pss, experience people, help me understand what to do next

[p_p]

Hi all,
calling out for some advice ...

I have a recipe for an oat stout which I plan to brew a few times while doing minor adjustments in an attempt to improve the recipe & learn in the process.
This recipe has been brewed twice before. The second time it turned out really nice to the point where I'd probably use this as my regression point if the next set of changes do not result in further improvements.

The caveat is that looking back at my notes, there was (based on my understanding) a couple of mistakes in the process and I wonder if I should carry them over or correct them now and go back to square one.

I used my tap water, which is very hard (~300ppm) and highly alkaline (~220ppm). I added phosphoric acid to the mash water. I didn't have a pH meter at the time, but spreadsheet calculations indicated 5.25 pH. I sparged with tap water as-is, no acidification.

So, the problem that I have now is that if I re-run calculations and attempt correcting what I believe the mistakes are, ie mash at a little higher pH and acidify the sparge water, the total amount of acid I'd have to add is almost double what I added before.

Now, the beer I brew with "mistakes" has a very clean, quite subtle and delicate flavor, does not feel acrid or acid or tannic and measured 4.2 pH de-carbed ... I fear adding that much more acid may just through it off.

My questions are:

Firstly, how come a beer brewed with those mistakes still turned out fine (is it possible the acid in the mash/grist may have offset the alkalinity in the water and got me to the right spot by chance? .. is my palate that bad? :/ )

Secondly, would you just trust the numbers and end up adding that much more acid on the next attempt?

thanks

 

[Bosh]

Dark grains (like you'd use in a stout) tend to be pretty acidic.

 

[gspot]

Hi all,

Firstly, how come a beer brewed with those mistakes still turned out fine (is it possible the acid in the mash/grist may have offset the alkalinity in the water and got me to the right spot by chance?

This, because of the dark grains like Bosh said, rather than the acid. You could probably even get by without acidulating the mash as you did previously. Adjusting the pH with acids only becomes important/worth it when making pilsner imo. Historically, people compensated for the hardness/alkalinity of their water by brewing only dark beers which automatically lower pH.

If you are NOT brewing a pilsner and would still like to soften your water a bit, I'd recommend diluting with 50% ro or distilled and skipping the acids. If you are brewing a pils, I'd go with 100% ro AND add acids and salts to mash and sparge water. Everybody's water is different though, so ymmv.

 

[gspot]

Duplicate post

 

[joshesmusica]

Secondly, would you just trust the numbers and end up adding that much more acid on the next attempt?

I can't really help you out with all of the water adjustments. Hopefully Martin will see this thread. Or you could just PM him directly, I would guess.

But, I would not just trust the numbers, personally. Those are really quite hypothetical, and you really want to make sure to measure your mash pH next time (at room temps, of course). Since you're using tap water, it could be inconsistent from season to season. So that's another good reason to always measure. But also, if you don't have the input on those spreadsheets 100% correct, the output will be off. So it's best to measure in order to make sure that the output is correct.

From my understanding so far, though, it's not necessarily the pH that is the endgame with the water, but what additions you made in order to arrive at that pH. So if you know the additions you're making will enhance the flavor profile you're aiming for, then measuring the pH is just to make sure you made the proper amount of additions. Although, I would say that the final product being satisfactory or not is a pretty good indication of how well you did with that!

I doubt you have a bad palate though. If it was tannic or acrid, I don't think it would be too hard to notice, especially not in a stout.

 

[p_p]

Thank you for your replies.

Considering brew day is scheduled for tomorrow I did a bit more research and my conclusion is that the buffering capacity of both the grains in the tun and the work collected from the first running was probably sufficient to overcome the alkalinity in the sparge water. So despite not having acidified the sparge water, it is likely that the sparge pH (2x batch sparge loads) did not rise much and the final beer pH probably didn't change much either.

I found information in Kai's website and blog where he published the results of wort titration experiments. In the website, he also gives a figure for the amount of acid/base required to shift pH of a mass of grist, and although I am not sure if the latter piece of info applies to grist left behind in the mash tun after first running, I will use the numbers anyway.

The numbers are probably not quite right, but hopefully are close enough to justify/explain what happened with the "mistakes" beer (here is my chicky call for backup > @mabrungard)

So, according to Kai, the buffering capacity of grist is (give or take) 40 mEq/pH*Kg. Additionally, when adding base to wort Kai publishes a buffering capacity of 64 mEq/pH*Kg for a 12.0 plato.

I measured my water to be ~240 ppm CaCO3 KH +/- ~9ppm. Assuming the test was to 4.3, then the alkalinity at 5.4 is ~220 ppm. So, the water contributes about 4.4 mEq/l of acid neutralizing stuff. I dumped 15 ltr of water during sparge, so that is 66 mEq.

Based on Kai's numbers the buffers in the grist and wort combined were roughly: 4kg grist, ~160mEq/pH and 8 ltr of first running wort, ~540 mEq/pH. Total ~700 mEq/pH. So the 66 mEq in my water probably shifted the sparge pH by +0.4 and the final wort pH by +0.1 (?) This is all probably very wrong but hey, I like pounding on the calculator.

My conclusion is that the beer I brew was all right, but just by the skin of a teeth as I probably raise the sparge pH to about 5.6 (still 5.8 limit supported by the literature) and the beer turned out ok because the wort had plenty buffering capacity so the kettle pH was not that bad either.

I am opting for acidifying the sparge water with phosphoric, hoping the conjugate base added does not affect the flavour. The water is coming at ~140ppm Ca, so don't mind loosing some in the process. I will make measurements this time :]

pp