Traditional Canning Methods Need Modern Science

Sometimes, with food, it's what you can't see that might hurt you. Martha Winter, a food specialist with the University of Illinois Extension Service Mount Vernon Center, in Mount Vernon, Illinois, said the extension service, and its sister service through the University of Georgia, host to the National Center for Home Food Preparation, recommend that every item canned at home be processed through a pressure canner or water-bath canned. Water-bath canning is the processing of putting filled jars in an open kettle of boiling water. Jars are held off the bottom of the pan with a wire basket to assure that the jars and the food inside heat evenly and thoroughly.

A website provided by the University of Georgia provides recommended times depending on what's being canned, the size of the jars and even the altitude where they're being canned at, since water boils at a lower temperature at higher altitudes.
"We still have lots of people that do it the old way," Winter said, "but we just strongly recommend against it."

The problem is that kitchens, no matter how clean, are not sterile environments, she said. So even if you sterilize your jars before beginning and fill them with a boiling hot liquid, there is no guarantee that microorganisms ranging from bacteria to mold spores haven't floated into the jar while it's being filled.

"Even jams and jellies, we recommend processing because we live, in my opinion, in the mold capital of the world. There are mold spores everywhere and processing simply resterilizes the food," she said. It's not unusual in jams and jellies that aren't processed to remove the lid and find a fine layer of mold on the lid or on the jelly.

"Years ago, the conventional wisdom was that you just scrapped the layer with the mold off and then ate the rest. Now, we know that mold creates toxins than infiltrate the food and we say if there is any mold at all, throw it out," Winter said.
Not only does processing destroy any yeast, mold or bacteria that might have drifted into the mix, but it also destroys any lingering enzymes in the vegetable product being canned, she said.

"Leaving active enzymes in your vegetable product can lead to changes in color, texture and flavor. A lot of people find their canned good are too soft because those enzymes weren't fully destroyed," Winter said.

"We tend to learn food storage techniques from generation to generation, but we live in a different world than our parents and grandparents did," Winter said. "They also had lots of loss due to spoilage. With the cost of the ingredients and the time we spend, we need to be a little more conscious of doing things right."

"I had one lady call me who was just devastated because she had spent hours canning tomato sauce and because of the way she did it, I had to recommend that she throw it all away," she said.

The National Center for Home Food Preparation has guidelines for all types of home food preservation from sun-drying your tomatoes to canning jams and jellies. The web site, maintained by the U.S. Department of Agriculture extension services through the University of Georgia, contains recipes that have been tested for both flavor and food safety. The web address is: www.uga.edu/nchfp