Stouts turning acidic

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Oct 6, 2021
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Hi everyone,

I'm curious to know why, as, to my surprise, googling this did not yield many obvious results, why are my stouts turning acidic. And not sour.

The last 2 stouts I brewed: One where I added some Reese's puffs and some peanut butter, The other one a breakfast oat-milk and hazelnut stout, both seem to be turning more and more acidic.

They're all bottled, and on both I missed my priming/carbonation (too low). So they're more flat that I would like them to be, but both seem like as time goes by, the acidity level to taste gets stronger and stronger.

I know roasted malts give a lower pH, but my base for the grain malt came from a recipe from a book. Any other style I brew do not turn acidic.

Open to any ideas or questions! Thank you
Local water is pretty awesome. This is not an issue for sure, as it only happened with my stouts. I might have added a bit of salt, but often do with all my beers.
Grists with high proportions of dark roasted malts can lower the mash pH A LOT, I have water with ~100mg/L bicarbonates, and still have to add a little baking soda in stouts to keep the pH from dropping too low. I'd suggest getting a water priming spreadsheet and see what your estimated mash pH for this recipe is.
How long has it been since you bottled the stouts. I find that my stouts are much better after some time so I rarely start drinking them for 3 or 4 months. Your may improve if you give them time. If you have an acetobacter infection you will taste that and it will get much worse with time, telling you that you need better sanitation.
Local water is pretty awesome. This is not an issue for sure, as it only happened with my stouts. I might have added a bit of salt, but often do with all my beers.
My brewing water is pretty soft and 'anaemic', in terms of minerals. Fine as it is for drinking and mashing very pale beers. Terrible for dark beers, like porters and stouts. It wasn't until I got my brewing water analysed properly and started treating it with brewing salt additions that things improved.
I'm with others and think this is going to come down to your water. Unless you modified your water significantly to keep the pH at an acceptable level for a stout, this is probably where the issue is. You say your water is awesome - what does that mean? Awesome for brewing a particular style? Can you give more detail?
Local water is pretty awesome. This is not an issue for sure, as it only happened with my stouts. I might have added a bit of salt, but often do with all my beers.

It's almost certainly your water. An awesome water for some beers, may not be usable for other styles. With respect to stout brewing, your water probably doesn't have enough alkalinity to keep the wort pH from falling too low.

Low pH is not necessarily perceived as 'sour', but it is likely to be tart or sharp. Add the flavor of roast grain in there and it could be perceived as acrid. A stout with proper pH is more likely to come across as richer, coffee- or chocolate-like.

Don't ignore your awesome water. There are no waters that are well-suited to brew all styles. That's where your knowledge and skill as a brewer comes in to make the water 'right'.
Hi everyone,

Thank you for your input. Sorry for the delay, but as I am gearing towards brewing another one, this problem resurfaced.
By pretty awesome I meant that for drinking water, for the skin... I am not able to get the chemistry details right now, but I live in Vancouver, BC, Canada. We get fresh water from the mountains just up North, distributed to the metro city I believe.

Would the idea then to add some baking soda to the mash, and no salt, when brewing a stout? In order to have a higher pH. I do not have any ways of measuring the pH but some strips, which I find pretty useless.

I'll certainly also mash at a higher temp because I want a higher FG.

PS: I brew 10gal Batches.
Fwiw I live in a suburb of Vancouver with the same water source. Here’s the numbers I use as a starting point on my water:

Ca 4
Mg 0
Na 1
Cl 2
So4 1
Hco3 10

Indeed the water is very soft, I would absolutely be adding baking soda when making a beer with roasted grains
Anyone living in relatively mountainous areas is likely to have water with low mineralization since it tends to be runoff with little groundwater interaction. I'm not surprised with the content reported for Vancouver. That water is similar to Wicklow Mountain water which is the supply for Guinness St James Gate brewery.

If your goal is brewing an Irish Dry Stout, then performing Guinness' technique of steeping the roast barley separately from the main mash is wise. That way the acidic grains are kept from the main mash of pale malt and raw barley and the pH of that mash stays within desirable limits.

If you're going to brew other porters and stouts, then mashing everything together and adding enough alkalinity to the mashing water is best. I like your approach with adding baking soda since it provides reliable alkalinity. I suggest that only adding baking soda might not be ideal since your water is low in calcium and 'flavor' ions. I'd consider including gypsum and calcium chloride in your salt additions.
Thank you for your answers!

I may have some calcium chloride around, will check into that, or figure that out. Would just need to figure out how much to add, in addition to baking soda.
@bjhbrew hwo much do you usually add ? Do you add any calcium chloride as well?
Other questions: should the calcium chloride and baking soda be added DURING the mash OR the boil? does it matter?
Other questions: should the calcium chloride and baking soda be added DURING the mash OR the boil? does it matter?
The post by @bjhbrew suggests you have water that might as well be RO or distilled (Ca 4, Mg 0, Na 1, Cl 2, So4 1, Hco3 10), so you would definitely want to adjust your water while it's heating up, before the mash. If you use Brewer's Friend software, set your "Source Water:" to "RO/Distilled", and your target water to London or Dublin, and fill in values for Calcium Chloride, Gypsum, Epsom, and Baking Soda. Don't worry about making your water's HCO3 as high as the London or Dublin HCO3 values, just bump up your Baking Soda amount enough to get the predicted mash pH up around 5.4 to 5.6.

At least that's how I figure out my water adjustments, but I do full-volume mash-in-a-bag, no-sparge.
Other questions: should the calcium chloride and baking soda be added DURING the mash OR the boil? does it matter?
It most certainly does matter!! Having enough calcium in the mashing water enhances oxalate reduction and enhances enzyme action. Having enough alkalinity from the baking soda during the mash helps prevent the mash pH from dropping too low and causing excessive proteolysis (which creates thin beer) and causing any roast flavors to get acrid tasting.

Add the proper salts to the mashing water and your beer will benefit. Skipping the salts from the mash and adding them to the kettle is not a good idea.
I don't see where I can set my source water to "RO/Distilled"?
I'm able to see where I can find target water, but not for the source
Use the full-blown recipe editor, since it will track predicted pH nicely as you make changes to your recipe... Also, it is just the "Distilled Water" option.

Now that I actually looked at the Brewing Water Chemistry page you linked, what you want to do is enter your actual water as reported by bjhbrew, and as I have filled in on the "Source Minerals:" line.

However, all those values are close enough to ZERO that you could just leave them all at 0.

Nonetheless, I like the water calc embedded in the full recipe editor better...

Thanks @Hoochin'Fool !
And how would you measure the additions of sodium bicarbonate NaHCO₃ and calcium chloride CaCl₂ to reach the desired ions? Sorry if I don't find this obvious, as they're not on proportional proportions. And my only way to measure pH is the stripes, which I find quite unprecise.
Thanks @hottpeper13 ! Would you have a reference, guide or link, for future purpose, that may indicate those proportions, ppm to g to add for each salts?