Maximum amount of phosphoric acid per litre?

[broskobandi]

I have been using lactic acid to adjust my mash pH but since it definitely impacts the taste profile, I thought I would give phosphoric acid a go. I have very hard water and according to Brewfather, it'll take 1.7ml of phosphoric acid to reduce my mash pH to 5.39. The volume of water I use for mashing in is 6.3L, the target post boil volume is 4.7L. I do no sparge full volume BIAB. Phosphoric acid sounds like, at least to me who is definitely not a biochemist, something that can kill me if I use too much of. Does anyone know of a maximum ml/L that is still safe for human consumption? Thank you!

 

[VikeMan]

The amount of phosphoric acid needed to adjust any real life mash pH isn't dangerous. It's very dilute after mixing.

 

[Hoochin'Fool]

LOL my ridiculous tap water means even with a stout/porter recipe, I need an ounce (29.5 ml) of 10% phosphoric acid per 4 gallons mash-water. And if I want to make something light, just go straight for distilled or RO water.

Oops, turns out I was mistaken, my stouts and porters end up needing more like 10 grams (ie, 1/3 of an ounce). Sorry for being dumb!

 

[IslandLizard]

I need an ounce (29.5 ml) of 10% phosphoric acid per 4 gallons mash-water.

I hope you don't buy the silly small bottles of Phosphoric Acid (10%) from the brew store...
No clue why they'd charge that much for so little...
At least Lactic is 88% for about the same price. And tastes better (in very small diluted quantities).

If you use that much, I recommend getting a quart (or a gallon) of 85% Ph. Acid from DudaDiesel, or so. A quart may hold you over for quite a few years. But note, the price difference compared to a gallon, after shipping, can be rather small.

I therefore split some of my gallon with a few others at our grain buy, a few years ago, which made 5 of us happy as drunken larks.

Thanks to @Silver_Is_Money, for providing this handy dilution table:
https://www.homebrewtalk.com/thread...ting-from-85-75-or-30-phosphoric-acid.674372/
I sometimes use it in cooking too.

 

[Hoochin'Fool]

I hope you don't buy the silly small bottles of Phosphoric Acid (10%) from the brew store...

Guilty...

Say, as long as I've got your attention, I've read the main reason for wanting to keep mash pH at 5.6 or below was to avoid harsh tannin extraction. But I've also read that this harsh tannin thing really only comes into play if you've got both the pH too high, and the grain husks are exposed to temperatures over 170F. Since getting a mill late last year, I'm not getting any floaty bits of grain husks escaping the brew-bag anymore, do I dare brew a beer with no acid (and a predicted pH around 6.0)?

 

[VikeMan]

Say, as long as I've got your attention, I've read the main reason for wanting to keep mash pH at 5.6 or below was to avoid harsh tannin extraction. But I've also read that this harsh tannin thing really only comes into play if you've got both the pH too high, and the grain husks are exposed to temperatures over 170F.

I see this all the time, but it's a misleading over-simplification.

Every beer has tannins (from the mash and from hops). Beer wouldn't taste like beer if it didnt. The higher the mash temp, the more tannins are extracted. The higher the pH, the more tannins are extracted. There's nothing special about a specific combination of pH and temperature as some sort of cutoff for excessive tannins.

 

[broskobandi]

The amount of phosphoric acid needed to adjust any real life mash pH isn't dangerous. It's very dilute after mixing.

Thanks, that's reassuring. Btw, I forgot to mention that I have 75% phosphoric acid which I'm supposed to be using 1.7ml of in my 6.3L mash. I'm guessing brewfather is smart enough to scream at me to stop what I'm doing in case I wanted to add lethal amounts of phosphoric acid... right?

 

[VikeMan]

I'm guessing brewfather is smart enough to scream at me to stop what I'm doing in case I wanted to add lethal amounts of phosphoric acid... right?

It doesn't need to be. Phosphoric acid isn't poison. Any danger lies with its acidity. When you use it to bring a mash pH down to 5.39 (or whatever...anything in normal mash pH range), most of that acidity has been neutralized.

 

[day_trippr]

I suspect there is more phosphoric acid in Coke and Pepsi than in beer...

Cheers!

 

[tracer bullet]

LOL my ridiculous tap water means even with a stout/porter recipe, I need an ounce (29.5 ml) of 10% phosphoric acid per 4 gallons mash-water.

I'm not saying you're wrong, but wow, are you sure of this?

 

[Hoochin'Fool]

I'm not saying you're wrong, but wow, are you sure of this?

