When we’re in the height of tomato season, we process them into mason jars (sauce, whole, and diced) to enjoy them in the off-season. In this post, we share our recipe for our basic canned stewed tomato (sauce).  The steps for canning whole or diced tomatoes are almost exactly the same with the exception of a couple steps.

Tomatoes are high in Vitamins A, C, and K, and the minerals iron, potassium, and copper.  Raw, uncooked tomatoes also contain lycopene, a very powerful antioxidant and the compound that makes the tomato red, but cooking tomatoes actually increases the amount of lycopene in the tomato that is easier to be absorbed by our bodies.

Note:  You will notice in the photo below that we can the entire tomato; pulp, skin, and seeds.  The skin and seeds make up only one-third of the weight of a single tomato but contains half of the antioxidants.

Note:  When we can tomatoes we usually don’t put anything other than kosher salt in them; no spices, herbs, or aromatics.  This is because we never know what cuisine they may be going into and the added flavors may conflict with the other cuisine-specific ingredients in the final dish.  Having said that we do add them if and when we have a specific dish or cuisine in mind.  Our three favorite versions to make are:  Mediterranean (garlic, basil, and oregano, black pepper), Middle Eastern (garlic, cinnamon, star anise, cloves, and black pepper), and Thai (ginger, Thai basil and chilis, kaffir lime leaves, and lemongrass).

Preparation Time:  1 hour (30 minutes to sterilize jars, lids, and rings; 30 minutes to prep tomatoes)

Cooking Time: 30 minutes (15 minutes to cook the Roma tomatoes; 15 minutes to pasteurize)

Yield:  4 lbs of fresh tomatoes will yield about 3 qts of puréed, stewed tomatoes.

Helpful Notes when canning Roma tomatoes…

The average weight of a Roma tomato is between 2 to 4 ounces.

1 lb of fresh Roma tomatoes will yield about 3 cups of puréed, stewed tomatoes.

If you’re canning 1 quart jars have two 1 pint jars handy.  This will enable you to adjust up or down depending on your actual yield.

Ingredients:

• 4 lbs Roma tomatoes, washed, quartered, trimmed
• 1 tbsp kosher salt
• 1/4 cup water

Preparation:

• Wash the tomatoes thoroughly, quarter lengthwise, trim off the tough stem base and discard (see photo above).  Place the quartered and trimmed tomatoes in large, non-reactive (stainless steel) soup or stock pot; set aside.
  • For whole, stewed tomatoes:
    • Wash the tomatoes thoroughly, use a pairing knife to cut out the tough stem base at the top of each tomato.  Place the whole and trimmed tomatoes in large, non-reactive (stainless steel) soup or stock pot; set aside.
  • For diced, stewed tomatoes:
    • Wash the tomatoes thoroughly, quarter lengthwise, trim off the tough stem base and discard (see photo above), slice the quartered tomatoes in half lengthwise, then slice crosswise into 1/2 inch pieces.  Place the diced tomatoes in large, non-reactive (stainless steel) soup or stock pot; set aside.
• Sterilize the jars and lids:
  • To determine how much water to put into a large canning pot:
    • Place the jars in the canning pot, fill the pot with enough water to have at least 1 inch above the top of the jars.
    • Bring to a boil for 1 minute.
    • Using canning tongs, carefully remove the jars and empty the hot water in the jars into the sink; set aside the sterilized jars.
    • Cover the pot and reduce the heat to medium-high heat.

Cooking:

• Place the pot containing the tomatoes (quartered, whole, or diced) on a burner set to medium-high, add the water and salt, cover and bring to a simmer, cook for 15 minutes.
• For puréed tomatoes:
  • Carefully ladle the cooked Roma tomatoes into a high-speed blender and purée until you get a smooth and consistent texture.
  • SAFETY TIP!:  BE CAREFUL!  Hold the top of the blender down when pureeing in a blender!
    • Hot liquids in a blender will react more vigorously when processed (i.e. the top will fly off the blender because of the expanding steam if the top is not held down )
  • You may need to add a little more of the purée if the level goes below 1/4 inch from the top.
  • Pour the puréed, stewed tomatoes into each sterilized jar to fill no higher than 1/4 inch below the top of the jar.  (Give each jar a couple of taps to ensure any trapped air is allowed to escape.)
    • You may need to add a little more of the purée if the level goes below 1/4 inch from the top.
• For whole or diced tomatoes:
  • Carefully ladle the whole (with liquid) or diced stewed tomatoes into each sterilized jar to fill no higher than 1/4 inch below the top of the jar.  (Give each jar a couple of taps to ensure any trapped air is allowed to escape.)
    • You may need to add a little more if the level goes below 1/4 inch from the top.
• Once each jar has been filled wipe the top of each jar with a clean paper towel.
  • This will ensure there aren’t any particles on the rim that would potentially cause a poor seal.
• Place the sterilized lid and ring on top of each jar and hand tighten.
• Raise the temperature of the canning pot to high and return to a boil.
• Using canning tongs, carefully place each jar in the boiling water, cover, and boil for 15 minutes.
• Using canning tongs, carefully remove each jar and place it on a rack to cool.
• Your canned stewed tomatoes are done.
  • Assuming a proper seal, the rings may be removed.  Store in a cool and dark space like a pantry or cupboard.  Use within one year.

Note:  You should hear a little “pop” once the jars have cooled and a vacuum is created inside the jar.  If you look at a canning lid you will notice a small, circular bump in the center of each lid.  If the canning process is successful and you have a good seal, once the pasteurized jars have cooled and created a vacuum inside the jar, that circular bump of the lid will be “sucked” into the jar, so to speak, creating that “popping” sound.  If you don’t hear that sound and the circular bump isn’t flat then you did not get a good seal.  Not a loss but you must refrigerate that jar because of the poor seal and use it within 30 days.

Enjoy!