Using shellfish to fight food poisoning

Shellfish is often blamed by diners if they feel unwell after a meal, but new research could recast crustaceans as the heroes rather than the villains in the fight against food poisoning.

Chitosan — a natural carbohydrate derived from crustacean shells — has been found to have potential to fight Clostridium perfringens food poisoning, which causes abdominal pain, stomach cramps, diarrhoea and nausea.

Present 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. It is the second-most common bacterial foodborne illness in the US after Salmonella poisoning. Patients often mistake it for a 24-hour virus, so many cases go unreported.

“People aren’t dying, but they’re getting sick,” said Oregon State University researcher Mahfuzur Sarker. “And many times people don’t report it, so there are likely way more people getting infected than we know about.”

The tests involved both laboratory growth medium and cooked, contaminated chicken meat left for several hours at 37°C. The study looked at the full life cycle of the C. perfringens 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. It was also found to inhibit spore germination and outgrowth, restrict the spore core from releasing dipicolinic acid, which is associated with an early step of spore germination, and limit the growth of vegetative cells that are actively growing as opposed to producing spores.

“In lab conditions, low concentrations of chitosan were effective,” said Sarker, professor of microbiology in OSU’s colleges of science and veterinary medicine. “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 mg/g 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 optimising 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.

The results were published in Food Microbiology.