Cinnamomum cassia oil, a spice widely used in Asian cuisine, could be a promising antimicrobial for the food industry because of its efficacy in inhibiting the top six non-O157 Escherichia coli STEC (Shiga toxin-producing E. coli) bacteria.
In research conducted at the School of Food Science at Washington State University, scientists found that C. cassia can inhibit growth of non-O157 STECs at a concentration as low as 0.025 percent (volume per volume or v per v). Using 0.025 percent (v per v) C. cassia oil completely inhibited the growth of all tested non-O157 STECs for at least 24 hours, according to the research reported online in the journal Food Control.
At high inoculation of 5 x 106 CFL per mL, the inhibition effect of the oil decreased. Including as low as 0.05 percent (v per v), C. cassia oil killed non-O175 STECs; 0.1 percent (v per v) showed bactericidal effects on all tested non-O157 STECs within 15 minutes, the researchers report.
Non-O157 STEC strains are now regarded as important foodborne pathogens worldwide. The six STEC serogroups (O26, O45, O103, O111, and O145) are regulated as adulterants in certain raw beef products in the U.S. The USDA Food Safety and Inspection Service began verification testing in June 2012 for non-O157 STEC in domestic and imported beef manufacturing trimmings from cattle slaughtered on or after June 4, 2012.
Co-author Mei-Jun Zhu, PhD, an assistant professor in the School of Food Science, says her and her colleague’s research with C. cassia is promising but there are problems to solve before the oil can be used for that purpose. One problem is that the oil is “volatile and poorly water soluble,” which adds to the difficulty of applying it directly into foods and incorporating it into edible films and coatings.
In addition, C. cassia oil’s aroma attributes are one of the important factors that limit the “sensory acceptance” of food products that contain the oil. “Last but not least,” Dr. Zhu says, “potential toxicity of cinnamon at high doses should be taken into consideration. Therefore, further studies are needed for the application of C. cassia oil in food as an antimicrobial agent.”
Cinnamaldehyde is the major component of C. cassia oil (59.96 percent). It gives cinnamon its flavor and is used also as a fungicide. In concentrated form, it can be a skin irritant and is toxic in large doses.