pH Readings

[iridium]

I just picked up some merlot grapes that I am looking forward to turning into wine. The shop that I got the grapes from reported the pH was 3.4 when they picked them. I got them home and my pH meter is reading 3.9. I do not trust my pH meter and I am ordering another one.

The question is should the pH have changed much from picking and crushing? Can I trust the reported pH from the farm because my meter is broken. I have not yet pitched yeast so I can add acid blend if needed.

Thank you.

 

[stickman]

You need calibration buffers for your pH meter so you can verify accuracy. I wouldn't make any adjustment based on a questionable pH meter. If you do end up needing acid, I would say acid blend wouldn't be my first choice for a pre-fermentation adjustment. Just use straight tartaric acid if needed.

 

[NorCal]

I have found pH one of the hardest measurements to get accurate. I have expensive meters and inexpensive meters. All have to be calibrated just prior to use. I have found that the probes themselves become inaccurate after 2 years. It is one of those costs you need to plan on if you make a lot of wine.