TN: 2012 Martinelli Zinfandel "Jackass Vineyard", Russian River Valley

[ToddFrench]

I love zinfandel, and always found it interesting how often it does not show its high abv, but seems balanced

[John_Morris]

Yes, that is interesting, isn’t it, Todd. I find the same thing with Ribera del Dueros and Brunellos. I think it may have something to do with the depth and concentration of the fruit. By contrast, in pinots, for instance, and Chateauneuf, the alcohol can stand out more. But there are lots of exceptions.

[larry_schaffer]

As Mike pointed out, the conversion factors can vary in wines depending upon the yeast used - but I’ve never read or heard of winemakers using specific yeast because they knew in advance that the conversion factor was ‘higher’ or ‘lower’ than normal.

That said, as Mike also pointed out, you can have a wine variance in the conversion factors, and it’s difficult to know for sure what your final alcohol will be.

Not sure what Joe was implying other than perhaps the ‘feeling’ that this is happening today versus then, but as Mike also pointed out, there is no research that I know of that shows this.

We also know that there are certainly ways to alter alcohol once the wine has finished fermentation - usually lower but you can, should you want to, blend to make it higher. Also, depending upon the humidity of where you store your barrels, you can alter, albeit slightly, the alcohol levels. Research has shown that humidity levels below about 75% will lead to a higher evaporation of water relative to alcohol, leading to a slight increase in the alcohol level. Likewise, wines stores in relatively humid conditions over 90% for instance, will actually see alcohol levels decrease slightly.

Interesting, eh?!?!?

[M_Officer]

@Chris Seiber

I wonder if my fractional understanding and memory of what Joe Davis was saying was, perhaps, that winemakers were using yeasts a few decades ago that had lower conversions, whereas today, yeasts are closer to the maximum conversion.

Or, maybe, I just misunderstood what he was saying entirely, which is a significant possibility over the table at a lengthy wine tasting dinner. Anyway, I’m at least glad it led me down the path to asking and learning from Mike in this thread.

Really the latter Chris. When I was a home winemaker in the '80s, my conversion factors were falling into the .59 to .61 range, regardless of yeast used, and regardless of whether I inoculated or not. Today, same thing. Our red ferments are falling into the exact same range. And it’s been like this for centuries. In 1821, Joseph Louis Gay-Lussac,a French chemist and physicist, showed that 1 g of sugar would yield .64 mL of alcohol via fermentation. In 1860, Louis Pasteur demonstrated that 1 g of sugar would provide .61 mL of alcohol. Fifty years later, Frederic Bioletti, a professor of viticulture and once a student of Eugene Hilgard, suggested a conversion factor of .59. Not sure when OIV (L’Organisation Internationale de la Vigne et du Vin) adopted a standard of .594 but I think it’s been quite a while.

Saccharomyces have not really changed. They are doing the exact same thing today that they’ve been doing for ages. What has changed, however, is understanding of them. We now know how to keep them happy and healthy during ferments, helping them withstand higher alcohol solutions.

[Peter_Petersen]

Since we are slightly off topic. Do fructose and glucose have the same conversion factors?

Looks like it, but glucose is fermented first.

[Nevin_Miller]

I never, ever had good experiences with aged Martinelli Zins. Not sure if anything has changed.

[Leonard_Maran]

I really don’t see this vino as “developing”.

[DougS]

@Rama Roberts

Regarding the yeasts and ABV, IIRC Sam Adams Utopias is naturally fermented to 27%, so there must be some really tolerant yeasts out there.

That’s what they claim, but I don’t believe it. Does anyone know of a yeast strain that will do this?

[larry_schaffer]

Doug,

I have witnessed a yeast take a wine to about 20% alcohol myself - and no, NOT one of mine And I know of at least one Aussie Shiraz that was listed at about 21.5% alcohol that was not fortified. Didn’t Tim Spear at Clos Mimi make some high octane stuff that stayed in barrel for a really really long time?!?!?

Cheers!

[Rick_Allen]

@larry schaffer

We also know that there are certainly ways to alter alcohol once the wine has finished fermentation - usually lower but you can, should you want to, blend to make it higher. Also, depending upon the humidity of where you store your barrels, you can alter, albeit slightly, the alcohol levels. Research has shown that humidity levels below about 75% will lead to a higher evaporation of water relative to alcohol, leading to a slight increase in the alcohol level. Likewise, wines stores in relatively humid conditions over 90% for instance, will actually see alcohol levels decrease slightly.

I talked to a Napa winemaker about this once. They had moved his winery’s cellar (very damp to drier) recently, and he went from a decrease in alcohol during barrel aging to an increase in alcohol, with the difference between the resulting alcohols being on the magnitude of 1%.

[John_Morris]

Interesting. That sounds like it corresponds to aging spirits. I think I recall reading once that bourbon becomes stronger with age while scotch loses alcohol. I think that’s attributed to differences in humidity and temperature (Scotland presumably being more consistently cold and damp, though Kentucky is no slacker when it comes to summertime humidity).

[larry_schaffer]

I looked up a little more about the Samuel Adam’s Utopia, and note that they are keeping almost a solera system of barrels originally used for whiskey, ranging back nearly 20 years if I read the materials correctly.

Based on varying humidity levels, these beers could certainly increase in alcohol levels given that much time.

Cheers!

[Paul_Miller]

Is this evaporation through the barrel, and thus concentrating what is left inside?

[larry_schaffer]

Yep, the ‘Angel’s Share’ concept . . .

[DougS]

Thanks for the responses. They kind of imply that their yeast can get it that high, which I still don’t think is happening (this isn’t the first time I’ve heard of high %teens or very low %20s, but I’ve never heard of anything beyond that), but the evaporation idea could explain it. I’ve been thinking they must be freezing some portion, but I suppose enough time in barrel could get it there.

[DougS]

@larry schaffer

I have witnessed a yeast take a wine to about 20% alcohol myself - and no, NOT one of mine

So, you’re part of the low alcohol movement, then.

[M_Officer]

@Doug Schulman

Thanks for the responses. They kind of imply that their yeast can get it that high, which I still don’t think is happening (this isn’t the first time I’ve heard of high %teens or very low %20s, but I’ve never heard of anything beyond that), but the evaporation idea could explain it. I’ve been thinking they must be freezing some portion, but I suppose enough time in barrel could get it there.

As I mentioned, a strain of Saccharomyces was isolated from Jackass Vineyard by Williams Selyem in the eighties that routinely ferments to 18%. This strain is commercially available. We have used it and can attest to its alcohol tolerance. And that’s 18% at the end of fermentation, not after a year in barrel in a low humidity environment.