Evaporation not Oxidation

WINE TALK
21

No, there’s no mention of evaporation of alcohol, because (IMO) that can’t be a factor. But the main takeaway is a) oxygen can’t do much to the wine itself in a short period of time (my addition: to a relatively young, sound wine), and b) the elimination of sulfur compounds (either through evaporation, or interaction with oxygen) is the main key to “revealing” the underlying wine, i.e., it’s the factor most responsible for the changes we perceive with aeration.

22

I have no view on evaporation of alcohol.

What you quoted makes no reference to the claim in the article in the OP that different flavor/aroma compounds in different grape types react to oxygen at quite different rates – some quite quickly, some only after quite extended periods. (I quoted that part above in posts #3 and #14, but I guess you haven’t committed my posts to memory. neener)

That adds another layer of complexity to the analysis. It suggests that evaporation of reductive elements, or their reaction with oxygen, is only one piece of the puzzle.

23

I’m curious about the skepticism regarding alcohol evaporation. I can’t review the 2016 study, but the abstract seems clear. For those that can, is the glass subjected to some sort of conditions that are abnormal? I’m reminded of a long thread here regarding the difficulty in perceiving a 1-2% difference in alcohol in blind tastings, so I question the sensory impact.

24

Love the discussion among you who have posted with inside info.

For me, the most profound statement in the summary was the last one: "In other words, while the chemistry counts, one shouldn’t forget the context surrounding the act of decanting and tasting, including the sense of ritual, the cuisine, and one’s company at a dinner or tasting occasion. “The wine does change over time,” Goode says, “but also we change as we consume the wine. We’re not measuring devices. It’s more like a relationship.”

25

Yes, but of course next you’ll be saying that decanting has no effect, and that a quick 5 minute swirl in the glass is all that’s needed. The rest is just us fooling ourselves, right?

26

That’s not how I see it. I decant most every bottle with some obvious exceptions.

27

“Differences between grape types” … been thinking about this. It makes total sense that different grapes would contain varied compounds which would react to evaporation differently. So, potential inputs to evaporation response could include:

Grape type
Pick date (i.e development of said grapes)
Seasonal variations
Winemaker decisions (everything from barrel type to temperature of fermentation(s) and many many more)
Storage
Amt of time bottle is opened
Decanting
Rotational velocity and duration of swirling (kind of a joke!)
Etc. etc.

The question is - which of these are weak inputs, which are strong? If we knew all this it would eliminate threads like “how long should I decant this bottle of 1996 Giacomo Conterno Francia Barolo?”

28

I’m working on the algorithm now with a bunch of wine-loving quants.

29

I hope everyone realized that I had my tongue firmly in cheek, and also don’t want to re-open that rather tedious previous thread.

30

I ran a little experiment: filled a glass with vodka (so ~40% ABV, or about 3 times that of wine). Marked the starting level, let it sit overnight, measured how much had evaporated. Pictures attached.

Start:

After (20 hours):

The sharpie line I marked is about 1/16" wide (top to bottom), so the level decreased by about half that, or 1/32". About 0.8 cups (190ml) of liquid in the glass, 3" diameter at the liquid level. A little units conversion and math gives the volume that evaporated as 3.6ml. Let’s assume the worst case that all of that is EtOH, though there is surely a little water in there as well. That means the ABV went from 40% to about 38%, a loss of 2%, over 20 hours, or 0.1%/hour. And that’s for a 40% alcohol solution, not 13 or 14%. If it scales down with alc concentration, that number becomes around 0.03% decrease. Negligible to anyone’s perception. Now, this was just a glass sitting there, with no circulating air to speed up the process. But that’s probably a realistic way to look at this. I’d say this myth is busted.

31

How cool is that Alan? Way to go. How was the vodka before and after?

32

Yeah, but did you say the magic words while swirling, Alan? [stirthepothal.gif]

33

Come on, you know I study your posts like you study Supreme Court decisions :wink:

It would be hard to argue that different grape varieties don’t introduce different compounds that react differently with oxygen. But, having convinced myself that one of the authors’ simplest claims is, hmm, lets call it “out to lunch”, I’m reluctant to sign on to something as complex and hard to demonstrate as this “variety oxygen chemistry” claim, particularly when not much is going to happen to those compounds in an hour or two. Keep in mind that those same compounds were exposed to oxygen for many months, even years, in barrel before they went into the bottle. Are we really supposed to believe that they are somehow magically susceptible to reactions during an hour in the glass?

As Carole Meredith famously quipped in Somm 2: “Can there be any other business where there’s so much bullshit?”

34

The article quotes one somm, but most of the content comes from Jamie Goode and an Italian professor of enology. And the alcohol evaporation data you dispute comes from the Journal of Agricultural and Food Chemistry. So this isn’t some somm’s blather. Maybe the alcohol study is wrong, but read it and tell us what’s wrong with the methodology rather than relying on your simple home experiment.

35

John, I was just being a little flip with Carole’s quote. I already said I think Jamie’s explanation of sugar and aroma in wine makes no sense, though I’m going just from you relating his claim. I do have his “Science of Wine” book, is it in there? I can try to find it.

As for the evaporation experiment, that one struck me as improbable on its face, given how long we all leave wines sitting in glasses or decanters all the time. There’s nothing wrong with the idea, but the methodology fails in trying to represent what might be happening in a real glass or decanter: no one is setting their glass down in front of a fan that constantly circulates are over and around it. For me, stretching that far to try and create a link to what happens during aeration qualifies it for description by Carole’s quote :wink:

36

The study abstract shows no loss in a covered glass, and significant loss when subjected to continuous airflow. That gives us a range, within which the real life scenarios exist. I’ll tell you, trying to drink wine when there’s a notable breeze is annoying. The aromatics are being blown out of the glass, so you have to swirl and cup the top with a hand to get any nose at all. It’s safe to say typical airflow would be much less significant.

37

My experience as well Wes which is why I prefer not to do outdoor tastings/events and if I were in the trade and wanted my wines to show their best, I`d do all indoors.

38

Goode’s statement about sugar and aromas was in an article in (I think) Somm Guide two years or so ago. I thought I’d kept it, but I couldn’t find it in my wine clippings files. I’ll keep looking.

The “Science of Wine” doesn’t have much on sensory perception. His more recent book, “I Taste Red” is all about perception. It’s a somewhat denser, more technical read, though. I started a thread about the book last year. Many people said they were going to buy it. You were one of them. Now I can’t trust anything you say. [wink.gif]

39

I also participate in a “Bookserkers” forum where we lament about how many books we have, how to get the hottest books right off the press, where to buy and sell books, the best time to read them, if they are old and over the hill, etc. There is thread on that forum titled “Monthly check-in: Library inventory reduction plan” [wow.gif] I’m waiting for a slot to open on my wine book shelf :wink:

40

We all fight these collecting/accumulation/hoarding urges across categories.

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