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Feature Articles: Food, Fitness and Cooking and Produce


“Can I Can Yellow Tomatoes?”
and Other Tomato Questions

Karma Metzgar, C.F.C.S. Former Northwest Regional Nutrition Specialist, Nodaway County Extension Center, University of Missouri Extension


"How do you can yellow tomatoes?" "Can I can pink tomatoes?" “Can I mix red, orange and yellow tomatoes?” "To can tomatoes safely, do I need to add acid?" “What causes the white spots under the skin?”

We often learn from other people's questions and these questions have earned the "most frequently asked" status the past few days. Here are just a few "tomato questions" which are a part of Extension's Search Food Preservation FAQ database available on the web at I typed in the search word tomatoes and here's a sampling of questions and answers I found. These questions are similar to ones called into local extension centers annually.

How do you can yellow tomatoes?

Yellow tomatoes are canned by the same method as red tomatoes. This holds true for pink, orange, and other rainbow colors of ripe tomatoes, so you can mix and match as you preserve salsa or canned tomato products.

I've been told that to can tomatoes safely, you must add acid. Is that true?

Tomatoes were once considered an acid food that could be safely canned in a boiling-water canner. However, because of problems in recent years with botulism in home-canned tomato products, certain precautions must now be taken. In Missouri, it is recommended that tomatoes have acid (in the form of crystalline citric acid or bottled lemon juice) added. Please refer to University of Missouri Extension guide sheet, GH1456, "Tantalizing Tomatoes," for safe canning directions. Guides are available through your local extension center or on-line at

How much lemon juice or citric acid should I use when canning tomatoes?
Add 1 tablespoon bottled lemon juice to pints and 2 tablespoons bottled lemon juice to quarts of tomatoes. Or add one-fourth teaspoon crystalline citric acid to pints and one-half teaspoon crystalline citric acid to quarts of tomatoes. Acid can be added directly to jars before filling. Four tablespoons of 5 percent acidity vinegar per quart may be used instead of lemon juice or citric acid, however, it may cause undesirable flavor changes. Add sugar to offset acid taste if desired. Note: Don't use fresh lemon juice as its acidity varies. Tomato canning tablets should not be used as they are ineffective.

I don't understand why the processing times for tomatoes are so long. Aren't they an acid food?
Actually, where home canning is concerned, tomatoes are right on the borderline between low-acid vegetables and acid fruit. Some of the newer tomato varieties have an increased sugar content and a decreased amount of acid. These factors were taken into consideration when the processing times for tomato products were researched.


Many of our tomatoes have white pitted areas under the skin. What causes this and is it safe to can these tomatoes?

White spots, also known as "cloud spots," right beneath the skin of the tomato are caused by insects sucking juice out of the fruit. This damage can be quite extensive. These spots heal over leaving scar tissue that appears as a white spot. The surface area remains quite smooth. The acidity of the tomatoes should not be affected and the spots can be cut out as the tomatoes are prepared for canning. This particular exception, however, does not affect our general recommendation of never canning tomatoes with soft spots, broken skin or decay.

Can I leave the salt out?
Absolutely! Salt’s function in tomatoes is flavor not preservation, so leave it out. Actually, salt is only necessary when making pickles - there it has a preservation function.






Last update: Tuesday, May 05, 2009




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