Sugar levels in mature German Rieslings

As offdry German Rieslings age and appear to taste less sweet in the bottle does the measurable sugar level drop or is it strictly a taste sensation? Just a perception of better balance or do the sugars somehow get used up?

I am cutting back on my sugars so this question is of high interest as Germans are my largest white holdings.

The sugars do polymerize. Or at least that is how the chemistry folks explained it to a physicist.

Thanks for your response David. For a layman, during polymerization do the sugars reduce in level or are they just changed?

I believe reduce, but am not entirely clear.

That would be welcome news.

Wait how?? Where does the sugar go? That’s fascinating. Not doubting just curious!

Somewhere in the archives here (and elsewhere) are explanations.

Look up the Maillard reaction.

Polymerized sugars are carbohydrates.

There are sugars that ferment and turn to alcohol, there are sugars that don’t ferment. Eventually, residual sugar will react with the many acids present - and Riesling is a fairly aidic grape. Tartaric acid also reacts with potassium to form tartrate crystals. There’s a lot of stuff going on in a bottle of wine as it ages.

We recently had a Spatlese from 1983 that was drier than most Kabinetts we’ve had from 2007. I guess the acids and sugar must cancel each other out for lack of a better description.

The acidity versus sugar is not what dried out your Spätlese. The sugar does reduce over time.

But what causes the sugar to reduce over time? It just doesn’t evaporate on it’s own - there MUST be a chemical reaction that changes it to something else that reduces the sweetness. Acid, or some other substance present in wine, HAS to break down sugar and turn it into something else because it can’t simply disappear while inside the bottle.

That may have more to do with the fact that, since 1999, German vintages have been much riper than they were in decades past. Sugar levels in the grapes have been higher, so grapes that qualify as Auslese are bottles as Spatlese and down the line. Kabinetts today are sweeter than they used to be.

Also, your perception of sweetness is dependent on the acid level; you can’t separate them. So a high acid-year can seem less sweet even though the R.S. level is the same. (I don’t remember what 1983 was like.)

So drying with age isn’t the only possible explanation for that 83 Spatlese seeming dryer than more recent Kabinetts.

OK I just have a big discussion about this…Thanks to whomever mentioned the polymerized sugars. I always wondered what happens to them.

Next nerd question, if a riesling or any wine for that matter has “sweetness” to it but it’s 0% RS are the winemakers fibbing? Where does the sweetness come from and where do the carbs/calories come from? Do the sugars convert into calories during fermentation?

Lyle Fass feels there is no decrease in sugar levels.

So when a sweet German Riesling gets old what happens? A comment I hear a lot is that it loses its sweetness. That is wrong. The sugar level in a wine is locked in from the moment it is bottled and that cannot be changed. Same with the acidity. But our perception of these components changes. As Riesling gets older it gets leathery, gamey and earthy like a forest floor and the sweetness recedes into the background but as I said before the levels as measured by a lab are locked in for the life of the wine. The acid may also be a little lower by our perception but chemically speaking 10 grams of acid is 10 grams of acid.

That’s wrong – it presupposes 10g/L of sugar tastes the same regardless of the type of sugar. Different sugars have different perceived levels of sweetness all else equal. As wine ages, the sugars polymerize (with each other and other compounds in wine) and form more complex molecules. There’s still 10g/L of sugar/carbohydrates there, but the perception of sweetness would change.

It’s no longer sucrose. What particular form does it become? That’s the question I do not recall an answer to.

Brandon J-alcohol has calories. And if the wine has 0 RS you are probably picking up on fruit tones that seem sweet.

Alcohol can give the perception of sweetness. Also, you can have some caramelized flavors from oak, that one associates with sweetness. In addition, low acid can increase the perceived sweetness. I think some combination of these contribute to the sweetness of a lot of New World chardonnay and pinot, for instance – even wines that may not have any R.S.

Other times the winemaker is just fibbing.

Also, glycerol tastes sweet. Certain yeast strains and grape characteristics can create relatively high levels of glycerol in finished wine, sometimes giving a sensation of sweetness without a detectable level of residual sugar. I think this is why wines from Mollydooker and Rombauer taste sweet.

I’m fascinated by the main discussion here. If anyone knows what the polymerized sugars become (are they some other type of sugar that doesn’t taste as sweet, or maybe some other form of carbohydrate?), please weigh in. I’ve long wondered why sweet wines (not just Riesling) often taste less sweet as they age. I remember this being mentioned before, but I’ve never seen much detail behind it. What David says does answer the question, but it leaves me with more questions.

Been doing a little bit of literature reading. Here’s a fun tidbit I came across:

Although present in minor quantities, the aromatic hydrocarbons: benzene, toluene, m-xylene, p-cymene, cumene, styrene… can be expected to contribute to the hydrocarbon-like aroma evident in these wines [aged rieslings]

Secondly, I don’t have access to the article itself (which discusses Madeira, but perhaps the principles can be applied to any wine with RS) seems it may also be relevant. Long story short:

…the kinetics of sotolon formation is closely related with residual sugar contents, suggesting that this molecule may come from a component like sugar.