pH adjustment

[justinb]

I recently pressed a 75/25 blend of Cab Sauv/Merlot and racked off gross lees yesterday. Currently, pH-3.9, TA-7.6. Prior to fermentation, pH-4.4, TA-6. pH still seems high to me. Should I add more tartaric acid before I start MLF? Is there a limit to the amount of tartaric acid you can add?

 

[cmason1957]

Did you drive off the CO2 in your sample, prior to taking the after fermentation Ph?? generally heating it for a minute or two in the Science Oven, will drive that off and give you a better Ph measurement.

I would go ahead and do MLF. Then make the adjustments after you have closer to finished wine. As a side note, not helpful for this, but in the future, it is generally better to reduce the PH prior to fermentation.

 

[justinb]

I racked it with a vacuum pump so I would think that most of the CO2 was gone, but maybe not. Thanks for the reassurance. I'll start MLF tonight

 

[cmason1957]

I racked it with a vacuum pump so I would think that most of the CO2 was gone, but maybe not. Thanks for the reassurance. I'll start MLF tonight

That first racking won't remove most of the CO2. It will remove some, and with the subsequent rackings even more. For me, it takes a full four rackings, with time (months) between each to remove most all of the CO2. Some folks report, that even with vacuum racking not all the CO2 comes out.

 

[1d10t]

I only do 6 gallon batches. My first rack is into a 6.5 gallon carboy. That gives me the head room to pull a good vacuum. After it settles a little I'll repeat a couple times and then rack to a 6.

 

[user 36973]

Currently, pH-3.9, TA-7.6

Wow the pH seems high for that TA. Those look like the kind of numbers I get with my Norton grapes, which are notorious for having high pH + high TA.

You may want to get some fresh standards if they are over a year old and recalibrate your pH meter. I'd be hesitant to add more tartaric at this point; you can always add it later after MLF. My $0.02 is to finish MLF asap and get a new reading on the pH & TA. Then you can make your acid adjustments prior to aging. If your TA is continues to be that high, then possibly adding some tartaric followed by cold stabilizing can help bring down the pH while managing the TA. You'll just have to be vigilant about your sulfites and protection from oxidation at that pH.

 

[NorCal]

At this point, I’d toss the meter and only add tartaric to taste. Post AF additions have a big impact on taste, so while you could adjust to hit a number, the wine may not be drinkable.

 

[justinb]

Thanks all. I went ahead and started MLF. I will re-test everything after MLF is complete and add sulfite as needed. I have a Vinmetrica 300 with new reagents so I would think my readings are accurate.

 

[Rice_Guy]

Did you drive off the CO2 in your sample, prior to taking the after fermentation Ph?? . . . it is generally better to reduce the PH prior to fermentation.

I would say the pH is always lower and TA is always higher after fermentation.

My standard method for carbonated drinks is; 50 ml microwaved for 30 seconds, stirring beaker to release CO2, cool to room temp, measure test material into a clean beaker and test as normal.