Having the pleasure of sharing in the tradition of wine making with so many people, the one question I hear most often is..
Why is my wine fizzy? While crafting Frizante' is sometimes the goal, very few people set out to craft wines with carbonation. Once again not only is prevention better than cure, it's easier and better for your wine.
During fermentation, yeast consume glucose and fructose, and the bi-products released are alcohol ☺ , carbon dioxide, and a very small amount of sulfur dioxide. The majority of carbon dioxide tends to be displaced as you punch down the skins in your must or stir you juice pails. This is the first step in being proactive in preventing "the fizz".
Punch down your cap frequently and thoroughly, this will also introduce oxygen to the must and keep yeast thriving. The same applies to your juice pails. It's a good idea to have some extra pails around to ferment in. Consider splitting your bucket of juice into two pails during primary fermentation. This will enable you to aggressively stir you juice without spilling it or having the carbon dioxide gas push it over the rim of the pail. Stir three or four times daily and vigorously. Continue this until your primary fermentation is complete.
Secondary fermentation or malolactic fermentation is another friend of "the fizz". This is the conversion of acid from harsh malic acid to supple lactic acid. This fermentation is commonly introduced by winemakers in various styles of wines to achieve better structural qualities in the mouth feel and finish of wines. A malolactic bacteria is introduced to produce the fermentation and once again CO2 is a byproduct of this process. A splash racking or decanting is usually sufficient to displace the CO2 levels generated in the malolactic conversion for home winemakers. Be certain to sulfite properly immediately after racking. Proper sulfite levels will disable any ML bacteria that remain preventing further production of CO2.
Another friend of "the fizz" is residual sugar in your wine. Make sure your fermentation is complete. .990 Specific Gravity is completely dry. Sulfite to proper levels when fermentation is complete. Be certain that if you are making a sweet wine, you have taken the necessary steps to prevent it from fermenting in the bottle. One gram of potassium sorbate per gallon should be introduced to the wine prior to bottling. This prevents yeast from reproducing so no re-fermentation is possible. More is not better with Potassium Sorbate. Weigh it judiciously, 1 gram per gallon is enough. Proper sulfiting again should be practiced before bottling also.
There are other microorganism that can create "the fizz" by feeding on the alcohol in your wine. Oxygen will promote the opportunity for microbes that consume alcohol to multiply and not only produce CO2, but turn your wine to vinegar. This is easily preventable by making sure that no head space is present in your bulk storage vessels. Clean and sanitize everything that comes into contact with your grapes, juice or wine. Proper sulfite levels must be maintained based on your wines pH levels. Make certain that the bottles you are using are clean and sanitized properly before filling.
Unfriend "the fizz", and enjoy better wines by following these rudiments of sound wine making practices.