Degassing
Because nobody ever paid money for a fizzy port wine
When yeast churns away, eating the sugars in the must, it not only makes the wonderful compound that is alcohol, but also releases carbon dioxide. While much of this CO2 bubbles on out of your airlock during the fermentation, a whole balloon-full remains dissolved inside the liquid. Fun factoid: good lord, there is a lot of CO2 in the ocean.
Imagine a fresh glass of ginger ale that you've set on the table -- all bubbly, fizzy, and effervescent. When you leave it out overnight, you might consider it gone flat, but if you look closely or shake it up a bit, you'll still see some bubbles form. Now, imagine four gallons of ginger ale. There's a lot of bubbles hiding up in that jug. Unless you're poppin' some Cristal or celebrating with some Dom Pérignon, people don't usually want their wine carbonated. Due to the lack of sugars in wine, the carbonic acid that hits the tongue as a result can lend a bitter flavor that clashes against the delicate flavor palette of the wine. So how do we get rid of it?
1. Time: Time is the mender of broken hearts, and the degasser of bubbly wines. Wineries, and people that are not in a rush in general, don't usually have to worry about degassing their wines, because, well, their wines sit long enough that they don't have to worry about it. From what I gather, if you're letting your wine sit on the order of 8-10 months, it will be as flat as a 2-dimensional object (if you'll permit a bit of Flatland humor).
I'm young and impatient. Plus, I don't have the available carboys to just let one batch Bogart one of my jugs for a whole year...
2. Agitation: Anyone who has dropped a pop can -- anyone who's been a victim of the knock-your-buddy's-beer-bottle-rim prank -- anyone who's seen Stone Cold Steve Austin get ready for a match -- all these people know that when you knock or shake up or disturb a carbonated beverage, you cause a lot of the gas to nucleate and ascend to the top of the liquid. Wine is no different.
I've heard any number of methods for agitating the gas out of wine:
- Stir, stir, stir, stir your wine, and then stir it some more (and not the circular way; go back and forth)
- Put your carboy on the washer and set it to the spin cycle
- Attach a paddle to a power drill and let-er-rip
If you do any of these enough, you'll eventually get to a point where agitating your wine will result in no more bubbles forming. Your wine is then successfully degassed.
3. Vacuum: "horror vacui": Nature abhors a vacuum, my friends. Which is why, if you were able to suck all the gas out of the head space of a carboy, the carbon dioxide in the wine will bubble to the top as fast as it can to re-fill that space to a certain point. This is due to the solubility of gases in liquid at varying pressures, but I'll try not to bore you with those details. Too late? Oh well.
Basically, the idea here is to just pump out as much gas as you can out of the carboy by whatever means and let the CO2 remove itself at an extremely accelerated rate. There are any number of shiny, efficient, powerful vacuum pumps that would be well-suited for this purpose, but I am a mere grad student of limited financial means. So, I go the manual route.
I present, the wine-saver evacuator pump
This puppy is the Snail Wine Saver hand-powered vacuum pump, and at a $9 price tag, it fits comfortably into my budget. It's made to preserve individual bottles of wine, but let me tell you, that task is like asking Hercules to pick up toothpicks off the floor -- it's not using it to its potential!
All you have to do is get a carboy bung with a hole the size of a wine bottle aperture, and BOOM, you've got a carboy vacuum pump. Just put the vacuum cap on the bung, put the bung on the carboy, and put the pump on the cap. Then, start pumping away and watch the foam froth up from out of nowhere. Just pump until it gets too difficult, and repeat every now and then over the next couple of weeks.
But wait, there's more! As an added benefit, if you have a wine that's done fermenting, you usually lose the protective barrier of CO2 that keeps your wine from oxidizing. This is why you don't often leave a lot of head space in the carboy for an ageing wine. With this method, however, you're actually pulling air out, forcing the atmosphere in the carboy to be mostly occupied by CO2 from the wine, and very little O2. It's a win-win!
Anyhow, if you haven't guessed yet, I prefer the vacuum pump approach. It quickens degassing while also having the added benefits of decreasing oxidation, and also eliminates the need of keeping my airlocks topped up with liquid. Where's the downside? (That question is rhetorical)
Four months later, this wine is completely degassed and looks as smooth as glass. Just about time to bottle!
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