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For some inexplicable reason from the ladies in my extended family (even friends!) seem to believe that vegetables/food should be subjected to as few freeze/thaw cycles as possible. The rationale put forward is that each such cycle reduces nutrition (sp. nutritive?) value, and accelerates rot.

I'm sceptical; Do repeated (sp. repetitive?) freeze/thaw cycles strip nutrition from vegetables/food?

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Not as far as I know, they do however open the frozen foodstuffs to infection. It is not a good idea to thaw and refreeze for that reason. –  terdon Mar 2 '13 at 18:37
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Repeated freeze-thaw has virtually no effect on macronutrients, such as proteins, lipids, and sugars, because these are broken down to their basic building blocks (such as amino acids and simple sugars) upon food digestion anyway.

According to this paper freeze-thaw has no effect on micronutrients, such as vitamins, as well.

What affects nutritious quality is the length of time the food remains frozen. Most household freezers maintain a temperature of -20*C. At this temperature the food doesn't get spoiled by bacteria, but degradation of vitamins still occurs, albeit at a slower rate. This is critical for some unstable vitamins, such as vitamin A and C. But elements such as iron, calcium, zinc, and phosphorus are not affected at all.

If you want to prevent vitamin degradation for a very long time, you need a freezer that maintains food at -80*C. This is only if you want to keep the food frozen for many months though.

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