How to Can Tomatoes

Guide Note

There is nothing better than feasting on your own home-canned tomatoes in the middle of the winter! Whether you're looking to store the excess of your own prolific crop, or are the beneficiary of a large bushel of farmstand tomatoes, this guide will help you preserve the delicious goodness of your tomatoes.

Table of Contents

Canning Tomatoes Tips

  1. You're able to can any type of tomato.
  2. You can store canned tomatoes for up to one year.
  3. Add lemon juice to the canning jars before adding tomatoes.
  4. Adding lemon juice lets you safely can, as its acidity guarantees safe storage, without any nasty surprises growing in your jars.
  5. Double its usefulness by using your canning pot to cook lobster.

Introduction

Canned Tomatoes. (Creative Commons photo by Benketaro)
Canned Tomatoes. (Creative Commons photo by Benketaro)
  • When canning tomatoes, you need to keep food safety in mind. The USDA has published guidelines to ensure the safe home processing of all foods. The most important document you can read (after this page, of course!) is the USDA Complete Guide to Home Canning, a downloadable PDF file which outlines the basics of safe home canning. There are two methods to use when canning tomatoes—Pressure Canning and the Hot Water Bath Method. This guide will focus on the Hot Water Bath Method, as instructions for using a pressure canner vary by make and model. All of the techniques used to prepare the tomatoes and the jars, however, are the same for both methods.

Ingredients

  1. Tomatoes
    1. Any variety of tomato can be safely canned, including yellow and orange varieties. Some people prefer to use Paste or Italian tomatoes, such as San Marzano or Roma, because the lower moisture content makes them easier to handle when canning.
    2. To can 7 quarts, you'll need about 21 pounds of tomatoes.
    3. Make sure the tomatoes you select are not overripe. Acidity decreases as tomatoes ripen, which makes for sweet eating, but unsafe canning. The tomatoes should still be fairly firm.
    4. Go through the tomatoes, and discard any with bad spots or insect damage.
  2. Lemon Juice
    1. The USDA recommends using bottled lemon juice, which has a standardized acid level for canning.
    2. Do NOT substitute fresh lemon juice, as you can't be sure that the acid level is high enough.
    3. Some canning instructions call for vinegar, instead of lemon juice. Make sure you select a vinegar with an acidity level that's at least 5%.

Equipment Needed

  • Canning does require some special equipment that you probably don't have on hand already.
  1. Several Pots
    1. Canning Pot
    2. Second pot, big enough to hold the jars and lids
    3. Third pot, big enough to hold the tomatoes
    4. Fourth pot, for extra water to refill the canner
  2. Canning Rack, designed to secure the jars while they're being processed in the canning pot.
  3. Jar Lifter, sometimes called "canning tongs," wide tongs designed to safely place jars in and lift them out of the boiling water.
  4. Tongs, to safely handle lids and seals.
  5. 7 Quart Size Canning Jars
  6. Canning Jar Bands, sometimes called rings.
    • These can be reused. Their only purpose is to stabilize the vacuum seal lid, so it stays in place, and is able to properly seal.
  7. Vacuum Seal Lids, which are coated with sealing compounded.
  8. Canning Funnel, used to fill the jars.
  9. Several clean towels to place jars and lids on.
  10. A thin rubber spatula, that you'll use to force air bubbles out of the tomatoes.

TIP: Your canning pot can usually double as a lobster pot, so you can maximize your biggest investment.

Prepare the Jars

  • Safe canning starts with properly preparing the jars and lids.
  1. Examine canning jars, and discard any with nicks, cracks, uneven rims or sharp edges.
  2. Check your canning bands to make sure they fit snugly.
  3. Examine vacuum seal lids to ensure they are free of dents and that the sealing compound is intact.
  4. Wash the jars, bands, and lids, either by hand in hot soapy water, or in a dishwasher, using the sanitizing hot water cycle.
  5. Dry the bands, and set them aside on a clean towel.
  6. Heat jars and lids in a saucepan of simmering (just below boiling) water.
    • You want the water hot, but not boiling, as boiling now could prevent the lids from sealing later.
    • Keep the water on the burner on low while you finish preparing the tomatoes.
    • Allow jars and lids to remain in hot water until ready for use, removing one at a time as needed.

