I found this old file that was lost in the Wt deluge. It is a little narrative and elliptical and now out of its context of several years ago, but it gets you there.
-J
There has been some discussion lately about the acid content of wines. Actually, it never stops, but the quantitation of this discussion is pretty recent. I’ve tried to give the numbers on wines that I’ve tasted in cellars or fairs. [Link to last year’s Loire summary and also to Proprietor]
In one thread, there was a discussion of Muscadet being a low acid wine. This was hard to understand, since good Muscadet sure doesn’t seem like a low acid wine. It seemed to require a special explanation, and I didn’t have one to give so I let it slide. But it nagged at me, and I think I finally have the answer—it’s an issue of currency conversion. To give the conclusion ahead of the explanation, the French calculate acid in wine using different units than many other people. It’s sort of the way Joe Dressner insists on calculating French land prices in Old Francs. He’ll deliver the price in Old Francs and smile smugly as you puzzle in incomprehension. But it’s fine if everyone else paid Old Francs for their house.
I was in France last week, and I queried some of the more technically inclined winemakers I met about this. It turns out that winemakers in France use acidity units based on sulfuric acid, while winemakers in many other places use units based on tartaric acid. Since all their neighbors use the same currency, no one bothers to explain what they mean by “grams of total acid.” It turns out that 1 gram by sulfate is 1.5 grams by tartrate. Much like prices in Euros, acids go farther in France. A Muscadet with 4.5 grams of acid in French (sulfate) would have 6.75 grams in the US or in Germany or Hungary (tartrarte) and taste the same. This cheerfully resolves the Muscadet problem, and also explains why demi-sec Tokaji tastes a lot like demi-sec Vouvray but has numbers that look different.
For the two of you who actually care and to whom it’s not already obvious, I’ll explain a bit about the chemistry underlying my former confusion. The biggest problem, frankly, is that everyone is using the wrong units. Any chemist will tell you that the right answer to the question “how much?” comes in units called moles, and that if you start messing around with grams instead you will quickly be in trouble. Moles are just a count of atoms, ignoring how much they weigh.
You may recall from high school chemistry a bit about the Brønsted theory of acids and bases, where an acid is a proton donor. A Brønsted acid has the form B:H, and can donate a positive proton to something (like your tongue) to give B- (known as the “conjugate base” and an H+ (the proton) on the something.
Wine has a variety of acids in it—tartaric, malic, lactic, acetic, and so on. The total amount of acid and the proportions of the different ones both matter to our perception, but it turns out that a count of the total amount of acid is a pretty informative number. This is obtained by a titration of the wine, I presume. The different acids are just different B’s in the Brønsted business, but they all donate the same proton. Some B’s are bigger than others.
But stupidly, rather than expressing this result in an internationally sensible and unarguable Esperantoish currency like moles of protons, which would just be a physiologically relevant count of protons donated, the different wine analyses instead falsely pretend that all the acid was tartaric (in the US and much of Europe) or alternatively pretend that it was sulfuric (when in reality essentially none of it was). Tartaric acid weighs half again per acid bit than sulfuric, so this bulks up the resulting number by 50%.
The whole business has a very 19thC feeling about it to me.
-J
There has been some discussion lately about the acid content of wines. Actually, it never stops, but the quantitation of this discussion is pretty recent. I’ve tried to give the numbers on wines that I’ve tasted in cellars or fairs. [Link to last year’s Loire summary and also to Proprietor]
In one thread, there was a discussion of Muscadet being a low acid wine. This was hard to understand, since good Muscadet sure doesn’t seem like a low acid wine. It seemed to require a special explanation, and I didn’t have one to give so I let it slide. But it nagged at me, and I think I finally have the answer—it’s an issue of currency conversion. To give the conclusion ahead of the explanation, the French calculate acid in wine using different units than many other people. It’s sort of the way Joe Dressner insists on calculating French land prices in Old Francs. He’ll deliver the price in Old Francs and smile smugly as you puzzle in incomprehension. But it’s fine if everyone else paid Old Francs for their house.
I was in France last week, and I queried some of the more technically inclined winemakers I met about this. It turns out that winemakers in France use acidity units based on sulfuric acid, while winemakers in many other places use units based on tartaric acid. Since all their neighbors use the same currency, no one bothers to explain what they mean by “grams of total acid.” It turns out that 1 gram by sulfate is 1.5 grams by tartrate. Much like prices in Euros, acids go farther in France. A Muscadet with 4.5 grams of acid in French (sulfate) would have 6.75 grams in the US or in Germany or Hungary (tartrarte) and taste the same. This cheerfully resolves the Muscadet problem, and also explains why demi-sec Tokaji tastes a lot like demi-sec Vouvray but has numbers that look different.
For the two of you who actually care and to whom it’s not already obvious, I’ll explain a bit about the chemistry underlying my former confusion. The biggest problem, frankly, is that everyone is using the wrong units. Any chemist will tell you that the right answer to the question “how much?” comes in units called moles, and that if you start messing around with grams instead you will quickly be in trouble. Moles are just a count of atoms, ignoring how much they weigh.
You may recall from high school chemistry a bit about the Brønsted theory of acids and bases, where an acid is a proton donor. A Brønsted acid has the form B:H, and can donate a positive proton to something (like your tongue) to give B- (known as the “conjugate base” and an H+ (the proton) on the something.
Wine has a variety of acids in it—tartaric, malic, lactic, acetic, and so on. The total amount of acid and the proportions of the different ones both matter to our perception, but it turns out that a count of the total amount of acid is a pretty informative number. This is obtained by a titration of the wine, I presume. The different acids are just different B’s in the Brønsted business, but they all donate the same proton. Some B’s are bigger than others.
But stupidly, rather than expressing this result in an internationally sensible and unarguable Esperantoish currency like moles of protons, which would just be a physiologically relevant count of protons donated, the different wine analyses instead falsely pretend that all the acid was tartaric (in the US and much of Europe) or alternatively pretend that it was sulfuric (when in reality essentially none of it was). Tartaric acid weighs half again per acid bit than sulfuric, so this bulks up the resulting number by 50%.
The whole business has a very 19thC feeling about it to me.