Low pH, Low TA

I harvested my Sangio recently and the grapes were both low pH and low TA. I don't have the exact numbers in front of me but from memory that pH was 3.3 and the TA was 0.47. I ran both numbers twice to confirm. I did a quick search of my basic winemaking books and the internet and did not find this situation discussed. Before I start to dig deeper, does anyone know what drives this condition? If I remember my high school chemistry I think these numbers are telling me that my Sangio has a disporportionate amount of strong acid and very little weak acid.

This was a very hot and dry year and other graps acid numbers were lower than in years past but only the Sangio showed anything this drastic.

[James Roscoe]

Brian could you translate for me? I understand what you mean by pH but what do you mean by TA? Also what are normal levels? I also wonder whether the soils in Southern Maryland are just naturally low in these chemicals or is this something derived from the atmosphere? (This is your site in St. Mary's County, correct?) I am curious as I the more I linger around here, the more I get the itch to fool around with this stuff. (I blame it on Howie mostly.) Good luck!

Sorry James. TA is titratable acidity or sometimes called total acidity. Both pH and TA are measures of acidity. If I remember pH is more a measure of the strength of the acid while TA is more a measure of all the acid present. At a pH of 3.3 I would expect that my TA would be above 0.7. Last year I harvested my Barbera at around pH of 3.6 and TA of 0.62. I don't have acid numbers from last year on the Sangio as it harvested so late and at such small quantities that I just made a few gallons of rose out of it.

It could be anything. My soil is relatively poor and for southern maryland (Charles County) low vigor. I did add some potassium and compost last year which could have had an impace. I had an afternoon shading issue that I have addressed for next season. We had a very hot and dry season with no night time relief. Yet with all that my other varieties did not have this problem to the same extreme. Across the board, TA numbers were lower than years past but only the Sangio was below 0.5.

If you get serious about growing let me know. Will gladly explain my experience.

[James Roscoe]

What part of Charles County? I worked In St. Mary's County for three years (Leonardtown) before working in Waldorf (Charles County for the uninitiated) for eight years. I have lived in Bowie in Prince George's County since 1982 so I am familiar with southern Maryland. I am more interested in wine making than growing but I Howie has me interested in all aspects!

What are good numbers for wine? Does it matter? Can you manipulate the acid in any way during the wine-making process? This is fascinating stuff.

Can you manipulate the acid in any way during the wine-making process?

Yes.

Target numbers depend a lot on the wine style one wants to make. Not that I would ever get it but I would love to see my Sangio come it at brix of 22.5 - 23, pH of 3.4 and TA of 0.65. Some manipulation is easy such as adding sugar to raise brix or adding acid when both pH is high and TA is low. Adjusting a low TA when the pH is already 3.3 is not an easy thing to do since most manipulations will impact both numbers. I plan to blend the Sangio in with some other juice as the easiest way to hopefully address the situation.

I live a few miles east of La Plata. if you know the area, I am just outside of the Amish colony.

I harvested my Sangio recently and the grapes were both low pH and low TA. I don't have the exact numbers in front of me but from memory that pH was 3.3 and the TA was 0.47. I ran both numbers twice to confirm. I did a quick search of my basic winemaking books and the internet and did not find this situation discussed. Before I start to dig deeper, does anyone know what drives this condition? If I remember my high school chemistry I think these numbers are telling me that my Sangio has a disporportionate amount of strong acid and very little weak acid.

This was a very hot and dry year and other graps acid numbers were lower than in years past but only the Sangio showed anything this drastic.

You're correct in your interpretation, Brian. Since TA is computed in the US as "equivalents of tartrate," your acids would have to be stronger than tartaric acid to give rise to this condition. One suspect would be citric acid, another might be isocitric and another could be oxaloacetic but I'm not familiar enough with plant biochemistry to come up with other candidates.

Mark Lipton

I think malate is more acidic than tartrate. pH will also reflect any volatile acids present such as carbonate or acetate, where as TA will not.

-Paul W.

[James Roscoe]

What are the causes of the low acidity? Is it the soil? Is it the weather? Is it a combination of the two? I don't recall Bryan saying what the brix level was on the grapes.

So Bryan, you are in Bryantown (231) or Dentsville (6)?

What are the causes of the low acidity? Is it the soil? Is it the weather? Is it a combination of the two? I don't recall Bryan saying what the brix level was on the grapes.

So Bryan, you are in Bryantown (231) or Dentsville (6)?

Dentsville.

Brix was 21.

[James Roscoe]

I know that area pretty well. Are you right on Route 6 or back in one of the subdivisions?

Isn't a brix level of 21 considered low? I would think it unusual to have low brix and low acid. How would that work? There is obviously a lot about this I do not understand.

I know that area pretty well. Are you right on Route 6 or back in one of the subdivisions?

Isn't a brix level of 21 considered low? I would think it unusual to have low brix and low acid. How would that work? There is obviously a lot about this I do not understand.

The brix is a little low. Harvest date was dictated by my schedule conflicts and not sugar or ripeness but in this case its best that I harvested when I did as I would not want the TA to drap any lower. While the brix was low, the seeds were brown and the stems had turned but the skins were still a little bitter. As noted before I did have an afternoon shading issue so I had a situation were there was high heat but the vines did not have all day sun. I expect that the brix would have been higher if not for the shading.

Its a very small subdivision. The back of my property borders a house that is right off of 6.

