Why should pH drop after fermentation?

Question

I've recently completed several batches of whites. In many of these, the initial pH of the juices were in the 3.6 range, but after commpletion, the batches now test in the 3.25 range. I can understand why pH might rise during wine production (MLF, precipitation of tartaric acid), but I don't see why the pH should drop.

The only additives that were put into these whites were the yeast, some yeast nutrients (in appropriate doses), some lysozyme, and also appropriate sulfite to bring them up to the 40 ppm range.

Any thoughts?

Lee

Joe Sallustio · Accepted Answer

Potassium probably dropped out, lowering the pH.  Other acids are alsoformed when fermenting, it's not uncommon for pH to drop.Joe

benrotter · Answer

understandCold stabilisation will cause a pH *drop* if the initial pH is belowaround 3.65, so your wine has performed as expected.At pH's below around 3.65, an HT- molecule is precipitated leaving afree proton and consequently decreasing the pH. Above about pH 3.65,the wine solution is more basic and precipitates tartrate ions inaddition to HT-. An extra proton is removed for each tartrate anion,thus increasing pH.BenImproved Winemaking

Lee · Answer

What's an HT- molecule?  Someone mentioned that "other acids areformed".  I've never heard this, and I'm not sure they'd drop the pHanyway.  Lee

Joe Sallustio · Answer

Lee, Acids formed during fermentation (other than ML): Succinic and the volatile acids; acetic, formic, propionic and butyric.

Succinic and acetic are in higher concentrations than the others.

HT- is the first dissociated tartaric anion.

Joe

Someone mentioned that "other acids are

Why should pH drop after fermentation?

Join the Discussion

Didn't find your answer?