Why do bag-in-box wines have an expiration date when bottles don't?

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Dear Dr. Vinny,

I’m concerned about box wine with a plastic bladder in a box. I noticed they have an expiration date. I’ve never seen that on a bottle of wine. My question is, is the wine safe to drink past the expiration date? Does it have an expiration date because chemicals from the plastic might seep into the wine after a certain period of time? I have several boxes that are a year past the expiration date.

—Lenny K., Riverside, Ill.

Dear Lenny,

I really appreciate the convenience, value, low-impact packaging and unbreakability of boxed wines, and there are some tasty options out there. You’re correct that bag-in-box wines have a limited shelf life, even if they haven’t been opened. It’s typically within a year or so from the time it was bottled—I mean bagged.

The expiration date has nothing to do with chemicals seeping into the wine—the plastic they use is food-safe and won’t affect the wine’s flavor that way. But the bags will let microscopic amounts of oxygen pass through, into the wine, and after a while, that oxygen will make the wine taste less fresh.

Bag-in-box wines aren’t meant for long-term aging, and that’s good, because the packaging doesn’t really allow for it (and this is why we don’t have cellars full of plastic bags of wine). Your “expired” wines won’t make you sick, but they might not taste like they did when you first bought them—the fruit flavors have likely faded, and they’ve taken on nutty, oxidized notes.

—Dr. Vinny

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