Botulism in Bordeaux: sterilization of “home-canned food” should be carried out with caution

The alleged culprit is known: “homemade canned sardines in oil” served at Tchin Tchin Wine Bar in Bordeaux (Gironde) until Sunday 10 September. At least ten people who ingested it subsequently developed symptoms consistent with botulism, a fatal disease in 5-10% of cases. One of them, 32 years old, died. “I had a batch of sterilized sardines and when I opened it, I had to throw away the ones that had a strong smell. Others appeared healthy and were served to customers,” a manager at the establishment, “devastated” by the news, told Sud-Ouest.

In France, “the majority of cases of botulism are still consistent with food poisoning” due to products that “have not undergone an extensive sterilization process,” the French Ministry of Health clarifies. “The trigger is very often home-canned food,” adds Gauthier Delvalles, deputy head of the CNR botulism unit at the Pasteur Institute. A fashionable practice among part of the population who love naturalness.

As for the Tchin Tchin wine bar, “we have noticed a real lack of control over the conservation process, which is very artisanal,” Thierry Touzet, deputy director of the Department of Public Protection, said Wednesday morning.

A safe process, “as long as it’s done well”

Sterilization is a fairly common preservation practice aimed at destroying all microorganisms. “This is the most successful and safest process, provided it is carried out correctly,” says Patricia Taillandier, professor of microbiology at the Toulouse School of Engineering INP-ENSIACET.

The principle is to increase the temperature to more than 100°C within a few tens of minutes. “There are minimum values ​​calculated for the most resistant microorganisms, including bacteria that can cause cases of botulism. In principle, this is 100°C for 30 minutes or 120°C for at least 20 minutes,” says the expert. The exact minimum temperature and duration that should be observed depends on the contents of the canning (vegetables, fish, meat, etc.).

Specifically, in the case of sardines, for example, the latter are placed in a jar, sometimes filled with oil, then the container is closed and placed in the device. Manufacturers often use an autoclave, a kind of large pressure cooker filled with steam. “For a homemade sterilizer, we usually fill a pressure cooker with water and immerse the jars in it,” describes Florence Mathieu, professor of microbiology at the Toulouse School of Engineering INP-ENSAT. Sterilized products can be stored at room temperature for at least a year.

“Throw away the can if it bulges or smells bad.”

But this process is not foolproof. One of the main risks is removing the cans too early, when all microorganisms have not yet been destroyed. “The heat distribution also needs to be very linear. In addition, if the jar is not airtight enough, for example if there is a small crack, or if it is not sealed well, bacteria can get inside over time,” describes Patricia Taylandier.

As for the bacteria that cause botulism, they resist heat better than others and do not require oxygen to live. As a result, “it can multiply and produce the toxin that causes botulism if the jar was not sterilized well,” notes Gauthier Delvalles.

If you have homemade jars at home, don’t panic! With an average of about ten outbreaks per year, botulism remains a minor risk. To limit problems, the expert recommends “throwing away the can if it’s bulging because bacteria is producing gas or smells bad.” At the moment of opening, “it should just explode,” says Florence Mathieu.

The manager of wine bar Tchin Tchin should have gotten rid of all the cans of sardines if some of them were deemed unfit for consumption, experts say. As a precaution, all canned food available in his establishment (fish, as well as stewed lamb, vegetables, etc.) were recorded.