Brewing salts and pH??

[dylpik]

why does everywhere I read suggest lowering the pH by using brewin salts? Most are pretty much just spectator ions and barely affect (if at all) the H+ concentration. Ex gypsum...CaSO4, add it to increase Ca+2.. cool, add it to increase SO4-2...also cool. Why are so many sources online saying it will decrease pH? It’s pka is 7! From my understanding if you want to lower the pH, add an acid, salts are buffers. Sure salts can be slightly basic or acidic but never as potent as their acid or base counterparts, to the point where it’s pointless to try and add these salts for anything except to change the mineral content.

 

[mabrungard]

Um, their pK's have nothing to do with the reaction that actually reduces pH. Ca and Mg cations react with phytin in the malt to release protons which drive pH downward.

However, your premise has merit. Brewers should not overly rely on this phytin reaction to acidify their mash. That can result in excessive mineralization. It is best to mineralize to the degree that's desirable for the resulting beer and then add an actual acid to the mash to reduce pH any farther degree.

 

[dylpik]

Thank you! That makes sense with the minerals.thats been bothering me lol

It seems I confused pka and pk

 

[Silver_Is_Money]

Be wary as to your approach with regard to how much downward pH contribution is due to mineralization within the mash. Mash pH programs and spreadsheets based strictly upon the pioneering work of Kolbach tend to typically over-emphasize the "real world" downward pH effect of calcium and magnesium mineralization upon the mash by around 20-30% to perhaps by as much as 50%. I believe that Kai Troester was the first to notice that Kolbach's formula was based upon his observation with regard to the effect of Ca++ and Mg++ mineralization upon specifically "knockout pH", and knockout occurs well downstream of the mash. Then Kai took actual measurements of the effect of mineralization within the mash itself to confirm it.

Kolbach never intended his formula to be applied to mash pH, let alone to pH measurements taken early within the typical 60-90 minute mash cycle, and due consideration for modification to account for this must be considered. Some of the most highly popular software does not consider or attempt to correct for this. A.J. DeLange has been trying hard to raise awareness of this for quite some time now, but to little avail it seems.

 

[ajdelange]

When calcium is present with phosphate at or near mash pH a tiny proportion of that phosphate will be in the form or the tribasic ion (PO4)-3. The various phosphates of calcium are very, very insoluble. Thus hydroxyl apatite precipitates removing some (PO4)-3 from the mix and upsetting the equilibrium between H(PO4)-2 and (PO5)-3. To restore the equilibrium some H(PO4)-2 --> H+ (PO4)-3. The relative quantities of the two species change and the pH goes down both of which lead to restoration of equilibrium.

There is lots of phosphate present in malt, most as the monobasic ion H2(PO4)- it reacts with calcium in several ways but the dominant reaction is

10Ca++ + 6H2(PO4)- + 2H2O --> Ca10(PO4)6(OH)2 + 14H+

Thus 13 protons are released for every 10 calcium ions that react. Kolbach's observation, mentioned in #4, was that calcium ion concentration [Ca++] would produce [Ca++]/3.5 H+ ions at knockout making it plain that most of the calcium present does not participate in the reaction as given. But still some H+ is produced and the pH is lowered. Suppose you have mashed a kg of typical base malt (Crisp MO) with 2L of water with 2 mEq/L (100 ppm) permanent hardness. You might expect mash pH of 5.72. Adding 5 mEq/L (100 mg/L) Ca++ is 10 mEq for the 2 L and, according to Kolbach, would release 10/3.5 = 2.86 mEq protons. Given that this malt has a buffering capacity of -46 mEq/kg•pH at pH 5.72 we might expect a pH shift of 10/3.5/-46 = -0.062 pH at knockout (in the mash it will be less than this) and so it is clear that calcium addition is not the way to control mash pH but it is also clear that if you have a lot of calcium present you need to consider its pH reducing effect in making pH estimates. It is interesting to note that the paper in which Kolbach offered his observations is really an appeal to his fellow brewers to get together and pressure the authorities to allow the use of external acids for pH control as is done by brewers everywhere in the world except Germany.

Finally, a salt, such as CaSO4, has pKs only in the sense that its acid does. In this case the acid is clearly sulfuric acid which has pK's of -10 and 1.99. That second pK lends SO4-- some alkalinity at mash pH but it is so small that it can almost always be ignored. Water with 500 mg/L SO4-- would have alkalinity of 2.6 ppm as CaCO3 with 1 ppm attributable to the sulfate ion.

 

[Yooper]

why does everywhere I read suggest lowering the pH by using brewin salts? Most are pretty much just spectator ions and barely affect (if at all) the H+ concentration. .

Not sure where "everywhere" you're reading is, but I've only seen that suggested a few times by non-expert brewers and I don't think it's a very prominent viewpoint.

I am a simple minded person, especially compared to experts, but I always say to think of brewing salts as like "seasonings" as you would use for food. A little garlic and onion in spaghetti sauce reminds me of a little gypsum in my IPA water. It's seasoning- for flavor. It's not for pH adjustment (although it could have a lowering impact as you noted but not much). Proper use of brewing salts can take a very good beer to a great beer, for enhanced flavor and mouthfeel perception.

 

[ajdelange]

Not sure where "everywhere" you're reading is, but I've only seen that suggested a few times by non-expert brewers and I don't think it's a very prominent viewpoint.

While you don't see it emphasized as much as we used to and while we (or at least most of us) now recognize that calcium is not the best way to regulate mash pH you don't have to go too far back to see lots of references to it in brewing texts and elsewhere.