Can a wine turn poisonous if the winemaking is less than perfect?

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Dear Dr. Vinny,

Can wine turn poisonous if the process of winemaking is less than perfect—for example, less sugar content and hence less alcohol?

—Dev, Greater Noida West, India

Dear Dev,

The short answer is no, wine cannot become poisonous. If a person has been sickened by wine, it would only be due to adulteration—something added to the wine, not intrinsically a part of it. On its own, wine can be unpleasant to drink, but it will never make you sick (as long as if you don’t drink too much).

The scenario you describe is actually a desirable style of wine for many who are looking for lighter, less alcoholic wines. But let’s say a winemaker uses grapes that most would consider underripe. You might end up with vegetal flavors, lighter colors, excessive acidity and less concentrated flavors and aromatics. It might also mean a difficult fermentation if the yeast run out of sugar to convert to alcohol. But no poison.

That’s not to say wines don’t have problems—just none of them are toxic to humans. A wine can start to ferment inside the bottle unexpectedly, get exposed to too much oxygen, have a spoilage yeast called brettanomyces, have excess sulfur compounds, contain too much volatile acidity or even be “corky” with the compound 2,4,6-tricholoanisole (TCA). But all of these issues—even if a bottle of wine turns to vinegar—just make a wine unpleasant to drink.

—Dr. Vinny

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