How to freeze food well

Why fast freezing matters

When food freezes slowly, water has time to migrate and form a few large ice crystals. Those crystals physically rupture cell walls and tear protein and starch networks, so on thawing the structure collapses and liquid runs out.

Frozen fast, the same water forms many tiny crystals that do far less damage. This is the entire difference between commercially blast-frozen food and something put in a domestic freezer in a large warm container.

So the practical rules follow: cool food before it goes in, freeze it in thin flat portions rather than deep blocks, spread things out rather than stacking them, and do not overload the freezer with warm items at once.

What survives, and what does not

Freezes very well

Bread and baked goods, raw meat and fish, stocks, soups, ragùs and stews, butter, hard cheese for cooking, pastry, cooked pulses, herbs in oil, cooked rice cooled quickly.

Freezes acceptably

Cooked vegetables destined for soup, milk, cream over 35% fat, cooked pasta in a sauce, most cakes.

Freezes badly

Anything eaten raw and crisp — salad leaves, cucumber, whole tomatoes. Potatoes in liquid, which go grainy. Egg-thickened sauces. Fried food.

Splits or separates

Custards, single cream, yoghurt, low-fat dairy, mayonnaise, flour-thickened sauces. Cornflour and waxy starches survive far better.

Goes watery

High-water vegetables — courgette, cucumber, lettuce, whole strawberries.

Freezing well

• Cool it first, quickly. Putting hot food into a freezer raises the temperature of everything around it. Cool in a shallow tray, then chill, then freeze.
• Freeze flat. A bag laid flat freezes in a fraction of the time of a tub, stacks better, and thaws far faster.
• Exclude air. Air is what causes freezer burn. Press bags flat, wrap tightly, or use a vacuum sealer.
• Portion it. Freeze in the amounts you will actually use. Refreezing thawed food is poor practice and often unsafe.
• Label everything with what and when. Unlabelled frozen food becomes archaeology.
• Open-freeze loose items — berries, chips, meatballs — spread on a tray, then bag them once solid, so they do not fuse into a block.

Freezer burn, and thawing

Freezer burn is dehydration. Water sublimes directly from the surface of the food into the freezer air, leaving dry, greyish, leathery patches. It is a quality problem rather than a safety one — the food is still safe, it simply tastes and feels worse — and the answer is airtight wrapping.

Thawing is where a lot of quality is lost. Thaw in the fridge wherever possible: slow, even, and it keeps the food out of the temperature range where bacteria multiply fastest. Thawing on a worktop is where food-safety problems arise.

Some things are better cooked from frozen — chips, peas, many fish fillets, and anything breaded — because thawing lets water pool and ruins the surface. For safe thawing and reheating of meat, poultry and cooked dishes, follow Food Standards Agency guidance rather than a rule of thumb; the consequences of getting it wrong are not culinary.

Common questions