How to Store and Reheat Leftover Food

Leftovers can cause food poisoning. Learn how to store cooked food in the fridge and the best way to reheat them.

Eating Leftovers

Even a tiny amount of harmful bacteria can be dangerous when we eat leftover food. While that packet of nasi lemak bought earlier in the morning might still seemingly smell and taste fine later in the day, it might have already harboured enough toxic pathogens to leave you feeling nauseated and ill.

“A healthy adult's immune system can manage small amounts of bacteria and viruses, but higher levels of exposure may lead to illnesses,” explains Ms Wong Yuefen, a Principal dietitian with NHG Polyclinics..

Indeed, vulnerable people such as pregnant women, people with weakened immune systems or the elderly can die from food poisoning.

Food Poisoning from Leftovers

Common symptoms of food-borne illness — usually known as food poisoning — can be mild or severe. These can include nausea, vomiting, diarrhoea, stomach cramps, headaches and fever.

While most episodes last only a day or two, some infections can be nasty. Hepatitis A or typhoid can cause severe illnesses lasting many weeks. Some food-borne illnesses can even result in long-term health issues involving the immune system, gut or kidneys.

Ms Wong says one of the most common causes of food-borne illness is the improper storage of cooked foods. While cooking destroys most pathogens, bacteria can be reintroduced to food later on, and leftovers can become a breeding ground for toxic strains such as Staphylococcus aureus, Salmonella enteritidis, Escherichia coli and Campylobacter.

Related: Food Poisoning

How to Store Leftover Cooked Food and the Best Way to Reheat Food

Eating reheated food is safe as long as we observe food safety. Here are the best ways to reduce the risk of food poisoning when taking care of leftovers:

Tip 1: Time is of the Essence

Once food has been cooked, it should be stored in the fridge or freezer once it is cooled or within two hours, says Ms Wong. Leftovers must be put in shallow containers or distributed into smaller portions for quick cooling and refrigerated at or below 4°C within two hours.

In general, refrigerated leftovers can be stored for three to four days in a covered container. Food destined for the freezer should be labelled with the freeze date and stored in freezer-quality resealable bags or sturdy glass/plastic containers.

Tip 2: Thaw Food in the Refrigerator

When food is left to thaw at room temperature, bacteria present can multiply to unsafe levels. While freezing does inactivate bacteria, some may remain alive and can begin to multiply when the food returns to room temperature.

Thaw frozen food in the refrigerator in a container to catch the drips (thereby preventing cross-contamination), or use a microwave oven. Thaw small items quickly under running water and place them in a leakproof bag. Cook all thawed food immediately and do not refreeze.

Tip 3: Use the Right Container

Take-out food containers are often made of foam, plastic or paper and may not be microwave-safe. Store and reheat take-out items in food-safe containers. Certain plastics are safe, while ceramics and glass are the best.

“Use only microwave-safe containers to reheat cooked foods. Recycled plastics containers that do not have microwave-safe labels may melt and cause chemical contamination to the food,” says Ms Wong. Avoid plastics and containers that are visibly damaged, stained or have a bad smell.

Tip 4: Get Hot, Hot, Hot!

Reheating food kills bacteria. It is important to use the right method of reheating to ensure all bacteria are destroyed. Whether oven-baking, sautéing or microwaving, Ms Wong recommends that leftovers be brought to 75°C and above for at least two minutes — use a food thermometer to check.

When using a microwave oven, give your leftovers a good stir in the middle of heating and allow the hot food to stand for a few minutes afterwards, as the heat will continue to radiate through the food. Do not forget to use a microwave-safe covered container — leftovers heat more evenly and retain their moisture better when covered.

Tip 5: Put the Right Food in the Right Place

Avoid cross-contaminating your food by storing cooked and ready-to-eat items separately from raw food, advises Ms Wong. Use a separate, properly-covered container for each food item, and adopt a “first-in, first-out” principle when consuming leftovers.

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This article was last reviewed on 28 Jul 2025