An acid salt is both an acid and a salt, rather than something that’s separate from either/both. Regarding acidity, potassium bitartrate has one hydrogen ion (as opposed to two with Tartaric) that that can dissociate.
Potassium bitartrate can be either a crystal or in solution.
Higher pH soils is one way to prevent potassium bitartrate…preventing it entirely is a spiritual goal.
Yes, that much I agree. However, it is a salt that can function as an acid, not an acid per se. This was the first time I’ve seen potassium bitartrate counted in as a separate acid, which it really isn’t - just a compound formed from tartaric acid. So usually potassium bitartrate is counted as a fraction of the tartaric acid content of wine.
Potassium bitartrate can be either a crystal or in solution.
Yes, of course. I mean, this is the basis of wine crystal formation.
Higher pH soils is one way to prevent potassium bitartrate…preventing it entirely is a spiritual goal.
Righty, so once you have a vineyard, there’s really not much one can do to prevent it? Apart from fingering the terroir by trying to adjust the soil pH?
And I still didn’t really understand how it is a spoiler in wine. After all, virtually all grape juice contains potassium bitartrate, as a portion of tartaric acid in grape juice is in potassium bitartrate form, right? How then it can be a spoiler? Am I missing something here?
Not as defined by Boulton and colleagues. “Total acidity” means adding up all the acids that you can measure individually in the wine, but those individual acid measurements don’t take into account the buffering effect of metal cations. So when we measure tartaric acid we are measuring the total amount of tartaric acid, including molecules that have exchanged a hydrogen for a potassium, say. If you have 2-3 g/L of potassium (fairly common), that means a lot of acid has already been effectively titrated and does not contribute to TA.
Quite often in grape juices the tartaric acid content alone will be greater than the TA. I found this very confusing when I first started working in organic acid analysis and was briefly convinced I was messing something up.
Editing to add: from an analytical chemistry perspective, this is because in general we measure organic acids by LC/MS/MS or ion chromatography, so we are measuring the tartrate ion rather than considering its local chemical environment. That’s also why people considering acid adjustments want to know both tartaric acid and potassium content to give them a potassium bitartrate concentration product.
Ben, your real world input is valuable, thanks. Though I can’t say I yet have a really clear picture of the subtleties. Titration with NaOH should find pretty much every available proton. Some have certainly been used in other reactions that have gone on, and I assume some tartrate has precipitated out as Potassium Bitartrate. Given the insolubility of that salt, is there any tartrate contribution to measure from KBitartrate?
I still think most of this is not applicable to the general consumer - and perhaps it needs to be ‘simplified’ if at all possible. How is pH perceived in a wine and how is TA perceived in a wine? If a wine has a low pH but low TA, does it come across as ‘flat’ or acidic? And if a wine has high TA but a high pH, will it come across as ‘crisp’ or ‘flabby’?
Cheers
There is quite a lot of tartrate that exists in wines as aqueous potassium bitartrate. Or rather, I should say that almost all red wines are actually saturated - or nearly saturated - in potassium bitartrate (KHT). Late in fermentation, most red wines become saturated in KHT because of progressive K extraction from skins and because of the lower solubility in KHT in ethanol. So KHT crashes out of a lot of red wines. Then when you drain and press and go to barrel, you have these wines that are essentially saturated in KHT that are then going into colder temps (in the cellar) than their fermentations. Some of these will precipitate further KHT, but KHT precipitation in red wines is actually not favored because the other components in wine really inhibit crystal nucleation and growth. Phenolics are a big part of this. If you add seed crystals of KHT to red wines at room temp, some of them will grow quite a bit in some cases. And, for white wines, there are commercial preparations of other crystallization inhibitors like potassium polyaspartate that are now being marketed as an alternative - or companion - to cold stabilization.
Sorry I got a bit off topic there. My point is, a significant portion of the organic acid pool in real wines is already buffered - or partly titrated, you could say - by the other components of the wine. Some portion of the theoretically donatable hydrogens has already been lost in exchange reactions with other cations. Or at least, that’s the theory. So an NaOH titration will only titrate the remaining donatable ions (up to the equilibrium speciation at the end point - I.e. not all of the protons will be thermodynamically available at pH 8.2).
