Since the global financial crisis, consumers have increasingly turned to using locally produced vegetables and fruits, as well as home canning to preserve them for longer periods. The downside of this practice is that if food is not preserved correctly, consumers can suffer from illness or even death due to food poisoning, according to research from the nutrition consulting program in partnership with the University of California.
When done correctly, home canning is both economical and safe. The canning process includes several steps, placing food in jars and boiling them to a certain temperature to kill microorganisms that can spoil the food.
(Illustrative image: The Atlantic)
During the heating process, air is expelled from the jars, and as they cool, the lids are sealed tightly to prevent air and microorganisms from re-entering.
If food processing is done following experimental recipes but not strictly adhered to, it can lead to the survival of microorganisms in the food, resulting in spoiled canned goods. Tragically, consumers can suffer from food poisoning due to improperly canned home foods. Food poisoning is a rare illness, but if not treated promptly, it can lead to death; in some cases, victims may experience paralysis due to neurotoxins from the bacterium Clostridium botulinum.
There are two safe methods for preserving canned foods: the boiling water method and the pressure canning method. The boiling water method is used for high-acid foods like fruits. The pressure canning method must be used for foods such as vegetables, meats, and sauces like spaghetti and salsa. Always check and follow the guidelines of canning recipes to ensure the safety of home-canned foods.
“It is very important to follow the guidelines of scientific research on canning to avoid illness,” says Susan Algert, nutrition advisor for the UC Cooperative Extension in Santa Clara County. “The boiling water method is safe for fruits, jams, jellies, pickles, and other high-acid foods,” she adds. In this method, the food jars are completely submerged in boiling water at 100 degrees Celsius and heated for a specific period.
High-acid foods such as natural peaches have a pH of 4.6 or lower and have sufficient acid to prevent the growth of Clostridium botulinum. Preserve high-acid canned foods using the boiling water method.
“Some foods like tomatoes, pears, and figs, with a pH of up to 4.6, need an additional acid to lower the pH, and can also be preserved using the boiling water method,” Algert states. The pH can be lowered by adding bottled lemon juice or powdered citric acid.
When making homemade salsa or other tomato products, Algert recommends following a scientifically proven method for safety and using bottled lemon juice to increase acidity.
“You cannot use juice from a fresh lemon because we do not know the exact amount of acid it contains,” Algert notes. “Commercial lemon juice meets the necessary acid standards.”
To preserve low-acid vegetables like green beans without a pressure cooker, you should first pickle the vegetables, which increases the acidity in order to inhibit the growth of Clostridium botulinum.
Clostridium botulinum can form spores (biofilm), a heat-resistant form of bacteria that can survive boiling temperatures. If the spores survive because you did not boil the water long enough as recommended, the bacteria can survive, grow, and produce toxins. Clostridium botulinum thrives in low-acid foods like meats and vegetables, even when jars are sealed and no air can enter.
“The only safe method to preserve vegetables, meats, poultry, and seafood to prevent food poisoning is pressure canning,” Algert states. “These low-acid foods require killing bacteria at temperatures of at least 116 degrees Celsius, for varying times depending on the product. This temperature can only be achieved using the pressure canning method.”
To ensure the safety of home-canned foods, Susan Algert advises everyone to use new lids with standard seals according to strict guidelines from a tested scientific process for home canning.