Sugar levels in mature German Rieslings

[John_Morris]

@Doug Schulman

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.

Yes, I’m curious to know more, too.

[alan_weinberg]

isn’t a polymerized sugar a starch?

[Ian_Sutton]

@D@vid Bu3ker

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

and to an engineer it goes something like this:
“The sugars do polymerize”
“Polymerize”
“P-o-l-y-m-e-r-i-z-e”
“No there’s no parrot”
“I give up”

[Eric_Ifune]

isn’t a polymerized sugar a starch?

Yes. Different carbohydrates have different perceptions of sweetness.

[Dennis_Kanagie]

@Eric Ifune

isn’t a polymerized sugar a starch?

Yes. Different carbohydrates have different perceptions of sweetness.

So the sugar changes to a different substance after a reaction while in the bottle. That means that the amount of molecules hasn’t changed - they’re just in a different structure which changes the perception of taste.

I’m pretty sure that’s what I was saying above.

[Charlie_Gierling]

Several years ago we discussed this among wine professionals and some non-wine-related chemists. The outcome was:

1. yes, mature sweet Riesling tastes less sweet than similar young Riesling
2. analytically sugar levels remain the same. (But the analytics we know about was never making differences between mono-sugars and oligomerized sugars.)
3. Oligo-sugars are supposed to tase less sweet than mono-sugars or sucrose (a disaccharide), have more colour and generally taste more like caramel.
4. the fact that mature sweet riesling gets colour (orange-brown), is less sweet and has caramel-like aromas (but not the burnt part of it) suggest that the process is somehow silinar to caramelisation. Caramelization - Wikipedia

Actually, what is missing is simply the chemical analysis of the sugars in mature Riesling. But we could not find any papers on this. Maybe in the meantime there are.

[KarlH]

But what about acids then. Do they remain constant but changes into some other type of acid that is perceived “softer”? Thanks /

[Phil_David]

@D@vid Bu3ker

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.

Not a lot of sucrose in wine. Grape sugars are largely glucose and fructose.

[David_Bu3ker]

Yeah…I knew that. Not sure what the heck I was thinking.

[Dennis_Kanagie]

@KarlH

But what about acids then. Do they remain constant but changes into some other type of acid that is perceived “softer”? Thanks /

Acids are chemical compounds too and therefore can break down. While the pH level might remain the same, there has to be something going on with the acids too to make them seem to smooth out.

I’m not a chemist so I can’t say what happens though. Has anyone ever done a long term definitive study on the chemical changes during the aging of wine?

[David_Bu3ker]

What is this “acid smooth out” you speak of? 20+ years (well over 1000 bottles) of drinking German Riesling, and I have never seen/tasted that.

[Dennis_Kanagie]

@D@vid Bu3ker

What is this “acid smooth out” you speak of? 20+ years (well over 1000 bottles) of drinking German Riesling, and I have never seen/tasted that.

So you’ve never had a Burgundy that the acid has seemed to mellow after a couple decades of age? I don’t know what causes it. I just know it happens. Members here mention the acidity toning down with age too.

[Charlie_Gierling]

German Riesling keeps the taste of its acidity over years. It is the best way to tell the vintage

[David_Bu3ker]

@Charlie Gierling

German Riesling keeps the taste of its acidity over years. It is the best way to tell the vintage

Precisely.

[Jurgens_E]

As it is a slow day in the lab I spent some time looking at papers on the decomposition of sugars during aging.

Perception of sweetness is something else as pointed out above. I depends on acidity and other compounds that taste sweet, or not, as well. Confirmation bias will also play a role of course. When you think aged wine tastes less sweet, they will do so.

Unfortunately I was not able to find literature measuring sugar stability. There is an increase in polysaccharides, and likely mono sacharides as well, during aging which are derived from yeast. This was studied in wine made with different yeasts and identical musts. Effect of different aging techniques on the polysaccharide and phenolic composition and sensory characteristics of Syrah red wines fermented using different yeast strains - PubMed

How sweet these monosaccharides are is not clear. It is also not clear to me if sugars that are oxidized, esterified etc. are still sweet.

However, this is all not very interesting compared to this paper that analyses the composition of 170 years old champagne. Massive quantities of glucose and fructose were still present.
http://www.pnas.org/content/112/19/5893.abstract

So, I conclude that sugar degradation is not a really important phenomenon but am ready to stand corrected…

[Eric_Ifune]

Acids can react with other compounds to form esters which contribute to the flavors and aromas of age.