There’s an expression in Bordeaux with regard to old Sauternes: il a mange son sucre/it has eaten its sugar.
This is a well-known phenomenon – some Sauternes seem to be nearly dry after a couple of decades. I recently experienced the same thing with an aged Alsace and, indeed, some very old Port can seem dry.
By dry, I don’t mean dried out. I mean simply “not sweet”.
What I’m wondering is how much of this is due to an impression, and how much may be due to the change in the wine’s chemical balance, either a combining of the sugar or its overshadowing by other constituents.
Any input would be much appreciated.
As far as I understand it, it’s a consequence of polymerization of the sugar molecules, i.e. they build longer chains over time that doesn’t interact with the taste receptors in the same way as sugar. So the sugar molecules morphs iver time into more complex molecules.
This is why I liked aged German riesling far more than young ones - once the sweetness diminishes and steps back, you can taste the terroir and the wine character. Same for dessert wines. You don’t want the sweetness 100% gone, though, just for it to have receded enough to get the full spectrum of the wine.
In terms of explaining the chemistry, I’ve got nothing, but that’s what I’ve always observed with these wines.
That’s very interesting. Are there any sources for this that you could point us to? Or maybe you have a more thorough understanding of the chemistry (which I wouldn’t understand) and are sure this happens? I don’t doubt it, but I’ve never seen an explanation for why sweet wines taste less sweet as they age.
By “impression”, I mean that there are things we think we perceive, but our senses have actually led us down the garden path.
A good example of this is optical illusions.
By the same token, acidity can make a sweet wine seem less sweet than it really is, alcohol can obsure a wine’s other oganoleptic characteristics, the pale color of a Burgundy can make one mistakenly think a wine is weak and inconsequential, etc.
In other words, we can think a wine is such and such a way when that is not the case…
The main thrust of my question was of a chemical nature: does the sugar content actually decrease over the years? Does the sugar break down and, if so, how so and into what other substances?
Could other complex organic compounds in the wine cancel out the taste sensation of sweetness?
Simple question: does a Port, Sauternes, or any sweet wine have less sugar after twenty years?
Or are we taking more about different types of sugar?
The TL;DR version: Odd is basically correct, and the answer to both your simple questions are yes. Yes, the sugar content decreases over time because they polymerize. Yes, the polymerization replaces one type of sugars (simple sugars like glucose, fructose, sucrose) with another type of sugars (long-chain sugars, like carbohydrates, which your tongue does not perceive to be sweet)
I think this is why, if you bite into a potato and just chew it in your mouth long enough, it starts tasting a bit sweeter. Chemicals in your saliva start to break down the carbohydrates (long-chain sugars) into simple sugars, which your tongue can taste. Which brings up an interesting corollary: if you drink an aged Sauternes, it should taste sweeter over time if you just keep swishing that sip in your mouth.
I caveat that this is my uneducated opinion based on the article and whatever I remember of introductory organic chemistry from way back when.
OK, thanks Alex. My even hazier memory of chem accords with Sam and Odd’s posts. I’d then only wonder whether our “expectation” of what we’ll taste triggers or catalyzes (false-starts?) any tastebuds on our tongue because we, um, “think them active” or somesuch.
Guys, do you think the polymerization process affects the aromatics too?
I wouldn’t call it an antioxidant. Actually, the sugars do oxidize and that’s a large part of what goes on when aging wine. The change in taste is also related to the change in color - most older whites turn amber.
There are several different reasons for the changes, enzymatic and non-enzymatic. For example, you have the Maillard reaction, which is the reaction between the simpler sugars mentioned and amino acids. That’s a complicated reaction usually associated with cooking, but it can occur at lower temperatures.
Wine has various things that act as catalysts in some of the reactions, for example iron, in which sugars are transformed, sometimes into something else. You can also have more direct oxidation.
in addition, remember that our perception of any flavor is attenuated by what comes along with it. In other words, we don’t necessarily have an isolated “sweet”, we have a sense of sweetness combined with various acids and other flavors. All of those, including the acids, change over time, either precipitating out or forming degradation compounds or changing in concentration and the gestalt is the total change in the wine and its perceived sweetness.
But that linked article was wrong in one respect. It says:
“Taste buds can register four types of sensation; sweet, sour, bitter and salt.”
That’s not the case and in fact, nobody really knows how many sensations we can register. It’s pretty well accepted now that the sensation we get from Parmesan cheese and soy sauce, umami, is a distinct sensation, as is the sensation we get from fat, which also has specific receptor cells on the tongue.
Yup, I read recently that fat receptors have been identified. There’s also another taste sensation that the Japanese have verified. Descriptions of that one do not clarify to me what it is, but taste sensations are impossible to describe verbally. By my count, that’s 7 known tastes, but I’ll bet there are at least a few more.
It’s certainly the case that older German wines become less sweet, at least to human perception. It’s less apparent with the very concentrated sweets wines like BAs and TBAs, or Sauternes, but from Auslese and down, rieslings do dry out with age. If everything is balance, they take on an etherial quality in the process. I love them in that stage.
Mike - theoretically, most or all carbon-chain compounds should be able to polymerize? So aromatics and other molecules in wine could potentially see polymerization, but you’d have to look at the specific compound and its chemistry (activation energy and other such considerations). As Greg mentioned, there’s a myriad of possible reactions between sugars, acids, tannins (tannic acid?), aromatics, etc.
Need a proper food scientist or chemist to answer this question at the next level of detail; I’m already way out of my element.
Whole lotta’ hand-waving going on here. I’m a chemist, and I have no idea. And I just tasted through a bunch of Climens wines tonight, ranging from 66 to 88, and they all seemed about equally sweet to me, taking into account vintage variation. In my own experience, “good” bottles of old Port and Sauternes, and other sweet wines don’t lose much of their sweetness with age, though obviously they change. My hunch is that more often than not, wines that have changed significantly are due to oxidation from imperfect cork seal.