Susan Hansen, Extension Educator Colfax County
Tomato Canning Basics
Tomatoes are one of the most popular foods to preserve through canning, drying or freezing.
Select disease free and preferably vine ripened tomatoes for optimum quality in a preserved product.
For nine pints of canned tomato products, you need 13-14 pounds of tomatoes. Approximately 23 pounds of tomatoes are needed for seven quarts of canned product.
Most tomatoes are considered acidic; however, some are not. Remember that a food needs to be higher in acid content in order to be canned by the boiling water bath method. To increase the acidity to a safe level, add 1 tablespoon of bottled lemon juice to each pint of tomatoes. For quarts, add 2 tablespoons of bottled lemon juice.
Is it okay to can tomatoes without salt? The answer is yes. The salt is used for flavor, not preserving, in tomato products.
Tomatoes are often canned in combination with many foods. If low-acid foods such as vegetables or meat are added, the product must be processed in a pressure canner.
Water boils at 212 degrees F at sea level. As the elevation increases, water boils at lower temperatures and foods take longer to cook. To ensure safely canned foods at altitudes above sea level, the processing time for boiling water bath canning methods needs to be lengthened. Be sure to check the current recommendations.
It is important to use a USDA tested and approved recipe for canning. Canning recommendations have changed over the years, based on new research. If you have a canning recipe that you are not sure whether it is safe or not, contact the extension office to see if it matches USDA recommendations.
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