degassing

[hades_ibex]

I'm just wondering, do commercial wine makers need to degas their wines after fermentation - that is, drive out the CO2 that has been dissolved? And how do they do it?
Thanks.

[Thomas]

The answer is no. CO2 dissipates over time and through temperature changes. Some winemakers add CO2 (low level) during bottling to prevent oxygen from doing damage.

[hades_ibex]

So is there an easier way to degas from a carboy besides shaking or stirring? I read about vacuum pumps that dramatically speed up the CO2 dissipation. Any ideas about this? Thanks.

[Thomas]

Why do anything? The CO2 will dissipate over time and through successive rackings, and when the weather--after winter--warms.

Winemaking is a natural process--if you do things to speed it up you invariably get results you don't like.

[This message has been edited by foodie (edited 07-22-2004).]

[hotwine]

Some winemaking supply houses sell a plastic stick about 24" long with a large paddle on one end and a small one on the other (both are perforated). The stick's end with the smaller paddle is inserted into the carboy and the larger paddle is grasped to enable a vigorous "whacking" motion, to encourage the release of CO2. It usually takes 4-5 whacking sessions over 30-45 minutes to see a change in the foam on the wine's surface from a froth of tiny gas bubbles to a looser layer of larger bubbles. The less gas that is present, the larger the surface are that is devoid of foam and bubbles, until the surface is completely clear.

That's the process I was taught in a custom wine-making shop in which I volunteered until recently. Is it valid? Dunno.

I agree with Foodie: natural is best.

[Thomas]

Sounds like you got your classes mixed up Hotsie. Are you sure you weren't in the sexology department by mistake??? Spanking wine, indeed...

Seriously, I cannot imagine any reason to treat wine so harshly, especially when the CO2 remaining after fermentation is generally benign and mostly gone by bottling time.

Now, if the CO2 is full and violent after fermentation, the fermentation may not have been completed.

[hotwine]

They're estimating completion of fermentation on measurements of specific gravity, generally looking for a reading of 1.01 after primary fermentation and 0.992 after secondary; at which point the wine is chemically stabilized, clarified and whacked (later comes the "rack to clear" process, then filtering). Their entire process of winemaking, from introduction of yeast to the must ("hello, must") to bottling, only lasts about six weeks, but longer periods are accommodated if SG readings indicate the need.

[Thomas]

One of the problems with reading specific gravity after fermentation is that CO2 skews the results--maybe that is the reason for all that whacking at the wine! And when the wine reaches so close to the end of dry fermentation, but not quite there, specific gravity readings aren't much help--best to take a direct residual sugar reading (if the wine is white you can use tablets originall designed to measure sugar in urine-if it is red wine, I cannot remember if there is a product for home winemaker use to read residual sugar).

[This message has been edited by foodie (edited 07-22-2004).]

[montepaulsen]

Profession winemakers sometimes need to de-gas wines prior to bottling. Generally the problem arises when bottling a young wine right after harvest, such as a white zin that you want to release by Thanksgiving.

Yound white wines and blushes are often fermented cool, and if we wish to finish the wine with residual sugar, we'll chill the tank at the very end, which slows fermentation drastically, but also serves to retain CO2. You can often tell if your wine has too much CO2 in it by pouring a glass out of a cold tank (or cool carboy) and setting it somewhere to rise up to room temperature. If it has too much CO2, it'll begin developing bubbles on the inside, not to mention having a slight spritzy taste. It can also be a problem with aged wines that are in a container with headspace, if you use CO2 to sparge the headspace. The problem is compounded by cooler storage temperatures.

The professional method for degassing is to lower a sparge stone (like an aquarium air stone, only stainless) and bubble nitrogen into the wine, which pulls out CO2 as it rises. You could simulate this on a small scale, using Nitrogen based wine bottle preservers, in those aerosol cans with the supplied plastic sparge tube. But be careful - that stuff shoots out pretty quick, and if you do indeed have a lot of CO2 in the wine, you'll have a frothy mess on your hands.

[californiagirl]

Welcome mp! Curious, where does your experience come from? You've obviously been in the wine business for quite some time!



[This message has been edited by californiagirl (edited 08-04-2004).]

[winoweenie]

Add me to the query. It's always a pleasure to have knowledgable people on board to equalize we amashurs. Plus, where is your abode? WW