To Reheat or Not to Reheat: Making the Most of Leftovers

How health and safety tie into leftover foods.

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TikTok’s parent company in Singapore recently experienced widespread food poisoning that hospitalized 60 employees, reports BBC News. Health and safety officials investigated the occurrence at ByteDance’s headquarters, where a wave of gastroenteritis caused mayhem.

Curiously, the location produces no food on-site and uses only third-party businesses for all catered events. Such an encounter only underscores how easy it is to contract foodborne illnesses or worse.

Foodborne Tragedy

In 2023, a Belgian student died after reheating a plate of spaghetti bolognese that had sat outside the fridge for five days. The 20-year-old, known as AJ, reported stomach pains to friends before attempting to sleep it off. AJ’s parents discovered his body the next day when he missed school.

Such high-publicity stories highlight the danger of foodborne diseases. The United States Centers for Disease Control and Prevention ( CDC ) estimates 48 million Americans per year contract food poisoning, resulting in 128,000 visits to hospitals and 3,000 fatalities.

Sometimes, foodborne illness outbreaks might appear across a state or even multiple states.

Bacteria to Avoid

Certain common bacteria trigger foodborne illnesses, including:

Clostridium perfringens, which forms using spores that can handle cooking temperatures. This forms when food isn’t cooled fast enough or even when cooked too far ahead in advance.

Salmonella is a pathogen caused by undercooked poultry and eggs, raw meat, and cross-contamination from bad hand hygiene.

Campylobacter comes from uncooked chicken, unpasteurized dairy, and dirty water.

Listeria might develop in ready-to-eat meals or compromised dairy products.

Vibrio cholerae (or cholera) is found in overexposed seafood, rice, vegetables, and millet gruel.

While some food lovers buy fresh produce daily or eat out frequently, others must cook from scratch, which invariably means using leftovers. Therefore, food safety is paramount, not least with young children and older people in the equation.

The Reheating Rule

A general rule for reheating leftovers is the less time after cooking the better, and food must only be reheated once. Katherine Zeratsky, R.D., L.D. at the Mayo Clinic writes that leftovers will last three to four days in the fridge. “After that, the risk of food poisoning goes up,” she concedes. “It’s also safe to cook foods straight from frozen.”

Furthermore, food that is left out must be eaten even sooner. Zeratsky mentions a bacterial breeding “danger zone” between 40 and 140 degrees Fahrenheit. It means food at room temperature must be eaten within two hours; anything above 90-degrees F has one hour before the risks begin.

No Cold Turkey

Sharon Liao writes for WebMD that eating cold leftovers is not an option. The safest method for reheating yesterday’s ingredients is bringing them to an internal temperature near 165-degrees F. She also advises against thawing frozen products in hot water, which supplies bacteria with a fertile breeding ground.

“There are three safe ways to thaw food: in the refrigerator, in cold water, and in the microwave,” writes Liao. “It’s also safe to cook foods straight from frozen.” In addition, the Food Safety and Inspection Service ( FSIS ) discourages using slow cookers to reheat leftovers. The food will not reach its necessary heat soon enough.

Leftovers Can Be Great

Some might read such advice and vow never to eat anything more than a few minutes old, but this shouldn’t be the case. With careful handling and healthy storage, leftover food can save time, energy, and money. Moreover, it means home cooks can get creative with their ingredients or cook with second-day recipes in mind.

A 2022 survey conducted by OnePoll for Bosch Home Appliances found 72% of Americans considered themselves “pro-leftovers.” 61% of American diners eat more leftovers since the pandemic. A further 46% declared they prefer the time and effort saved, while another 32% cited the cost-saving factor.

Leftovers Are Here to Stay

One can imagine people’s relationship to leftovers hasn’t changed, considering how inflation has increased grocery bills.

The same poll found that the country’s favorite reheated meals were as follows:

Soups had a 79% approval;

Pizza came in second with a 63% score;

Meat came in third at 62%;

Pasta was a close fourth, with 60% backing;

Rice made the top five at 55% popularity.

There are great arguments for overusing certain ingredients that make perfect next-day meals. Often, leftovers taste better the next day, especially those cooked on the day they were served. For instance, roasting an extra chicken leaves a whole spare bird for use in a plethora of recipes.

Smoking Leftover Meats

Any meat is worth recycling, and plenty of techniques will give protein a repurposed life.

Smoked turkey is great the first time round, and it also gives wonderful depth to quesadillas, salads, or Asian-style stir-fries. Even pre-cooked meats work in the smoker, though they obviously require less cook time.

Meat smoking enthusiasm platform Bradley Smoker explains that like with any leftovers, the correct core temperature will lower the risk of food poisoning. A chef’s thermometer is a useful tool for keeping any re-smoked leftover food at the required temperature.

Balancing a Fine Line

Leftover meals balance a fine line between disaster and failure; understanding food safety is an essential step toward recreating the perfect next-day recipe.

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