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TomHill

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Dissolved CO2 in Austrian Wines...

by TomHill » Fri Sep 21, 2018 12:51 pm

Next week, at SantaFe W&C Fiesta, Val Masten will be giving a Seminar on Austrian wines. Below are some questions I've sent to her on the subject of Dissolved CO2 in Austrian Wines:
Val,
I will be attending your Seminar on Austrian wines Fri morning. I have a few questions on
Dissolved CO2 in Austrian wines. You can address them in the Seminar or, preferably, to me
directly afterwards.

I first started observing dissolved CO2 in NZ SauvBlancs a fair number of yrs ago, but paid it little attention.
As I drink a lot of Austrian wines, over the last 3-4 yrs, I've been observing the presence of dissolved CO2
in Austrian wines with greater & greater frequency. Generally the tip-off of dissolved CO2 is a distinct "pop"
when the seal on the screwcap is broken.

Mostly, I observe the presence of CO2 by sight in the glass:
1. Sometimes there is a cloud of tiny/tiny bubbles that swirls around in the glass in almost a cloud, that persist for
quite a long time (many/many minutes). This swirling cloud can be absolutly mesmerizing and interesting to watch.
2. Sometimes there is a cloud of less tiny bubbles that immediately cling to the side of the glass and only dissipate
with persistent swirling of the wine.
3. Sometimes there is a cloud of tiny bubbles that immediately agglomerate to a chain of small bubbles that encircle the
glass on the surface. Sometimes they dissipate very rapidly, othertimes not, even w/ persistent swirling.
4. Never do I observe a stream upwards of tiny/tiny bubbles like you get in a fully carbonated sparkling wine, indicating
that the amount of dissolved CO2 is much less than a Champagne.

Then I observe the impact of the dissolved CO2 on the palate:
1. Sometimes there will be a distinct spritz on the palate, not unlike Lambrusco, that persists.
2. Sometimes there will be a tiny prickle on the palate on the front of the mouth that immediately disappears.
3. Sometimes this prickle will immediately disappear and leave behind an utterly vapid wine. It seems as if this
prickle gives an ersatz acidity that disappears immediately, leaving nothing behind.
4. Sometimes this prickle will disappear immediately and leave behind a solid wine w/ a bracing acidity. This seems
to be the majority of the cases. You get a brief prickle, it's gone, and the wine is good..very little impact on the wine.

From what your read, leaving/imparting this dissolved CO2 in a wine is designed to impart a sense of acidity to the wine.
I don't find this imparted acidity quite the same as the true acidity you get in a wine. It seems to be an ersatz acidity.
This dissolved CO2 can come (primarily) two sources:
1. The dissolved CO2 is left in the wine as a leftover product from the CO2 production during fermentation and the
winemaker intentionally makes efforts to preserve this dissolved CO2 in the wine up to bottling.
2. The wine is actually sparged with CO2 at bottling to "freshen" the wine.

Of course we "know" (as we've been told by the experts) that #1 is a more "natural" process for achieving CO2 in the
wine and #2 is "not natural", is interventionist winemaking. That, somehow, the dissolved CO2 leftover from fermentation
is somehow "better" than adding CO2 at the bottling time.

So, I have a few questions on this subject of dissolved CO2 in wines, specifically as it applies to Austrian wines:
1. Do your observations of dissolved CO2 in Austrian wines coincide with my observations above? Both the
visual aspects and the tactile aspects?

2. Has there been a conscious effort by Austrian winemakers to preserve/add dissolved CO2 in their wine
over the last few yrs?

3. When the winemakers prepare to bottle their wine, is the amount of dissolved CO2 something they
actually measure or do they just let whatever happens/happen?

4. Is leaving dissolved CO2 in a wine a good thing or a bad thing? Or is it just simply a stylistic choice by
the winemaker?

5. Is adding CO2 at bottling time an "unnatural" act, to be deprecated, and preserving the "natural" CO2
from fermentation somehow more "natural" and, therefore, "better"??
I am, of course, baiting a bit the believers
in "natural" wine, which I think many of your Skurnik wines are.

Don't waste your time, Val, responding directly to these questions. But I would like to hear your thoughts on the subject
whilst you're at the SFW&CF next week.


Would, of course, be interested in the thoughts of all the esteemed folks here on this board as well on the subject.

