What do these home fries, this shrimp étouffée, and these root beer-braised short ribs have in common? Besides being delicious, they also call for the same partial ingredient: half of an onion.
Though recipe developers like me prefer to call for whole ingredients as often as possible, sometimes an entire onion is just too much for a recipe—you don’t want your crispy home fries to be overshadowed by oniony flavor after all!
And what about that lonely other half of the onion? Surely it won’t be too long until you find another use for it, but how do you keep it fresh until then?
I spoke to Caroline West Passerrello, MS, RSN, LDN, instructor at the University of Pittsburgh and spokesperson for the Academy of Nutrition and Dietetics about the best ways to store this frequently leftover ingredient.
The Best Way To Store Half an Onion
West Passerrello told me that storing halved onions in plastic wrap, resealable plastic bags, or resealable containers in the fridge is the way to go.
The most important thing is that these storage methods are airtight, so make sure you’ve got a tight seal on your bag or container, or have tightly wrapped your onion in plastic wrap so that the odor and moisture aren’t escaping during refrigeration and make your whole fridge smell.
If you choose plastic wrap, store your halved onion cut-side down on the shelf for further protection.
West Passerrello says a properly stored half an onion will last five to seven days. I’ve certainly held onto cut onions longer than that, but the longer they sit in the fridge, the more intense and bitter their flavor becomes, so I’d recommend cooking older cut onions rather than using them raw.
If the cut edge looks dry, you can cut off a quarter-inch slice before prepping it for your next recipe.
A Smart Tip for Extending the Life of Your Halved Onion
To increase the lifespan of your leftover onion, West Passerello also recommends leaving the dry outer skin on as an added protective layer to keep moisture and odor inside the onion. And no worries if you’ve already removed it—you can still safely store it in an airtight container.
If you’ve held onto your onion a bit too long, or won’t have time to use it before it goes bad, freezing is an option.
Be sure to chop your onions before freezing, and store them as you would in the fridge, in an airtight container. Freezing the onions will cause their texture to deteriorate, so West Passerello recommends using them only in cooked applications, like in a meatloaf or a vegetable stock.