question about lactic acid and mash ph

Thu Jan 28, 2010 8:39 am

my question is about adjusting mash ph with lactic acid.

for instance: say i make adjustments to my water with salts for a particular brew. i mash in, and i find the ph is a bit high still. what should be my approach to acidifying the mash with lactic acid? is there a general rule that states X amount of lactic acid will reduce ph of Y amount of fluid by some amount? im sure there is no hard fast rule... but where do i start? how much time should i wait before taking another reading? also, what is the limit to which i can add acid before i start to affect the flavor?

thanks for any help.
-Tyson
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whiteManCanHop
 
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Re: question about lactic acid and mash ph

Thu Jan 28, 2010 9:12 am

There is a rule of thumb for Sauermalz: 1 % sauermalz in the grist will yield an 0.1 unit pH drop. Given that the lactic acid content of sauermalz is around 2% and that the lactic acid solution usually available from home brew shops is 88% (by weight) and has a density of 1.21 g/cc we ought to be able to work back from that. For 100 lbs of grain 1 pound of sauermalz (455 grams) would drop pH by 0.1 and be equivalent to adding 0.02*455 = 9.1 grams of lactic acid or 9.1/.88 = 10.34 grams of 88% solution. At a density of 1.21 g/cc this amounts to 10.34/1.21 = 8.54 mL. For a 10 pound grist with a desired drop of 0.2 you would, thus need 2*0.854 = 1.75 mL. As the 1% per 0.1 pH is just a rough estimate so too is any amount of liquid lactic acid you calculate.

Given the approximate nature of the calculation it is probably best to add half the calculated amount and see what happens. You may have to wait quite a while to see the full effect. In my experience with sauermalz (I find this easier to use than the liquid acid - don't need a graduated cylinder to measure it out) the pH often goes quite low initially only to gradually rise eventually. Only experience will let you hone in on the correct amount. If you don't get caught up in the "I want a 50 SRM beer so I need RA of 700" trap a couple percent sauermalz will usually get you a decent mash pH.

As for the flavor threshold - I have to say that would depend. It really starts at 0% - lactic acid is pretty flavorfull stuff but the flavor is not unpleasant. Again, my experience is with the acidualted malt and I would be wary about adding more than say 5% though I think there are noticeable flavor effects at the 2-3% level but these effects are, IMO, positive ones. No question of sourness at these levels but rather the beer seems to have additional complexity.
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Re: question about lactic acid and mash ph

Thu Jan 28, 2010 10:58 am

thanks, ajdelange. i was hoping you would chime in on this.

pardon my ignorance...
so, if i doughed in and notice my ph is .2 units higher than i would like, i can stir in some milled sourmalz (equal to about 2% of my grain bill) to bring down my ph by approximately .2 units?

i use the sourmalz as needed as i would lactic acid? its just in a form of milled grain rather than liquid.

am i understanding this correctly?
-Tyson
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whiteManCanHop
 
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Re: question about lactic acid and mash ph

Thu Jan 28, 2010 12:58 pm

whiteManCanHop wrote:.... if i doughed in and notice my ph is .2 units higher than i would like, i can stir in some milled sourmalz (equal to about 2% of my grain bill) to bring down my ph by approximately .2 units?

i use the sourmalz as needed as i would lactic acid? its just in a form of milled grain rather than liquid.

am i understanding this correctly?


Yes, you are.
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Re: question about lactic acid and mash ph

Thu Jan 28, 2010 1:45 pm

Personally, I use an 88% lactic acid solution in place of ever using acid malt. After speaking to a Weyermann rep, he said the lactic acid content in their acid malt was roughly 1-2% by weight, which is achieved by spraying it down with a 50% lactic acid solution at the malting house. I know many have success with acid malt, but personally, I think there's too much variability in the acid content to yield determinate and consistent results. Using a graduated dropper with an 88% solution is a practical and accurate method of administering LA.
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SacoDeToro
 
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Re: question about lactic acid and mash ph

Thu Jan 28, 2010 1:55 pm

thanks guys. i just picked up a bottle lactic acid and a glass pipette. i will try the lactic acid first... but i am intrigued by the sourmalz.

julian,
what sort of response time for the ph to change do you experience when using the lactic acid?

do you use a meter or strips to check ph? i only have strips... is this good enough? or should i invest in a meter?
-Tyson
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whiteManCanHop
 
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Re: question about lactic acid and mash ph

Fri Jan 29, 2010 6:44 am

SacoDeToro wrote:Personally, I use an 88% lactic acid solution in place of ever using acid malt.


That's absolutely fine and the reason I'm saying that is what follows may look like a rebuttal which it isn't intended to be. If you want to accuse me of proselytizing I would probably have to plead guilty but I'm not trying to shoot down the use of the acid by any means. I think one of the real virtues of this site is that the readers get to see various perspectives on brewing problems and chose for themselves what seems the best thing for them to do. Here's why I use sauermalz.

