Bananas turn black in the freezer.
Tomatoes and onions turn to mush.
Hot dogs are OK.
French bread is fine and doesn’t change.
Hot dog buns turn musty and thaw out damp.
Well, in the case of fruit (and vegetables), I think it’s because the water in the plants’ cells expands, and ruptures the cells.
Same reason we have problems thawing cryogenically stored people, IIRC.
The ice crystals problem SftD mentions is by far the biggest one. Affects not onlly the integrity of plant cells, but the tissues in between. Moreover, the latter issue is why fresh meat, poultry or seafood (if it’s actually fresh) is generally considered better than frozen. Meat cells don’t burst, but the connections among them get torn, causing more water than usual to leak out during cooking.
Three other issues of significance are that (i) freezing does not stop (though it slows) enzymatic reactions, hence the bananas, for example; (ii) is does not stop (though it slows) the gradual rancidity of fats (which is a taste and texture, rather than safety, issue), which is the main reason for expiration dates on frozen foods; and (iii) it “breaks” most emulsions, hence the difficulty of freezing most sauces. Solving the third problem - mainly by using modified food starches - was one the the main hurdles that had to be overcome before TV dinners, pot pies and many other complete meal products could be produced.
For more information, consult a book on “putting up food,” or even a chapter on the subject in a general purpose cookbook. Will go into more detail than is practical here.
I freeze banana’s all the time and they never turn black, but I always peel them first, then freeze them for later use in smoothies.
Evaporation of moisture still occurs below freezing, so foods can dry out (I think this is called ‘freezer burn’)
PBear or anyone: What’s freezer burn. Why is the smell so bad and why does the smell stick to your hands? Does putting baking soda in the freezer just help the smell or actually stop the process of freezer burn?
Here is why I am asking: my dog Tara just had an operation on her leg. The vet said that a bag of frozen peas works as well if not better than an bag of ice. So I dug around in the freezer and found a bag of frozen peas. They were probably put in that freezer well over a year ago. So I go ahead and put the bag on Tara’s sore leg to reduce the swelling. Then I start to smell the freezer burn. After awhile it got really bad. I threw the peas away and washed my hands and Tara’s leg. That was yesterday. Today I can still smell the freezer burn on my hands and my dog. What’s up with freezer burn?
Coincidence, I think. Freezer burn is simply sublimation of ice. (Like evaporation, only there’s no liquid phase.) It is important for reasons of texture, not odor. Freezer-burned meat can smell funky because of the fat rancidity problem, since it usually has also spent a while in the freezer, but those independent processes. Properly wrapped meat will go rancid eventually but never develop freezer burn; and poorly wrapped meat can be burnt long before it goes rancid.
Peas, on the other hand, won’t go rancid. That is, ordinarily they’d be tough and unpalatable but not stinky. My guess is that they picked up odors from other things in the freezer and the fact that they were freezer-burned was merely a second concomitant of a common cause, i.e., the long sojourn in the freezer.
Not a mere speculation, btw. Just last week, I discovered I had some peas that had gone freezer-burned (all together now, "It’s a small world after all … ") and they didn’t have any odor. Not proof positive of my diagnosis, though, as they were only slightly burnt, whereas I gather yours were fossils. Still, suggestive.
Thanks for your quick response. I think something else is going on besides things going rancid or not. The smell I smelled & the smell that stuck to my dog & myself was the same smell that you get when you leave ice cubes in the freezer too long. I guessing your right with the sublimation but why? You don’t get that kind of smell when water evaporates.
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Definitely NOT rancidity. That’s something that happens to fats. Peas have essentially no fat. QED, not rancidity.
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Not sure how better to explain sublimation. (If it helps, that’s what the ‘smoke’ coming off dry ice is, though there it’s because the CO2 is thawing.) Evaporation remains the best analogy. Water in a closed bottle stays there. In an open pan, it evaporates. With a fan blowing across, it evaporates faster. Same principle as makes a frost-free freezer work.
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Dude, you gotta clean that freezer. Move out the food. Turn it off. Give it a good scrub. Rinse well. Turn it back on.
A quick tip for baked goods that have been frozen-thaw them completely while still wrapped up, that way the condensation forms on the outside of the wrapper and you don’t get the dampness problem.