Acid Reduction without pH shift

[Gerry Weiler]

Is there a way to reduce the TA by 2.0g/l without getting a big increase in pH? I typically use KHCO3 for the initial TA reduction but the pH shoots way up. Adding tartaric acid will reduce the pH back to something acceptable, but the TA increases to something very close to the original level. Any thoughts on this?
Gerry W, North Vancouver

 

[Ajmassa]

Hey man. Welcome to the forum. Right down to business it seems!
Can you hit us with some particulars about the wine ? What type, and what’s the current ph and TA?
And why specifically 2.0g/L ? That’s a lot. Curious to hear what you’ve got goin on.

 

[Gerry Weiler]

Thanks for the quick response. I have a Sangiovese from a Yakima vineyard that had an initial pH of 3.41 and TA of 7.0. It was picked a little early with a BRIX of 23, but I prefer the lower alcohol levels for this wine. After fermentation and 4 weeks of ML, the PH was 3.45 and the TA is 7.7. I had anticipated a small pH increase and a reduction in the TA. Typically for these type of reds, I try to keep the pH in the range of 3.3 to 3.8. A TA of 7.7 is too high and I prefer to have it in the range of 6.0 t 6.5. That works well if starting with a very low pH and a high TA.

I did some bench tests with 1g/l KHCO3 (potassium bi-carbonate), and the TA dropped down to only 6.9. But the pH jumped up to the 3.8 range. I added 1g/l Tartaric acid to knock back the pH and it seem to work, settling out at 3.5. But the TA want up to 7.8. Those number were obtained after 4 full days in the cooler at -8C. I was hoping to achieve a final pH of not more than 3.3 and a TA of 6.5. In other words, it didn't help at all.

The 2.0 g/l reduction is sometimes needed for some of the white wines. I like the pH to be low, about 3.0 to 3.3, and the TA at 6.5 to 7.0. But that is difficult to achieve if starting with high pH and acid levels.

 

[stickman]

Did you verify with chromatography that the ML went to completion? I would have expected the TA to drop a little.

 

[Gerry Weiler]

Did you verify with chromatography that the ML went to completion? I would have expected the TA to drop a little.

The ML started off well with the wine at an elevated temperature. I then moved it all (250 liters) into a tank, but this was kept in a room where the temperature is only 15C (59F). My last chromatography indicated that the ML was only partially completed, but I became concerned about potential spoilage and added 50ppm SO2. That may have slowed or killed off the ML.
But that isn't my concern now. I am trying to find some other way to safely reduce the TA without significantly affecting the pH. KHCO3 didn't work and I assume that K2CO3 wouldn't be any better. What about CaCO3 (calcium carbonate) for a finished wine? I read somewhere that the effect on pH is reduced, but no details were provided. I also considered Acidex, but apparantly, it doesn't reduce the Malic acid if the pH is less than 4.0. I can cold stabilize again and filter the wine afterwards if necessary.

 

[stickman]

In order for the bench trial to work, you have to raise the pH to 3.6 and then do the freeze thaw, decant the wine and run TA. If that's what you did and it didn't work, then the issue may be high malic acid considering that the ML didn't complete. Ultimately it comes down to taste which is driven by the TA, nothing wrong with a finished red wine pH of 3.8 or 3.85 if it tastes good. I haven't used calcium carbonate before, so I can't comment from experience, though there are plenty of published documents available explaining the procedure.

 

[Ajmassa]

In order for the bench trial to work, you have to raise the pH to 3.6 and then do the freeze thaw, decant the wine and run TA. If that's what you did and it didn't work, then the issue may be high malic acid considering that the ML didn't complete. Ultimately it comes down to taste which is driven by the TA, nothing wrong with a finished red wine pH of 3.8 or 3.85 if it tastes good. I haven't used calcium carbonate before, so I can't comment from experience, though there are plenty of published documents available explaining the procedure.

Why raise to over 3.6 first though? Adding tartaric just to take it away again.

