“What’d life be without homegrown tomatoes, only two things that money can’t buy, that’s true love and homegrown tomatoes” (G.Clark 1983)
These song lyrics may reflect a Minnesotan’s anticipation of the first “homegrown” tomato of the season! Tomatoes are the most popular home preserved food. The variety of preservation methods and the versatility of preserving tomato juice, salsa, jam, dry tomatoes, pickled green tomatoes, and more, make it a treasured treat of summer and beyond.
We think of tomatoes as “high acid”, but research tells us that the acid varies by the variety, heat, moisture, soil, and ripeness. Current canning recommendations require that acid be added to (almost) all canned tomato products whether water bath processed or pressure canned.
So, when canning “plain” tomatoes:
• Quarts: add 2 Tablespoons bottled lemon juice or 1/2 teaspoon citric acid
• Pints: add 1 Tablespoon bottled lemon juice or 1/4 teaspoon citric acid
Bottled lime juice can be used in exchange for bottled lemon juice. Tomato products like salsa may use vinegar to acidify and add flavor. Acid can be added directly to jars before filling or after filling, prior to applying the lid.
Home-canners have asked if heirloom tomatoes are acidic enough to be canned without adding acid. Horticulture researchers have concluded the acidity of heirloom tomato plants is no different from the non-heirloom varieties. In fact, there are some heirloom varieties that are more low-acid than hybrid varieties. As a result, the same recommendations apply for adding acid when canning heirloom tomatoes.
See University of Minnesota Extension for preserving tomatoes and salsa information at http://z.umn.edu/g38.