“Leftovers don’t have to go bad, just heat them up and they’ll be fine”? Share this with your family after reading this

“Leftovers don’t have to go bad. Just heat them up a few times and the bacteria and viruses will be killed.”

Many people think: "Food doesn't have to go bad, just heat it up. As long as the temperature is high enough and the time is long enough, the bacteria and viruses will be killed and you won't get an upset stomach."

Rumor Analysis

That is not the case.

There are not only bacteria in leftovers, but more deadly are the various toxins they produce. Many toxins have a certain tolerance to high temperatures and can easily cause food poisoning.

First of all, what is deadly in leftovers is not only the bacteria themselves, but also the various toxins they produce. Many toxins have a certain tolerance to high temperatures.

Compared to the bacteria themselves

The toxins they produce are even more deadly

Although heating is a good way to kill bacteria in many cases, after all, common foodborne pathogens are not resistant to high temperatures. But sometimes, even if the bacteria themselves are killed, food poisoning can still occur. This is because it is not the bacteria themselves that are infected, but its "derivatives".

1

Fumonisic acid

Fumonisin, which has been frequently searched in recent years, is a high-temperature resistant toxin. It is a toxic metabolite of Burkholderia gladioli, which can withstand high temperatures of 120°C . Burkholderia gladioli is widely distributed in the natural environment. Fermented foods (such as cold noodles) and soaked foods (such as black fungus) are prone to produce fumonisin toxins in hot and humid weather.

Fumaric acid poisoning mainly affects important organs such as the liver, brain, and kidneys, and only 1 mg can be fatal. In simple terms, even if the rice noodles contaminated with fumaric acid are heated and eaten, they will still cause poisoning.

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2

Botulinum toxin

Clostridium botulinum is an anaerobic bacterium that often appears in dairy products and dried foods such as bacon . It even has strong survival ability in canned and sealed pickled foods. It is one of the most toxic bacteria. This is because it secretes botulinum toxin during the reproduction process. It is a highly toxic neurotoxin . 0.00000005 grams can be fatal, and the mortality rate of poisoning is very high.

Although botulinum toxin can be killed by heating at 90℃ for two minutes, sometimes people can be infected by inadequate heating - for example, heating it in a microwave oven at low power for a few dozen seconds may seem warm, but it actually has no effect . The most common symptoms of botulinum toxin poisoning are difficulty swallowing, blurred vision, slurred speech, movement disorders, etc., and severe cases can lead to respiratory muscle failure and paralysis and death.

3

Aflatoxin

Aflatoxin is a metabolite produced by Aspergillus flavus and Aspergillus parasiticus, which mainly contaminates grains, oil crops and their products, such as aged rice and flour, peanuts and melon seeds. Acute aflatoxin poisoning can cause liver damage, and severe cases can cause edema, coma and death.

In addition, long-term intake of small doses of aflatoxin can cause chronic poisoning and lead to chronic liver diseases such as cirrhosis. At the same time, aflatoxin is also the most carcinogenic chemical known to date. So, if you find that rice and flour have changed color and taste, or dried fruit snacks have become bitter, don't feel bad and throw them away immediately, and don't think "it will be fine if they are cooked."

Some bacteria cannot be killed by high temperatures

In addition to the fact that bacterial metabolites cannot be killed by high temperatures, some bacteria and bacterial spores themselves are also highly resistant to high temperatures.

1

Bacillus cereus

Bacillus cereus is widely present in nature and often contaminates food. Room temperature of 25℃ to 30℃ is its favorite breeding environment, and almost all types of food can be contaminated by it. Bacillus cereus poisoning can cause vomiting, abdominal pain and diarrhea, and sometimes the incubation period can be as long as half a day.

Generally speaking, food contaminated with Bacillus cereus can only be effectively killed by heating it at 100°C for 20 minutes, and its free spores can only be killed by heating it at 120°C for one hour under dry heat sterilization conditions. In other words, if you want to kill Bacillus cereus, you need to heat it at 100°C for more than 30 minutes in a steamer, and at 100°C for more than one hour in an oven.

2

Clostridium perfringens

Clostridium perfringens is also a thermostable anaerobic bacterium that is commonly found in nature and in the human intestines. It can reproduce at a temperature of about 45 degrees and often infects raw food such as meat and poultry. Although high temperatures can kill them, their spores are heat-resistant, so the process of heating and cooling food will promote their growth and reproduction. The bacterial reproductive bodies that enter the human body with food will re-form spores in the intestines, and cause poisoning through a complex reaction process in the intestinal environment.

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Heating also requires methods and techniques

Although most pathogens can be killed by the high temperatures generated by the cooking process, the heating time and method are also important. Whether it is raw food or leftovers, if they are heated but not heated properly, it can easily cause food poisoning.

1

Helicobacter pylori

Helicobacter pylori, the culprit of many stomach diseases, can be inactivated in about 10 minutes at a high temperature of 100°C. However, it is worth noting that the cooking temperature must be at least higher than 80°C , because Helicobacter pylori may revive even in an environment close to 80°C.

2

Staphylococcus aureus

Staphylococcus aureus is the most common foodborne pathogen. It has a certain tolerance to high temperatures. Generally speaking, it can only be completely killed by heating at a high temperature above 80°C for 30 minutes .

3

Spores of various bacteria

Spores are dormant bacteria that are very resistant to high temperatures, ultraviolet light, and even chemicals. Although most bacteria are not as temperature resistant as the Clostridium perfringens spores mentioned above, they still require sufficient temperature and time to be completely killed.

In short, it is more important to find ways to limit the reproduction of pathogenic bacteria than to blindly believe in sterilization methods. To put it simply, you must pay attention to the storage method of raw and cold foods and do not store them for too long. In addition, if you can avoid leaving leftovers, do so. If you must eat leftovers, try to seal and refrigerate them while they are still hot at below 60℃, and fully heat them for a long enough time before eating .

Looking in the mirror of rumors

It is difficult to persuade the elders to change some of their inherent dietary concepts. We can help them identify them through the following methods:

First, build trust. Establish good communication and trust with the elders and let them know your intention is for their health.

Second, explain in simple, understandable language why certain rumors are untrue. Avoid using overly technical terms that might confuse them or make them feel disrespectful.

Third, provide alternative information. If elders often get information from social media or unreliable websites, guide them to more reliable news sources and health information websites.

Planning and production

Author: Likely Popular Science Creator

Review｜Zhang Yu, researcher/PhD, Chinese Center for Disease Control and Prevention, national health science expert

Planning丨Yang Yaping

Editor: Yang Yaping

Proofread by Xu Lailinlin

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