Supreme Pizza / Slice 1 of 6
Leftover pizza: the clock, the fridge and the reheat
Leftover food that has been out of the fridge for less than 2 hours can go back in; after 4 hours out, the NSW Food Authority says to throw it away. Once it is in the fridge, the Authority says to eat leftovers within 3 days and to reheat them until steaming hot, at least 60°C.
General information, not medical advice. The official places to check are the NSW Food Authority and Food Standards Australia New Zealand.
The 2-hour/4-hour rule
The rule exists because of temperature. Food poisoning bacteria grow best between 5°C and 60°C, the range the NSW Food Authority calls the ‘temperature danger zone’. Its rule counts how long leftover food has been out of the fridge:
- Under 2 hoursEat it now, or return it to the fridge to eat later.
- 2 to 4 hoursUse it now or throw it out.
- Over 4 hoursThrow it out.
The clock does not reset when the box goes back in the fridge. The Food Authority says the time between 5°C and 60°C is cumulative, so you add up every spell out of the fridge. A slice that sat out for an hour at dinner and another hour the next afternoon has used its 2 hours.
Food Standards Australia New Zealand (FSANZ) gives the same three steps for cooked or perishable food left at room temperature: back in the fridge if it has been out less than 2 hours, eaten straight away between 2 and 4 hours, thrown away after 4.
The Food Authority says most food poisoning bacteria do not make food look, smell or taste bad, so food that seems normal can still carry enough of them to make someone ill. Its advice when in doubt is not to eat it and to throw it out.
Cooling and storing the rest of the box
The Food Authority’s steps are to cool and cover leftovers and put them in the fridge or freezer within 2 hours, to store them below 5°C, and to keep them apart from uncooked food such as raw meat. Splitting leftovers into smaller portions helps them cool faster.
The Food Safety Information Council adds a detail on timing: let hot food cool on the bench only until it stops steaming, then put it in covered containers and into the fridge.
The fridge itself matters. The Food Authority says home fridges should stay below 5°C at all times, suggests checking with a fridge thermometer, and notes that cooking, putting groceries away and catering for parties can raise the temperature of some fridges.
Three days, or one
The official pages give slightly different spans for refrigerated leftovers, so here they are side by side. The NSW figure is the shorter of the two numbers given for most people.
| Source | In the fridge | In the freezer |
|---|---|---|
| NSW Food Authority, leftovers | Eat within 3 days. | Keeps up to 3 months. Thaw it in the fridge, then eat it within a day (24 hours) of thawing. |
| FSANZ, Bacillus cereus | Throw out refrigerated leftovers not eaten within 3 to 4 days, or within 1 day for vulnerable people. | Not given on this page. |
| FSANZ, food safety basics | “Keep perishable leftovers in the fridge and use them up within a few days.” | Not given on this page. |
People at higher risk
FSANZ says some people have a greater risk of getting sick from food. In its words, “These people include pregnant women, their unborn and newborn babies, the elderly and people whose immune systems have been weakened by illness or drugs”, with drugs like cortisone among its examples. For leftover cooked food, the Food Authority’s advice in pregnancy is to store it covered in the fridge, eat it within a day and always reheat it to at least 60°C.
Hot all the way through
The Food Authority says to always reheat leftovers until steaming hot, at least 60°C, because reheating kills harmful bacteria that may have grown since the food was cooked. In the microwave, it says to stir the food while it heats so that it ends up hot all the way through. FSANZ puts it as reheating cold food quickly until it is piping hot.
Heat cannot be counted on to undo time spent on the bench. FSANZ says Bacillus cereus, a bacterium common in the environment, can form spores and toxins that cooking or boiling does not destroy, and the Food Authority warns that some bacteria make heat-stable toxins when food is left too long at room temperature or reheated multiple times. That is why the clock comes first, and the reheat second.
Before you eat a leftover slice
- Has it spent less than 2 hours, all told, out of the fridge?
- Has it been in the fridge for 3 days or less, or a day or less if you are pregnant or at higher risk?
- Is it steaming hot all the way through, at least 60°C?
- If you are not sure about any of these, the Food Authority’s answer is to throw it out.
Leftovers that went wrong somewhere earlier can still make someone sick. If that happens, food poisoning, and who to tell covers the signs and where to report food you bought.