By Allison Jarrell, Inside Science

For centuries, cinnamon has been used to enhance the flavor of foods, but new research shows that the spice could also help make foods safer.

According to a study by Meijun Zhu and Lina Sheng, food safety scientists at Washington State University in Pullman, the ancient cooking spice could help prevent some of the most serious foodborne illnesses caused by pathogenic bacteria.

Zhu and Sheng studied concentrated, or essential, oil extracted from the cassia variety of cinnamon – the most popular type for cooking in the United States. Cassia cinnamon has a stronger, spicier flavor compared to Ceylon, the second most popular variety, which the scientists did not test. Bakers and aficionados argue about the relative quality and best uses of the two varieties.

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The cassia cinnamon oil successfully killed several strains of E. coli that produce a substance called the Shiga toxin. These Shiga-toxin-producing varieties of E. coli causes approximately 110,000 cases of foodborne illness each year in the United States, ranging in severity from mild diarrhea to life-threatening hemorrhagic colitis, according to the U.S. Centers for Disease Control and Prevention.

Varieties of cinnamon have historically been used for medicinal purposes, with many ancient societies utilizing the cooking spice for conditions such as respiratory and digestive problems, loss of appetite and diabetes, according to the National Institutes of Health.

Zhu said cinnamon has previously been reported as one of the most effective essential oils for killing or inhibiting microorganisms. Specifically, cassia cinnamon oil has been found to kill other foodborne pathogens as well, including strains of salmonella and listeria.

Zhu and Sheng’s findings, which were published online in the journal Food Control, suggest cassia cinnamon oil can work effectively as a natural antibacterial agent in the food industry. The study, which spanned about a year, involved adding drops of the cinnamon essential oil to mediums, such as nutritionally rich Luria broth, and assessing its effectiveness in inhibiting the growth of Shiga-toxin-producing bacteria.  

The cinnamon essential oil was found to be effective in low concentrations – about 10 drops diluted in a liter of water killed all of the Shiga-toxin-producing bacteria strains within 24 hours. Zhu said the study focused on the “top six” strains, which were classified as contaminants by the Food Safety and Inspection Service branch of the U.S. Department of Agriculture in 2012.

Zhu and Sheng’s objective throughout the study was to explore plant-derived compounds that can control foodborne pathogens – something food safety microbiologist Don Schaffner of Rutgers University in New Brunswick, New Jersey said has been a popular, and important, topic in the food safety world.

“In general, this kind of research has been going on for a long time,” Schaffner said. “There’s been a lot of interest in spices for centuries.”

In terms of real-world application, Sheng said the cinnamon essential oil could be added into films and coatings in the packaging of meat and produce, or incorporated into the washing of meat, fruits and vegetables to eliminate microorganisms.

But Schaffner said there’s still no practical application for everyday use. He added that extraction of such natural compounds can often be expensive.

“It seems simple in theory,” he said, “but the science is more complicated than that.”

Schaffner said the technology for incorporating cinnamon essential oil into packaging has yet to be developed and would face several challenges. If, for example, pathogenic bacteria are located in the center of a cut of meat, the oil may not be able to diffuse through the layers of meat in time for consumption. Or higher oil concentrations could be needed to kill certain bacteria, which might affect the flavor of the food.

A cinnamon hamburger, Schaffner pointed out, may not be too tasty.

Zhu said the real world implications of the research have not yet been examined and that they don't yet know how much oil would be needed to protect a given vegetable or cut of meat. She added that the findings are promising.

“The efficacy of the oil will depend on the [E. coli] strains, load, food matrix, food processing environment and many other factors,” she said, “which warrants more research.”

Reprinted with permission from Inside Science, an editorially independent news product of the American Institute of Physics, a nonprofit organization dedicated to advancing, promoting and serving the physical sciences.

Allison Jarrell is a contributing writer to Inside Science News Service.