Tom
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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Fri Sep 21, 2018 1:14 pm

Not getting back in that mud pit with you.
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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Fri Sep 21, 2018 1:31 pm

In my wine making experience, residual CO2 from fermentation is eliminated during the filtration step, just prior to bottling. I wonder if sparging with CO2 at bottling may have developed in conjunction with the need to prevent reduction reactions which were somewhat common in the early days of Stelvin screw cap closures.
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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Fri Sep 21, 2018 1:41 pm

Howie - with fully dry wines that sterile filtering is not always needed or used.
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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Fri Sep 21, 2018 6:20 pm

David M. Bueker wrote:Howie - with fully dry wines that sterile filtering is not always needed or used.
Almost all white wines and many reds, whether dry or not, are filtered prior to bottling for clarity. I didn't mention sterile filtration.
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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Fri Sep 21, 2018 6:46 pm

Tons of wines are not filtered - mainly top tier wines. Sterile or otherwise.

Lots are.

FWIW, I know several Austrian wineries that do not filter at all - none.
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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Sat Sep 22, 2018 6:07 am

Tom Hill mentioned
I first started observing dissolved CO2 in NZ SauvBlancs a fair number of yrs ago, but paid it little attention. As I drink a lot of Austrian wines, over the last 3-4 yrs, I've been observing the presence of dissolved CO2
in Austrian wines with greater & greater frequency. Generally the tip-off of dissolved CO2 is a distinct "pop" when the seal on the screwcap is broken.
So, my question is, are the increase in the use of Stelvin screwcaps and the increase in CO2 in the bottles related? If the wine was not filtered, the CO2 could be residual. If it was filtered, then the CO2 must have been sparged in. Either way, the question is; Is the practice of bottling with CO2 a reaction to the increased risk of reduction when bottling with screwcaps? I did a search and found this from: https://grapesandwine.cals.cornell.edu/sites/grapesandwine.cals.cornell.edu/files/shared/Research%20Focus%202016-3a.pdf
H2S is usually formed from S-residues in the latter half of the fermentation, which means that it does not
coincide with carbon dioxide production. As a result, H2S formed will not be lost immediately to carbon dioxide entrainment, and must be removed by other methods. There are several approaches to removing excess H2Spost-fermentation:
i) H2S is highly volatile, and can be readily removed through sparging with inert gas, although this approach will be less effective against other (less-volatile) sulfurous off-aroma compounds.
ii) H2S is also easily oxidized, so aeration (i.e. through racking) may also be used, particularly for reds. Although some texts claim that aeration should be avoided because of the danger of forming other noxious S-compounds, such as disulfides, there is little data to support this concern in recent scientific literature. However, oxidation can cause a loss of desirable S-containing compounds if done to excess, such as the fruity “grapefruit, passionfruit” compounds critical to Sauvignon Blanc and many other
fruity white wines.
Last edited by Howie Hart on Sat Sep 22, 2018 7:03 am, edited 1 time in total.
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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Sat Sep 22, 2018 6:57 am

So when I was I Never Boston in June to taste the wines of the Theise portfolio (German and Austrian), I asked about bottling prep for screwcaps. Nobody mentioned sparging or otherwise using CO2. I actually asked two producers about CO2 because their wines have shown a touch spritzy. Both (Strub from Germany and Ott from Austria) said they use no CO2 in prep, and that any dissolved CO2 is from very careful & minimal handling of the wines pre-bottling.
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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Sat Sep 22, 2018 7:05 am

Has anyone ever had a wine that has had both spritz and rotten egg smell?
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Re: Dissolved CO2 in Austrian Wines...

by Victorwine » Sat Sep 22, 2018 9:07 pm

Some might find the following article written by Tim Patterson interesting

https://www.winesandvines.com/columns/s ... -Its-a-Gas

Howie wrote:
I wonder if sparging with CO2 at bottling may have developed in conjunction with the need to prevent
reduction reactions which were somewhat common in the early days of Stelvin screw cap closures.

Tell you the truth Howie, the tehnique of sparging with CO2 (transfer hoses. tanks, or bottles) was most
likely developed to reinforce the technique of "reductive winemaking".

