Deacidification of Grape wine

[Trigger200]

Hello,
I'm looking for guidance on deacidification of wine. I've been making wine from grape juice for a few years now and the I don't like the sharp "bite" to the finished wine which i'm attributing to the acid.

I just purchased 5 gallons of Fredonia grape juice - The "acid" level from the company says 1.22 and the pH is 2.94. From my research this is on the high end of the scale. I should be looking at an acid level of about .95 for the must?

I purchased potassium bicarbonate from the store which says to use 1-1/3 TSP per gallon to reduce the acid level by 0.1%. This is much higher than what I've read online. Can someone point me in the right direction as to how much potassium bicarbonate I should add?

Thanks!

 

[Johnd]

Hello,
I'm looking for guidance on deacidification of wine. I've been making wine from grape juice for a few years now and the I don't like the sharp "bite" to the finished wine which i'm attributing to the acid.

I just purchased 5 gallons of Fredonia grape juice - The "acid" level from the company says 1.22 and the pH is 2.94. From my research this is on the high end of the scale. I should be looking at an acid level of about .95 for the must?

I purchased potassium bicarbonate from the store which says to use 1-1/3 TSP per gallon to reduce the acid level by 0.1%. This is much higher than what I've read online. Can someone point me in the right direction as to how much potassium bicarbonate I should add?

Thanks!

Different grapes respond differently, so go slow, adding in your chems, stir, give some time, measure, repeat as needed. I’m not familiar with your varietal, but moving your pH upwards much more that .2 - .3 would at least get you into the 3.2 range. Fermentation May increase that a bit more. Malolactic fermentation will also move you in the less acidic direction.

 

[Ajmassa]

Your right. That's way high. Conversion to volume from weight can be very rough.
If you've got a scale then the true ratio is .9 grams per liter of wine added reduces TA by 1 g/L. Or 3.4g per gal.
Without a scale I read 1/4 tsp per gal for .1% reduction
Always adding about half of what's needed. (1/4 tsp/gal already accounts for this) Checking and adding again if needed. Adjustments to must tend to unpredictable.
Clueless about Fredonia but target ph for successful ferment should be at least 3.2-3.3. Id think.
**please do me a solid though and don't make decisions based on my reply**. There's some factors involved I'm unsure of. Namely removing acid pre-ferment and Fredonia grape target levels are variables that may effect how to proceed.

 

[LoveTheWine]

FermCalc is a great program for calculations:
http://web2.airmail.net/sgross/fermcalc/

Whatever you do, be careful with any additions, take it safe and measure accurately with PH meter after each one!


My two cents:
Concentrate on PH...
The low PH is a big concern as MLF will not start this low. If you can get that up to 3-3.1 before ferment by using Pot bicarb or any sutable means then the following should do the rest naturally for you:
-Ferment with Lalvin 71B yeast or another Malic acid munching yeast. This will eliminate 20-30% of the malic acid and raise PH enough so MLF will start.
-Do a Malolactic ferment after primary
-cold crash and more acid will fall out as crystals.

If it is still out you can adjust a small amount after these steps.

 

[Trigger200]

The replies are greatly appreciated! I will tread slowly with the Potassium BiCarbonate addition.

I will cold stabilize after the addition per the instructions and then I'll start the fermentation process.

 

[Floandgary]

D-E-A-C-I-D-I-F-I-C-A-T-I-O-N..... The word alone should be enough to get rid of any excesses!!! LOL

 

[Trigger200]

Ok, I have a potentially foolish question - the place I purchased the juice from stated the grape juice had an acid of "1.22" with no unit of measurement....I took that as % tartaric...
But how can a percentage by higher than 100? Maybe I'm overthinking this. Can this be correct?

 

[Ajmassa]

Ok, I have a potentially foolish question - the place I purchased the juice from stated the grape juice had an acid of "1.22" with no unit of measurement....I took that as % tartaric...
But how can a percentage by higher than 100? Maybe I'm overthinking this. Can this be correct?

The percentage is actually for g/100 mL. So 1.22% of 100mL or simply 12.2g/L. If your interested in the chemistry this is a good link that explains acids in wine in great detail.
Also I'm not sure cold crashing must is typically done. Hopefully someone can offer advice about removing acid before fermentation for ya.
http://www.gencowinemakers.com/docs/Acids Presentation.pdf

 

[Smok1]

Im in the same boat right now, i got two frontnac varietals both around the same numbers 2.8 ph 1.1 sg and 1.3% ta. I used potasium bicarb on the red to get too 3.1 ph and used 71b to ferment and its now done fermenting and being cold crashed in a fridge. The frontenac gris i bought some rennisance vivace made a good starter but seems the yeast cannot handle the 2.8 ph, i will treat with pott bicarb tonight if i dont see any activity.

 

[Johnd]

Also I'm not sure cold crashing must is typically done. Hopefully someone can offer advice about removing acid before fermentation for ya.
QUOTE]

I don't typically cold crash before fermentation, knowing that later in its life the wine will be sitting in my chilled cellar for a year or more, with plenty of opportunity to precipitate as needed.

