probably find that produces beers more to your liking.

Mash pH is one of the final frontiers in wort tailoring. The capability to target a mash pH for the degree of fermentability, tartness, residual sweetness are all important considerations. That is a reason why I suggest that range of about 5.3 to 5.5 for mash pH in Bru'n Water.

Enjoy!