White onion is delicious, nutritious, and can be prepared in a variety of ways, from sautéing or sweating it on the stove to roasting it in the oven.
Not like pork chops or chicken cutlets, white onion is a little trickier to portion out. And if you cooked too much of it, you may be wondering how to store the leftovers and how long they will keep.
For the answers to your questions and the ones you didn’t know you had to ask, read on below.
How Long Can You Keep Cooked White Onion?
Cooked white onion lasts 1-2 hours at room temperature and 3-4 days in the fridge. Frozen cooked white onion stays safe to eat indefinitely, but only retains its best quality for 9-12 months.1“Leftovers and Food Safety,” Food Safety and Inspection Service, U.S. Department of Agriculture, https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/leftovers-and-food-safety
The most important thing when it comes to safely storing cooked white onion is not to keep it at room temperature, which food safety experts call the danger zone.2“How Temperatures Affect Food,” Food Safety and Inspection Service, U.S. Department of Agriculture, https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/how-temperatures-affect-food, for too long.
Bacteria multiply rapidly in the temperature range of 40°F (4.4°C) to 140°F (60°C) and grow well on cooked white onion. A dozen bacteria on your leftover white onion probably won’t do much harm, but a few hundred can do plenty.
Can Eating Old Cooked White Onion Make You Sick?
If you suspect that the cooked white onion has been on your kitchen countertop, dining room table, or in your refrigerator for longer than the times specified above, err on the side of caution and dispose of it.
You can get food poisoning from eating cooked white onion that hasn’t been stored properly or that’s been kept for too long, even if it looks perfectly fine and doesn’t feel, smell, or taste spoiled.
This is because the pathogenic bacteria that cause food poisoning are not the same as the spoilage bacteria that cause the white onion to spoil. Disease-causing bacteria don’t alter the cooked white onion’s texture, aroma, or flavor in any way, and so they’re virtually undetectable.3“Do spoilage bacteria make people sick?” AskUSDA, U.S. Department of Agriculture, https://ask.usda.gov/s/article/Do-spoilage-bacteria-make-people-sick
How to Store Leftover Cooked White Onion
If you made more white onion than you and the family can eat in a single meal, remove it from the heat, allow it to cool down as quickly as possible, then refrigerate or freeze it.
Fridge temperature (40°F/4.4°C or lower) slows down the grown of bacteria on our food, but doesn’t stop it. So use up the cooked white onion within no more than 4 days from refrigeration, or it may become overgrown with bacteria and no longer be safe to eat.
To refrigerate leftover cooked white onion, place it in a ziplock bag or food storage container with the lid closed and store it in the lower compartment of your fridge, where it is coldest.
Freezer temperature (0°F/-18°C or lower) puts all bacterial activity on pause. This means that, technically, frozen cooked white onion stays safe to eat forever.
However, it will eventually dry out and lose its texture, aroma, and flavor, so be sure to use it up within 9-12 months.
To freeze leftover cooked white onion, place it in a freezer bag or heavy-duty food storage container with the lid closed and store it in the freezer. Wrapping the white onion loosely in aluminum foil or plastic wrap isn’t enough as it may get freezer-burnt.
How to Tell If Cooked White Onion Is Spoiled
As with all other vegetables, there are some very specific signs you should look for to determine if the white onion you cooked has gone bad.
First, touch the white onion. If it feels sticky and slimy to the touch, then it’s probably spoiled. Second, give it a whiff. If you notice any off odors, whether sour or musty, this is also a sign that it’s past its prime.
The last and final sign of spoilage is the taste. If the cooked white onion is unpleasantly bitter or has a funky, unpleasantly weird taste, DO NOT eat it.
The problem with spoiled food is that you have no reliable way to tell if it’s safe to eat, so it’s better to just play it safe.
As a general rule of thumb, cooked white onion lasts:
- 1-2 hours when left out on the kitchen countertop or dining room table
- 3-4 days when properly refrigerated
- 9-12 months when frozen
Cool the white onion down quickly after you’re done cooking it and refrigerate or freeze it, but don’t let it sit out at room temperature. Now, you know the reasons why.
- 1“Leftovers and Food Safety,” Food Safety and Inspection Service, U.S. Department of Agriculture, https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/leftovers-and-food-safety
- 2“How Temperatures Affect Food,” Food Safety and Inspection Service, U.S. Department of Agriculture, https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/how-temperatures-affect-food
- 3“Do spoilage bacteria make people sick?” AskUSDA, U.S. Department of Agriculture, https://ask.usda.gov/s/article/Do-spoilage-bacteria-make-people-sick