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Eating leftover food is safe, but until when? It depends on the food. A microbiologist explains.
The exquisite dish gained a name in Portugal with a French, gourmet and chic tone. “Redon” (YESTERDAY’S LEFTOVERS) saves us time and energy and prevents food waste. Many people enjoy a nice slice of cold pizza — some people, right away for breakfast. But as delicious as it is to devour cold pizza, there is also the risk of food poisoning if you’re not careful.
Food poisoning is caused by eating food contaminated with pathogenic bacteria, fungi or viruses. While most people know that food poisoning can be caused by undercooked food or risky preparation practices, poorly stored leftovers are also a major cause. Therefore, it is very important to be careful when storing leftovers to avoid harming your health.
Here’s a microbiologist’s advice for staying safe when consuming your favorite cold leftovers.
The leftover pizza
You can get food poisoning from cooked pizza in several ways. It can happen because some ingredients are raw, undercooked or spoiled, or because the pizza has come into contact with a contaminated surface (including having been handled by someone who hasn’t washed their hands).
Surprisingly, the dried herbs and spices that many people sprinkle on pizza (like basil, pepper, and oregano) can also be subject to microbial contamination. This contamination can occur during harvest and production, or due to inadequate storage by consumers. Some of the foodborne pathogens that can survive in dried herbs include food poisoning bacteria such as Salmonella, Bacillus cereus e Clostridium perfringens.
Even if these dried herbs have been sterilized by the heat of a freshly baked pizza, if they are left at room temperature for too long after cooking, these or any other toppings can become the perfect food for potentially harmful microorganisms.
So, if you like your pizza cold, the best way to reduce the risk of food poisoning is to ensure that any leftovers are refrigerated within two hours of delivery or making. This should make the pizza safe to eat cold later.
Once placed in the refrigerator, the pizza must be stored covered (to avoid contamination by airborne germs) and consumed within two days. Note that placing food in the refrigerator only slows bacterial growth, so leftovers should be consumed within two days at most.
If pizza is left at room temperature for more than a few hours, microorganisms multiply quickly. This can make the pizza unsafe to eat the next day, regardless of how it looks or smells.
The chicken example
Cooked chicken is highly perishable once it cools. Its high water and nutrient content, and low acidity, favor the growth of bacteria that cause food poisoning, especially if it is not stored correctly after cooking.
It’s also important to save chicken for leftovers. only if it has been well cooked. If there is any trace of blood in the juices of the cooked chicken, don’t eat it—and certainly don’t save it for later.
This is because raw chicken can be contaminated with germs that cause food poisoning, such as Campylobacter, Salmonella ou Clostridium perfringensso cooking chicken well is essential.
Even if a small part of the chicken is undercooked, microorganisms still present in the tissues can begin to multiply even when the meat is stored in the refrigerator. These microorganisms may not be detectable by smell or appearance.
To stay safe, once you remove the chicken from the oven or rotisserie packaging, any portion you do not consume immediately should be covered and refrigerated as soon as it cools. Ideally, you should not stay at room temperature for more than two hours.
Cooked chicken can be stored in the refrigerator up to three days. But, once again, if you notice blood anywhere on the chicken, you should not eat it — whether cold or reheated — as this indicates that it has not been properly cooked and may be contaminated.
And the rice?
Leftover rice, of any type — be it fried rice or risotto — has a high risk of food poisoning. This is because raw rice can contain spores of Bacillus cereus, a common bacteria that prefers starchy foods.
Although Bacillus cells are destroyed by the heat of cooking, its spores are heat resistant and can survive. If cooked rice is left at room temperature for more than two hours, the spores have time to turn into bacteria and multiply. These spores can also release toxins into the rice, which can cause intense vomiting and diarrhea for up to 24 hours.
If you need to store cooked rice, you should cover it after cooking, cool it quickly and refrigerate it for at least maximum 24 hours.
Cooked rice can be eaten cold, but only if it has been cooled quickly after cooking and stored in the refrigerator as quickly as possible. It is also advisable to consume it within 24 hours as B. cereus spores can germinate over longer periods of storage.
You canned
To safely store leftover canned food, it is essential to keep it covered and refrigerated to avoid contamination by airborne microorganisms.
It is considered safe to store food in the original can, as it has been sterilized during processing. However, for flavor reasons, you may prefer to transfer them to a plastic or glass container with a lid.
Highly acidic foods, such as canned tomatoes, can be stored in the refrigerator for five to seven days. Canned foods with low acidity, such as meat, fish, fruits, vegetables and pasta, should be consumed within a maximum of three days. Acidic foods last longer because acidity inhibits the growth of bacteria that cause food poisoning.
Leftovers may be safe to eat cold. Just make sure you refrigerate them as quickly as possible after cooking and consume them within a day or two.
