Preserving your Garden Bounty: Safe Canning Practices for High Elevations

By Gayle Gratop

If you’ve ever practiced home canning, there’s a distinct sound every canner loves: the ping of a lid sealing to the jar. It’s one step toward eating peaches from your garden in January, green beans in March, and the satisfaction of filling your pantry with colorful jars from the season’s harvest. But behind that satisfying sound lies a scientific process that keeps food safe. Done wrong, spoilage can result from microorganisms such as molds, yeasts, and even the bacterium that causes the silent killer, botulism. Done right, it’s one of the most rewarding ways to preserve food.

Canning began as a solution to a problem. In 1795, Napoleon offered 12,000 francs for a new method of preserving food to feed his troops in the field. Frenchman Nicolas Appert won the prize in 1809 by discovering that sealing food in jars and heating them could preserve food for months. Soon after, tin cans appeared in England, and in 1858, American inventor John L. Mason patented the Mason jar.

When Congress passed the Smith-Lever Act in 1914, creating the Cooperative Extension Service, it also established the position of Home Demonstration Agent to teach essential home skills, including food preservation. Today, research-based canning workshops are still offered by Family, Consumer, and Health Sciences (FCHS) Agents through Cooperative Extension, continuing a tradition that began over two centuries ago.

The history of canning is also rooted in the fight against deadly foodborne illnesses, which helped shape the home food safety practices we follow today. When done properly, canning creates an anaerobic, or oxygen-free, environment, which is perfect for preserving food, but also ideal for Clostridium botulinum, the bacterium that produces an odorless, tasteless, and invisible toxin responsible for botulism. Although rare, this illness can be deadly. The safest way to prevent it is to follow tested recipes and proven canning methods. Learning and understanding these practices are the first step toward keeping yourself, your family, and your food safe.

Understanding pH is key to safe canning because it affects whether C. botulinum can grow in your canned goods. High-acid foods like peaches, pickles, and jams can typically be safely processed in a boiling water bath. Low-acid foods, such as vegetables, meats, and soups, require pressure canning to prevent the growth of bacteria. Following a USDA-approved recipe, which takes pH into consideration, helps you choose the right canning method and is an essential part of safe home food preservation.

While Grandma’s handwritten recipe may hold sentimental value, it probably doesn’t meet today’s safety standards. The USDA Complete Guide to Home Canning includes tested recipes that factor in food acidity, jar size, appropriate method, and processing time. Think of canning as chemistry. These recipes have been carefully tested by food safety experts to protect against pathogens like botulism, and their instructions must be followed exactly unless the recipe specifies otherwise.

If you want one go-to book on your shelf, So Easy to Preserve, from the University of Georgia Extension, is a great choice. With more than 185 tested recipes containing clear, easy-to-follow instructions, it also reminds home canners of crucial steps for high-altitude areas like Flagstaff--such as the all-important note, “Remember to Make Altitude Adjustments.”

In Flagstaff, we’re nearly 7,000 feet above sea level. For canning, this matters because water boils at a lower temperature here. For water-bath canning, you’ll need to add extra minutes to the time your jars are in the boiling water, requiring you to use your math skills. For pressure canning, both additional pounds of pressure and time are needed.

Canning is more than a hobby; it is a tradition rooted in science. By following the proper methods, adjusting for altitude, and using research-based recipes, you can fill your winter pantry with safe, delicious food that you worked so hard to grow during the gardening season. So, when you hear that satisfying “ping” of your lids sealing, you’ll feel good knowing you’re not just preserving summer, you’re preserving peace of mind.

Gayle Gratop is the FCHS Agent with the University of Arizona Coconino County Extension. She is partnering with local chef Laura Chamberlin of Culinary Concepts Southwest to offer a water bath canning workshop on December 8^th. Participants will learn how to safely preserve jams using research-based recipes. To register, contact Gayle Gratop at gaylejennifer2@arizona.edu.

Participants learn how to pressure can salsa with Coconino Extension in 2024. Photo Credit: Joanna Mona