Random thoughts…
The perceived acidity of a wine is usually considered to primarily be a function of TA, along with other influencing factors (RS, alcohol levels, possibly the presence of bitter compounds, etc). pH really doesn’t enter into it much sensorily.
High pH wines often have less vibrant color, and less clarity. They also can have a somewhat viscous, “slippery” feel to the palate. But I don’t find that pH influences perceived acidity to any extent. And I believe that most wine-related sensory studies bear this out.
High pH wines also have stability issues, and are more prone to oxidation and microbial spoilage, so I would not buy large on high pH wines unless I felt certain that they would hold up.
I politely disagree. This is quite obvious when one drinks a dry base wine for sparkling wine clocking in at 8 g/l TA and pH 2.88 that feels noticeably more acidic than a dry yet ripe Chenin Blanc or Muscadet clocking in at 8,5-9 g/l TA and pH 3.3.
It seems to be a combination of so many different things (pH, TA, RS, dry extract, ripeness and the quality of resulting flavors, tannins, whatnot) that the perceived acidity simply cannot be reduced to TA alone.
High pH wines often have less vibrant color, and less clarity.
I’ve had lots of high pH wines with very vibrant color and complete clarity. Clarity primarily is a function of visible compounds in a solution, so fining and filtration have a larger impact on the clarity than pH. Conversely, often high pH-wines can have a more vibrant, purple hue, which slowly turns duller dried-blood red color as pH drops. However, overall I haven’t noticed that the color vibrancy would be impacted noticeably by the pH.
I’ve mainly seen that pH primarily influences the hue of the color (the higher pH, the deeper the blue and purple hues; the lower pH, the less pronounced the blue hues become, making the wine appear more red - blackish red if the wine if very deep in color or has less clarity (like Aglianico or an extracted Sangiovese), cherry or blood red if lighter in color (like Pinot Noir or Nebbiolo).
Seems like an apples to oranges comparison, Otto.
Most sensory studies on the subject involve starting with a base wine and adjust either pH or acidity sizeably in one direction or the other, and noting the effect on perceived attributes.
Its possible to do this at home, as long as care is taken… a very strong acid would shift the pH of a wine quite strongly without adding as much to the TA.
That’s why winemakers might periodically address high pH-high TA musts with an addition of something like sulfuric or phosphoric acid… the pH drops like a stone while the TA doesn’t shift all that much and the wine post-acid addition won’t taste acidified.
It seems to be a combination of so many different things (pH, TA, RS, dry extract, ripeness and the quality of resulting flavors, tannins, whatnot) that the perceived acidity simply cannot be reduced to TA alone.
I agree.
I tried to say that. Perhaps I worded things poorly.
Clarity primarily is a function of visible compounds in a solution, so fining and filtration have a larger impact on the clarity than pH.
Undoubtedly.
That wasn’t my point, though.
Cheers,
Great post. Well written and digestible.
Greta post Ben (and thanks also, Alan!). I was feeling the need to make the point about titratable acidity (never heard of total acidity in a lab analysis report!) so thanks! We are fortunate in the U.S. that our TAs are shown as tartaric acid equivalents, and the lab analyses also give us pH, of course, but also malic and lactic acid concentrations. This gives wine makers a lot of information (re possible tartaric acid adds (not an issue in my AVA), how your wine’s pH will change if it goes through ML fermentation, the need for cold stabilization in white and rose’ wines, etc.)
I would just add that pH is important to winemakers not just for taste implications, but also when evaluating the microbiology of the wine. ML bacteria for example do poorly in a high-acid, low pH wine matrix (difficult, but not impossible below 3.2; there are many strains and some do better than others). A host of spoilage organisms such as lactic acid bacteria and pediococcus can be pretty much eliminated in wines below 3.4 pH. Brett. is unfortunately more adaptable but nonetheless will usually not flourish as easily. Tech sheets are mostly read by distributors and retail wine buyers. Many (most?) are naturally concerned about stability and they key in on the pH and filtration info (cross flow or other “sterile” filtration thus being common in red wines above 3.4pH, and also for the 90%(?) of white and rose’ wine styles that either have residual sugar, and by the way, are loaded with malic acid and produced without MLF). If you’ve ever experience a bit of fizz on a still wine, it’s probably MLF.
David,
That ‘fizz’ could also be due to dissolved CO2, especially in the cases of wines fermented and aged entirely or mainly in stainless steel.
