University of Wisconsin - Extension

When those big, plump tomatoes in your garden turn from blushing pink to red, it's time to think about canning this delicious vegetable. Tomatoes can please the palate and the eye at any meal of the day, they provide abundant vitamins, and are low in calories.

Tomatoes are without a doubt the most widely home-canned product in the United States. But to avoid spoilage and risk of food poisoning, be sure to follow a tested recipe, according to Barb Ingham, University of Wisconsin-Madison/Extension food science specialist.

Ingham recommends the following:

Start with the right ingredients. Choose a variety of tomatoes designed for canning. Many people prefer to can 'paste' or 'Roma' tomatoes because they are lower in water content and produce a thicker sauce.

Choose tomatoes that are ripe and free from damage, and growing on healthy vines. Avoid overripe, damaged or decayed tomatoes, or fruits harvested from dead or frost-killed vines. If tomatoes are overripe, or decayed, or if they are growing on dead vines, they can be lower in acid and unsafe for canning.

Add acid to home-canned tomato products. Since many factors can affect the acidity of tomatoes, all tested recipes now require that acid be added to home-canned tomato products. There are two types of acid that can be added to tomatoes to ensure safety of home-canned products:

-- Citric acid. Available in some drugstores or canning supply stores. Use 1/4 teaspoon citric acid per pint, or 1/2 teaspoon per quart.

-- Bottled lemon juice. This is widely available in grocery stores. Use only bottled lemon juice of standardized acidity; do not use freshly squeezed juice. Use 1 Tablespoon per pint, or 2 Tablespoons per quart.

Do not substitute vinegar for lemon juice unless directed in the recipe to do so, otherwise an unsafe product may result. To balance the flavor of the added acid, you may wish to add a small amount of sugar, about 1 teaspoon per quart.

Process tomatoes according to a tested recipe. There are so many ways in which to process your garden tomatoes. From whole tomatoes in juice, to tomato juice or spaghetti sauce, the varieties are almost endless. And many tested recipes will allow you to process tomatoes in either a pressure canner or a boiling water canner. For a tasty treat, try this tested recipe for Canned Crushed Tomatoes.

Use crushed tomatoes with no added liquid for a high-quality product, ideally suited for use in soups, stews, and casseroles. An average of 22 pounds is needed per canner load of 7 quarts; an average of 14 fresh pounds is needed per canner load of 9 pints. A bushel weighs 53 pounds and yields 17 to 20 quarts of crushed tomatoes -- an average of 2-3/4 pounds per quart.

Wash the tomatoes and dip in boiling water for 30 to 60 seconds or until skins split. Then dip in cold water, slip off skins, and remove cores. Trim off any bruised or discolored portions and quarter. Heat one-sixth of the quarters quickly in a large pot, crushing them with a wooden mallet or spoon as they are added to the pot to exude juice. Continue heating the tomatoes, stirring to prevent burning. Once the tomatoes are boiling, gradually add remaining quartered tomatoes, stirring constantly. These remaining tomatoes do not need to be crushed. They will soften with heating and stirring. Continue until all tomatoes are added. Then boil gently for five minutes. Add bottled lemon juice or citric acid to jars (see above). Add one teaspoon of salt per quart to the jars, if desired. Fill jars immediately with hot tomatoes, leaving 1/2-inch headspace. Adjust lids and process.

Boiling Water Canner: Hot pack: pints 35 minutes; quarts 45 minutes. (Add 5 minutes processing time for elevations over 1,000 feet.)

Dial-Gauge Pressure Canner: Hot pack: pints or quarts, 20 minutes at 6 pounds pressure OR 15 minutes at 11 pounds pressure.

Weighted-Gauge Pressure Canner: Hot pack: pints or quarts, 20 minutes at 10 pounds pressure OR 15 minutes at 15 pounds pressure.

UW-Extension has a publication series available on preserving foods from the garden. The Wisconsin Safe Food Preservation Series by Barbara Ingham includes the revised Canning Fruits Safely (B0430), Making Jams, Jellies and Preserves (B2909), Freezing Fruits and Vegetables (B3278), Canning Vegetables Safely (B1159), Canning Salsa Safely (B3570), Tomatoes Tart and Tasty (B2605), Homemade Pickles and Relishes (B2267) and Canning Meat, Wild Game, Poultry and Fish Safely (B3345).

These and other gardening and food preservation publications are available from your county UW-Extension office or from Cooperative Extension Publications (877-947-7827) and online at http://www1.uwex.edu/ces/pubs .

To learn more, see the Complete Guide to Home Canning (1994), USDA Agriculture Bulletin no. 539. It is available on the web at: http://www.uga.edu/nchfp/publications/publications_usda.html .

###

http://www.uwex.edu/ces/news

File: Food safety, Gardening