Microbiologist Issues Warning on Dangers of Eating Cold Leftovers
Experts emphasise that careful storage of leftovers is crucial to avoid serious health risks, as improper handling can lead to food poisoning. Primrose Freestone, a senior lecturer in clinical microbiology at the University of Leicester, provides essential advice for safely enjoying cold leftovers, based on recent insights published in The Conversation.
Why Leftovers Pose a Food Poisoning Threat
Food poisoning occurs when food becomes contaminated with pathogenic bacteria, fungi, or viruses. While many people are aware of risks from undercooked meals or poor preparation habits, improperly stored leftovers are a significant contributor to illness. It is vital to handle and store leftovers correctly to protect your health.
Cold Pizza: A Popular but Risky Choice
Cold pizza is a beloved breakfast option, but it can harbour foodborne pathogens if not stored properly. Contamination can arise from raw or undercooked ingredients, contact with germ-laden surfaces, or even from dried herbs and spices like basil and oregano, which may carry microbes such as Salmonella or Bacillus cereus.
To reduce risk, refrigerate leftover pizza within two hours of cooking or delivery. Store it covered to prevent airborne contamination and consume it within two days, as refrigeration only slows bacterial growth. Leaving pizza at room temperature for extended periods allows germs to multiply rapidly, making it unsafe to eat regardless of appearance or smell.
Leftover Chicken: High Perishability Concerns
Cooked chicken is highly perishable due to its high water content, nutrients, and low acidity, which favour bacterial growth. Only save chicken that has been thoroughly cooked, with no traces of blood in the juices, indicating undercooking and potential contamination with pathogens like Campylobacter or Salmonella.
After cooking, cover and refrigerate chicken promptly, ideally within two hours of cooling. It can be stored for up to three days in the fridge, but discard any portions showing signs of undercooking to avoid illness.
Leftover Rice Dishes: A Major Bacterial Hazard
Rice dishes, including fried rice or risotto, pose a high risk due to Bacillus cereus spores present in uncooked rice. While cooking kills the bacteria, heat-resistant spores can survive and germinate if rice is left at room temperature for over two hours, releasing toxins that cause severe vomiting and diarrhoea.
For safety, cool cooked rice quickly, cover it, and refrigerate within two hours. Consume cold rice within 24 hours to prevent spore germination and toxin production.
Leftover Canned Foods: Storage Guidelines
Canned leftovers should be covered and refrigerated to avoid contamination. It is safe to store food in the original sterilised can, but transferring to a plastic or glass container may preserve flavour better. Highly acidic canned foods, like tomatoes, can last five to seven days refrigerated, while low-acidity items such as meat or vegetables should be consumed within three days due to slower bacterial inhibition.
General Safety Tips for Cold Leftovers
Leftovers can be safely eaten cold if refrigerated quickly after cooking and consumed within a day or two. Always prioritise proper storage to minimise health risks and enjoy your favourite meals without worry.
