Tomatoes are a popular vegetable, especially those grown in our Illinois gardens. As a result, many consumers preserve tomatoes by canning or freezing so they can enjoy the flavor and taste year round.

To freeze tomatoes, the National Center for Home Food Preservation (NCHFP) recommends using firm, ripe tomatoes with deep red color. The next step is to decide if you want to freeze them raw or cooked.

To freeze raw tomatoes, wash with cold water then dip in boiling water for 30 seconds to loosen skins. Core and peel. Freeze as whole tomatoes or in pieces. Pack into freezer containers, leaving 1-inch headspace. Seal, label, and freeze. Use only for cooking or seasoning as tomatoes will not be solid when thawed.

For freezing cooked tomatoes, remove stem ends, peel, and quarter ripe tomatoes. Cover and cook until tender, about 10 to 20 minutes. Place pan containing tomatoes in cold water to cool quickly. Pack into containers, leaving about 1-inch headspace. Seal, label, and freeze.

If canned tomatoes are desired, be sure to follow the most current recommendations from the United States Department of Agriculture (USDA).

In the summer of 1988, USDA made some major changes in the processing times for home-canned tomato products. The major USDA recommendation on all home-canned tomato products is to acidify them prior to processing.

USDA research shows common garden bacteria break down the acid in a jar of tomatoes as the bacteria multiply. This bacteria, Bacillus licheniformis, survives the old processing times. While the bacteria itself is not harmful to us, the bacteria breaks 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. The frightening aspect of botulism is there is no change of color, taste, or odor.

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, the University of Illinois Extension suggests using 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.

Canning salt is recommended in home-canned tomatoes, but may be omitted if desired.

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

Boiling water bath is the recommended canning processing method for tomatoes.

Processing time for raw packed tomatoes is 85 minutes for pints and quarts in a boiling water bath canner. To reduce this time, hot pack the tomatoes before canning. By boiling the tomatoes for 5 minutes before canning, the boiling water bath time is reduced to 35 minutes for pints and 45 minutes for quarts. Note, acidification is still needed.

But, they may be processed in a pressure canner. The processing time for pressure canning is 25 minutes for raw packed pints and quarts at 11 pounds for dial gauges and 10 pounds for weighted gauges. Raw packed pints and quarts may also be processed for 40 minutes at 5 pounds with weighted gauge or 6 pounds pressure with a dial gauge canner.

For more information on freezing or canning tomatoes and tomato products, visit the National Center for Home Food Preservation Web site at: http://www.uga.edu/nchfp.

Jananne Finck, MS, RD, Nutrition and Wellness Educator, University of Illinois Extension Springfield Center.

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