Freezing and Thawing Food the Right Way

What freezing protects, and what it doesn't

Freezing stops bacteria from growing, which is why food keeps for a long time. It does not kill them, though, so they start growing again once the food thaws. Even in the freezer, moisture slowly escapes and fats oxidize over time, so taste and texture gradually decline. It is more accurate to think of the freezer as a place that buys you time rather than storage that lasts forever. A home freezer should hold -18°C or below, and opening the door often or packing it too tightly lets the temperature rise, so keeping it organized is part of good storage.

Freezing with less loss of quality

How fast food freezes and how it is wrapped decide how it tastes after thawing. The slower the freezing, the larger the ice crystals that form inside, so more juice runs out and the texture goes soft when it thaws. Spreading food thin and flat helps it freeze fast and thaw quickly and evenly.

• Freeze on the day you buy or cook it, while it is fresh, not when it is about to spoil
• Divide it into single-use portions
• Squeeze as much air as possible out of zip bags and press them flat
• Laying bags on a metal tray helps them freeze faster
• Once frozen, stand bags upright like books so they are easy to find
• Write the contents and the date frozen

Preventing freezer burn and odor transfer

You have probably seen meat that has been in the freezer too long turn white, dry and tough on the surface. This is freezer burn, caused by moisture evaporating from surfaces exposed to air. It is not dangerous to eat, but taste and texture suffer badly, so it is better to trim those parts off. The fix is to reduce contact with air. Wrap food tightly in cling film and then put it in a zip bag, or use airtight containers with little empty space. Seal strong-smelling foods separately so their odor does not spread to others.

What freezes well and what doesn't

Not every food takes well to freezing. Meat, fish, bread, cooked rice, rice cakes, blanched vegetables, soups and stocks freeze well and are still good after thawing. Watery raw vegetables such as lettuce and cucumber, on the other hand, turn limp when thawed. Cooked potatoes tend to become grainy, and dishes dressed with mayonnaise are prone to separating. Raw eggs in their shells expand when frozen and can crack. Tofu changes to a chewy, spongy texture full of holes, which some people like so much that they freeze it on purpose. Vegetables keep their color and texture better if blanched briefly and drained before freezing rather than frozen raw.

Thawing in the fridge is the default

The safest way to thaw is slowly in the fridge. It takes time, so get into the habit of moving food from the freezer to the fridge the night before. Put it in a dish on a lower shelf so juices do not drip onto other food. If you are in a hurry, submerge the sealed food in cold water and change the water about every 30 minutes; it thaws faster than in the fridge. A microwave's defrost setting is quickest, but the edges tend to start cooking, so cook the food straight after. Avoid leaving food on the counter or in the sink to thaw at room temperature, because the outside thaws first and sits for a long time at temperatures where bacteria grow easily.

Foods you can cook straight from frozen

Not everything needs thawing before cooking. Frozen dumplings, blanched frozen vegetables, thinly sliced meat, and frozen stock or soup can all go straight into the pan or pot. Cooking takes longer than with thawed food, so check that it is heated right through. Large cuts of meat and whole chickens tend to cook on the outside while staying underdone inside, so thawing them first is safer. For frozen products, following the cooking instructions on the package is the most reliable approach. Frozen cooked rice reheated straight in the microwave comes out close to freshly cooked.

Can you refreeze it?

Refreezing food that has been thawed definitely lowers its taste and texture. For safety, what matters is how it was thawed. Food thawed in the fridge and kept cold throughout can be refrozen without cooking, although quality suffers. Food thawed in cold water or a microwave should only be refrozen after it has been cooked. Food left at room temperature for a long time should not be refrozen. A dish made from thawed raw meat can be cooled and frozen again. The best way to avoid these questions is to freeze in single-use portions from the start.

Common mistakes and signs to throw it out

If the freezer goes off in a power cut or breakdown, keeping the door shut helps hold the temperature. Once it is back on, check for signs that food thawed. The mistakes below are common, so it is worth a quick check. Smell and appearance cannot always tell you whether food is safe, so when in doubt, throw it out. Do not force yourself to eat food that shows signs of having thawed and refrozen, or that you cannot date.

• Putting hot food straight into the freezer without cooling it first
• Not labeling dates, so you have no idea when it went in
• Freezing in one big block and thawing all of it every time
• Letting juices from thawing raw meat drip onto other food