What is the effect of bound sulfur?

[Oswaldo Costa]

Discussions of SO2 seem to focus on free SO2 as being the only one that matters, and I found little info online about the effect of bound SO2. Only a reference from Peynaud saying that bound acts as an anti-bacterial agent, but that's about it.

Maybe this is because bound is no longer active, so people focus on what can still play a role.

All this because I wonder if bound SO2 is not at least partially responsible for wines closing down. Hard to imagine it has no impact whatsoever on the aromas.

Much obliged if anyone can cast some light.

 

[Ian Fitzsimmons]

50 shades of yellow.

 

[MLipton]

What is meant by "bound sulfur" are the various reaction products of bisulfite ion with the molecules found in wine. Ones that I know of are the sulfite esters of glucose and anthocyanins and the bisulfite addition complexes of acetaldehyde and other aldehydes. Because all of these reaction products are more stable under acidic conditions, there is a gradual release of SO2 from "bound sulfur" as the wines ages (there are two effects going on there: alteration of equilibria per Le Chatelier's Principle as free SO2 is consumed and shifting of equilibria as the pH of wine rises with age). It is generally agreed, I think, that these "bound sulfur" compounds do not have an appreciable sulfur taste or smell.

I had a very interesting experience in the cellars of Marcel Lapierre where he presented us with two samples of the same wine, both his S and N bottlings. The sans souffre wine was more open, fruitier and fresher than the sulfured wine. He told us that, in his experience, the sulfured wine would recover within a month or two of bottling.

Take from that what you will.

Mark Lipton

 

[Oswaldo Costa]

Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

 

[MLipton]

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

 

[Florida Jim]

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

Finally, a concise and understandable explanation of this part of the aging process.
Turns out, I’m getting a little softer too, as I age.
Best, Jim

 

[Jeff Grossman]

originally posted by MLipton:
I had a very interesting experience in the cellars of Marcel Lapierre where he presented us with two samples of the same wine, both his S and N bottlings. The sans souffre wine was more open, fruitier and fresher than the sulfured wine. He told us that, in his experience, the sulfured wine would recover within a month or two of bottling.

During my visit to Julien Labet he poured two wines to compare: same lot, same vinification, but one sulfured and one not, both bottles already open for 6 days. The unsulfured wine was becoming soft and round and generic while the sulfured one was still tight and true (and no rotten egg smells).

 

[Oswaldo Costa]

originally posted by Jeff Grossman:

originally posted by MLipton:
I had a very interesting experience in the cellars of Marcel Lapierre where he presented us with two samples of the same wine, both his S and N bottlings. The sans souffre wine was more open, fruitier and fresher than the sulfured wine. He told us that, in his experience, the sulfured wine would recover within a month or two of bottling.

During my visit to Julien Labet he poured two wines to compare: same lot, same vinification, but one sulfured and one not, both bottles already open for 6 days. The unsulfured wine was becoming soft and round and generic while the sulfured one was still tight and true (and no rotten egg smells).

That just serves to show you.

 

[Ian Fitzsimmons]

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

Would the reaction with sugars therefore also help to explain, in your opinion, the slow reduction in sweetness discerned in, say, aged MSR Riesling wines?

 

[MLipton]

originally posted by Ian Fitzsimmons:

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

Would the reaction with sugars therefore also help to explain, in your opinion, the slow reduction in sweetness discerned in, say, aged MSR Riesling wines?

Absolutely.

Mark Lipton

 

[robert ames]

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

a half life of months doesn't sound that slow. a half life of 11 months would mean that the acid would be 90% gone in approximately 3 years. i don't find that wines often go flabby that fast.

 

[MLipton]

originally posted by robert ames:

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

a half life of months doesn't sound that slow. a half life of 11 months would mean that the acid would be 90% gone in approximately 3 years. i don't find that wines often go flabby that fast.

It's not quite that simple because even at completion not all the acid is consumed (in fact, the value would be just over 50%).

For the masochistic interested, what's going on is an equilibrium:

RCOOH + R'OH RCOOR' + H2O

in which the change in free energy is damn near zero, but just slightly negative. Additionally, and most pertinently, the rates of both forward and reverse reaction are painfully slow, meaning that the system takes a long time to reach true equilibrium. The reaction going on here is known as Fischer esterification, named after the great Emil Fischer (who, coincidentally, was the person who worked out the structure of glucose back in the early 20th C).

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en.wikipedia.org

Mark Lipton

 

[Jayson Cohen]

originally posted by MLipton:

originally posted by robert ames:

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

a half life of months doesn't sound that slow. a half life of 11 months would mean that the acid would be 90% gone in approximately 3 years. i don't find that wines often go flabby that fast.

It's not quite that simple because even at completion not all the acid is consumed (in fact, the value would be just over 50%).

For the masochistic interested, what's going on is an equilibrium:

RCOOH + R'OH RCOOR' + H2O

in which the change in free energy is damn near zero, but just slightly negative. Additionally, and most pertinently, the rates of both forward and reverse reaction are painfully slow, meaning that the system takes a long time to reach true equilibrium. The reaction going on here is known as Fischer esterification, named after the great Emil Fischer (who, coincidentally, was the person who worked out the structure of glucose back in the early 20th C).

