Science Questions

Why does food change in the freezer?

Sun, 18th Sep 2011

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Sean Hoskins, via Facebook asked:

Why does food change in the freezer? When one defrosts a slab of steak that has been in a freezer for a year... it has a much different consistancy than a chunk that has only been frozen for a week. I can only assume that evaporation is the issue. Is there any degradation when something is frozen in nitrogen?


Barry -   There's a problem as Lorna said all along with ice.  Domestic freezers only cool steaks down to about -10 to -15 C.  There's plenty of mobile water there and the ice will re-crystallise over time so you get larger ice crystals, and you do get evaporation directly, cold evaporation.  So you're left with a freeze burn effect which changes the texture and changes the overall flavour value.

Chris -   And I guess also if your vegetables are frozen and then you cook them, the vegetable tissue is riddled with holes.  So the goodies are more likely to float out and they're going to be less good for you than fresh.

Barry -   Yes.  You get the mushy strawberry effect, I think.  If anybody could freeze strawberries really well then they could make a fortune.

Chris -   Mushy peas are good though.  Lorna, anything to add to that?

Lorna -   Just a tip, puree your strawberries before you freeze them and then you don't have the mushy strawberry effect.


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