Don't be swayed by the implied advice that one should not use acid malt. Some of the larger craft breweries do with great success and there is no reason home brewers shouldn't use it too and for the same reasons. It is an effective and reliable means of pH control and it adds those nuanced additional flavors to beer which, IMO, make the difference between good and great beers. I can still remember the first time I used the stuff. I was really surprised at how much it improved the beer (a Vienna) and have used it in every beer since then.
It only makes sense that there is going to be some variability in the acid content of the product but as I'm still on the first sack I bought I have not seen that. Nonetheless a pH check of any mash which contains it is doubtless a good idea (actually it's a good idea in any mash - sauermalz or no).
This is, of course, a matter of taste and so I would advocate trying it and comparing the result with beers in which pH was controlled with another acid (such as phosphoric). Then use whichever gives you the best result.
My comments are based on the use of sauermalz with German and Bohemian lagers and ales. It, and its cousin sauergut, are traditionally used in those beers to control pH as Biersteuergesetz disallows mineral acids (or any acid that is not naturally produced in the brewery). An interesting and often missed point is that Kolbach's paper in which he describes RA is often read to the point where that is discussed and then put aside. Thus readers often miss the real intent of the paper (translation avaiable at www.wetnewf.org
). It is really an appeal for the use of mineral acids in German brewing.
If things work out just right one can tweak chloride and sulfate and neutralize alkalinity at the same time with the proper mix of sulfuric and hydrochloric acid. Some of the safety concerns with those have already been mentioned but the ability of concentrated sulfuric acid to rip water out of anything it touches (remember the demo in high school where some was poured of table sugar) was not and that is, to my way of thinking, its principle hazard.
In the UK a suitably diluted mix of food grade sulfuric and hydrochloric acids is sold as CRS (Carbonate Reducing Solution). It is not, AFAIK, available in the US. One can go to the hardware store to obtain hydrochloric and to the auto parts store to obtain sulfuric but I don't want a product put up for removing the laitance from concrete in my beer.
Of the organic acids lactic is really the only practical choice with citric a possibility. The others are too strongly flavored. If malic acid tasted good wine makers wouldn't bother with malo-lactic fermentation (converts it to lactic) and we all know what vinegar (acetic) tastes and smells like. Lambics do contain some but I just can't imagine it in other styles. Of course it eventually comes down to taste. If you like it, use it.
If you look in the old home brewing books (Bravery, for example) a tsp of citric acid was de rigeur. Don't know why it isn't any more as the idea of lowering mash pH is definitely a plus. I expect the citric flavor it imparted was what put it out of favor. But it's now a brave new world with Citra hops out there.
Phosphoric is flavor neutral and one can always argue that as there is already lots of phosphate in malt it can't hurt to add a bit more for control of alkalinity.