Question on PH and CO2

[stickman]

@Michael Zeller Most of the time the pH change upon storage is from tartrates dropping out, if the pH starts below 3.6 the pH will drop, if above 3.6 the pH will increase. Even after cold stabilization, if you add anything that contains potassium, even kmeta, the wine may drop more tartrates and the pH will change accordingly. Check with a flashlight to see if there is any potassium bitartrate "glitter".

Usually when the wine drops tartrates it will taste less tart, even if the resulting pH drops, so I can't say why yours seems to be more tart. If the wine was racked and sulfited and topped up, then microbes generating volatile acidity shouldn't be an issue. Did you test for ML completion? It would be difficult to complete at 3.1 pH, so maybe after raising the pH, some ML activity started once the sulfite levels dropped off during storage, in this case, you may be correct as CO2 might be the issue with tartness.

 

[Michael Zeller]

Thanks all for the responses, I really appreciate the feedback. Using a flashlight, I’m not able to see “glitter”, the wines all look cleared. But after a decent amount of agitation, I’m getting a lot of bubbles and foam - below is a pic. I didn’t degas the wine after primary or ML, so perhaps with using a solid stopper and changes in atmosphere, the CO2 built up? I ordered a wine whip that should be here today, so I’ll see if there’s a change in pH after degassing.

ETA - I do need to top up these carboys but wanted to degas them first. Then I’m planning to rack and sulfite again, and top up.