Ice Cubes: Shrinkage, Bad Taste and Freezer Burn

Why do ice cubes in my freezer shrink over time?

In a word: sublimation. It’s a phase transition where a solid goes directly to a gas/vapor, with no liquid intermediate phase.  Fun fact: evaporation happens at that temperature as well. That’s how very cold places like the North Pole still have snow storms.

Evaporation and sublimation are not synonyms – there’s a meaningful difference.  Under normal circumstances, a phase transition would be solid to liquid to gas, while sublimation is solid to gas without the stopover in the liquid state.  Specific conditions which have to be met in order for sublimation to occur.

Why do “freezer burned” ice cubes taste bad?

A freezer isn’t at a constant temperature. Other things in the freezer are sublimating as well. The liquid inside the frozen peas… that mystery meat in the back you’ve forgotten about… etc. Trace amounts are being refrozen into those ice cubes. You’re tasting the flavors of various spoiled things.

It starts as soon as you put the ice in the freezer as water.  You can minimize the impact by putting the ice cube tray in a bag, and using filtered/demineralized water.  But ice is porous, as is plastic. If it sits long enough, everything but probably glass will absorb odor.  So you’re probably best to prepare a tray before you need the cubes.

What is freezer burn, exactly, and how does it happen?

It most commonly occurs with frost-free freezers.

On a regular basis, freezers will heat up the walls so any frost build-up melts. During this time, the outside layer of anything in there can melt a little.  Once the defrost cycle is done, everything refreezes – usually with a fresh layer of condensation from the temperature bounce, which will damage the cells in the food over time. Ice cream will taste icy and bland, frozen peas will get mushy, etc.  A chest freezer doesn’t do this, and so you see much less freezer burn.