Healthy adults and children may ingest tiny amounts of pathogens with few or mild effects—which is what we usually call food poisoning. Infants, elderly people, and anyone with a compromised immune system are always in danger. The threat of serious symptoms increases over time as bacteria grow in hospitable environments—not too hot or cold, with just enough air and not too much acid.
It’s important to remember that these cases are news because they are rare. But growing interest in whole food and raw food has increased the consumption of raw milk and related products, often the source of listeria. And successful home farming has led to increased interest in food preservation. Canned low-acid foods are uniquely subject to botulism proliferation.
Due to the success of the local food movement, production and handling considerations once relevant only to commercial manufacturers now pertain to home kitchens as well. But with the right equipment, scrupulous cleanliness, a supply of pH-measuring strips, and a USDA-approved recipe, experienced and conscientious cooks can fearlessly stock their pantries and load up their friends with safe canned gifts from their own kitchens.
There’s no substitute for a strict cleanliness regimen when handling food and everything that touches it. The most serious food pathogens are transmitted by contact with bacteria in feces. A little thought about potential sources can yield surprising insights about just how widespread the presence of such invisible bacteria may be in the home, and just how much they might multiply in food preparation and storage.
To communicate with and help home food-handlers, several government agencies related to food, agriculture, and disease control collaborate on an up-to-the minute site at FoodSafety.gov. The site’s homepage summarizes critical food-preparation basics with a rubric of “Clean, Separate, Cook, Chill,” presented in easy-to-digest videos. Even long-time cooks can benefit from the refresher and may even find something new in recent research.
For the canning process, the best counsel comes from Cheralyn Schmidt, founder and senior program director of the UA’s Garden Kitchen. She cautions that safe canning requires an understanding of food chemistry and an abundance of respect for bacteria.
For proven techniques and recipes for safe canning, Schmidt recommends the USDA’s Complete Guide to Home Canning, 2009 revision, which can be downloaded for free at the website for the National Center for Home Food Preservation (Nchfp.uga.edu); and what’s known as the canning Bible, The Ball Blue Book of Preserving, in any edition since 1994. Both are technically comprehensive, amply illustrated, and indispensable for every skill level. Both also provide detailed information for safe alternative preservation through freezing and drying.
“Freezing and drying are much better ways to preserve things,” Schmidt says. “If you freeze something, you slow down the bacterial progression. If you dry something, you remove the water so the pathogens can’t grow.”
Pickling preparations canned in water baths are the least risky for southern Arizona’s common late summer corn and zucchini, both low in acid and vulnerable to botulism. The Complete Guide and the Blue Book both have recipes for several kinds of zucchini pickles.
Schmidt suggests freezing summer fruits and the juice of prickly-pear fruit, or tunas, coming ripe this season. In winter, preserve a pomegranate crop the same way, as juice. Plan to boil and dry cholla buds in the spring, but nopales will require pressure canning by experts only. “The pressure cooker is like the calculus of cooking,” Schmidt says. “You need to work up to it a little bit.” Advanced canners may want to try a vacuum packing method to preserve their mesquite flour.
Some crops perhaps shouldn’t be canned at all. Schmidt points out that canned goods should be used within a year, but potatoes and hard winter squash will do just fine on their own for six months when stored in a cool, dry place. Canning them could be a waste of time and tie up jars that could be used for something else.
And if it’s nostalgia for old family canning recipes that’s inspiring a venture into food preservation, Schmidt seems to respectfully suggest that you can it. “You never use a canning recipe that’s 50 years old,” she says,” because vegetables and pathogens can change over time.” For instance tomatoes used to be a lot more acid, with a lower pH level. And did that heritage recipe originate at the same altitude? “Elevation changes the atmospheric pressure and the temperature at which water boils,” Schmidt notes. Boiling temperature, pressure, and pH level all require precision control for safe canning.
Schmidt says that in any case in grandma’s day canning was a party. It was a community event similar to the Tohono O’odham traditions of saguaro fruit gathering, and the Mexican tradition of tamale-making. For anyone curious about canning, she suggests a tomato-canning party with friends who have experience and a collection of the right gear, which can be costly to assemble.
The party is ideal for folks who’ve planted determinate tomatoes—plants that bear fruit at the same time. Even better, you can organize and invite friends for a tomato-canning party at the Garden Kitchen, which frequently hosts such private and public events. The party could include training in knife skills as well as canning basics, and everyone can go home with new skills and great memories along with their freshly canned tomatoes. ✜
The Garden Kitchen. 2205 S. Fourth Ave. 520.621.0476. TheGardenKitchen.org.
Linda Ray has written for the Tucson Weekly, the Chicago Tribune, and the Chicago Reader. She and her valiant pup, Gozo, live in an unmanageable landscape in Central Tucson.