Leftovers: fridge or freezer, and for how long

Cooking once and eating twice is one of the best habits in a kitchen. It saves time and money and cuts waste. It also gives bacteria a chance, because cooked food that sits warm is exactly what they like. Food safety agencies on both sides of the Atlantic agree on the basic rules, with a few differences of detail worth knowing.

Cool it quickly

Cooking kills most bacteria, but not all, and some leave behind spores that survive heat. While food cools slowly through the warm middle range of temperatures, those survivors multiply. The aim is to get through that range fast.

• Within one to two hours. The UK Food Standards Agency advises cooling cooked food at room temperature and putting it in the fridge within one to two hours¹. The US Department of Agriculture's limit is two hours from cooking².
• Split it up. A big pot of soup or stew cools very slowly in the middle. Divide it into smaller, shallow containers or freezer bags¹². Standing the pan in a sink of cold water speeds things up.
• Do not put hot food straight in the fridge. The FSA advises against it¹; it warms everything else on the shelf.
• Rice is special. Chill leftover rice as quickly as possible, ideally within one hour, and do not leave it to cool in the rice cooker or pan³.

Fridge: how cold and how long

Your fridge should be between 0 and 5 °C, and the FSA recommends checking it with a fridge thermometer once a week¹. The dial inside a fridge is a setting, not a reading.

How long leftovers keep is where the two agencies differ:

If you want a single rule, follow the stricter one: eat leftovers within two days, rice within one, and freeze anything you will not get to.

A few habits help: store leftovers in clean, covered containers; keep raw meat, poultry and fish sealed on the bottom shelf, where they cannot drip onto cooked food¹; and keep chilled food out of the fridge for as short a time as possible while you cook, four hours at the very most¹.

Freezer: safe indefinitely, best within months

Your freezer should be around -18 °C¹. At that temperature, the USDA explains, food always stays safe: freezing puts microbes into a dormant state, although they become active again once food thaws⁵. What suffers over time is quality, which is why the USDA suggests eating frozen leftovers within three to four months for the best taste and texture².

What freezes well: soups, stews, curries, sauces, cooked grains, bread, cooked meat, raw meat and fish, most baked goods and blanched vegetables. Raw meat keeps its quality longer in the freezer than cooked meat⁵.

What does not: mayonnaise, cream sauces and lettuce freeze poorly, and canned food and eggs in their shells should not be frozen⁵. Eggs can be frozen once cracked into a sealed container, whole, beaten or separated³.

Pack it well. Air on the surface of frozen food causes freezer burn: dry, greyish-brown patches that are safe but tough⁵. Use airtight containers or freezer bags with the air pressed out, and label everything with what it is and the date. Freeze food as fresh as possible: freezing preserves quality but does not improve it.

Thawing

• In the fridge is the safest method, though the slowest. Put the food in a container that will catch drips¹.
• In the microwave on the defrost setting, immediately before cooking or reheating¹.
• Straight from frozen works for many dishes. The USDA notes it is safe to reheat frozen leftovers without thawing, in a pan or microwave for soups and stews, or in the oven for casseroles; it simply takes longer².

Once fully thawed, use the food within 24 hours¹. On refreezing, the USDA says food thawed in the fridge can be refrozen without cooking, with some loss of quality, but food left out of the fridge for more than two hours should not be refrozen⁵.

Reheating

Reheat until the food is steaming hot all the way through. The FSA's measure is that the centre should reach 70 °C for two minutes, or an equivalent such as 75 °C for 30 seconds or 80 °C for 6 seconds⁶. The USDA's target is 74 °C (165 °F) on a thermometer, and it advises bringing sauces, soups and gravies to a rolling boil².

Stir food while reheating it in a microwave, because the edges can be very hot while the middle is still cold³. And reheat only once: the FSA says cooked rice should never be reheated more than once, and previously cooked and frozen meat only once³. Take out the portion you will eat and leave the rest in the fridge.

For crisp leftovers such as pizza, roast potatoes and fried chicken, our guide to reheating in an air fryer gives temperatures and times. For building meals that make good leftovers in the first place, see the weeknight pantry.

The rules on one card

1. Fridge within one to two hours, in shallow containers.
2. Fridge at 0 to 5 °C; check it weekly.
3. Eat within two days; rice within one.
4. Freeze what you will not eat in time, labelled and dated.
5. Thaw in the fridge; use within a day of thawing.
6. Reheat once, until steaming hot right through.