pH change that happens during the mashing
- mashing=precipitation of phosphates(found in brewing water)+amino acids derived(taken) from the malt
- phosphoric acid(H3PO4) disassociate
- (if calcium ions are present)calcium phosphate disassociate, leaving behind hydrogen ions
- higher(than 10-7mol/L) H+ concentration in a solution=acidic link
- (if magnesium ions are present)magnesium phosphate do the same thing, but the effect on pH is less dramatic
- if calcium sulfate is added, the calcium ions react with the amino acid group(present within the solution)then leave behind hydrogen ions
- these changes in mineral composition+the precipitation of calcium salts->pH decrease(prior to fermentation)
- the carbonate(CO3-2), bicarbonate(HCO3-) ions act as buffers to pH decrease
Proper mash pH
- optimal pH of an infusion mash: 5.2~5.6
- high pH during the mash increase the amount of dextrins, less fermentable wort
- polyphenols(such as tannins), silica compounds easily extracted under high pH: instability, astringency*
- *when sparging, pH of the last running climbs to 5.8~6.0, stop the sparging
Controlling Mash pH
- with lots of carbonate ions in the water(high mash pH):
- add calcium ions from gypsum(calcium sulfate) or calcium chloride
- or add organic acids(phosphoric acid, lactic acid)
- if a brewer is using very soft water(low mash pH):
- add a little bit of chalk(calcium carbonate), baking soda(sodium bicarbonate)
- link Understanding residual alkalinity&pH
The importance of boil pH
- during the boil, calcium phosphate continue to be precipitated
- optimal post-boil wort pH: 5.0~5.2
- Maillard reactions are not favored at lower pH(for light colored beer)
- to lower pH, add a little bit of calcium(gypsum, calcium chloride, acid)
Fermentation
- optimal ending pH less than 4.4(larger 4.2~4.6, ale 3.8)
- during fermentation, pH continue to drop:
- yeast take in ammonium ions(strongly basic) and excrete organic acids
other helpful articles
Effective hardness=Ca(ppm)/1.4+Mg(ppm)/1.7
RA=Alkalinity(as CaCO3)-Effective hardness or (50*Bicarbonate)/61-Effective hardness
full size Residual Alkalinity Nomograph link
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