The Winemaker’s Think Tank: Vol 1- Why is My Wine Fizzy?


Wine expert testing wine silhouette image


The Winemaker’s Think Tank? 

Every Thursday we will post about a few frequently asked questions that our winemaker has answered. If you have a winemaking question you would like to have answered, please email us at support@juicegrape.com and we will try to get into next week’s post. Cheers! :)


Why is my wine fizzy?

Wine may be fizzy for one of two reasons: trapped gas within the wine leftover from fermentation, or a re-fermenting wine. Yeast exudes two substances upon fermentation: alcohol and carbon dioxide. Often times, carbon dioxide is exuded in such small bubbles that the weight of the liquid wine is too heavy to allow the gas to escape. This gas can easily be discharged through a process called degassing. Degassing involves the extreme agitation of the wine via stirring or pumping over. If you own a pump, you can set up the hoses in a circuit, and pump over vigorously to allow the gas to escape. You can also buy a degassing stirring wand that attaches to a cordless power drill. Simply attach it to the drill, place in the wine, and stir. The agitation will allow any trapped bubbles to rise to the surface and dissipate.

The wine may also be fizzy due to a re-fermentation. Even after racking, there may still be suspended yeast cells within the wine. The addition of potassium metabisulfite is necessary to ensure the killing off of remaining yeast cells, especially if the wine has any residual sugar or if the winemaker has plans to back sweeten the wine. Potassium sorbate is also strongly recommended if the winemaker intends upon back sweetening a white wine. The potassium sorbate will encapsulate the yeast cells, rendering them sterile and unable to ferment any sugar that is then added to the wine. (Note: Potassium sorbate cannot be used on any wine that has gone through Malolactic fermentation.) If the winemaker would prefer physical rather than chemical sterilization, a sterile grade (.45micron) filter may be used to physically remove any yeast or bacterial cells and prevent any further fermenting from occurring in the bottle.

*Please Note:

  • Brettanomyces is carbon dioxide as well.
  • The issue of filtration raises a host of issues.  Sterile in winemaking is not achieved unless using an absolute filter (cartridge filter at the 0.45 or lower) and not a nominal filter (plate or pad filter  such as the Grifo or SuperJets).  The cartridges for the Enolomatic filter set-up are not rated as sterile either.

We hope this information helps with your winemaking. If you have any follow up questions or winemaking questions in general, please email us at support@juicegrape.com. 

2 Responses to The Winemaker’s Think Tank: Vol 1- Why is My Wine Fizzy?

  • Mark Peters says:

    Could it not also be going through a late malolactic fermentation, which could also cause fizzy wine.

    • cmusto says:

      If the wine is still fizzy, a few months after primary fermentation, and after multiple rackings, the trapped CO2 could also be a result of malolactic fermentation. Malolactic fermentation is a secondary bacterial fermentation in which the bacteria metabolize the malic acids into lactic acids and carbon dioxide. This transforms the malic acid, which is perceived as being sharper and more astringent upon the palette, to lactic acid, which is perceived as being smoother and less harsh upon the palette. If the bacteria strain is not inoculated purposefully, with a strong lab culture of bacteria, the natural lactobacillus present upon the grapes and juice will take over and begin the process. Due to the lower concentration of naturally occurring bacteria, the conversion process will take a very long time, posing risk to the overall health of the wine. The malolactic bacteria do exude some carbon dioxide as a byproduct of this fermentation, which could be a cause of fizziness within a wine. If the winemaker has not purposefully inoculated the bacterial culture, and has properly fermented and degassed the wine, yet still has a fizzy quality within the wine, it is very important to obtain some lab cultured malolactic bacteria and further along the secondary fermentation process that has most likely already begun naturally.

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