Prepare the Canning Pot

  1. Fill your canning pot with water, but just to the halfway point.
  2. Bring a second pot of water to the boil.
    • You'll use this water to "top off" the canner pot after you've loaded the jars.
  3. Place the canner rack in the canner pot, in the elevated position.
  4. Heat water to simmering.

Prepare the Tomatoes

Blanched Tomatoes. (Creative Commons photo by Benketaro)
Blanched Tomatoes. (Creative Commons photo by Benketaro)
  1. Bring another pot of water to a boil.
  2. Wash tomatoes to get rid of surface dirt.
  3. Blanch the tomatoes:
    1. Remove the stem end of the tomato.
    2. Cut an "x" at the bottom end of each tomato.
    3. Drop the tomatoes, a few at a time, in the boiling water for 60 seconds.
    4. Remove them and place them in cold water to cool off.
  4. Peel and core the tomatoes.
    1. After blanching, the skin should slide off.
    2. The simplest way to core the tomatoes is to hold the tomatoes over a bowl, and squeeze.
      • The seeds will fall into the bowl.
    3. You can also use a more conventional method of coring with a knife, but you risk losing more of the tomato flesh that way.
  5. After each tomato is peeled, and squeezed, place it in the pot big enough to hold all your tomatoes.
  6. When all the tomatoes are in the pot, bring them to a boil.
  7. Boil the tomatoes for 5 minutes before beginning to fill the jars.

Fill the Jars

  1. Remove a canning jar from hot water with the jar lifter.
  2. Set the jar on a towel.
  3. Add 2 tablespoons bottled lemon juice to each jar.
  4. Place the canning funnel on top of the jar.
  5. Spoon tomatoes and their juices into your jar, leaving 1/2 inch headspace between the tomatoes and the top of the jar.
  6. Slide a narrow rubber spatula between the tomatoes and the jar; press on tomatoes to release trapped air bubbles.
    • Repeat the procedure with the spatula two or three times, until you're sure any trapped air has been expelled.
  7. Clean rim and threads of jar with a damp cloth.
  8. Remove a vacuum lid from hot water using tongs.
  9. Place lid on jar, centering sealing compound and resting the lid securely on the jar rim.
  10. Select a band from the towel you have them waiting on.
  11. Screw the band on the jar.
    • Don't overtighten. "Hand tight" is fine.
  12. Repeat until each of your jars is filled.

NOTE: If you have extra tomatoes, don't overfill the jars. Refrigerate or freeze the extra for another use.

Hot Water Bath Processing

  1. As each jar of tomatoes is filled, place it in the canning rack (which should still be in its elevated position in the canning pot).
  2. Adjust heat so that pot remains at a simmer.
  3. After all jars are filled and placed onto the rack, lower rack into canner.
    1. Water must cover the the jars by 1 to 2 inches.
    2. Add boiling water from second pot if needed.
  4. Put lid on canner.
  5. Bring water to a boil.
  6. Process quarts for 45 minutes if you are less than 1,000 feet above sea level.
    • For higher altitudes, contact your local county extension office for instructions.
    • Make sure water stays at a slow boil for the entire 45 minutes.
  7. If the water level drops, top it off with water from the second pot.

Check the Seal

Jars of Tomatoes. (Creative Commons photo by Laura Burns)
Jars of Tomatoes. (Creative Commons photo by Laura Burns)
  1. When processing time is complete, turn off heat and remove canner lid.
  2. Let canner cool 15 minutes before removing jars.
  3. Remove jars from canner, using the jar lifter, and set them upright on a clean dry towel.
  4. Do not retighten bands, as this could disturb the seal.
  5. Let jars cool 12 to 24 hours.
  6. After jars have cooled, check lids for a seal by pressing on the center of each lid.
    1. If the center is pulled down and doesn't move when you push on it, you have a good seal.
    2. If there is not a good seal, you can refrigerate or freeze the tomatoes, or reprocess them if it's been less than 24 hours since the initial attempt.
  7. Label the jars with the date of canning.
  8. Store jars in a cool, dry, dark place and use them within one year.

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