Well, I *was* sure until you wrote this! Looked back at my recipe and it's 10 grams of phosphoric 10% acid, not 1 ounce!
Tap water has HCO3- at 259 ppm

(Tho BrewersFriend thinks adding 30 grams of phosphoric 10% -instead of 10 grams- would only change the pH from 5.6 down to 5.47)

 

[broskobandi]

It doesn't need to be. Phosphoric acid isn't poison. Any danger lies with its acidity. When you use it to bring a mash pH down to 5.39 (or whatever...anything in normal mash pH range), most of that acidity has been neutralized.

That makes sense, thanks!

 

[IslandLizard]

I've read the main reason for wanting to keep mash pH at 5.6 or below was to avoid harsh tannin extraction.

Not exactly.
You want to bring your mash pH to a level where the enzymes perform best, 5.2-5.6.*
Ideal mash pH also depends on the beer (style) you're brewing.

Then, you want to acidify your sparge water in order to keep the runoff (wort diluted by sparge water) under a pH of 5.8 (or 6.0 at the very limit) at all times.
This becomes more important toward the end of the sparge, as runoff contains less wort, hence less acidity. Over-sparging can cause tannin extraction when the pH rises too high, over 6.0.

When batch sparging, say 2x, using equal volumes, you may want to aim for a pH of 5.4-5.6 for you first sparge, and 5.5-5.8 for the 2nd.

* Is a pH above 5.4 ok? | Bru'n Water

Also note, that temp references to the mash and sparge pH are as measured at room temps. At typical mash/sparge temps the measured pH will be somewhat lower, around 0.2-0.3 pH lower than they would be at room temps.

 

[day_trippr]

Where did the 5.8 come from?
I've always used "end of runnings pH" of 5.6 worst case...

Cheers!

 

[IslandLizard]

Where did the 5.8 come from?
I've always used "end of runnings pH" of 5.6 worst case...

I always thought that too, until I found several references to as high as 5.8 and 6.0.*

The reasoning is, the mash has a much lower pH, 5.2-5.6 typically, with a fairly high buffering capacity due to the high mineral content from the grist and added salts. Therefore, when sparging, the runoff will always have a pH (well) under the sparge water's 6.0.

* I'm going by AJ's post here, referencing sparge water to be pH 6.0 or lower:
https://www.homebrewtalk.com/threads/adjusting-sparge-water-ph.512617/post-6641993

 

[day_trippr]

I have definitely had batches where the mash pH at 60 minutes was on the money at 5.4 @ room temp but the end of runnings were very close to the historically recommended 5.6 maximum. I would consider anything above that a brew day error...

Cheers!

 

[Silver_Is_Money]

I suspect there is more phosphoric acid in Coke and Pepsi than in beer...

Cheers!

If one presumes the pH of Coke and Pepsi to be about 2.4, and the pH of wort after adjustment within the mash to be 5.4, this represents 1,000 times more H+ (acid) ion within Coke and Pepsi.

Beer somewhat closes the gap by finishing at about 4.3 pH, give or take, but that's not due to phosphoric acid.

 

[whattabrau]

I suspect there is more phosphoric acid in Coke and Pepsi than in beer...

Probably, even in terms of "bulk" phosphoric acid. It takes 0.40mL/L of 75% phosphoric acid to drop the pH of DI water to 2.5, and I think coke or pepsi is still a bit lower in pH. I have very alkaline water and I don't think I've ever used more than .30mL/L of 75% phosphoric acid in a beer. Though, I do augment it with a cocktail of other acids for a minimum of ~7mEq/L of aggregate acid in the kettle, so I *could* easily go >0.40mL/L and end up with a spot-on pH (at 5.0 0.4m/L 75% H3PO4 gives ~5mEq/L).

With all the buffering in wort, you have to use too much phosphoric acid on purpose for it to be dangerous (in the order of 100x too much), and your common sense should prevent you from pouring 1dL/10L concentrated acid into a brew. Even then your sense which is meant to prevent you from consuming dangerous things will tell you that something is wrong if you try to drink it. Besides, it likely won't ferment if the pH is 2, but on the bright side, at least you washed your yeast.

 

[day_trippr]

lol!

 

[broskobandi]

Thanks a lot for all your responses. I have just tasted the beer I made with seemingly scary amounts of phosphoric acid and it was fine. In fact, I could not pick up any significant difference between that and the ones I made with ridiculous amounts of lactic acid. This makes me wonder if lactic acid really does have such a huge impact on taste. I thought I finally found the thing that will fix "that home brew taste". Looks like I still have some more batches ahead of me before I find the magic ingredient.