When canning tomatoes or any other produce, remember to take your time and use safety precautions.
Have all your utensils ready and absolutely clean, wash hands often and dry with paper towels. Use standard canning jars, never any commercial jars (such as pickle jars, peanut butter, mayonnaise, etc.). Use up-to-date resources and avoid using publications dated 1994 or earlier. This is one time when old family recipes should not be used.
Tomatoes are the most popular home preserved food item. There are a variety of ways to preserve tomatoes, simply as a sauce, but also as tomato juice, salsa, jam & jelly, relish, pickled green tomatoes, and more. Many think that tomatoes are high in acid. But depending on the variety, growing conditions and ripeness, that can vary. An average of 3 pounds of tomatoes per quart is needed when canning. If canning pints, you need a little less than 1 1/2 pounds for each pint. Current canning recommendations require that acid be added to almost all tomatoes that are canned. This can be citric acid, lemon juice, lime juice or vinegar. If you are short on time, you can also freeze tomatoes. They may be frozen either raw or cooked.
An excellent source for food preservation recommendations and a wide variety of recipes is the National Center for Home Food Preservation at https://nchfp.uga.edu. Also, visit the University of Minnesota Extension office at https://www.extension.umn.edu/food.
The following guidelines are from the University of Minnesota-Extension website:
An average of 21 pounds is needed per canner load of 7 quarts; an average of 13 pounds is needed per canner load of 9 pints.
Wash tomatoes. Dip in boiling water for 30 to 60 seconds or until skins split, then dip in cold water. Slip off skins and remove cores. Leave whole or halve. Add additional acid to jars: add two tablespoons of bottled lemon or lime juice or 1/2 teaspoon of citric acid or four tablespoons of vinegar with 5 percent acidity per quart of tomatoes. For pints, use one tablespoon bottled lemon or lime juice or 1/4 teaspoon citric acid or two tablespoons of vinegar with 5 percent acidity. Add 1 teaspoon of salt per quart to the jars, if desired. Fill jars with raw tomatoes, leaving 1/2 inch headspace. Press tomatoes in the jars until spaces between them fill with juice. Adjust lids and process.
Processing Times and Methods
Boiling Water Bath, Pints or Quarts – 90 minutes
Dial-Gauge Pressure Canner, Pints or Quarts – 25 minutes @ 11 PSI or 40 minutes @ 6 PSI
Weight-Gauge Pressure Canner, Pints of Quarts – 25 minutes @ 15 PSI or 40 minutes @ 10 PSI
Options for Freezing Fresh Raw Tomatoes
1. Slice tomatoes into at least one-half inch slices. Put slices on a cookie sheet and freeze for two hours. Remove slices and put them into freezer bags or containers.
2. Slice tomatoes into at least one-half inch slices. Package in a rigid airtight container and fast freeze.
3. Wash tomatoes. Dip wholes tomatoes in boiling water for 30 seconds to loosen skins. Core and peel. Freeze whole or in pieces. Pack into containers, leaving l-inch headspace. Seal and freeze.
Tomatoes will not be solid when thawed and are best used in cooking. Frozen sliced tomatoes should be eaten in a near-frozen state for fresh taste.