One can have any of the four combinations: low pH and low acid, low pH and high acid, high pH and low acid, high pH and high acid. Weather, vine nutrition (and therefore soil condition), crop levels, probably other stuff, can all affect those relationships. In my experience, at least moderately low pH is desirable. Typically at low pH, color is more vibrant, fruit expression more energetic, balance superior, everything's in better focus. pH tends to rise gradually as grapes ripen, and then, at some point, the rise becomes more precipitous. If my grapes are picked past that point, I'm always disappointed in the resulting wine. Every time.

I think malate is more acidic than tartrate.

Nope. Malic acid's first pKa is 3.4, L-tartaric has a first pKa of 2.8. It makes sense when you consider that the difference in their structures -- the extra hydroxyl on tartaric -- should help acidify tartaric.

Mark Lipton

Low-acid sangiovese, that's a first.

Low-acid sangiovese, that's a first.

Funny I know but when I did my initial scan for info on the internet the only info I found was on Winepress.com where someone had very similar numbers from some Sangio they purchased from California. Their brix were higher but the pH and TA numbers were almost a perfect match. It did make me wonder if Sangio is more prone to this condition.

With the pH at 3.3, I'd suggest adding sugar to 23 Brix, and making no adjustment for acidity at this point, keep the SO2 low and inoculate with malo-lactic culture close to the end of yeast fermentation. When malo-lactic completes, check your acid numbers again and add tartaric acid to raise TA to about 6.0, as long as the pH doesn't go too low. I'm usually dealing with low pH and high TA, but not this year. I've got good numbers on PN, Cab Franc and Merlot.

I went to see Howie last week to get some Steuben he had picked up while we were away. After transferring it to my carboys we went into his garage. The first thing you see is his pride and joy, a big shiny motorcycle. He had ridden it to Syracuse, about 3 hours, in August when we met for the NYS Home Winemaking Awards. Behind the bike stood a big blue barrel full of Cab Franc, 30 gallons as I remember. Howie looked happy as a kid in a candy store as he pushed down the cap and told me about how he was getting some Merlot to blend in and an oak barrel later that day. In such a great year, this was the time to go for it. The Niagara River is not far from his house and I just had driven along it. So I suggested he call the wine Niagara Right Bank. Watch out St. Emilon!

With the pH at 3.3, I'd suggest adding sugar to 23 Brix, and making no adjustment for acidity at this point, keep the SO2 low and inoculate with malo-lactic culture close to the end of yeast fermentation.

Thanks Howie. That is exactly what I did.

When malo-lactic completes, check your acid numbers again and add tartaric acid to raise TA to about 6.0, as long as the pH doesn't go too low.

I was planning to blend with other juice instead of add tartaric. Most of my other grapes came it with pH in the 3.4-3.45 range and TA in the 0.55 - 0.65 range. I will not be able to get the final TA up to 0.6 but I should not have to worry about dropping the pH too low either.

I've got good numbers on PN, Cab Franc and Merlot.

Good to hear.

As Brain pointed out TA stands for not just Total Acidity but Titratable Acidity. Being an amateur winemaker I would think a TA determination will include both Fixed Acidy (FA) and Volatile Acidy (VA) that are present in my wine or must (juice). But my calculation for TA will be based on what I (we-amateur winemakers) think the dominate acid is). I could isolate the VA of a wine or juice sample by running my sample through a VA still apparatus and then do my titration and just calculate for % VA (expressed as acetic acid).
And then TA – VA (expressing both in the same acid) = FA (Fixed Acid).

When it comes to weak acids in wine or juice there is no real correlation between TA and pH. A low pH and low TA means is that a “large percentage” of the acid present in my wine or juice sample is ionized.

Salute

Brian,

Personally, I would not call a pH of 3.3 on Sangiovese too low (better that than >3.6), though I do concede that the TA and Brix is a little low. Given it was a hot year, the fruit's probably got more tartaric than usual (which pushes pH down more than malic does). Sounds like there was decent ripeness (seeds); I would think some bitterness in Sangiovese skins wasn't necessarily a bad thing (think of the slight pleasant bitterness of the tannins of Tuscan Sangiovese)... but more importantly how was the flavour?!

I haven't worked with Maryland fruit, but I'd be pretty happy with a pH of 3.3 on Sangiovese. TA's in the 5 to 6 g/l range aren't terrible IMO, though many would want more than 4.7 in a Sangio. If you really wanted to acidify/chaptalise, I'd go with tartaric to somewhere around 5.5 g/l and I would not chaptalise to 12 to 12.5% pabv. But I think blending with other must would be better (and your other juice at pH 3.4 to 3.45 and TA 5.5 to 6.5 g/l sounds good). I would advise against acidifying post-fermentation (and certainly not more than about 0.5 g/l if you absolutely feel you have to) - it tends to result in more obvious/disjointed acidity. IMO, the time to acidify (if you must) is pre-fermentation.

(BTW, technically speaking, titratable acidity and total acidity are not the same thing. We're really talking titratable in this thread, though the difference between the two is not really significant for the purposes of this discussion.)

I think malate is more acidic than tartrate.

Nope. Malic acid's first pKa is 3.4, L-tartaric has a first pKa of 2.8. It makes sense when you consider that the difference in their structures -- the extra hydroxyl on tartaric -- should help acidify tartaric.

Mark Lipton

Yep, you're right. But malic acid does seem to tickle the palate as more sour than tartaric, at least in my experience.

-Paul W.