Onions are without a doubt a culinary staple. They can command center stage in a main dish such as french onion soup, support a sumptuous meal as a side dish like onion rings, and sneakily make their way into sauces and bases for plenty of recipes. Thanks to this versatility, you might be tempted to buy them in bulk, but you probably already know, unfortunately, the vegetable often becomes soft, wilts, or starts to sprout pretty quickly. So can you store your onions to ensure freshness for longer? The answer depends on the type of onion.
Red, Yellow, White, and Sweet Onions
According to the US Department of Agriculture (USDA), you should keep dry bulb onions (like red, yellow, white, or sweet onions) in a cool, dry, well-ventilated place that's dark, like a pantry or a cellar. You could also put them in a brown paper bag and use a hole puncher to generate vents that will allow air to circulate — although the grocery store sells bulb onions in large plastic bags, you should remove the vegetables from that packaging because the lack of air will reduce their life. And remember to avoid storing potatoes and onions together, because the potatoes emit a gas called ethylene, which will cause premature sprouting in onions. The USDA confirms that fresh onions can last up to 30 days if stored properly.
In addition, avoid storing whole bulb onions in the refrigerator. The chilly conditions of the icebox will cause the vegetables to become mushy and spoil faster, because they easily absorb moisture. This does not, however, apply to a sliced or diced onion. The USDA indicates that the shelf life of refrigerated bulb onions peeled, cut in half, wrapped in a wet paper towel, and sealed tightly in plastic wrap can be up to two weeks. Diced onions in an airtight container stay fresh in the refrigerator for about 10 days, while diced onions can last up to three months in the freezer if properly sealed in a plastic bag. Just make sure to eliminate as much air as possible from the bag and seal tight.
Scallions and Spring Onions
Green onions, also known as scallions or spring onions, need special care. To keep them from becoming brown and slimy, place the white sprouted end in a jar with one to two inches of water. Not only will the onions stay fresh, but they'll also continue to grow. As long as you maintain the water levels, the USDA says your green onions should last about seven to 10 days.
As an alternative, you can wrap the white ends of your green onions with a moist paper towel and place the vegetables inside a loose plastic bag stored in the refrigerator. Reapply moisture to the paper towel as necessary, and expect this technique to give your onions a similar shelf life as the jar method. Diced green onions and scallions can also last for about two days or up to three months in the freezer if sealed in an airtight plastic bag.
Cooked onions can be placed in a container and remain fresh in the fridge for three to five days. Should you need them to last longer, transfer them to an airtight plastic bag and store them in the freezer for 10 months to a year.
Bottom line, no matter what type of onions are on the menu, be sure to follow proper storage techniques to ensure fresh veggies every time you go to the pantry or fridge.