Ask Extension for answers to commonly asked questions.

Canning Tomatoes

Source: University of Wisconsin

Although tomatoes are the most widely home-canned product, you must can tomatoes carefully to avoid the risk of spoilage and food poisoning.The natural acidity in tomatoes varies widely because of differences in ripeness, growing conditions, injury or disease on the fruit, and vine conditions.Because of these factors, you should add acid in the form of lemon juice or citric acid to all home canned tomato products.Add two tablespoons bottled lemon juice or 1/2 teaspoon pure citric acid per quart of tomatoes, tomato juice or other tomato product.Add one tablespoon lemon juice or 1/4 teaspoon citric acid per pint.This will ensure the tomatoes are sufficiently acid to avoid the risk of botulism.

Control spoilage by adequately heat processing filled jars of tomatoes in a boiling water canner or a pressure canner.Processing times have been carefully recalculated by researchers at the Pennsylvania State University and differ somewhat from those recommended before 1987.

Select only disease-free, preferably vine-ripened firm tomatoes for canning.Do not can overripe, damaged or frosted tomatoes, or those harvested from dead vines.Such tomatoes are much lower in acid.

You can use three different packing methods for tomatoes.However, each requires a different process time.To can quartered or crushed tomatoes by a hot pack method, peel the tomatoes, remove cores and quarter them.Heat rapidly in a large kettle and simmer gently for five minutes.

Add two tablespoons bottled lemon juice or 1/2 teaspoon citric acid to each clean quart jar, then fill with the hot tomatoes.Add one teaspoon salt if desired.Seal with two-piece canning lids; process quarts 45 minutes in a boiling water bath canner.

If you want to process them in a pressure canner with a dial gauge process at 7 pounds pressure for 20 minutes, or 12 pounds pressure for 15 minutes.With a weighted gauge canner, process 20 minutes at 10 pounds pressure, or 15 minutes at 15 pounds pressure. Time and temperature vary as altitude change.

To pack whole or halved raw tomatoes, you can choose between a water pack or a juice pack method.For a water pack, add two tablespoons bottled lemon juice or 1/2 teaspoon citric acid to each clean quart jar and fill with raw whole or halved tomatoes.Cover with hot water and adjust lids.Process quarts 45 minutes in a boiling water bath.If you use a dial gauge pressure canner, process for 15 minutes at 7 pounds pressure, or 10 minutes at 12 pounds. In a weighted gauge canner, process 10 minutes at 10 pounds pressure or 1 minute at 15 pounds pressure. Juice pack has a longer processing time.

Additional information on this topic is included in the Extension bulletin HE-175, "Canning and Freezing Tomatoes," which is available at your county office of the NDSU Extension Service.

Back to Canning Menu
Go to Ask Extension Index Page
For More Information Contact your North Dakota County Extension Office of the NDSU Extension Service for additional information or see our main NDSU Web Page for publications and articles on Agriculture, Horticulture, Youth and Family, Business and Community and Food and Nutrition at  http://www.ag.ndsu.nodak.edu/