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Food Safety & Preservation

Latest food safety and preservation information from Cook County Extension

Canning Tomatoes Safely

Posted by Ron Wolford -

Twenty years ago, in the spring of 1988, the U. S. Department of Agriculture (USDA) changed the recommended processing times for home canned tomato products. USDA's purpose was to ensure the safety of home-canned vegetables, according to Jananne Finck, Nutrtion & Wllness Educastor, with University of Illinois Extension.

The major USDA recommendation on all home-canned tomato products was to acidify tomatoes prior to canning. Research shows common garden bacteria breaks down the acid in a jar of tomatoes as the bacteria multiply. This bacterium, Bacillus licheniformis, survives the old processing times. While the bacteria itself are not harmful to us, the bacteria break down the acid within the jar, and botulism spores may begin to grow. It is critical to avoid this growth, as botulism is a deadly form of food poisoning.

Acidification of tomato products is accomplished by adding 2 tablespoons of bottled or frozen lemon juice, or 1/2 teaspoon citric acid, per quart. For pints, add 1 tablespoon of lemon juice, or 1/4 teaspoon citric acid.

Tomatoes can also be acidified with vinegar. Unfortunately, this gives a taste that is objectionable to many. For this reason, Extension suggests using the bottled lemon juice or citric acid, as this is less likely to be tasted. If vinegar is added, a quart requires 4 tablespoons. A pint needs 2 tablespoons. Add the acid directly to the jar to be sure you have enough acid in each jar.

Salt is recommended in home canned tomatoes, but may be omitted if desired.

Tomatoes used in home canning shouldn't be green or over-ripe. Don't use decayed, softened or freeze-damaged fruit either.

Boiling water bath is the recommended processing method for tomatoes, but they may be processed in a pressure canner.

Processing time for raw packed tomatoes is 85 minutes for pints and quarts in a boiling water bath canner. The processing time for pressure canning is 25 minutes for raw packed pints and quarts. Dial gauges must be operated at 11 pounds pressure and weighted gauges at 10 pounds pressure.

Processing time for hot packed crushed tomatoes in a boiling water bath is 35 minutes for pints and 45 minutes for quarts. The processing time for pressure canning is 15 minutes for pints and quarts. Dial gauges must be operated at 11 pounds of pressure and weighted gauges at 10 pounds pressure.

For more information on home canning tomatoes and tomato products contact your local University of Illinois Extension office or visit the National Center for Home Food Preservation website at: www.homefoodpreservation.com.

Source: Jananne Finck, Extension Educator, Nutrition and Wellness, finckj@uiuc.edu



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