Loading…

en.wikipedia.org

Mark Lipton

Do you mean steady state, not true equilibrium? Or are you defining them the same way?

 

[Ian Fitzsimmons]

A downhill reaction with a gentle slope and small equilibrium constant?

What is R?

 

[MLipton]

originally posted by Jayson Cohen:

originally posted by MLipton:

originally posted by robert ames:

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

a half life of months doesn't sound that slow. a half life of 11 months would mean that the acid would be 90% gone in approximately 3 years. i don't find that wines often go flabby that fast.

It's not quite that simple because even at completion not all the acid is consumed (in fact, the value would be just over 50%).

For the masochistic interested, what's going on is an equilibrium:

RCOOH + R'OH RCOOR' + H2O

in which the change in free energy is damn near zero, but just slightly negative. Additionally, and most pertinently, the rates of both forward and reverse reaction are painfully slow, meaning that the system takes a long time to reach true equilibrium. The reaction going on here is known as Fischer esterification, named after the great Emil Fischer (who, coincidentally, was the person who worked out the structure of glucose back in the early 20th C).

Loading…

en.wikipedia.org

Mark Lipton

Do you mean steady state, not true equilibrium? Or are you defining them the same way?

Jayson, in this context the two terms are synonymous (as in “steady state equilibrium”). There is a distinction in kinetics, with steady state intermediates, but I doubt that they exist in this instance.

Mark Lipton

 

[Oswaldo Costa]

originally posted by MLipton:

originally posted by Ian Fitzsimmons:

originally posted by MLipton:

originally posted by Oswaldo Costa:
Thank you, Mark, that's helpful.

Didn't know that pH rises with age.

The acids in wine will slowly react with the alcohol and/or the sugars and anthocyanins to form esters. When I say slow, I mean really slow (half lives of months, maybe years), but they do seem to occur and to account for the softening of wines with age.

Mark Lipton

Would the reaction with sugars therefore also help to explain, in your opinion, the slow reduction in sweetness discerned in, say, aged MSR Riesling wines?

Absolutely.

Mark Lipton

Before this thread I was under the misapprehension that acidity did not decline with time, only sweetness (i.e., fruit), so that the older the wine, the greater the chances that acidity would overwhelm what fruit was left.

Now that it has been exposed that acidity too declines, can it at least be said that sweetness declines faster (has a shorter half life) so that it remains true that, over the long haul, a wine will tend to become relatively more acidic than sweet?

 

[Ian Fitzsimmons]

Sweetness is not fruit, in my understanding of things. Sweetness comes from sugars, fruit conventionally connotes a variety of qualities in the flavor and aroma dimensions. Many dry wines may be enjoyed before shutting down for their 'youthful fruit.' Dry Gewürztraminer is an example of a variety yielding wines that taste sweetish, because of their floral aromas, with little or no RS.

As to relative rates of sugar and acid decay, if they are comparable, would tend to support the dictum that youthful balance is a key indicator of long-term quality - balanced in youth => balanced in maturity.

 

[Oswaldo Costa]

originally posted by Ian Fitzsimmons:
Sweetness is not fruit, in my understanding of things. Sweetness comes from sugars, fruit conventionally connotes a variety of qualities in the flavor and aroma dimensions. Many dry wines may be enjoyed before shutting down for their 'youthful fruit.' Dry Gewürztraminer is an example of a variety yielding wines that taste sweetish, because of their floral aromas, with little or no RS.

As to relative rates of sugar and acid decay, if they are comparable, would tend to support the dictum that youthful balance is a key indicator of long-term quality - balanced in youth => balanced in maturity.

Since fruit is sweet, I tend to conflate sweetness with fruit, but I agree with your first three sentences.

In the fourth, I didn't understand the phrase "wines that taste sweetish because of their floral aromas" (even with the comma after sweetish) since aroma and sweetness are unrelated.

In the fifth, I've never heard that dictum (but I may move in the wrong circle of platitudes) and it seems very unlikely that the rates of decay are in any way similar.

 

[mark e]

originally posted by Oswaldo Costa:

In the fourth, I didn't understand the phrase "wines that taste sweetish because of their floral aromas" (even with the comma after sweetish) since aroma and sweetness are unrelated.

Neither do I. Dry gewürztraminer is low in acidity, often high in alcohol and has a glyceral quality that synergistically impart a sense of sweetness. However, it's really quite different than residual sugar.

 

[Jonathan Loesberg]

There are gewurztraminers that taste completely dry, though not many in Alsace. Our own Kay Bixler makes a very good one, Eminence Road. I also understand what Ian meant by the floral perfume creating the impression of sweetness. Oswaldo is right that sweetness is one of the basic taste sensations, but floral associations no doubt have an effect on impression. Still, something else is going on in Alsatian wines that say they are vinified to dryness, because, as I said, one can find gewurztraminers that taste completely dry.