Chitosan, a naturally occurring carbohydrate derived from crustacean shells, shows promise as a bulwark against a bacterium that sickens more than a million people in the United States each year.
Clostridium perfringens food poisoning is the second-most common bacterial foodborne illness in the U.S, after salmonella poisoning. Living in soil, decaying vegetation and the intestinal tracts of vertebrates, C. perfringens typically infects humans when they eat meat that hasn’t been thoroughly cooked or properly stored, allowing the bacteria to multiply.
An international team of scientists studied the effect of chitosan on C. perfringens and published the results recently. Chitosan is a linear polysaccharide that results from treating the exoskeletons of shrimp and other crustaceans with an alkaline compound.
Team member and Oregon State University researcher Mahfuzur Sarker, said:
“People aren’t dying, but they’re getting sick. And many times people don’t report it, so there are likely way more people getting infected than we know about.”
The work involved both laboratory growth medium – bacteria in solution – and cooked, contaminated chicken meat left for several hours at 98.6 degrees Fahrenheit. The study looked at the full life cycle of the C. perfringen bacterium, which produces tough, metabolically dormant spores that are able to survive many food processing approaches.
The researchers found chitosan blocked C. perfringens growth in cooked chicken. They also found chitosan inhibits spore germination and outgrowth.
It also blocks the spore core from releasing dipicolinic acid, which is associated with an early step of spore germination and inhibits the growth of vegetative cells – cells that are actively growing as opposed to producing spores.
Sarker, professor of microbiology in OSU’s colleges of science and veterinary medicine, said:
“In lab conditions, low concentrations of chitosan were effective. In meat, the concentration needs to be higher because there are a lot of ingredients in the cooked meat that can inhibit the activity of the antimicrobial chemicals.
But the larger dose of 3 milligrams per gram of food is still a good dose that can be used in making food products. This is the first time chitosan was shown to work consistently both in lab conditions and in chicken meat.”
Sarker said the next steps are researching chitosan’s effectiveness in other types of meat and meat products and optimizing the conditions for using it. It’s possible, for example, that chitosan may work best when combined with other food preservative chemicals such as sorbate and benzoate.
Maryam Alnoman et al.
Chitosan inhibits enterotoxigenic Clostridium perfringens type A in growth medium and chicken meat
Food Microbiology (2017). DOI: 10.1016/j.fm.2016.11.019
Image: Clostridium perfringens. Credit: Oregon State University