"Is Leftover Pizza Safe to Eat the Next Day?"... Even Scholars Puzzled by Surprising Results Stir Debate

Bacterial Surge on Cheese Pizza After One Day
Fresh Pepperoni Slice Shows Higher Contamination

A microbiologist in the United States has sparked curiosity among internet users by releasing a video in which he personally experiments to see how bacteria multiply on leftover pizza. While the intention was to show how microorganisms increase on everyday foods, some unexpected results led to considerable debate online.

A microbiologist revealed the results of an experiment comparing the amount of bacteria growing on leftover pizza. Pixabay

According to reports from the UK’s Daily Mail and others, Nicholas Eicher, a microbiologist conducting research in Chicago, conducted an experiment comparing the degree of bacterial growth by sampling slices of takeout pizza immediately after purchase and again after one day. He released a video of this process on his social media account.

In the video, Eicher is seen swabbing samples from freshly delivered cheese and pepperoni pizzas, transferring them to petri dishes, and then repeating the same procedure with slices left at room temperature for a day. He then cultured the samples to observe bacterial growth.

The results of the cultures both aligned with and contradicted common expectations. In the case of cheese pizza left at room temperature for a day, a distinct bacterial colony formed, confirming the risks of leaving food out for extended periods. On the other hand, a surprisingly large amount of bacteria was found on a fresh slice of pepperoni, which even Eicher found puzzling. Even more interesting was the fact that the day-old pepperoni slice showed less bacterial growth than the fresh one.

Experts analyzing these results explained, "While pepperoni's high fat content may seem to favor bacterial growth, the salting process used in its production could mean that, over time, the salt inhibits the growth of certain bacteria."

Eicher explained the purpose of his experiment by saying, "I wanted to show just how many different microorganisms exist in the foods we eat without a second thought."

Nevertheless, the video’s comment section was filled with pizza lovers expressing their unwavering loyalty. One user wrote, "Even after this, I still can't give up pizza," while another argued, "Pepperoni is too salty for bacteria to really grow on it anyway."

Eicher previously gained attention with a video testing the so-called "five-second rule," which claims that food dropped on the floor is safe to eat if picked up within five seconds. At the time, he dismissed the myth, stating, "Bacteria can transfer the moment food touches the floor."