Phosphoric acid drawbacks?

[biestie]

I was listening to Dr. Homebrew from 9/17/15. He was giving someone advice on adjusting his ph. In the podcast he stated "... If you have access and training for such things, a little food grade phosphoric is probably more like what the big guys use." The caller said "I'll stick with lactic." Their response was "Good call."

That left me scratching my head. Maybe just dumb luck, but I started using 85% phosphoric several years ago, when I moved to an area where I had no choice but to build from RO. I add it initially to the mash and sparge water, and also have had success using it for on the fly adjustments if needed. All of this obviously backed up by ph readings using a reasonably accurate meter.

What am I missing? I have no intention of changing things, but more curious than anything.

 

[TheMadKing]

Either one works just fine, the only difference is the strength of the acid and which minerals it adds to your beer. I believe lactic is slightly stronger so you need less of it, but I'm not 100% sure on that point.

 

[ajdelange]

88% lactic acd is 11.4 N to pH 5.4 and 85% phosphoric is 14.8 N (1 mL of 1 N acid delivers 1 mEq of protons) so the phosphoric is a little stronger. Lactic acid leaves lactate ions in the beer and phosphoric acid biphosphate ions. The former are more flavorful than the latter which may or may not be a good thing depending on what you are trying to do. Dilute (10%) phosphoric acid ( 1.08 N which makes measurement a snap once you have figured out how many mEq you need) is readily available from home brew suppliers. The more concentrated stuff is harder to get in food grade and requires some care in handling. Lactic at 88% strength is pretty safe to handle and is sold by most LHBSs.

A great alternative is acidified malt (sauermalz) as this carries lactic acid and its own specialty malt flavors.

 

[brewfun]

AJ

I'm of the impression that Phosphoric acid readily binds with calcium, where lactic doesn't? Phosphoric then having some benefit in use with highly mineralized water sources, such as might be close to a Dortmund or Burton profile?

 

[ajdelange]

It isn't phosphoric acid that bids calcium but phosphate ion and there is only a tiny bit of phosphate present at mash ph. There are circumstances where calcium will precipitate but the water has to be very hard and quite alkaline. There are some curves in the Palmer water book.

 

[biestie]

I get what you're saying. The Dr. Homebrew show seemed like they were implying that home brewers shouldn't be using phosphoric unless we're highly trained. I'm kinda reading between the lines but they definitely suggested something along those lines. I haven't really heard a downside to it.

 

[Effinbrewer]

One major disadvantage of using phosphoric, is that it forms a much harder to remove deposit on electric elements (in the HLT and Kettle) than calcium carbonate. this leads to premature failure of the elements. I know it doesn't matter with gas, apart from having to scrub the deposit of the walls of the vessels, but for electric brewers it can be a real problem.

 

[ajdelange]

As I indicated in #5 very little of the phosphate from phosphoric acid coalesces with water and malt calcium to for apatite (what precipitates). Was does coalesce with calcium in wort is biphosphate from malt. Thus I don't think that the choice of phosphate as opposed to lactate is going to make much difference unless you have the hard alkaline water I referred to in #5. Perhaps you have apatite confused with beerstone (calcium oxalate).

 

[Beezer94]

I get what you're saying. The Dr. Homebrew show seemed like they were implying that home brewers shouldn't be using phosphoric unless we're highly trained. I'm kinda reading between the lines but they definitely suggested something along those lines. I haven't really heard a downside to it.

It's just a safety thing. The 10% Phosphoric Acid sold by most homebrew shops is both safe and easy to use because of it's dillution.

It's the 85+% stuff that is corrosive to skin/eyes if you are not careful (i.e. drinking while brewing or around pets/children).

 

[Effinbrewer]

As I indicated in #5 very little of the phosphate from phosphoric acid coalesces with water and malt calcium to for apatite (what precipitates). Was does coalesce with calcium in wort is biphosphate from malt. Thus I don't think that the choice of phosphate as opposed to lactate is going to make much difference unless you have the hard alkaline water I referred to in #5. Perhaps you have apatite confused with beerstone (calcium oxalate).

Beerstone can be relatively easily removed, using PBW, but what forms on the elements won't shift easily, it's not calcium carbonate either as that can be shifted using kettle descaler (citric acid usually). Strong mineral acids like sulphuric and hydrochloric will shift it, usually to the detriment of the coating on the element. Phosphoric won't touch it.

 

[ajdelange]

Beerstone is a deposit of calcium oxalate embedded in a protein matrix. The matrix needs to be oxidized and the pH lowered to dissolve the precipitate. This is traditionally done with a mix of nitric (the oxidizng agent) and phosphoric acids.

Beerstone can be relatively easily removed, using PBW,

PBW is an alkali celaner (mix of sodium metasilicate and sodium carbonate). The high pH might help to denature the protein but the associated high pH is only going to hold the calcium oxalate together. Even with the proper acid blend (5 Star does sell a product for this but not to home brewers) a third ingredient is required: elbow grease. Beer stone is not, once it has reached buildup proportions, easy to remove.

..but what forms on the elements won't shift easily, it's not calcium carbonate either as that can be shifted using kettle descaler (citric acid usually).

That suggests that it is beerstone.

Strong mineral acids like sulphuric and hydrochloric will shift it, usually to the detriment of the coating on the element. Phosphoric won't touch it.

That suggests it is not as none of those acids by itself will remove beerstone.

The hypothesis here is that the deposit is apatite. It is easy enough to verify that apatite is readily soluble in sulfuric and phosphoric acids and even in ordinary household vinegar (I just tried all three). So perhaps it needs to be 'baked' onto a metal substrate to make it difficult to remove. I tried that too and found that even vinegar will readily remove it from a brass fitting. But I also found that a blob of apatite baked into a solid chunk does not dissolve nearly so fast in vinegar as freshly spun down apatite precipitate. So perhaps that is your problem. If there were a thickish layer of apatite baked onto your element you would have to scrub or otherwise break up the deposit to the point where the acid can reach it or at least stir the acid continuously so that it is moving past the deposit surface.

But as I've pointed out a couple of times already using phosphoric acid isn't going to increase the amount of apatite appreciably. Using 200 ppm (4 mEq/L) allkalinity as a rather extreme example you'd need 90% of that much phosphoric acid to neutralize it i.e. 3.6 mmol/L (1 mmol phosphoric acid yields 1 mEq protons at mash pH). You would have no calcium stripping in the water unless the calcium concentration were greater than about 480 mg/L. But at mash pH you would have 3.6*96 = 345 mg/L monobasic phophate ion in the treated liquor. Assuming mashing at 2 L/kg the water would contribute 690 mg/kg but malt itself contains, according to Briggs, about 12400 mg phosphate per kg. Thus the phosphoric acid added to the water increases the phosphate in the mash by 5.5%. That should not make much of a difference. If it is indeed hydroxyl apatite on the element then 94.5% of it came from malt phosphate.

 

[Effinbrewer]

I accept what you are saying, however, using phosphoric acid for alkalinity reduction resulted in a very hard to remove precipitate in the HLT (on the elements) and in the kettle, changing to hydrochloric and sulfuric resulted in a soft coating that was easy to remove. I have a number of beers that I make on a regular basis, with a fairly constant grist, and have done back to back brews, phosphoric results in the coating, hydrochloric and sulfate does not

 

[ajdelange]

Interesting. Phosphoric acid is very popular this side of the pond as we don't have AMS/CRS. I wonder if people over here are seeing this. I can explain why it shouldn't happen but I can't explain why it does!