How to Can Tomatoes

In this posting, I'll show you how to can tomatoes using both the hot water bath method and with a pressure canner.  By canning your tomatoes,  you'll be able to enjoy produce from your garden all Winter long.

Two Roads to the Same Destination

The hot water bath and pressure canning method of preserving tomatoes preserve food based on the same preservation principles.  Specifically, the tomatoes are preserved using a combination of heat and acid to kill any bacteria that might cause them to spoil.  The difference between the two methods is really one of equipment and timing.  

From an equipment perspective, the hot water bath method is probably the least fussy since it only requires a large pot and an inexpensive wire rack for the pot that keeps the canning jars from making direct contact with the bottom of the pot.  But canning using hot water bath method takes 40 minutes while using a pressure canner takes only 10.  If you have lots of tomatoes to can, you may want to make the investment in a pressure canner.  For more information about pressure canners, see my post "Preserving Your Harvest By Canning."

Regardless of which method you use, the basic preparation steps are the same.

How To Can Tomatoes (Basic Preparation)

1. Make sure your canning jars are clean and there are no cracks or uneven rims that would prevent them from sealing properly.
2. Wash and rinse the jars and lids in warm soapy water to make they are clean.
3. Place the jars into a stock pot and the lids into a saucepan of simmering water to sanitize them. (Don't boil.  Allow the lids and jars to remain in the simmering water until you are ready to use them)
4. Wash and stem all the tomatoes so they are ready to go.
5. Remove the skin from this batch of tomatoes by blanching --Cut a small "X" into the bottom of each tomato with a sharp knife.  Then drop the tomatoes in boiling water for 1.5 minutes to loosen the skin. Remove the tomatoes from the hot water and cool them to stop the cooking process and make them easier to handle. (Traditionally, blanching is done by placing the tomatoes in an ice water bath but I find that putting them in a colander and running cool tap water over them works just as well.)  Remove the skin.
6. Using your hands, squeeze out some of the juice and seeds from each tomato so that you are left with large chunks.  (I do this over the sink to make clean-up easier)
7. Put the tomato chunks into pint canning jars and add either 2 tablespoons of lemon juice or 1/4 teaspoon of citric acid (you can buy citric acid powder from a canning specialty store or on-line merchant)  The jar should be filled to within 1/2" of the top of the jar.
8. Wipe the lip of the jar with a paper towel so it is free of any tomato juice and cap with a clean lid.
9. Repeat the above procedure until all your tomatoes are in cans and ready to go into the pot or canner.

Using The Pressure Canner

1. Place the jars in your pressure caner and fill so that the water level is about an inch and one-half above the bottom of the canner. (Please note that the amount of water you use for pressure canning is different than that used for the hot water bath method. For pressure canning only a portion of the jar is covered by water)  
2. Place the lid on the canner and clamp down the lid by screwing down the wing nuts that surround the edges of the pot.
3. Turn up your stove to high.  When the water comes to a boil, you'll notice steam coming from the vent on the pressure canner.  Allow the stem to vent for 10 minutes before placing the weight on top of the canner.
4. Cook for 10 minutes at 10 pounds of pressure.  (Note: As the steam vents from the canner it will cause the weight to make a chattering noise.  If the stove is too hot, it will cause the weight to chatter constantly.  If it's too low, the weight won't chatter at all.  The proper stove temperature is one where the weight chatters briefly about once every minute. )
   
5. Cook for 10 minutes.
6. Now turn off the heat and let the canner to cool down.  You can speed the process along by removing the weight from the top of the canner.  However, the minute you do this, steam will shoot out of the vent.  To prevent burning yourself, let the canner cool for at least 5 minutes before attempting to remove the weight and then do so with a pair of kitchen tongs so that your hand is not near the vent opening.
7. Allow the canner to continue to cool.  You want the pressure gauge to return to zero before removing the lid.
8. Open the lid and remove the jars from the canner.  Allow them to continue cooling on a dry towel on your counter.
9. After the jars have cooled completely, test the seal by pressing down on the center of each lid.  If the center of the lid is pulled down and does not flex, the cans are properly sealed.

Using the Hot Water Bath Method

1.  Fill your canning pot with water and bring to a simmer.
2. As each jar is filled, place onto the elevated canning rack.
3. After all the jars are on the rack, lower them into the simmering water.  The water level should be about 1 to two inches above the top of the lids. (Please note that the amount of water you use for the hot water bath method is different than that used for pressure canning. For the hot water bath method the cans should be completely under water)  
4. Cover and bring the water to a rolling boil.  For pint sized jars cook for 40 minutes.  (Because boiling temperatures vary by altitude, you should adjust your processing time based on the below chart.  I've provided altitudes for some major U.S. cities but you can check the altitude of your town by doing a Google search.)
5.  Once your tomatoes are processed, turn off the heat and uncover your pot.  Let the cans sit in the water for 5 minutes before removing jars.
6. Remove the jars from your canning pot and allow them to continue cooling on a dry towel on your counter. After the jars have cooled completely, test the seal by pressing down on the center of each lid.  If the center of the lid is pulled down and does not flex, the cans are properly sealed.

 
Chart: Adjustment times for canning tomatoes using the hot water bath method.

Comments

[Asmarti]

You don't have to post this comment, but I just wanted you to know that Albuquerque is approximately 5400 ft. So increase processing time for 10 minutes not 15 min.

[H. Mark Delman]

Hi Thanks for the comment. I checked and you are probably right. The altitude at the airport is 5400. I dont know the city at all and its probably true that most folks live at that about that elevation. According the Wikipedia the elevation of the city has a large range and some parts would be 10 min and others 15. Thanks for fact checking.

Albuquerque
has one of the highest elevations of any major city in the United States,
though the effects of this are greatly tempered by its southwesterly
continental position. The elevation of the city ranges from4,900feet(1,490m)above
sea level near the Rio Grande (in the Valley) to over6,700feet(1,950m)in
the foothill areas of Sandia Heights and Glenwood Hills. At the airport, the
elevation is5,352feet(1,631m)above sea level.