Kitchen Experts Reveal the Best Way to Keep Cut Onions From Stinking Up Your Fridge

Onions are one of the most essential pantry ingredients around. In both raw and cooked form, they’re used as a building block for countless dishes from soups and casseroles to sauces to salads. No matter which type you choose, onions are a versatile, flavor-boosting ingredient and luckily, they also have a long shelf life.

If you’ve found yourself with a bunch of leftover chopped onions after prepping your favorite French onion recipes, you might be wondering what to do with them. How long will they last, and how should you store them? To find out everything you need to know about storing cut onions, we tapped two registered dietitians: Brittany Brown, R.D., in Nova Scotia, Canada, and Diane Han, M.P.H., R.D., of Woking Balance Wellness in San Francisco, California.

How to Store Cut Onions

Onions have a famously long shelf life, and whole red, white, and yellow onions are easy to store—just pop them in a mesh bag or basket in a cool, dark, and dry location. You should avoid storing whole onions in the fridge, as the cold, humid environment can cause them to soften and spoil more quickly. Once those onions have been cut, though, plan to keep them in the fridge.

Brown and Han say cut onions should be stored in the fridge, ideally around 40°F or below. Han recommends wrapping cut onions tightly in plastic wrap or transferring them to an airtight container to store in the fridge. “This prevents moisture loss and keeps the odor from spreading,” she says.

After onions have been cut and exposed to oxygen, they will spoil more quickly. They’re also more likely to transfer their distinct smell and flavor onto other foods, so keeping them in an airtight container, bag, or plastic wrap is key.

“I’ll never forget when my dinner party guest commented on my onion-flavored cake,” Brown says. “It turns out that it’s best if you refrigerate onions in an airtight container after they’ve been cut, not next to your dessert. Not only will this keep them fresh and safe for consumption, but it also prevents other foods from picking up their flavor.”

How Long Can You Store Cut Onions?

While onions have a long shelf life—properly stored, they can last up to three months—the clock starts ticking once they’ve been cut.

Brown and Han both recommend storing cut onions in an airtight container for no more than seven to 10 days. “Proper storage of cut onions helps prevent odor from spreading, lowers the risk of foodborne illness, and maintains freshness,” Han says. “Improper storage may lead to a loss of flavor and texture and may also increase the risk of foodborne illnesses (such as E. coli or Salmonella).”

Red, yellow, and white onions all have a similar shelf life once they’ve been cut, but Brown notes that red onions in particular tend to lose some of their coloring the longer they are stored. If you’re looking to keep those onions a bit longer, you can also try pickling them.

Signs of Spoilage in Cut Onions

Not sure if the cut onions in your fridge are still safe to use? Brown and Han recommend tossing your onions if they exhibit any of these common signs of spoilage:

• Slimy or mushy texture
• Mold (white, green, or black spots, or fuzz)
• Translucent, watery discoloration
• Sour or rotten smell

Can You Freeze Onions After Cutting?

Got a lot of onions on your hands? Good news: You can freeze both whole and cut onions to extend their shelf life a bit longer. “Cut onions can be stored in the freezer for later use, and their nutritional value isn’t compromised,” Han says. “In fact, freezing can help slow down the loss of nutrients compared to storing them in the fridge.”

That said, keep in mind that onions have a high water content, so freezing will affect their texture and flavor. “The texture becomes more mushy and watery, and less crisp and crunchy,” Han says. “Because of this, frozen cut onions are better suited for moist dishes like soups and stir-fries. Freezing also makes the flavor less pungent and sharp compared to fresh cut onions.”

To freeze cut onions, Brown says to follow these steps:

1. Dice or slice the onion.
2. Freeze onions in a single layer on a baking sheet for a few hours until solid.
3. Transfer into an airtight (or zip-top) container to store for up to 3 months.