Onion is an essential ingredient that adds depth and flavor to almost any dish—whether it's French onion soup, a rich sauce for roast or pasta, or even a fresh salad topping. But you don’t always need a whole onion. Often the recipe calls for only half, and the remaining part ends up tossed in the fridge until it becomes mushy, slimy, smelly, moldy, and ultimately thrown away.
Many of us are used to saving leftovers, but we don’t always know how to do it properly. When it comes to onions, there are simple and natural solutions that can keep them fresh, moist, and flavorful for reuse—without compromising on quality or taste.
Keep the Peel – and Place the Cut Side Down
While many people peel the entire outer layer before use, chef Katie Rosenhouse recommends leaving the peel on the unused half. She explains that the peel protects the onion from drying out and helps maintain its moisture and texture. The half you didn’t use should be placed in the fridge with the cut side facing down, to further protect it from air exposure.
A Sealed Container – or at Least a Tight Wrap
If you've already chopped or sliced the onion, the best option is to transfer it into an airtight container or a Ziploc bag, making sure to remove any excess air. This reduces moisture loss, slows down spoilage, and prevents unpleasant smells from transferring to other foods in the fridge. This, too, is a completely natural and chemical-free solution.
The Vegetable Drawer Is the Right Place in the Fridge
Like other vegetables, cut onions are best stored in the vegetable drawer, where humidity and temperature levels are more stable. Heat and cold fluctuations—like those near the fridge door—speed up spoilage.
Want to Keep It for Even Longer? You Can Freeze It
If you know you won’t use that half onion within a few days, freezing is an efficient solution. Chop the onion in advance, spread it on a tray, and freeze in a single layer. Once frozen, transfer it to a bag or airtight container and store it in the freezer—where it will keep for up to six months. Note that freezing will change the onion’s texture (it will become softer), but for soups, stews, and frying, it’s perfect.
So How Long Does It Last?
A whole onion stored in a cool, dry place can last for months. But a cut onion will last about a week to 10 days in the fridge—only if stored properly. If you notice a sour smell, slimy texture, or signs of mold, it should be discarded immediately.
If you store it correctly, you’ll gain freshness, flavor, and less food and money waste.