The Science of Home Food Preservation: Yes, It Matters!
Participants in Penn State Extension home canning classes frequently tell educators they have been canning with a family or friend's favorite recipes, recipes found somewhere online, from various cookbooks, or make up their own recipes. This article will explain why these recipe sources are unsafe by describing the food safety science behind research-based home canning recipes and will show how you can use or adapt your favorite recipes for safe home canning.
Research-based safe home canning recipes that Extension can recommend have been tested at a University Extension or United States Department of Agriculture laboratory. During testing, researchers standardize the recipe, including
- measurements of all ingredients,
- size of the jars,
- measurements of the pH,
- time,
- temperature,
- and pressure.
Other factors that food scientists measure for safe home canning recipes include:
- water activity (how much water the food contains),
- how well the heat penetrates the jar,
- the thickness of the food product,
- size of the food pieces,
- raw and hot pack methods,
- canning at various altitudes,
- and amount of headspace (measurement of the distance between the food and rim of the jar).
These factors interact to affect the final temperature and time needed inside the jar to reach levels to kill pathogenic (foodborne illness-causing) bacteria and bacterial spores.
Cooking temperatures of 180-212°F destroy most bacteria, mold, and yeast that can cause spoilage and potential foodborne illness. These temperatures will also inactivate enzymes in the food that negatively change color, texture, flavor, and nutritional value. However, to kill bacterial spores, such as the potentially deadly Clostridium botulinum, home-canned low-acid foods (pH greater than 4.6), such as most vegetables (unless pickled or acidified tomatoes), meats, and poultry, and combinations with these foods, must reach 240°F. The only way to raise the temperature to 240°F or above is under pressure.
This safe home canning recipe research can only be conducted in a lab with special equipment and trained food scientists. How can you safely home can one of your non-research-tested recipes?
- Find a USDA or University Extension recipe that is very similar and use it. For example, many people have a family favorite spaghetti sauce recipe. Penn State Extension's Let's Preserve: Tomatoes has several spaghetti sauce recipes, so find one that is similar.
- Next, if you have other ingredients in your recipe that are not in the research-tested recipe, add them only when you are ready to cook and serve the spaghetti sauce, such as added vegetables or herbs.
- Note, you cannot alter a research-tested home food preservation recipe unless it specifically states you can. The exception is for salt; you can change the amount as it is not used for preservation, simply for taste.
So now you know a little more about the science behind safe home canning and using only research-tested recipes that will help keep you and your family safe. To learn more about safe home canning procedures and recipes, visit Penn State Extension's website or the National Center for Home Food Preservation.
Source
LaBorde, L.; Zepp, M.; & Hirneisen, A. (2023, August 1). "Let's Preserve: Tomatoes". Penn State University.
National Center for Home Food Preservation. (n.d.). "Canning". University of Georgia.