Great discussion - but I think more focus needs to be on the ‘practical’ nature of pH and TA and how it is perceived by the ‘average wine consumer’. Many winemakers I know focus solely on pH and don’t take into account the fact that a wine or grape must with the same pH can have radically different TA levels, and therefore winemaking decisions based on just the one factor may lead to outcomes that are not as expected or intended , . .
Cheers
Good points
We’re talking about perceived acidity based upon pH ans TA, but we should also include that tartaric acid, malic acid, and lactic acid all perceive differently as well. Tartaric acid, while being the strongest acid as far as pH goes, is the most integrated acidic flavor. Malic has the green apple note, and while relatively weak compared with tartaric, has a distinct acidic perception. Lactic, while texturally more pleasant than malic in red wines, still has a less integrated perception(to me) than tartaric.
Acid maturity is very important, and wines with higher levels of of malic and lactic tend to perceive as equally acidic, and less pleasant, or with more aggressive acidity, than those with higher levels of tartaric(and typically a lower pH). Also, low pH makes a huge difference in efficacy of Sulfur in the wines for freshness and stability.
And as Alan noted, the term “total acidity” is typically interchangeable with titratable acidity. Whether that’s simply a malapropism that has endured or something else I couldn’t say.
Also, which lab are you using? Core Enology provides TA, which is Titratable acidity, and also Tartaric and malic amounts in a sample. But I haven’t ever heard of TA being expressed in Tartaric acid equivalents(this would be a challenge because TA contains other acids than just tartaric).
And finally, we have finished malo on Chardonnay under 3.2pH for years. The only limiting factor seems to be total sulfur level. If you use SO2 at the press pan, then it can be a challenge. If you defer using any SO2 until post malo, then the bacteria usually can consume the malic in a similar timeline to the Pinot Noirs.
What do you mean? Usually wine’s titratable acidity is given in some equivalents and virtually every country except for France uses tartaric acid equivalents.
So if the TA of a wine is 6.7 g/l, it means it doesn’t have 6.7 g/l acidity per se, but instead if all the acids in the wine would be tartaric acid, then there would be 6.7 g/l. Or, in other words, the amount of base required to titrate the wine up to pH 8.2 is equal to the amount of base required to titrate a solution of 6.7 g/l tartaric acid to pH 8.2.
Otto and David,
You are right about that. My apologies, on mispeaking. I appreciate the correction.
This thread needs some shouting from the unwashed bleacher seats. Think missing teeth, four day beard, stained football jersey with the name of some retired player, and creative Cockney epithets. I volunteer.
From a non-scientific consumer point of view, when I see a review of a red wine that says high pH, I think Parkerized past my tolerance level for Parkerization (I’m OK with some Parkerization, I still have a love affair with aged 1998 Australian Shiraz). Yes I know there is no scientific basis for this, but it does inform my decisions about what to drink. It tells me, big soft ripe warm and blowsy, fruit with no discipline. And when winemakers treat their fruit that way, they tend to go all in and throw a lot of new French oak on top of the mess.
A few decades ago, Americans like me saw high acid lighter colored wines from Europe as sour, weird, and no fun, and the cult cabernets from 1992 through 1996 as the epitome of pleasure. In a way we were right. Then, starting with the 1997 vintage (2001 being a nice exception), wine, like some other things lately, became polarized in style. My friends, including Alan Rath, have shown me that slightly higher acid European wines are wonderful, while my personal opinion now is that the crowdpleasing wines (selected expensive wines from Tuscany, Napa, central California depending on the winemaker, plus the Prisoner Apothic Caymus Meiomi bunch) have become, not merely big and ripe, but DNPIM gross, and they all have high pH.
All good points.
My post was spurred on by larry’s very good suggestion that we focus on “the ‘practical’ nature of pH and TA and how it is perceived by the ‘average wine consumer’”.
Since the OP was about looking at technical data sheets particularly with regard to Cal Cab, I thought it would be wiser to focus on TA.
I imagine some data sheets might list quantites of different organic acids separately, but they must be pretty few and far between.
You are probably correct about the data sheets. And if my post came off as a correction, that’s not my intention. Your posts on this thread have been great, my intention was to add another aspect to what you covered(an, “oh yeah, this too” post.)