How long should I keep a cut onion?

When I use fresh onions, we store the unused parts for up to a week in our fridge in either a ziploc or a sealable rubbermaid-style container. For particularly pungent onions they go in the crisper drawer to keep the smell from being too strong in the rest of the fridge, but usually they're just on one of the shelves. Stilltasty says 2-3 days but my personal experience says otherwise.

Generally in our house, they don't last long enough for the flavor to degrade too much, but they will get a little dried and the smell will get stronger over time. After a week, they shouldn't be bad in the sense that you'll get sick - but you'll want to use them in a meal where the onion is the star, as the aroma will take over the dish.

Another option that I'm a big fan of is to dice or strip the leftovers (or, a 5 lb bag at once!) and freeze them on a cookie sheet (instead of in a bag, where they'll turn into a giant clump). Once fully frozen, dump them into a plastic freezer bag, and store in the freezer for easy access to a handful at a time. For most applications, you can defrost them right in the pan/pot/casserole as you cook, so they're very handy and accessible. We do the same with peppers in our house for convenience.

I've had good luck with sealed glass containers ... including when storing sliced or diced onions. I find that plastic containers can start to pick up the onion smell if you leave onion in there for too long.

I've kept a halved, but otherwise in one piece, onion for over a week. If it dries out a little, you can always just take a slice off the cut side.

Cut up onion can keep for about a week, but it helps to have used a sharp knife -- a dull knive damages more cells and it'll start to break down faster. (and if it's sharp enough, you can slice it up, but keep the shape, so there's no extra exposed cut surface to lose moisture from). The more damage you do to the cells, the stronger the 'oniony' smells will get.

My judge on if it's still okay to use is to look at it -- if it's gone translucent, smells funny or looks funny (including dried out), I pitch it.

If you have no container, you can also use a piece of plastic clinging wrap to cover the cut part. If you notice that the cut dries out or does not look appetizing anymore, simply cut of one thin slice and presto, it's fresh and juicy again.

Another option is to caramelize one or two onions in a frying pan, and then freeze the pre-cooked onions in smaller portions. (I tend not to like cooking with frozen onions, since the extra water will steam the onions rather than allow them to cook at the higher temperature you could achieve without the extra water.

A couple of years ago I found a container designed to store cut onions. It looks like a plastic bowl with a rubber and metal lid. The smell is kept inside the container and the onion lasts several weeks.

I don't know how it works, but it most certainly does! Before I had it, I would wrap an onion in plastic and it wouldn't last quite a week.

I tend to put them in a sealed container with just a small splash of vinegar or lemon juice.... Seems to help them to not dry out.. :-)

I just wrap it up in foil. It will start to smell when it's going bad. You're not supposed to save onions, since they are so cheap. You can also buy already diced onions at Walmart. I believe they stay good for at least two weeks.

Cut onion can be stored 7-10 days in a sealed container in the refrigerator. I've not experimented specifically with glass or plastic, but I can understand how glass would be better. I'll have to give that a try. Sharp knives are key, that was a spot on tip!

With regard to the comment about cut onion absorbing bacteria, that is false. Anyone interested in more on that can click here: http://onions-usa.org/faqs/onion-flu-cut-myths

http://onions-usa.org/all-about-onions/how-to-select-cut-prepare-store-onions

straight from those who know what we are crying about..

I like to store them in a bottle, they will last at least a week.