Does chopped onion attracts to the outside environment immediately.

[alankar]

Cutted onion if kept for long hours or for a day, does any chemical reaction occurs..

[ChrisTaylor]

I take it you want to know how long it takes before a sliced onion starts to deterioate. Are you vac sealing it? Storing it under cling film? Parking it in the fridge? Leaving it out, sans cling film, in a warm room?

[SylviaLovegren]

Cut onion that sits around always gets a very strong sulfur taste which I assume is from the chemical reaction that occurs from cutting. Refrigerating the cut onion seems to slow down the development of the sulfur taste -- but that's from my experience, not science!

[Ttogull]

Rinsing the cut onion right after cutting significantly reduces the strong taste over at least a couple of hours. I've never paid attention to longer periods.

[alankar]

hello Chris Taylor,

I mean to say, sometimes it happens, we just need a help of half of the onion, at such times, I use to keep the onion in freeze, but, then I observed some difference in taste of onion being kept in freeze.

[Lisa Shock]

If you only need to use half an onion, use the top half. Cut it at the equator and put the bottom half, with the root stub intact, in a plastic bag or wrap tightly. The onion will still be alive and will last much longer than diced onion, or any part cut away from the root.

[ePressureCooker]

What Lisa said. Or if you don't want to keep the other onion half in the fridge, you could saute it and then freeze it for later use (that takes up less room).

[furzzy]

If you only need to use half an onion, use the top half. Cut it at the equator and put the bottom half, with the root stub intact, in a plastic bag or wrap tightly. The onion will still be alive and will last much longer than diced onion, or any part cut away from the root.

Great! I didn't know that! So, you mean that so long as the root stays in tact, we're golden for much longer than w/o it?

[Lisa Shock]

If you only need to use half an onion, use the top half. Cut it at the equator and put the bottom half, with the root stub intact, in a plastic bag or wrap tightly. The onion will still be alive and will last much longer than diced onion, or any part cut away from the root.

Great! I didn't know that! So, you mean that so long as the root stays in tact, we're golden for much longer than w/o it?

Yes, as long as there looks like some little bits of root, you're fine. I routinely keep partial onions for weeks+, and, even if there's just a little left it still works because it's still alive. Avoid buying onions that don't have any root, they will not last. That said, if you leave a partial onion with the stump on it in the fridge too long, the center will start to grow. -There's nothing wrong with that, it's just uneven to cut.

[alankar]

Thanks all here, for your comments..