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University of Minnesota Extension

Canning crushed tomatoes using a boiling-water canner

Food safety starts with cleaning!

Wash hands for 20 seconds

  • Wet hands under hot running water. Add lots of soap.
  • Rub and wash back of hands, wrists, between fingers and under fingernails for 20 seconds.
  • Rinse well under running water.
  • Dry with paper towels.
  • Use paper to turn off the water faucet.

Clean and sanitize sink and counter tops

  • Wash counter tops and prep sinks with hot soapy water.
  • Fill squirt bottle with 1 quart water. Add 1 teaspoon of unscented regular chlorine bleach or ¾ unscented ultra (6% sodium hypochlorite) chlorine bleach. Or use commercially prepared cleaner and follow directions on label.
  • Spray counter tops and sink with bleach solution. Let air dry.
  • Wash hands.

Clean as you go

  • Wash dishes, utensils, cutting boards, etc. in hot soapy water.
  • Let air dry.

Canning directions

  1. Prepare jars.

    • Inspect jars for chips and cracks.

    • Wash jars in hot soapy water; rinse well.

    • Fill the canner half full with clean, warm water.

    • Center the canner over the burner and preheat the water to 140 degrees F for raw-packed foods and to 180 F for hot-packed foods. Use a food thermometer to monitor temperature.

    • Put jars into canner so they fill with water.

    • Prepare tomatoes while preheating jars.

  2. Wash tomatoes.

    • Tomatoes (disease free and firm).

    • Wash tomatoes well under running water (10 degrees warmer than tomatoes). Scrub gently with a soft clean cloth or clean hands. The number one cause of sour-flat spoilage in tomatoes is related to improperly washed tomatoes. 

    • You will need approximately 3 pounds of tomatoes per quart jar (4 medium round tomatoes = 1 pound).

  3. Blanch, peel, core and prep tomatoes.

    • Bring a pot of water to boil.

    • Put tomatoes in boiling water for 30 to 60 seconds or until skins split.

    • Dip tomatoes in a pot of COLD ice water.

    • Remove skins with knife.

    • Remove cores. Trim off any bruised or discolored portions and quarter.

    • Place in bowl or container.

  4. Heat tomatoes.

    • 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 release juice so no water needs to be added. Continue heating the tomatoes, stirring to prevent burning.

    • Once the tomatoes are boiling, gradually add remaining quartered tomatoes, stirring constantly. These remaining tomatoes don't need to be crushed. They will soften with heating and stirring.

    • Continue until all tomatoes are added. Then boil gently 5 minutes.

  5. Prepare jars.

    • Use jar lifter to remove jars from canner.

    • Add 2 tablespoons bottled lemon juice to each quart jar (1 tablespoon per pint).
      (OR add citric acid: ½ teaspoon per quart; ¼ teaspoon per pint).

    • Add 1 teaspoon canning salt to each quart jar (½ teaspoon per pint). This is optional.

  6. Prepare lids.

    • According to research done by the Jarden Home Brands’ quality assurance team, pre-heating metal canning lids is not necessary.

    • To prep lids, wash with warm, soapy water and keep at room temperature.

  7. Fill jars.

    • Ladle tomatoes into hot jars using a funnel (jar filler).

    • Insert a plastic utensil to remove trapped air bubbles. (Don't use metal as it can scratch the glass increasing risk for breakage.)

    • Re-adjust headspace if needed by adding extra tomatoes.

    • Wipe top of the jar rim with a damp clean paper towel.

    • Apply screw band, finger tight. Do NOT over tighten.

  8. Load the canner.

    • Place filled jars in canner one at a time using a jar lifter. Make sure the jar lifter is securely positioned below the neck of the jar (below the screw band of the lid). Keep the jar upright at all times. Tilting the jar could cause food to spill into the sealing area of the lid.

    • Add more boiling water, if needed, so the water level is at least 1 inch above the jar tops. For process times over 30 minutes, the water level should be 2 inches above the jars.

    • Turn the heat setting to its highest position, cover the canner with its lid and heat until the water boils vigorously.

    • Set timer. Process quarts for 50 minutes and pints for 40 minutes.

    • Lower heat setting if needed. Be sure to maintain a gentle complete boil for the entire process time.

    • Add more boiling water during the process, if needed, to keep the water level 1-2 inches above the jar tops.

    • If the water stops boiling at any time during the process, turn the heat on its highest setting, bring the water back to a vigorous boil, and begin the timing of the process over from the beginning (using the total original process time).

  9. Unload canner.

    • When timer rings, turn off heat and remove cover.

    • Wait 5 minutes before removing jars to prevent ‘spill overs' and ensure good seals.

    • Using a jar lifter, remove the jars one at a time, being careful not to tilt the jars.

    • Place jars directly onto a towel or cake cooling rack, leaving at least 1 inch of space between the jars during cooling.

  10. Cooling and storage.

    • Let the jars sit undisturbed while they cool, from 12 to 24 hours. Don't tighten ring bands on the lids or push down on the center of the flat metal lid until the jar is completely cooled.

    • Remove ring bands from sealed jars. Test seal. Press the center of the lid. It is sealed if there is no clicking sound.

    • Put any unsealed jars in the refrigerator and use first.

    • Wipe jars and lids with a wet cloth.

    • Label with name of contents and date.

    • Store in a cool, dark, dry place for up to 1 year.

Suzanne Driessen, Extension educator

Reviewed in 2021

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