The Best Ways To Keep Onions Fresh

Onions are a classic staple ingredient to keep on hand. Onions can be added raw to salads, sautéed with other vegetables for an omelette, cooked down with celery and carrots to create the base of many recipes, or even sliced thin and included in a French onion soup recipe. But if you're not someone who uses onions often, you might wonder what to do with those left in the bag to keep them from going bad. If you know the best ways to store and keep onions at home, you can actually extend the shelf life of the produce for much longer than you might expect. 

While onions that are kept under very specific conditions and between temperatures of 30 to 50 degrees Fahrenheit can stay fresh for up to a year (via Bon Appétit). But you might not need to meet those terms to keep your onions good for long enough. As long as you know how long you need to keep onions fresh or when you plan to use them next, you can easily store them using two techniques to ensure they won't go bad before you need them.

There are a few key conditions to keep in mind when storing onions for up to a month and maximizing their chances of staying fresh. Onions like the same conditions as potatoes, but they cannot share the same space because both foods will cause the other to turn bad more quickly (via Have a Plant). That's why you need to find two separate storage areas that are dark, dry, and cool. Not just any container will do, though. Whatever you choose to store onions in needs to offer some airflow. That means you should opt for something like a bag with holes.

Under these conditions, onions can stay fresh for up to a month (via PopSugar). The lack of sunlight will prevent the onions from sprouting, and the airflow will prevent the onions from absorbing too much moisture and becoming soft. So, if you need to stash whole leftover onions for more than a few days, this is your best option.

While the moisture of a refrigerator is not the optimal place to store most whole onions, though some such as Vidalia onions or onions with green tops like green onions do well there, it is a great place for cut onions (via The Pioneer Woman). Whole onions that have been cut, sliced, diced, or chopped will stay fresh in the fridge, but you still need to give the type of container you store them in some thought. If you don't want other foods in your fridge to absorb the aromatics of cut onions, you need an airtight container that also won't absorb any scents. That tends to mean you should use a glass container and avoid using plastic wrap over a regular dish or plate.

Using this method, cut onions or diced onions will stay fresh for several days (via Bon Appétit). Avoid leaving cut onions out on the counter top where they could sweat if they become too warm as well.