CORVALLIS - Incidents of botulism happen rarely in Oregon, but a recent case in the Willamette Valley apparently caused by a jar of home-canned venison stew has caused concern among some Oregonians.
Carolyn Raab, a food safety and nutrition specialist with the Oregon State University Extension Service, said botulism can result if low-acid, home-canned foods - including meats, fish, poultry and non-pickled vegetables - haven't been processed correctly to kill Clostridium botulinum bacteria spores.
These spores can grow and produce a toxin without creating any visible signs of spoilage.
However, there are ways to avoid eating food that might contain the toxin, said Raab, who is a professor in OSU's Department of Nutrition and Food Management.
"If you're given home-canned food during the holidays, first check it for signs of spoilage such as unusual sediment, a loose or bulging lid, or spurting liquid when the jar is opened," Raab said. "Even if the food looks and smells normal, it is wise to boil low-acid, home-canned foods for 10 minutes as an extra margin of safety.
"The boiling will destroy toxin that could have formed," she added.
Raab said Oregonians shouldn't be deterred from home canning, though she suggests they closely follow safety procedures. She recommends using a pressure canner for low-acid foods and processing them for a sufficient length of time to destroy the Clostridium botulinum spores.
"It's important to use laboratory-tested processing times," Raab said, "and these times vary depending on the size of the jars - whether they're pints or quarts. Processing times also will differ according to the acidity of the food, the way it is prepared (such as whole versus sliced), and whether the food is packed into the jars cold or hot."
At sea level, Raab said, low-acid foods should be processed at 11 pounds of pressure with a dial gauge, or 10 pounds with a weighted gauge. The pressure must be increased when the altitude is above 1,000 feet with a weighted gauge, or above 2,000 feet with a dial gauge canner, she emphasized.
"Consult a newer canning publication for canning instructions," Raab said.
Instructions have changed throughout the years as the result of new research and "you shouldn't use any guidelines printed before 1988" - the last year the U.S. Department of Agriculture updated its recommendations.
2 Raab said canning instructions should always be followed exactly, or home canners run the risk of under-processing their foods. Likewise, if the canner isn't operating properly, the risk increases that not all the harmful bacteria will be destroyed.
"To be on the safe side, you should check dial gauges for accuracy each year," Raab said. "Pressure canners should be vented for 10 minutes before closing the petcock to prevent cold spots."
Raab said processing recommendations can be downloaded from the OSU Extension Service website - http://eesc.oregonstate.edu - and also are available at local county Extension offices.
She also recommends the U.S. Department of Agriculture's "Complete Guide to Home Canning," available at the National Center for Home Food Preservation website at http:/www.uga.edu/nchfp/publications/.
Research-based recommendations also are available in commercial publications, such as the Ball Blue Book.