Sparkling to still?
Some of our wine turned from still to sparkling. Can we change it back to still at this point? Will nitrogen sparging take care of it or do we need to add sorbate?
Conway, South Carolina
Like I mentioned earlier, winemakers do have some control over how much fizziness we bottle our wine with. We can use a sparging stone in-line with a pump and hose (or in the bottom of a keg, if you have smaller amounts) to add carbon dioxide or, interestingly, we can sparge with nitrogen in the exact same way to remove dissolved carbon dioxide.
Sparging for carbon dioxide removal only works, however, as long as your carbon dioxide is not being constantly replenished by microbial activity. If you have an active fermentation going on, either from unfinished sugars from the primary fermentation, from an incomplete malolactic fermentation or from a microbial infection of any kind, no amount of sparging with nitrogen will remove the CO2 if it keeps getting produced. Before you sparge to strip out the CO2, you should determine if you just have residual dissolved gas or if it’s being created by an unwelcome source. If it is, you could “sterile” filter (through a 0.45 micron nominal pad or membrane), which just by moving your wine through the filter alone, may remove some of your dissolved CO2.
If you want to use nitrogen to strip out some of the dissolved carbon dioxide, I find it works best if my starting dissolved CO2 is under 2000 mg/L. The challenge with nitrogen gas is that it can also strip out aromas when you bubble it through your wine — it’s like swirling your glass repeatedly and liberating all of those nice smells you may actually want to keep in your wine. Sometimes I find that you can lose a lot of the carbon dioxide just by splash-racking (works well for young red wines especially, who can often use oxygen anyway at that stage) and moving the wine around the cellar. This doesn’t strip aromas nearly as much as a large sparging would. Of course, this doesn’t work for delicate whites that you may not want oxidized, in which case I would sterile filter, then proceed to sparge with nitrogen until the wine is at the level of dissolved carbon dioxide you desire. Don’t be afraid of using the easiest tool to degas: time. Often, if there is no microbial activity, a wine will lose all of its dissolved CO2 during the 12–18 months you may age it before bottling.