barrels and degassing

[winemaker81]

I started reading the following free article by Tim Vandergrift on WineMakerMag:

https://winemakermag.com/technique/wine-kits-fermenting-degassing
and this line caught my eye:

If the wine is aged in barrels the gas escapes even faster, as sealed oak barrels develop negative pressure, actually vacuuming the CO2 out of solution.​

This makes sense, but it never crossed my mind.

He also talks about temperature and how it affects the yeast. It's a good article.

 

[cmason1957]

I got two takeaways from the article:
1) Don't add the fining agents on the schedule kit winemakers use, unless you are at the temperatures they suggest. Wait, if you are at a lower temp.
2) Tim gives a great example of the difference that temp can make to CO2 solubility (one soda in a hot car, one in ice), but normally we don't see such drastic differences in temp. My Chem background isn't good enough to determine the change in solubility of a wine at 70F compared to 60F. Does it make that big of a difference??

 

[winemaker81]

2) Tim gives a great example of the difference that temp can make to CO2 solubility (one soda in a hot car, one in ice), but normally we don't see such drastic differences in temp. My Chem background isn't good enough to determine the change in solubility of a wine at 70F compared to 60F. Does it make that big of a difference??

My cellar temperature in ~70 F in the summer and ~58 F in the winter, and over the course of 3 months in the winter, some wines will drop crystals, often during their second winter, but not the first. My memory of Chem is not that great, but I'm guessing 10 degrees F makes a noticeable difference.

 

[cmason1957]

My cellar temperature in ~70 F in the summer and ~58 F in the winter, and over the course of 3 months in the winter, some wines will drop crystals, often during their second winter, but not the first. My memory of Chem is not that great, but I'm guessing 10 degrees F makes a noticeable difference.

I was hoping some of our residents Chemists/Chemical Engineers, etc. might weigh in and tell me how wrong I am. I have had the same thing with crystals, but that's a different kind of reaction than CO2 degassing, I am thinking. 58 F = 14.5 C and 70 F = 21 C, which is only 6.5 degress and I am betting that the C Delta is what gets used. It might even be the Kelvin Temp, but that's the same delta. And that's about as far as my memory takes me

@ibglowin - Mike is probably having to much fun out in Hawaii to jump in and correct me on how far wrong I am (Which is a good thing for the next guy coming along)

 

[sour_grapes]

This is pretty off the cuff. I have not worked hard to make sure this is correct.

Yes, Kelvin will be the important quantity. And it is not directly the delta that is important, it is the ratio. But then that ratio appears in the exponent.

So the two temps in question are 287.5 K and 294.3 K. Their ratio is 0.977. And exp(-0.977) is 0.376. So I think the colder wine will degas at a rate that is 37% of the rate that the warmer wine will degas. Unless I am wrong!

 

[cmason1957]

That number just might be close. I found a link to CO2 Solubility in Water, and yes I know, wine isn't water, but generally it's 85% or more water, so this chart should be at least in the ballpark. Ballparking those numbers at 20C we see 1.6 g\kg (maybe 1.7) water and at 15 C we see 2 g\kg and that ratio is .8 or 20%, Certainly we can see that the difference is in the linear part of that chart, so that 5 C delta matters more than we (or maybe just me) might have thought.

https://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html