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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Sat Sep 22, 2018 9:42 pm

Victorwine wrote:...Tell you the truth Howie, the tehnique of sparging with CO2 (transfer hoses. tanks, or bottles) was most
likely developed to reinforce the technique of "reductive winemaking".
Salute

That makes no sense to me. Why would any winemaker want to promote rotten egg smell in their wine?
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Re: Dissolved CO2 in Austrian Wines...

by Victorwine » Sat Sep 22, 2018 11:02 pm

Since when did "reductive winemaking" mean a "rotten egg" smell? Only when it is overdone. I always thought of it as a technique to promote primary fruit flavors and a way to release a wine earlier for consumption.


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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Sat Sep 22, 2018 11:14 pm

Plenty of wines made reductively with no rotten egg smell. The great Hans-Gunter Schwarz worked reductively at Muller-Caroir for decades. No rotten egg smells there.
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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Sun Sep 23, 2018 6:02 am

Okay, so I guess it's a matter of degree. I always considered both reduction and oxidation to be a flaws. I read this: https://www.winespectator.com/drvinny/show/id/46633
Reductive winemaking is when a winemaker takes extra steps to limit the amount of oxygen a wine has exposure to. It’s not easy—air is everywhere. But if you think of traditional winemaking as “oxidative,” reductive winemaking might have fermentations take place in closed-top or stainless steel containers (vs. open-top, or barrels). They can also blanket a wine with inert gases, so there’s less oxygen exposure.
The point of reductive winemaking is to preserve fresh, fruity, vibrant notes. You probably won’t be able to tell just by tasting a wine what kind of winemaking style was employed. But you might be able to pick out “reduced” notes. These generally result from the presence of a volatile sulfur compound, or mercaptans, and can be the result of reductive winemaking. Wine needs a certain amount of oxygen to polymerize (have its molecules combine), and if it doesn’t, the reduced notes may come in.
How do you recognize reduced notes? Sometimes there’s a whiff of rotten eggs, rubber, struck matches or even sewage. When it’s just a whiff, decanting or swirling the wine in your glass might allow these notes to “blow off,” and it’s not considered a flaw—there might be a really beautiful wine underneath those notes. If there’s more than a whiff and those notes won’t go away, it’s not a good thing.
What is called "reductive wine making" in this article I would just consider sound wine making practices, with a balance between oxidation and reduction. Too much of either is not good and neither should be obvious. Maybe I have a semantics problem.
Incidentally, I made a Riesling in 2009 that was awarded a silver medal at the NY State Fair. It was bottled about a month before judging, but 3 months later, it was all about rotten eggs. Shortly after that I read a WTN here (probably one of David's) describing a German Riesling with some age that had a reductive funk that blew off over time and the wine was very good. So I decided to let the remaining bottles age. I think I opened one about 3 years ago and it had improved somewhat. I will open a bottle later today and see how it is and report back. That being said, I would never strive for such a result.
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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Sun Sep 23, 2018 12:18 pm

Nobody strives for overly reductive.

There is winemaking with minimal oxygen exposure, commonly referred to as reductive winemaking, and reduction as a flaw, where things go too far, and rotten eggs or burnt rubber aromas obscure the wine.
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Re: Dissolved CO2 in Austrian Wines...

by Howie Hart » Sun Sep 23, 2018 8:31 pm

As I promised above, I opened a bottle of my 2009 Riesling, which had been plagued by reductive funk. The second thing I noticed was the color had become a deep gold. There was no hint of reductive funk. However, it tasted "well aged", with hints of honey, but not over the hill. It was quite pleasant with less acidity than any of my other Rieslings and still semi-dry (bottled with about 1.5% RS). That being said, I don't know if my tasting it has much to do with the conversation, as the first thing I noticed was that it was bottled using synthetic corks. I don't know how that may have played into this. I only have one other batch where I used synthetic corks: 2011 Riesling and I only have 1 or 2 bottles of that left. hmmmm?
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Re: Dissolved CO2 in Austrian Wines...

by David M. Bueker » Sun Sep 23, 2018 10:45 pm

The synthetic corks ruined many a commercial wine.
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Re: Dissolved CO2 in Austrian Wines...

by Robin Garr » Mon Sep 24, 2018 9:04 am

David M. Bueker wrote:The synthetic corks ruined many a commercial wine.

And a few corkscrews. They might have been okay for commercial wine not meant for storage, but they just couldn't do the long haul. Long meaning three or four years. :P

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