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I recently freezed a huge bunch of apple slices, and thawed them again a few days later. After thawing, I noticed a few things compared to a batch that I had put in the fridge (no freezing)

  • The apples turned brown far quicker
  • After pureeing, they tasted sweeter

I know that slow freezingg can destroy cell walls in animals due to crystallization. My guess what has happened here is that the same mechanism also broke up long chain sugar polymers. Thus the sugars are chemically more active, oxidize more easily after contact with air, and taste stronger than in the other batch.

But is my guess plausible? Do polymers actually break under those mechanical stresses? Is this or a similiar effect observed elsewhere?

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  • $\begingroup$ I think the question has nothing related to organic chemistry and especially to physical chemistry. But the home-experiment tag is appropriate. $\endgroup$
    – Alexey Popkov
    Oct 15, 2013 at 15:31
  • $\begingroup$ physical chemistry - you are probably right. organic - behavior of organic polymers, I think it's relevant. I'll adjust if someone else chimes in. $\endgroup$
    – mart
    Oct 15, 2013 at 15:51
  • $\begingroup$ Generally speaking, the term "organic polymers" is not about polymers observed in living organisms as well as organic chemistry is not a science about processes in living (or natural) organisms. Organic chemistry is a science about hand-made objects and the word "organic" should not confuse you! The sciences about chemical processes in living organisms are enzymology and molecular biology, and NOT organic chemistry. $\endgroup$
    – Alexey Popkov
    Oct 15, 2013 at 16:04
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    $\begingroup$ I thing organic chemistry should stay. I removed physical chemistry and added food chemistry which is appropriate, as well as home experiment. $\endgroup$
    – Ben Norris
    Oct 16, 2013 at 0:38
  • $\begingroup$ @AlexeyPopkov - The sciences about the chemical processes in living organisms are biochemistry and molecular biology. I argue that enzymology is a more specialized field lurking in between the two. $\endgroup$
    – Ben Norris
    Oct 16, 2013 at 0:40

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Freezing breaks the cell structure of an apple, not individual chains of short polysaccharides you can feel the taste. What happens is probably enzymes which the apple contains in cell structures go out of these structures and split long polysaccharides (which have no taste) into short sugars which you feel as sweet.

In other words, the apple digest itself by its own enzyme systems after breaking the cell structures.

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  • $\begingroup$ sounds plausible but do you have a source? $\endgroup$
    – mart
    Oct 15, 2013 at 15:16
  • $\begingroup$ I cannot recommend you a book where such question is considered. I can only say that I never saw any evidence in scientific literature that freezing can break short polymers. Moreover, the term "mechanical stress" is unsuitable when we speak on molecular level because "mechanical stress" is strictly macroscopic phenomenon. $\endgroup$
    – Alexey Popkov
    Oct 15, 2013 at 15:41
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    $\begingroup$ I don't have a reference handy either, but this is an effect commonly known in kitchens. Potatoes, cabbage, etc. - their starch gets broken down in sugars not only when frozen, but also at normal fridge temperature. $\endgroup$
    – rumtscho
    Oct 13, 2014 at 19:45

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