Ph adjustment and calculation

[nicklausjames]

I have a cab franc in primary on the skins fermenting. For various reasons I wasn't able to measure the ph until after pitching. I took the ph today and it was 3.97. Is now an appropriate time to adjust ph? It's been fermenting about 2 weeks.

If yes what is the optimal ph for this wine?

Finally I was thinking of lowering it to about 3.5. Am I correct that 3.8 g x 5 gallons would give a .1 reduction so I would add 19g tartaric? It is 5 gallons must.

 

[JohnT]

hmmmm, 3.9? Do you also know the TA?

I would at least adjust to about 3.6, wait until the wine clears, then make another adjustment based on taste.

 

[nicklausjames]

I measured the ph again and it was 3.9. The ta was 8.8 g/l. The brix is 4 and originally was 30.

 

[salcoco]

measurement of Ta while fermenting is inconclusive because of CO2. I would press the wine, place in carboy with airlock, rack once wine reaches a sg=1.00. rack again in three weeks. adjust PH at that time insure proper so2 additions as you have a high ph wine. the ideal level is between 3.3-3.4.

 

[nicklausjames]

Ok. Should I correct the ph before adding malo bacteria?

 

[WineQuest]

Whoa.....3.3-3.4 for a Cabernet Franc? That is way low. Plus, you would have to add A LOT of tartaric to change pH that much and I would bet you would not like the resulting taste.

If this has been fermenting for two weeks and you are down to 4 brix you have already missed the pre-ferment adjustment window. I would let it finish, put it through ML then test again. Don't adjust based on a desired set of numbers but instead adjust based on taste. A pH of 3.9 would be expected for grapes harvested at 30 brix. Personally I would have watered back to 24-25 brix but like I said, all pre ferment activities are moot at this point.

 

[skipdonohue]

measurement of Ta while fermenting is inconclusive because of CO2. I would press the wine, place in carboy with airlock, rack once wine reaches a sg=1.00. rack again in three weeks. adjust PH at that time insure proper so2 additions as you have a high ph wine. the ideal level is between 3.3-3.4.

3.3-3.4 is crazy low for Cab Franc, I'd finish fermentation, press, rack off gross lees after 48 hrs, then test pH again, and maybe bump it down to 3.7... I, personally wouldn't feel comfortable adding that much tartaric to go to 3.5

 

[WineQuest]

3.3-3.4 is crazy low for Cab Franc, I'd finish fermentation, press, rack off gross lees after 48 hrs, then test pH again, and maybe bump it down to 3.7... I, personally wouldn't feel comfortable adding that much tartaric to go to 3.5

My thoughts exactly. Don't forget to degas the sample prior to testing. There will be a lot of dissolved co2 in solution (which is also known as carbonic acid) that will skew the results.

 

[salcoco]

I donot think you can do MLF with a PH of 3.9. also MLF will raise the PH. any ph higher than 3.65 invite bacteria activity let alone heavy doses of SO2.
adjust the ph to the level best required by your mlf bacteria. take a one liter sample add tartaric acid while measuring with the meter immersed in the wine. when 3.4 achieved stop. add your result to remainder of wine. add opto-malo a malolatic bacteria nutrient and bacteria to achieve MLF. once complete then age for three months before doing taste tests.

 

[WineQuest]

I donot think you can do MLF with a PH of 3.9. also MLF will raise the PH. any ph higher than 3.65 invite bacteria activity let alone heavy doses of SO2.
adjust the ph to the level best required by your mlf bacteria. take a one liter sample add tartaric acid while measuring with the meter immersed in the wine. when 3.4 achieved stop. add your result to remainder of wine. add opto-malo a malolatic bacteria nutrient and bacteria to achieve MLF. once complete then age for three months before doing taste tests.

I apologize if this comes off as being less than nice but this is not enologically sound advice.

ML bacteria thrives in high pH wines. Think about it. You just said that there is a risk of increased bacteria activity in wines above pH 3.65 but in the same paragraph said you don't think ML (bacteria) in a wine with pH 3.9. Contradictory statements.

Check into most high scoring red wines. Grab your pH meter if you must. Nearly all of them are high brix -> high etoh and almost all have high pH's.

The reason we have to add more SO2 to high pH wines is because of the shift that occurs in the SO2 equilibrium. We are measuring FREE SO2 because that is what we are able to measure with our aeration/oxidation or vinmetric equipment. But what protects the wine is the MOLECULAR form of SO2. Typically in red wines we want a molecular SO2 level of 0.5 mg/l. As the pH increases the balance shifts towards the free side of the equilibrium thus we need more total SO2 to maintain the molecular level of 0.5 mg/l. This is the equation if you are so inclined: Molecular SO2 = Free SO2 / ( 10(pH - 1.81) + 1 ) The high pH wines are not unstable they just need more free so2.

As to the concern about smelling this increased SO2, don't worry. We smell the molecular form at about 2 mg/l (varies by the person). It doesn't matter how much FREE so2 is needed to attain the desired MOLECULAR so2 as we cannot detect free with our nose.

Your 3.9 pH whine is no less stable than the 3.4 pH wine if the molecular so2 levels are maintained at the same levels, typically 0.5 mg/l

 

[nicklausjames]

I just wanted to update this forum and see if anyone has any recs going fwd. so I pressed the wine, racked off the gross lees and it is now sitting in the fermenter. I tested ph and ta again. The ph is still 3.95 and the ta is now 6.4 g/l. I have not added mlf bacteria yet but plan to over the weekend with some oak. My question is should I lower the ph first by adding tartaric acid? If so to what? I was thinking maybe 3.6. I am not experienced enough in winemaking to adjust the acid by taste yet.

 

[ibglowin]

Where did this fruit come from? If you add acid to get it too a pH of 3.6 you will more than likely way overshoot the TA and end up with a very tart wine. You need to add just enough to up the TA no more than 7.5g/L and taste it and check pH. You might be able to push a little higher on the TA but again it all depends on the accuracy of your readings. That is where tastebuds come into play.

 

[Boatboy24]

Mike is right. At some point, numbers should only be followed so far and you should let your taste take over. I'd suggest you calculate what you need to get you halfway to the 7.5g/L and then taste. If it still feels flat, adjust the rest of the way.

 

[nicklausjames]

Grapes are from California. I added 3 tsp tartaric and am going to measure new ta soon. I tasted and it didn't taste awful.

 

[nicklausjames]

Ok so I tested the ph and it improved to 3.8. However i tried testing the ta and the 5 ml ta titrant syringe ran out before the meter beeped. I ran again and the same thing happened.

 

[ibglowin]

What is supposed to "beep"??????

If the syringe runs out. Reload.

 

[nicklausjames]

The ph meter beeps. The calculation is 2*(5 - how much is left in the syringe). If you reload and use another ml for example it would be 2*(5-6) or 2*-1 equals -1. That would be a negative ta???

 

[ibglowin]

Perhaps you should try 2 x (the total volume NaOH you added combined)……..

 

[nicklausjames]

There was another formula in the owners manual. Using that I got a ta of 14.

 

[ibglowin]

Not possible with that pH.

Formulas are dependent on volume of sample as well as strength of NaOH and are not interchangeable.

What was the sample size?
What is the strength of NaoH?
How much total NaOH was added?