Canning

by Jean Ann Pollard

Clostridium botulinum produces the serious neurological and potentially fatal disease commonly known as botulism.” (Fox, Nicols. Spoiled: The Dangerous Truth About a Food Chain Gone Haywire, HarperCollins, N.Y., 1997, p. 59.)

Home canning has always been “a notorious breeding ground for a bacterium called Clostridium botulinum,” reports Nicholas Bakalar in Where the Germs Are: A Scientific Safari. Botulinus, which is “actually a group of seven separate organisms distinguishable by an odorless type of nerve poison they produce,” lives in the soil all around us; and its effects can be – well – fatal.

The bacterial spores can survive cooking, even boiling, then can germinate and produce toxin once food is cooled. Botulinus doesn’t require oxygen, so it’s happy in a container of preserved garden produce. In fact, most cases of botulism are transmitted in vegetables.

As new cooks turn to canning to preserve their organic produce, they need to know that certain long-time “safe” techniques – and even vegetables – have changed. Tomatoes, for instance, because of their high acidity, were once safely processed in a boiling-water bath rather than a pressure canner. But as Fox points out in Spoiled: the Dangerous Truth About a Food Chain Gone Haywire, growers have selectively bred for sweeter, lower-acid tomatoes, and “several outbreaks of botulism have appeared in salsa made with these varieties.”

Although foodborne botulism is now rare in the United States (approximately 10 outbreaks per year), more than 90 percent of outbreaks between 1976 and 1985 were due to home-processed foods. Symptoms can be serious: double vision, vomiting, muscle weakness, problems with breathing and clear speech, difficulty swallowing, final paralysis.

Between 1910 and 1919, the death rate from botulism was 70 percent. By the 1980s, mechanical ventilators reduced the rate to 9 percent; in 1993 it was less than 2 percent, and only one outbreak, involving two people (who both survived), was reported to the CDC in 1997.

In 2002, however, a 40-year-old Aroostook County man and his 13-year-old son ate home-canned tomato sauce, then suffered serious, prolonged illnesses from botulinus poisoning. They stayed in the hospital for one and two months, respectively. Occupational and physical therapy followed, according to the Maine Bureau of Health, which recommends “that most foods be canned in pressure cookers in order to maintain temperatures high enough (above 212 degrees F. for 10 minutes) to kill the spores.”

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