Bacterial spores in food pose one of the least known risks in food safety. While most people understand that if food is cooked to a certain temperature most bacteria are killed, the fact that spores produced by bacteria are a threat even in well-cooked food is less known. The bacteria can also affect food quality.
Most spores, which are reproductive structures that help the bacteria survive under unfavorable conditions (i.e. cooking), are heat resistant. In fact, they are remarkably like a bomb shelter for bacteria. All of the bacteria’s genetic material is stored in the spore; it just needs moisture, food, and the right temperature to germinate. And when they grow, the new bacteria produce toxins that are also heat-resistant.
So a research team at the Nofima Norconserv AS in Stavanger, Norway,
associated with the Norwegian School of Veterinary Science, decided to investigate a different cooking method to destroy the spores.
Most processed refrigerated ready-to-eat foods are heated to temperatures between 149 and 203 degrees F at the plant, which kills most bacteria. The spores survive, however, and can become more dangerous since competing bacteria are killed off and they don’t have competition for food and water. And the heat can actually help the spores germinate.
The scientists tested a method called double heat treatment. In this method, the food is heated to activate the spores, cooled so the spores germinate, then heated again to kill the new bacteria that grow in the cooler temps. In the tests, Bacillus cereus spore levels were reduced by 99.9%.
This treatment may be used by food companies to make processed ready-to-eat foods safer.
