pH keeps changing

[pkeeler]

I'm making a malbec from frozen grapes. Been going for about 6 weeks now. Everytime I take the pH (pH meter) reading of this wine, it changes. Over the past four weeks I have gotten results from 3.3-3.8. The wine is split into two carboys. The pH between the carboys seems to be the same each time. I check the calibration of the meter each time. TA numbers range from 6.4 to 7.5.

Does the pH of red wine change a lot when it is this young? It tastes good, so I'm not worried. But since the pH was 3.3 when I did the sulfiting, I only put about 20 ppm in (using the online calculators). But if the pH is really 3.8, then that is not at all enough sulfite. I did put MLB into the wine at the end of primary fermentation. I have not ponied up the money for a chromatography kit. My first reading post primary showed a drop in TA, which I took as a sign the MLF happened (I know). The wine has been at 55-62 the past three weeks.

I understand there is CO2 in solution. Would that lower the pH? Or is it raising the pH? CO2 lowers the pH of water to 5-6, but when the wine's pH is under 4.0, would CO2 then be raising it?

I've used the meter on beer and other country wines and the numbers are pretty consistent and believable.

 

[ibglowin]

The pH of a wine will change not only as it goes through fermentation but also as it undergoes MLF and Malic Acid is replaced by Lactic Acid. CO2 bubbles can also wreak havoc on obtaining stable readings. You should try and rid your sample of CO2 first before trying to get a reading if it has CO2. You can just do the finger over the end of the wine thief and shake well trick to oust the CO2.

If your pH meter is calibrated and stable in the buffer solution, I would trust the reading and adjust accordingly after you are sure MLF has completed.

 

[homer]

Where did you get the frozen Malbec grapes? bk

 

[pkeeler]

From Brehm. Last red grapes in Hatfield.