I viewed it like this right away—- (but maybe I’m missing something). It was stated that the desired levels want to be around:
>3.3ph and 6.0-6.5ta
Currently at:
3.45ph and 7.7ta

And the wine is already under the magic number of 3.65ph. So when adding potassium carbonate (not bicarbonate) and cold stabilizing wouldn’t it theoretically move where desired? I was under the impression the levels also can move proportionality this way.
So adjusting TA by .12 down to 6.5 could get ph to 3.33 potentially. And also- a lengthier cold soak is needed for this they say. More like 2-3 weeks rather than a few days.
Finished wine at
3.33 and 6.5
from 3.45 and 7.7 *in theory!*

 

[stickman]

I didn't say over 3.6, I said 3.6, that is the pH where the greatest precipitation of tartrates occurs. The freeze thaw is an overnight complete freeze, then thaw, not just chill proofing, this is a quick bench trial to determine how much acid will drop out. My point was that if the TA of the bench trial was still too high, then the problem is most likely high malic acid, which can't be removed via this technique. With high malic acid, calcium carbonate is usually used pre-fermentation on a portion of the must to remove malic and tartaric acid. I have heard of people using this technique on wine, I think I've seen a few posts on this forum in the past, but again I haven't played around with calcium so can't comment from experience.

 

[Ajmassa]

I didn't say over 3.6, I said 3.6, that is the pH where the greatest precipitation of tartrates occurs. The freeze thaw is an overnight complete freeze, then thaw, not just chill proofing, this is a quick bench trial to determine how much acid will drop out. My point was that if the TA of the bench trial was still too high, then the problem is most likely high malic acid, which can't be removed via this technique. With high malic acid, calcium carbonate is usually used pre-fermentation on a portion of the must to remove malic and tartaric acid. I have heard of people using this technique on wine, I think I've seen a few posts on this forum in the past, but again I haven't played around with calcium so can't comment from experience.

Yea man. The world of deacidification can become quite involved for sure.
And for what it’s worth- all the acid levels being discussed here don’t seem to be at any extreme levels. Depending on the taste- I know I’d be perfectly comfortable rolling with 3.45 and 7.7.

 

[GreginND]

The pH is affected by more than just the acids present. Other buffering happens in solution and it is not always predictable. If your pH changes quickly with acid changes, then buffering capacity is low and you won't be able to drop TA without raising pH.

All that being said, you have not said one word about how it tastes. That should be the number one criteria for deciding on whether or not to adjust acid. I would not adjust acid if it tastes ok.

Your numbers look about perfect for me, but I do live in the land of high acid. You wine will likely be lively and long lived and go well with food with the numbers you have.

 

[Gerry Weiler]

I have very much appreciated your comments on this subject. And I agree that the most important parameter is in the "taste". I read somewhere that there is something called "Index of Acidity, IA" or "Acid Taste Index". This is simply the TA(g/l) minus the pH. The desired range should be 3.2 to 3.4 for whites and 3.3 to 3.5 for reds. Off dry whites can be more, 3.8 to 4.8. That isn't a hard and fast rule, but is more of a guideline for achieving the best taste characteristics. But this implies that we really do not want a large gap between those two properties. A red wine with a TA of 7.7 and pH of 3.45 would have an IA of 4.25 well above the guideline. And I personally find that to be too high in acid for my liking - would prefer to have 6.5 Ta and 3.5 for pH. That equates to an IA of 3.0. Seems like a good approach method for comparing taste with measured properties.

I am now trying a different approach with this wine but using Calcium Carbonate. My initial findings have been that the pH shift is less than that from the Potassium Carbonates. The only concern is if CaCO3 imparts other undesirable properties such as chalkiness. I would like to keep this discussion open with you and will let you know what I find in the next couple of weeks.

