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frenchn00b 08-27-2007 03:34 PM

Why frozen food gets rotten faster comp. to non-frozen food?
 
Off-topic, here we go:

Go the mall, buy food, just freeze it.
Afterwards, never you notice the frozen food gets rotten faster comp. to non-frozen food?
So, to freeze, is it really healthy (with regular -20 to -18C) ? What about germs (multiplication, are we eating that then?) ?


Who is scientist on the board to give us a clear reply ?

MensaWater 08-27-2007 04:04 PM

Freezing breaks down cell walls. The food so long as it is frozen is reasonably safe (assuming it was safe when you put in the freezer in the first place). However, once you defrost it you're already on the way to "rotting" because of what happened when it froze and defrosted. Non-frozen food on the other hand didn't go through these two state changes so start the rotting without the cell walls already broken down. This is why frozen food products often tell you to use them within a few days (if not hours) of defrosting.

Frozen food is safe but many people will tell you they can taste a difference (I can with things like ground beef and orange juice) where others can't. Its more a matter of taste than of safety.

P.S. Freezing does NOT kill germs like boiling. Some people mistakenly think its safe because it is frozen but that isn't the case. It is only safe if it already was when frozen. If it had botulism at the time you froze it and you don't cook it well after defrosting the botulism will still kill you.

P.P.S. They've found some organisms that can live in boiling water in undersea thermal vents so even boiling isn't foolproof.

We're all going to die someday... :eek:

teek 08-27-2007 05:15 PM

I agree with every thing you say but I just might add that repetitive freezing and defrosting of food is a good method of sterilization though. However, because the crystallization of water is destructive to cells and since most your food consists of cells, you also alter your food structure and aid bacteria in the rotting process as soon as the food defrosts.

On top of that, living (that is dividing and metabolizing) for bacteria requires liquid water, to my knowlegde no bacteria can live in ice.

unSpawn 08-27-2007 05:15 PM

Quote:

P.P.S. They've found some organisms that can live in boiling water in undersea thermal vents so even boiling isn't foolproof.
True. And scorpions apparently survive a nuclear war so nuking your food ain't foolproof either. I'm pretty sure deep-frying scorpions will kill them so deep-fried food is definately good. I'd return my food if it had scorpions in it though.

colucix 08-27-2007 08:01 PM

Quote:

Originally Posted by teek (Post 2872618)
to my knowlegde no bacteria can live in ice.

Not bacteria, but some kind of spores. If you freeze a penguin, when you defrost the spores can develop to bacteria. By the way, why we should freeze linux!?

sundialsvcs 08-27-2007 08:20 PM

When water freezes, it expands. So it expands in all those millions of cells and ruptures them.

IBall 08-28-2007 07:15 AM

Quote:

Originally Posted by teek (Post 2872618)
I agree with every thing you say but I just might add that repetitive freezing and defrosting of food is a good method of sterilization though.

Perhaps if you do so in a short period.

The worst thing that you can do is take it out of the fridge or freezer, let it warm up to room temperature and then cool it again repeatedly.

In general, once food is thawed, never re-freeze it again. Also, never defrost at room temperature - always in the fridge or microwave. Use thawed food immediately.

I find thawed food tastes different. Meat is tougher, and milk separates. There is nothing worse than milo with crunchy bits of cream and watery milk ;)

--Ian

robpbyw 08-28-2007 07:53 AM

robpbyw
 
To understand what is happening during freezing and thawing you need to know some physical chemistry, in particular, the law of mass action (Le Chatelier) which states that the speed of a reaction increases as a function of the concentration of the reactants. We are here talking about a hydrolytic reaction (degradation by water). The effective concentration of the foodstuffs you are trying to conserve increases enormously as you remove water and turn it into ice. During the last few seconds of the freezing process, you are also removing the water, so the reaction stops.

Conclusion: there is nothing magical about -20 deg. C,
probably -10 is as good, what is most important is: freeze fast.

The same goes for thawing: thaw fast as in a microwave oven, get really hot, and then consume (or discard) the thawed product.

dickgregory 08-28-2007 08:23 AM

Quote:

Originally Posted by unSpawn (Post 2872619)
True. And scorpions apparently survive a nuclear war so nuking your food ain't foolproof either.

Nuking, as in a microwave oven, has nothing to do with nuking with an atomic bomb. A microwave simply subjects the contents to high frequency electro-magnetic energy. A nuclear bomb consists of a nuclear chain reaction resulting in enormous radioactive radiation.

Contrary to the spectacularist media and some action groups, there is no more real radioactivity emitted from a microwave oven than from your computer.

brianL 08-28-2007 08:28 AM

Do scorpions taste better deep-fried or microwaved...and is it safe to eat the sting??

MensaWater 08-28-2007 08:30 AM

Quote:

Originally Posted by unSpawn (Post 2872619)
True. And scorpions apparently survive a nuclear war so nuking your food ain't foolproof either. I'm pretty sure deep-frying scorpions will kill them so deep-fried food is definately good. I'd return my food if it had scorpions in it though.


Deep fried scorpions and mush created by repeatedly freezing and thawing food - sounds like one heck of a meal. :D

Deep fried scorpions is at least something I'd probably try if I knew others had eaten it safely. So far the only food I ever refused to try in my life was chitlins - those things look and smell disgusting even if you don't know what they are.

Frog legs oddly enough taste like fish and I thought escargot tasted like buttered mushrooms, buffalo is much like beef but a bit stringier and aligator tail is similar to calimari. All of which puts the lie to the idea that everything tastes like chicken.

Going off to hunt kittens now...

nx5000 08-28-2007 08:50 AM

Oyster anyone?
:)

MensaWater 08-28-2007 08:53 AM

That reminds me of old rhyme (I think this came from B.C. Comic)

By far the bravest man ever I saw
Was he who first ate an oyster raw

nx5000 08-28-2007 08:58 AM

Hey, the oyster is supposed to be still moving when you eat it! Try it but take care where you buy it :)

robpbyw thanks for the explanation

Larry Webb 08-28-2007 09:15 AM

Love them oysters, they definitely are far better fresh than frozen then thawed. In fact that can be said for any seafood.


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