Name: Ed W.
Sorry to hear that your wine has gotten a little out of control. Let’s see if we can figure out what’s going on. There are basically two ways a homemade wine can end up fizzy or bubbly. I’ll go over them here:
This is the most common way to get a fizzy wine. When a fermentation stops it usually means that it has finished. That means all the sugars in the wine must have been fermented into alcohol. There are no more sugars to ferment.
But on occasion a fermentation will stop before the sugars are all gone. This is known as a stuck fermentation. This can happen for a number of reasons: wrong fermentation temperature, using distilled water, etc. (see The Top 10 Reasons For Fermentation Failure) For this reason it is important that you check the must with a wine hydrometer to confirm that all the sugars have been fermented before moving on to the next step.
If you continue on with the wine recipe and end up bottling the wine with sugars still in it, then a fermentation could start up within any or all the wine bottles at any time in the future, even months down the road. It is important to remember that even the slightest amount of fermentation can cause a lot of fizzy within the wine.
The only exception to the above is if you have added potassium sorbate to the wine, also known as wine stabilizer. If you have added this before bottling, then the chance have having a re-fermentation within the wine bottles is greatly diminished. The same holds true if you have sweetened the wine before bottling. You need to add potassium sorbate along with the sugar to eliminate a potential for a re-fermentation within the wine bottle.
2. Bacterial Infection:
This is not as common of a reason for a homemade wine being fizzy as a re-fermentation, but it happens. If the fermenters, stirring spoons, hoses, wine bottles, corks and anything else the wine comes into contact with has not been sufficiently sanitized, then you run the risk of infecting your wine with a bacteria.
There are many excellent sanitizers on the market. We recommend Basic A because it is very safe and simple to use. You should also add sulfites directly to the wine after the fermentation, and again, right before bottling the wine. If you miss killing some bacteria, then adding sulfites such as Campden tablet or sodium metabisulfite to the wine will go a long way towards protecting it.
One thing you have mentioned is that the wine is fizzy instead of bubbly. If the wine has re-fermented, most people would describe it as bubbly and not fizzy. The CO2 bubbles from a fermentation are pretty good size. Fizzy sounds like the bubbles are smaller than that. That is what you would expect to find with a bacterial infection.
You also said that it fizzed for a long time. This is fairly definitive. When you get a fizzing that bubbles evenly for a period of time, that is also an indicator of a bacterial infection. Carbonation from a re-fermentation is more explosive and short-lived. A bacterial infection is not explosive. Once you open the bottle, it take a few seconds for it to build up a head of steam and get going.
I’m not sure, because I am not there, but I would guess the reason your homemade wine is fizzy is because of a bacterial infection. That being the case, sanitation of equipment and use of sulfites needs to be the focus when making future batches.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.