 

[Stressbaby]

I have very much appreciated your comments on this subject. And I agree that the most important parameter is in the "taste". I read somewhere that there is something called "Index of Acidity, IA" or "Acid Taste Index". This is simply the TA(g/l) minus the pH. The desired range should be 3.2 to 3.4 for whites and 3.3 to 3.5 for reds. Off dry whites can be more, 3.8 to 4.8. That isn't a hard and fast rule, but is more of a guideline for achieving the best taste characteristics. But this implies that we really do not want a large gap between those two properties. A red wine with a TA of 7.7 and pH of 3.45 would have an IA of 4.25 well above the guideline. And I personally find that to be too high in acid for my liking - would prefer to have 6.5 Ta and 3.5 for pH. That equates to an IA of 3.0. Seems like a good approach method for comparing taste with measured properties.

I am now trying a different approach with this wine but using Calcium Carbonate. My initial findings have been that the pH shift is less than that from the Potassium Carbonates. The only concern is if CaCO3 imparts other undesirable properties such as chalkiness. I would like to keep this discussion open with you and will let you know what I find in the next couple of weeks.

I think it is well known and understood that the pH shift with calcium carbonate is less than potassium bicarbonate. The issue if I recall correctly is the time it takes to precipitate. It takes several months for this process to occur. So the adjustments must be made several months prior to bottling or else the precipitation will occur in the bottle.

I'd never heard of the "acidity index," but after searching for it, I'm seeing much different desirable ranges. Dry reds 2.0-3.0, dry whites 2.7-3.7. That's a much bigger range than what you have specified above. Link. It doesn't really seem logical in the sense that 1) the two numbers are not independent factors and 2) the two numbers are not related in a linear way.

 

[1d10t]

AJ DeLange? has looked at this in terms of water profiles for beer. Calcium carbonate simply isn't all that soluble in water. Looking at historical water profiles for waters that contain large amounts leads people to want to heap these into their brewing water. Not that simple. He explains what it would take to reach the levels that are pumped up from under ground. If I remember correctly it is something like running lots of CO2 through the water with calcium carbonate to get it to go into solution. You may be experiencing the same thing here.

 

[Gerry Weiler]

I haven't been able to find a publication that specifically indicated a pH shift due to CaCO3 is less, but it does seem to be that way, particularly when using Acidex. Precipitation can be a problem as you suggested, but with most of my red wines, several months is not a problem. But I have sometimes noticed that the pH is immediately reduced after a TA adjustment and then becomes static, whereas the TA tends initially increases but tends to drop down over time. Cold stabilzation can accelerate that process and hopefully, final filtering should take care of any suspended precipitate

I made a mistake in my previous posting. In my haste, I inserted the wrong numbers. The range for the Acidity Index should have been as you stated, Reds 2.0-3.0, Whites 2.7 to 3.7. And these are only an opinion by the author, Bill Collins, but it does help to provide some rough guidelines. It would seem that high TA and low pH may not provide the best results. The other numbers that I indicated were taken from another paper published in 2001 by Charles Plant called "Why are pH and Titratable Acidity (TA) not proportional", where he suggested a desired pH range for white (3.2 to 3.4) and red (3.3 to 3.5) wines. Again, these are guidelines that do not necessarily work in all cases and I'm sure there are plenty of exceptions.

So for now, I'm experimenting with trying to reduce the TA with CaCO3 while keeping the rate of increase in the pH to a minimum. It wouldn't be as much fun if all the grapes were perfect. I will keep you posted as to the results, but it might take some time.

 

[Stressbaby]

https://ohiograpeweb.cfaes.ohio-sta...f_wine/2. Acid reduction in must and wine.pdf

 

[Gerry Weiler]

https://ohiograpeweb.cfaes.ohio-state.edu/sites/grapeweb/files/imce/pdf_wine/2. Acid reduction in must and wine.pdf

Thanks for the good article. It appears that I'm on the right track for suppressing of the pH gain and it appears that cold stabilization can increase calcium tartrate precipitation. It is the the calcium L-tartrate instability that concerns me and I'm not sure what, if anything, can be done to prevent that. Fortunately, I can avoid bottling my wine for an extended period of time if necessary.