Tomato Canning Tips, Techniques, & Safety

   (Editor’s note: Responding to a reader recipe we recently published, Dr. Barbara Ingham, a UW–Extension food scientist, submitted the following information with a caution to consumers getting ready to can tomatoes.)

Research published in the last 10 years has shown that tomatoes vary in acidity depending on variety, soil, climate, and so forth. This variation in acidity means that canned tomato products must be handled carefully to avoid risk of poisoning from Clostridium botulinum (the bacterium that causes botulism poisoning). Production of botulism toxin in tomato products is most effectively prevented by the addition of acid to all canned tomato products. It has been perhaps 15 years since our last case of botulism poisoning in Wisconsin, but this illness must be avoided since it is often fatal. Below is a recipe for a tomato-vegetable juice blend and canning/freezing options. A good source for canning and other food preparation information, please go to http://www.wisc.edu/foodsafety/.