Question from a reader: “What information do you have about the idea that onions pose a risk if left in the refrigerator after cutting? It is something most of us have always done and now there is information floating out there in the internet world that this is not a safe practice. Thanks for any insight!”
Don’t you just love the internet? All of these “tales” can cause us to worry about everything! According to Snopes, this one has been going around since 2008 and there isn’t any scientific proof to support this statement.
Nothing mysterious happens to onions once they are in the refrigerator. Like all fruits and vegetables, once cut, onions should be kept in the refrigerator (National Center for Home Food Preservation and National Onion Association). I’ll refer you to another article I wrote about Keeping Fruits and Vegetables Safe.
Once a fruit or vegetable has been cut, the barrier to the outside world has been broken and the plant’s natural defenses have been compromised. This opens the food up to the environment. Plus, the moisture and natural sugars in fruits and vegetables help create a great place for bacteria to grow. Refrigerator temperatures, on the other hand, can help slow this development of bacteria. The biggest problem with onions in the refrigerator is the odor. Be sure to wrap well or keep in a sealed container.
But don’t store your uncut onions in the refrigerator. Whole unpeeled onions should be kept in a cool, dry, well ventilated place. Don’t store them in a plastic bag. Sweet onions tend to have higher water content and are more susceptible to bruising and will have a shorter shelf life than yellow onions. Once peeled or cut, onions should be stored (well wrapped or covered) in the refrigerator at 41 degrees or below. A peeled or cut onion will be of good quality for 7 in the refrigerator.
If you have a few too many chopped onions they can be frozen. I have frozen leftover chopped onions (without blanching) for a short time, they are not crisp when thawed, but work great for cooking. Be sure to wrap well. Use within 3-6 months for best quality. For longer freezer storage, The National Center for Home Food Preservation (nchfp.uga.edu) recommends they be blanched and cooled before freezing.
One final tip: according to the National Onion Association (www.onion-usa.org) it’s the sulfuric compounds in the onions that cause us to cry when cutting onions. To help reduce this,they recommend chilling the onion before cutting and cutting into the root end of the onion last.
Cheryle Jones Syracuse, MS
Professor Emeritus, The Ohio State University