mew said:
I've heard of people using CaCO3 to make a mash more basic, but is that the only option? and what about making the mash more acidic?
Some excellent intro articles from Zymurgys past escape me so I'll paraphrase from data from Fix's "The Principles of Brewing Science"...
Calcium tends to acidify the mash.... so adding Calcium chloride and/or Calcium Sulfate (in its hydrated [gypsum] or unhydrated forms) will acidify the mash... the reason is that the calcium reacts with the hydrogenated phosphates to precipitate calcium phosphate (the white-ish residue on the bottom of your brewpot after a long boil).
Ca2+ + HPO42- --> H+ + Ca3(PO4)2
(calcium cation)+(phosphate anion) --makes-->(acid)+(precipitated salt)
Unlike calcium chloride and calcium sulfate (which contain anions that are the conjugate bases of strong acids), Calcium carbonate contains the carbonate anion which is by itself a weak base.... therefore carbonate can react with those H+ acids released by the reaction of calcium and phosphate and neutralize the effects of added calcium...
The trick with using CaCl2 and CaSO4 is not to add too much ions to the mix. Ions in excess can add off-flavors. Fix recommends if acidification is really needed... that food grade acids such as lactic acid can be used (he even states that some breweries use sulfuric acid.) So I guess my question is.... (after the rambling...)
...is how acidic are we talking here? If you post the concentrations of CO32- [carbonate] and bicarbonate [HCO3-] from your water source and if you tell me a desired pH, I can post the amounts of lactic acid, phosphoric acid, or sulfuric acid you would need to add to get there... or... the previously mentioned buffer can take you all the way to 5.2!
Peace,
kalTOrak