Recipes that have been handed down that cannot be verified with a science-based recipe should not be canned.
Kimberly Baker, ©2023, Clemson University Extension
The Question: People have been canning for a long time, and it appears that not too many people died from it. Why can’t the old-time recipes be used? If the recipes were passed down from generation to generation or were published by Mason Jars and companies that made canners, why can’t they still be used? Is it all right to freeze an old-time recipe instead of canning it?
The Response:
Freezing old-time recipes is a good idea—no unique safety issues are associated with freezing.
We recognize that some folks will continue to use old or unsafe methods regardless of Clemson Extension’s recommendations to the contrary. Spores of the organism that causes botulism are present in most foods. I am not willing to recommend playing Russian roulette with canned foods.
Several factors contribute to older, previously recommended recipes now being considered unsafe. Re-tests of some previously recommended processes using the best scientific methods indicated that the process did not reach the temperature to kill the botulism-causing spores throughout the jars. Some re-tests indicated that the same final temperature was not reached in all jars; thus, the heat process was not reproducible. We now know that following these previously recommended processes is risky; Clemson Extension cannot recommend a process that has been found to be inadequate, or that cannot be reproduced reliably.
Eating preferences have also changed. More folks like foods that are cooked less, and it is more common for canned foods not to be reheated. The botulism toxin is destroyed by boiling for 10 minutes. Boiling a low-acid canned food before eating provides an additional safety measure, but longer cooking times are less commonly used.
Some foods have changed over time. For example, tomato varieties have been bred for ease in harvesting; as a result, many now have a milder flavor and lower acidity than ancestral tomatoes. Testing has shown that some current tomato varieties have pH values at or above 4.6; a few have pH values of 5 or even greater. But adding the recommended amount of lemon juice lowers the pH of all tested varieties enough to allow for safe water bath canning. That is why acidifying tomatoes is now recommended; it allows for safe processing in a boiling water bath canner.
For multiple reasons, old-time recipes may not be considered safe for canning. Clemson Extension recommends only currently tested and scientifically validated recipes. For more information, see HGIC 3001, Finding Reliable Recipes for Safe Food Preservation.