I readily admit that I'm pretty enamored of sauermalz because it has, IMO, improved my beers noticeably. Now it may simply be the case that I am more focused on mash pH and I would have gotten the same results using acid from the bottle but I don't think so as there are definite, but subtle, flavor differences. I'll also admit to just not feeling "right" about acid from a bottle (not that I haven't ever used it) - hangups from trying to adhere to Reinheitsgebot, I guess.

SacoDeToro wrote:After speaking to a Weyermann rep, he said the lactic acid content in their acid malt was roughly 1-2% by weight, which is achieved by spraying it down with a 50% lactic acid solution at the malting house.


That's interesting because it sort of conflicts with what it says on their web site (that lactic acid comes from naturally occuring bacteria on husks of grain). And it would seem that if they were spraying acid of known concentration onto a known amount of grain they would be able to do better than 100% uncertainty in the amount of acid in a kilo of malt. Perhaps they are making sauergut (lactic fermented wort) whose acid content they don't know that well (though 50% seems awfully high for sauergut) innoculating the sauergut with husk bacteria.

Pertinent to the original question: they have a recipe for a Berliner Weiße which used 8% acidualted malt. It is clear that you would be able to taste the acid in that brew.

SacoDeToro wrote:I know many have success with acid malt


Perhaps because of my interest in it I am more sensitized to it than I used to be but I have begun to notice more and more references to its use by professional brewers. In fact a recipe from a professional brewer was posted here the other day in which it was used. As another example I know that a company with multiple breweries around the US uses it from talking to their brewers.

SacoDeToro wrote: ...but personally, I think there's too much variability in the acid content to yield determinate and consistent results.


Yes but I don't think it really matters that much. There would be variability in results with the bottle acid too from variability in the buffering capacities of the malts and of the water (alkalinity), it's calcium content, the malt phosphate and malt organic acid contents and probably several other factors too. If these uncertainties are greater than the uncertainty induced by uncertainty in sauermalz acid content they will dominate as uncertainties combine by RSSing. So for, example, if you were counting on dropping pH by 0.2 using the rule of thumb you would need 2% sauermalz. Given that the distribution of acid content is uniform between 1 and 2% (the worst case - it's doubtless Gaussian) the standard deviation would be 0.3% and at .1 pH per percent (grist) at 1.5% (acid content - this is the mean) the standard deviation in the pH drop would be 2*.1*.3/1.5 = 0.04. If the uncertainties from the other factors were 0.1 pH then the total would be 0.108 i.e. the sauermalz uncertainty would not be an appreciable factor. As I'm not a professional brewer who brews the same beer from the same lots of malt day after day the uncertainty from the other factors is sufficiently high (i.e. greater than 0.1 pH) that I have to check pH on every mash and adjust after dough in. Adding more sauermalz is just a matter of tossing in a handful or 2 of grain. I think the question as to whether this is easier than pipetting acid from a bottle is kind of moot.

In a pro situation where everything else is under control, or at least the same (there will always be some variability) the uncertainty in acid content could dominate. Is 0.04 pH significant in such cases? If the desired pH shift were as much as 0.4 pH (nominally requiring 4% sauermalz which is beginning to get up to where it would be tasted) the uncertainty would be 0.08 pH. Is that significant? Pro brewers do use the stuff so they live with that level of uncertainty or they may take steps to reduce it. For example, the acid content of the sauermalz I use is exactly the same, from brew to brew, because I bought a sack of it and put it in a Vittles Vault. At a couple of pounds per brew that sack will last me a long time. A professional could do this. One 25 kg sack "treats" 1250 kg grist (at a 2% rate) and so a few pallets should last a craft brewery quite a while. Or they could blend from several lots. "Regression to the mean" will bring the blend closer to the average (1.5%) i.e. reduce the standard deviation. This is clearly something a homebrewer could do as well (with 1 lb bags - not 25 kg sacks).

A pro might also do a titration to measure the actual acid content or, more likely still, get an analysis for each lot from the maltster and add, e.g., 10% more sauermalz if the new batch has 10% less titratable acidity (e.g. 1.1% of grist with the less acidic malt where 1% sufficed previously).

SacoDeToro wrote:Using a graduated dropper with an 88% solution is a practical and accurate method of administering LA.

I might be reluctant to put "graduated dropper" and "accurate" in the same sentence ("pipetter" or "graduated cylinder" seem to resonate better with "accurate") but as it doesn't appear that very good accuracy is required anyway I can agree with this statement.
Last edited by ajdelange on Fri Jan 29, 2010 9:12 am, edited 1 time in total.
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Re: question about lactic acid and mash ph

Fri Jan 29, 2010 7:43 am

I have nothing to add to this thread other than I love these conversations. I'm a pH whore, too and any topic on i grabs my attention.

And I like the different methods used.
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