 

[Smok1]

So still no activity. Ph must be too low for yeast to take off. I treated each 50 liter batch with 80 grams of potassium bicarbonate, ph changed from 2.8 to 3.2 ( bouncing off 3.1 to 3.2 on my ph meter) going to rehydrate 71b with goferm tomorrow and pitch, hoping its malic acid metabolizing abilities will eat up some of the acid enough to keep the ph at 3.2 or maybe bump it up to 3.3 so i can mlf it safely. I used 71b on one of the frontenac noir batches, i used potasium bicarb to get the ph to 3.1 hoping the 71b would metabolize enough of the acid to bump it up to the 3.2 safe mark for mlf but it did not. Ph stayed at 3.1, so now its being cold crashed and im hoping to drop enough of the tartaric crystals out to get into the 3.2/3.3 safe mark for mlf. High acid low ph grapes are a bugger to deal with, as i was warned by the winemaker.

Numbers for the two varietals

Frontenac noir
Ph:2.8
Ta:1.5%
Sg:1.103

Frontenac gris
Ph:2.8
Ta:1.3%
Sg: 1.096

 

[Trigger200]

Ha... I have 0 clue on 90% of what you said. But out of curiosity how long will you cold stabilize for?

 

[Smok1]

Probly two weeks or however long it takes to drop out the crystals

 

[stickman]

During cold stabilization, your acid level (TA) will drop, but your pH will also drop due to being below the magic 3.65 range.

 

[Smok1]

During cold stabilization, your acid level (TA) will drop, but your pH will also drop due to being below the magic 3.65 range.

I hope it doesnt drop too much, how does ph go lower when your removing acid from the wine? If ta is the amount of acid and ph is the strength then less acid should mean higher ph no?

 

[LoveTheWine]

During cold stabilization, your acid level (TA) will drop, but your pH will also drop due to being below the magic 3.65 range.

Not saying it can't happen... but
I personally have never seen the PH go down on my wines and I cold stabilize every one. Even so, if this did happen, as long as TA goes down so does the tartness of the wine so its really not a bad thing. Usually mine start around 3.2PH and finish around 3.3 or 3.4

 

[Stressbaby]

I hope it doesnt drop too much, how does ph go lower when your removing acid from the wine? If ta is the amount of acid and ph is the strength then less acid should mean higher ph no?

This is the way I think of cold stabilization.

T is tartaric acid. It has 2 hydrogens to give, and gives the first at average pH of 2.9, second around 4.3.

H2T <--> HT- <--> T--

The max amount of HT- is at pH of 3.6, right in the middle of 2.9 and 4.3. Whenever you cold stabilize, you are precipitating potassium bitartrate, or KHT. KHT removes HT- from the equation. The wine wants to maintain equilibrium.

So if the pH is above 3.6, you are on the right half and you can ignore the left half of the equation. Removing KHT as wine diamonds removes HT-, and to maintain equilibrium some T-- grabs a hydrogen, converts to HT- and raises the pH.

If your pH is low, you can ignore the right and only worry about the left half of the equation. Remove KHT and in order to maintain equilibrium H2T converts to HT- and H+, which means it gives up a hydrogen, decreasing the pH.

 

[Smok1]

Not saying it can't happen... but
I personally have never seen the PH go down on my wines and I cold stabilize every one. Even so, if this did happen, as long as TA goes down so does the tartness of the wine so its really not a bad thing. Usually mine start around 3.2PH and finish around 3.3 or 3.4

Good to hear. I just dont want to drop below 3.2 because i want to mlf

 

[Smok1]

This is the way I think of cold stabilization.

T is tartaric acid. It has 2 hydrogens to give, and gives the first at average pH of 2.9, second around 4.3.

H2T <--> HT- <--> T--

The max amount of HT- is at pH of 3.6, right in the middle of 2.9 and 4.3. Whenever you cold stabilize, you are precipitating potassium bitartrate, or KHT. KHT removes HT- from the equation. The wine wants to maintain equilibrium.

So if the pH is above 3.6, you are on the right half and you can ignore the left half of the equation. Removing KHT as wine diamonds removes HT-, and to maintain equilibrium some T-- grabs a hydrogen, converts to HT- and raises the pH.

If your pH is low, you can ignore the right and only worry about the left half of the equation. Remove KHT and in order to maintain equilibrium H2T converts to HT- and H+, which means it gives up a hydrogen, decreasing the pH.

Now you have me worried because the frontenac noir is already low ph, and high ta, i need to mlf, i thought by using potasium bicarb i could drop out some of the tartaric acid raising the ph, if its gonna go the opposite way i should rethink my stradegy

 

[LoveTheWine]

Good to hear. I just dont want to drop below 3.2 because i want to mlf

I always cold crash the wine after MLF. Right after it is complete I rack, add sulfite, then cold crash for a month. My Foch always drops crystals and if acid is dropping out then the wine gets smoother.