The Science of Food Preservation

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Canned pickled vegetables. The jars are filled with jalapeños, red onions and cucumbers.Many people tell me that they hated science when in school but they are avid canners and food preservers who make delicious foods to eat all year round. You may ask how is food preservation an example of science? When we preserve foods either by canning, freezing, pickling, fermenting or drying we are changing the food to decrease the chances of spoilage, bacteria and mold grown and to reduce the risk of getting sick if we eat the food later.

This is the science. We do this by changing the water availability or moisture of the foods or the acid level of the food. We also can heat the foods which can kill bacteria, molds and yeasts and stop or slow down enzyme activity which contributes to breaking down the food. The process and recipes we follow in food preservation are what is allowing the food to be able to last and be eaten later in the year.

Since it is a science, we are always learning new things about food preservation and sometimes this leads us to make new recommendations or caution using older recipes or ways of preserving. Some of the changes over the years have been, in 1994, we started recommending to add acid to tomatoes when we learned more about how the acid levels in tomatoes can vary and at times during the growing season the acid level can be low enough for there to be a risk for botulism. You can find information on adding acid to your tomatoes when canning them at the National Center for Home Food Preservation.

Another change over the years is to recommend only freezing, pickling or dehydrating (drying) your summer squash. They no longer recommend canning summer squash due to the fact that summer squash changes when reaching the high temperatures during pressure canning. This results in the squash getting too soft and packing into the jar too tightly to determine consistent times to heat in order to thoroughly decrease the risk for botulism. For more information and other questions about canning safely, read through the Frequently Asked Canning Questions.

So instead of canning your zucchini this summer, try this favorite pickling recipe from the National Center for Home Food Preservation, Pickled Bread-and-Butter Zucchini.

If you have questions, or just want to stay up-to-date on the latest recommendations or to check If a process, recipe or food is safe to preserve the way you want, call our office at (828)- 652-8401 or email We hope to have hands-on classes later in the summer so look for those announcements to come.