What does it mean if a still white wine like Chardonnay has bubbles?

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Dear Dr. Vinny,

Why would a still white wine, such as a Chardonnay, when poured into the glass, have little bubbles on the bottom, and have a slightly effervescent taste?

—Deborah, Boca Raton, Fla.

Dear Deborah,

There are a few scenarios that I can think of here, and in all of them, the source of the bubbles and that effervescent tingle on your tongue is carbon dioxide. Carbon dioxide is a byproduct of fermentation, totally harmless, and sometimes it hasn’t all escaped before a wine is bottled.

Some winemaking practices can increase the presence of carbon dioxide, like particularly cold cellars (carbon dioxide is more soluble at colder temperatures) or leaving some solids in the wine by not filtering or fining.

Some winemakers might also choose to use carbon dioxide as a sort of invisible blanket or inert gas to prevent a wine from oxidizing or spoiling during the winemaking process, and again, some of that carbon dioxide might remain in the wine when it’s bottled. Usually it will dissipate with some swirling, and as the wine warms up to room temperature.

Finally, there’s a chance that the wine has started to re-ferment in the bottle, but if that were the case, it would also likely appear hazy, not to mention smell a little skunky. Again, nothing that would make you sick, but it probably wouldn’t taste very good.

—Dr. Vinny

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