Your newly fermented kit wine is saturated with CO2. Winexpert indicates that a kit will produce approximately 150 cubic feet of carbon dioxide (CO2) during the fermentation. That’s a lot of gas to get out of your wine. Does it all need to come out?

In the December 2006 Enology Notes, Bruce Zoecklein, Head of the Enology-Grape Chemistry Group at Virginia Tech, makes the following statement about CO2 “As a result of out-gassing and post fermentation processing (racking, fining, etc.), levels drop to near 1,000 mg/l during the first several months of aging.” He also indicates that decreases of 100 mg/l or more may be seen during the first year and not much thereafter. This implies that there may be some CO2 remaining in the wine.

Smalloak, a wine consultant in South Africa in their article titled “The Use of Inert Gas in the Wine Making Process” stated “As a rule of thumb the CO2 content in red wines should be below 900 mg/l and that of white wines below 1400 mg/l.” They also state that too little CO2 in the wine can be as detrimental to taste as too much CO2.

The International Organization of Vine and Wine conducted a study to determine the repeatability of the modified EBC method for determination of carbon dioxide. Samples were sent to nine different laboratories in Europe for testing. Included in the samples were a white wine and a red wine. Testing revealed that the mean carbon dioxide content of the white wine was 1337 mg/l and of the red wine 595 mg/l.

I have recently performed the following test on commercial wines. After pouring a glass of wine, I place my thumb over the top of the bottle and give it a brisk shake. In the dozen or so red wines I have tested in this manner, all have resulted in a layer of foam of 1/4 to 3/8 inch thick. I do not taste excess CO2 in the sample I have poured. My preferences tend to red rather than white wines, so I have not tested enough white wines yet to reach a conclusion.

From the above information it seems to me that finished wine contains some CO2. It is not necessary to remove all the CO2, it is only necessary to remove the amount that adversely affects the taste of the wine. As I write this I can hear the chorus, “So, how do we determine that?”

The most frequently recommended test is the “Poof Test”. A 375ml bottle is half filled with wine, the thumb is placed over the opening and the bottle is briskly shaken. The thumb is removed from the top and the winemaker listens for a “poof” that indicates the presence of CO2.

I believe that too much emphasis is placed on listening for the “poof” and not enough at looking at the level of foam produced by the shaking. Generally, if shaking produces 1/2 inch or more of foam, additional degassing is necessary. Try this first with several commercial wines to establish a reference level. It is important that the wine and the test bottle be at the same temperature. Cold water in a warm bottle will “poof” and I don’t think it’s from excess CO2.

Another popular method among those using the brake-bleeder vacuum pump is the length of time the pump can hold 20 inches of mercury. As a vacuum is created, CO2 is pulled out of suspension and the vacuum is reduced. If a vacuum is created that results in a reading of 20 inches of mercury on the gauge and it holds for 30 minutes, the wine is considered to be degassed.

My preferred method is the “taste test”. It can be used in place of the above tests or it can supplement them. In this test, wine is taken into the mouth and allowed to spend some time on the tongue. If there is a prickle sensation on the tongue, the wine probably contains too much CO2 and additional degassing is required.

So, how do you get rid of that gas? The three most often mentioned methods are: bulk aging, whipping and vacuum pumping. I am not going to cover degassing procedures in this article. For the whipping method see http://www.finevinewines.com/Stirring-Your-Wine-Kit.htm and for the vacuum method see the featured article at http://www.finevinewines.com/March_2007.htm. I would however like to make some comments on some of these methods.

Have you heard or read a comment similar to this, “I have bulk aged my wine for six months and it still has excess CO2”? I believe that wine in a barrel will degas itself. But I do not believe that wine just sitting in a glass carboy for six months will degas itself.

When I started making wine, degassing was not an issue. It wasn’t discussed in the procedures generally available to home winemakers. What was covered in the material of the day was the importance of bulk aging. I remember bulk aging wine for at least nine to twelve months. I also remember racking and sulfiting every three months during the process. I believe it was these cellar processes and the exposure to changing temperatures and barometric pressures during the aging that degassed the wine rather than it just sitting in a carboy.

There are also some questions about vacuum degassing. Will the vacuum remove alcohol, sulfur dioxide or the esters contributing to the aroma and taste? According to Tim Vandergrift, technical services manager for WinExpert, you cannot extract a measurable amount of alcohol or significantly change sulfite levels with a vacuum apparatus and even high levels of vacuum (>24 inches mercury) don’t damage ester levels.

This article started with the statement that a newly fermented wine is saturated with CO2. Regardless of the degassing method or methods employed, it is essential to the taste of the wine that much of this CO2 be removed. Remember also that too much or too little CO2 can be detrimental to the wine. Don’t get carried away with your method, just because some is good doesn’t mean that more is better. I have found that a combination of the three methods works best for me. Finally, do not drive yourself crazy trying to get all of the CO2 out of your wine. As you taste your wine at each stage, also taste to determine the effectiveness of your degassing efforts.