Tuesday, April 29, 2008

Pressure, Pressure.. oh, the relief!

Spring has sprung in eastern Massachusetts over the past few weeks. The birds are singing and gettin' busy--last week I backed out of the garage in the morning to find two pairs of wild turkeys in my yard with the males in full courtship display. The snow is gone, and it's been shorts weather a couple of days. What I've found interesting is how the weather has affected my cranberry-niagra grape wine. A couple of posts ago, I mentioned how stubborn this wine has been in clearing. In contrast to the cranberry-banana that was started and fermented at the same time, the cran-niagra has very, very, very slowly clearing. A couple of weeks after the first racking in February, there was a definite strata in the wine with the bottom 2/3 cloudy while the top 1/3 began to clear. And this strata stayed there through the month of March and first week of April. But rather interestingly, the high pressure system that moved into New England and stayed over the past 2 weeks with 60-70° temperatures suddenly caused the wine to drop all of its sediment. The carboy is clear from top to bottom with a good layer of lees on the bottom. It's still not as translucent as the cranberry-banana, but I would call it clear.

I believe this atmospheric pressure-initiated clearing may be a result of degassing as the wine has risen in temperature about 10 °F. My basement has gone from about 45 °F this winter to about 55 °F this month. Cold wine dissolves more residual CO2 from the fermentation. The warmer temperatures brought by the high pressure system may have let the wine warm up to get enough CO2 to degas and let the small protein particles fall out of the suspension. The warmer temperatures have also caused the wine to expand as it warms, as I've had to suck a little out of each carboy to keep it from expanding into the airlock.

Not only is wine all about the chemistry, but it's also all about the physics! If only I had been told that in high school physics!

a Wine Student

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