It seems that the tomato plants are finally bearing fruit and we are starting to get tomato canning calls at AnswerLine. Callers are sometimes confused about canning times and recipes.
It can be hard for callers to understand that we recommend using only safe, tested canning recipes. The National Center for Home Food Preservation, the Ball Company, Iowa State University Extension and Outreach are great resources for these recipes. We do not recommend old family recipes or recipes from random places on the internet. Those recipes were not tested to ensure you would preserve a safe product. Sometimes callers want to extrapolate canning times from one recipe to another. The canning times really differ between methods for tomatoes. If you skin, core, and cook the tomatoes before placing in the jars, the canning time is 45 minutes for quart jars in a boiling water bath canner. If you merely skin and core tomatoes and pack them into jars with no added liquid, the processing time in a boiling water bath canner is 85 minutes. The differences in canning times reflect the rate of heat transfer inside the jar. For a denser product, the canning time increases.
I spoke with a caller for a long time yesterday explaining that if she were using a tested recipe, the exact processing time and method of preparing the tomatoes would be included in the recipe. If she is asking about the correct processing time, and comparing several recipes, then the recipe she was looking at was likely not a tested recipe.
We want you to use a tested recipe, exactly as written. We want to help you keep your family safe while you are preserving food this summer.
Remember that you can take a canning class through Iowa State University Extension and Outreach. The class, Preserve the Taste of Summer, begins with an online section. Get started today.
I usually can only hybrid tomatoes, and Rutgars. this year I have a lot of Brandywine heirlooms. If it okay to can them along with the others? I was always under the impression they had lower acid and did not lend to safe canning. I read lots to the contrary on the internet, but nothing I see is from an extension agency.
thanks,
Pam
Hi Pam, Ripe tomatoes of every color and/or variety are considered equivalent in terms of acidity for home canning purposes and can be used interchangeable safely. However, the “equivalent” factor comes with the requirement that they are canned following the USDA’s acidification process which will put them all into the safe, high acidity range for home canning. You will find this same information from several land-grant universities; two that come up in a regular Google search are Penn State and Uni of Minn. Follow this link from the National Center for Home Food Preservation to properly acidify your tomatoes and can your heirlooms if you like.