How to Can Tomatoes
1. The firm, ripe tomatoes from your garden are the best ones to use for canning. Make sure that they are completely red and have no soft spots. Before you peel the tomatoes, dip them into boiling water for about half a minute. Next, plunge them into cold water. Cut out the stem ends and peel the tomatoes.
2. Wash your bell jars in the dishwasher and make sure they finish the rinse and dry cycle. Heating the jars right before you use them not only cleans them, but it kills any bacteria. Quarter the peeled tomatoes and bring them to a boil. Pour boiling-hot fruit into clean glass jars, leaving a half-inch clear space at the tops of the containers. If tomatoes are very ripe or bruised, add 1/2 teaspoon citric acid or 2 tablespoons lemon juice per quart. Wipe jars with a damp cloth. Secure lids and tighten metal rings.
3. Put filled jars into canner containing boiling water; add more boiling water if necessary to bring liquid an inch or two over tops of containers. If you do not have this device, then you can use a boiling pot of water on the stove, following the same basic principle of covering the lids with water. Process hot-packed tomatoes for the following times, starting when the water in your canner comes to a rolling boil:
Pints: 35 minutes
Quarts: 45 minutes
4. Boil gently and steadily throughout the period; add boiling water if necessary to keep containers covered. Remove jars immediately when processing time is up. Let cool, and then store in a cool, dark place until you're ready to use them. Store open cans of tomatoes in the refrigerator, and use within one week of opening.