Reduction in Riesling?

M

MLipton

Mark Lipton
Tonight was Day 3 of a bottle of 2007 Schloss Gobelsburg Riesling that was sealed under screwcap. On opening, it had an overwhelming petrol character, but after several days in the fridge the petrol had receded and some stone fruit had come to the fore. So, is the petrol character of Riesling a byproduct of reduction? Perhaps I've been reading too much Gilman, but I have noticed that young dry Rieslings sealed under screwcap tend to show that petrol character in spades. Those of you better versed in the manifestations of reduction, please weigh in with your thoughts.

Mark Lipton
 
Independent of the answer with respect to petrol and reduction, just a reminder that, per Michel Augé, screwcaps never cause reduction, only prevent it (and other things, presumalbly petrol too, if independent) from dissipating through gradual oxygen exchange with the outside of the bottle.
 
originally posted by Oswaldo Costa:
... per Michel Augé, screwcaps never cause reduction, only prevent it (and other things, presumalbly petrol too, if independent) from dissipating through gradual oxygen exchange with the outside of the bottle.
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Not sure I buy this.

I hate getting involved in this religious war, but I don't think a good cork exchanges enough air to matter, particularly in the short term.

A cork may supply a bolus of air to a bottle when it is compressed and inserted, though.

Petrol flavors to me depend on two things--how much precursor is made (mysterious), and how quickly it is freed from its non-smelly glycoside (pH and enzyme dependent).
 
originally posted by robert ames:
make some strong coffee and start reading. . .

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www.wine-pages.com
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Many thanks, Robert. The most salient point from his essays:

Interestingly, according to tests conducted by AWRI, natural cork closures absorb as much as 50% of the TDN found in any wine, while Altec and "One + One" technical corks can remove as much as 70%, and the most absorptive synthetic closures no less than 98%! Screwcaps actually preserve TDN, but I'm a screwcap fan, and TDN is not the only thing that corks absorb.

From this, I conclude that it is not reduction per se but rather lack of sequestration of TDN that leads to increased petrol character in screwcapped bottles.

Mark Lipton
 
originally posted by SFJoe:
Petrol flavors to me depend on two things--how much precursor is made (mysterious), and how quickly it is freed from its non-smelly glycoside (pH and enzyme dependent).
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To complicate the TDN story, the concentration of the compound in a wine can be elevated by high temperature shipping

Effect of Simulated... (abstract)

and storage

Effect of Storage... (pdf)

temperatures, in addition to the other glycoside-cleaving reaction parameters.
 
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