Tips on Canning Tomatoes

SEASONAL CHEF
Finding and using locally produced food

A Word About Jars

For best results use only Mason-type jars designed for canning. Mayonnaise or salad dressing jars have a narrower sealing surface, so the metal canning lids may not fit correctly. Also, these jars are tempered less than Mason jars, and may be weakened by the repeated contact with metal spoons or knives as you use their contents causing the jars to crack or break while you are processing them.

Discard any metal lids that are older than 5 years, the gasket compound may not soften and flow to seal the jar. Metal lids may only be used once. The metal screw bands, of course, can be used indefinitely, as long as they are not bent or rusted. Follow the manufacturer’s directions for preparing the lids for use.

Why Hot Packing Is Best

Hot packing is the method generally preferred for tomatoes. Heating removes air from the tomato’s cells and prevents the tomatoes from floating after they are processed. It also causes the tomatoes to shrink and become more pliable, and thus allows more tomatoes to be packed into each jar.

A Primer on Canning Tomatoes

From the Common Ground Garden Program
of the University of California Cooperative Extension
in Los Angeles County

If you want to preserve your tomato crop, or that flat of tomatoes you bought at the farmers market, you need a kettle or pot large enough to hold several jars and deep enough to allow water to cover the tops of the jars by about 2 inches. The jars must be kept off the bottom of the pot, so use a wire rack or improvise one from jar screw bands or even a folded dish towel. If you purchase a "canning kettle" it will come with a rack.

Before you begin, either wash the jars in your dish machine or by hand using hot soapy water. Since you will be processing your tomatoes for longer than 10 minutes, you don’t need to sanitize (we use to call it "sterilize") the jars. Keep the jars hot.

If you want to "put up" just plain tomatoes, you will need about 3 pounds of tomatoes for each quart. Do not use overripe or soft tomatoes. Wash the tomatoes and, if you wish to peel them, dip them in boiling water for about 30 seconds or until their skins split; then into cold water. The skins will slip off. Remove the core and any bruised or discolored parts. You may leave the tomatoes whole or halve or quarter them. Now, either proceed with the raw tomatoes or cook them.

To pack tomatoes raw:
Fill the canning pot halfway with water and heat to a simmer. To each hot quart jar add 1 teaspoon of salt (optional) and 2 tablespoons bottled lemon juice or 1/2 teaspoon citric acid. For pints use 1 tablespoon lemon juice or 1/4 teaspoon citric acid. Pack the raw tomatoes tightly into the hot jars. Press the tomatoes down after each addition to fill the air spaces. Ladle hot water over the tomatoes. Leave l/2 inch of headspace at the top of the jar. Release any air bubbles by running a rubber spatual (not metal) around the inside of the jar--I use a wooden chopstick. You may need to add some additional hot water. Wipe the top of each jar with a hot damp towel and place the metal lid. Screw on the metal band--do not over-tighten. Put the jars on the rack in the canner, allowing some space in between, and add additional hot water to cover them by about 2 inches. When the water comes to a boil, begin to count the processing time. When the processing time has passed, remove the jars from the canner and allow them to cool, undisturbed, at room temperature. Do not retighten the lids. When cool, check each jar for a tight seal. Remove the screw bands and wash the jars. Do not replace the bands. Label and date the jars and store them in a cool, dark, dry place.

Process raw pack tomatoes: 40 minutes for pints and 45 minutes for quarts.

To pack tomatoes hot:
Add water to cover the tomatoes and boil them gently for five minutes. Add the salt and lemon juice to the jars. Immediately pack the hot tomatoes into the hot jars and cover with the hot tomato liquid left in the pot. Leave1/2 inch headspace. Follow the directions for raw pack tomatoes.

Process hot pack tomatoes: 40 minutes for pints and 45 minutes for quarts.

*This information is provided by the University of California Cooperative Extension, August, 1997. For food safety and food preservation information contact the Extension’s Common Ground Garden Program at 2 Coral Circle, Monterey Park, CA 91755.