I recently found an interesting article about the dangers that onions can present when left out, refrigerated or frozen. This information goes all the way back to the Black Plague when many were saved because they had placed onions and garlic around inside their homes. Tests have shown that onions absorb bacteria when not cooked immediately.
Most people are aware that they should not leave potato salad sitting out after a meal for fear that it will spoil. Well, they are right about that, but for the wrong reason. Most think that mayonnaise is the culprit, but it’s not the mayonnaise. It’s the onion and the potatoes. Both attract bacteria. Commercially made mayonnaise is completely safe. In fact it doesn’t even have to be refrigerated, although most of us do.
Refrigerating or freezing cut leftover onions does not remove the danger. It’s already contaminated just by being cut open and left out for a while. This also applies to those onions served with your ballpark hotdog.
Cook your onions as soon as they are cut open.
Next time I get the flu I’m going to test this theory by leaving a cut onion next to my bed and will report here on the results. But don’t hold your breath. I rarely get the flu or even a cold. If someone else wants to test it I’d like to hear about it.