What Is Freezer Burn?

Step 1 of 5

Ice can skip the liquid stage.

Water molecules at the surface of ice sometimes have enough energy to leave directly as vapour. No melting is needed at all.

Step 2 of 5

Freezer air is extremely dry.

Cold air holds almost no vapour, and the freezer's cooling coils are constantly stripping out what little there is. Water always leaves the food.

Step 3 of 5

The lost water reappears as frost.

The escaped vapour refreezes on the coldest thing nearby — the packet or the freezer wall. The frost in the bag is your dinner.

Step 4 of 5

What is left is dry and oxidised.

The dried patches are grey and leathery, and with no water shielding it the fat there reacts with oxygen and turns stale-tasting.

Step 5 of 5

Air is the enemy, so squeeze it out.

Vapour needs a gap to cross. Wrapping tightly against the surface, or vacuum sealing, leaves it nowhere to travel.

Freezer-burnt food is still safe to eat. It has lost texture and flavour, not safety.