Home Canned Tomato Purée

One of my goals with home canning is creating a few convenience products for the pantry.  I have to tell you I don't can a lot of whole, diced or crushed tomatoes because I can take the tomatoes to the next level before canning.  This means I prefer canning tomato sauces and ready to use tomato products over plain tomatoes if I have to make a choice.  I canned 7 - 750 ml and 6 - L jars of tomato purée.  Tomato purée is thinner than tomato paste but thicker than tomato sauce.  It unseasoned so can be used as a base for tomato based sauces, ketchup, soups and tomato powder.

In their 1994 revision of home canning guidelines, the USDA warns against using some recycled jars (eg. mayonnaise jars) as there may be more breakage especially if processing using a pressure canner.  The reason for this is two fold.  First, the interior of the jar can be scratched from using metal utensils like knives.  Second, manufacturers have gone to a thinner glass for mayonnaise jars.  However, some store bought pasta sauces are packaged in 750 ml Atlas mason jars.  At one time, Atlas did manufacture mason jars specifically for the purpose of home canning.  Of note, the word 'mason' does not refer to the jar itself but rather the design of the threads.  I have about a dozen of the Atlas mason jars recycled from store bought pasta sauces  generously saved for me by family and friends.  They end up being used two or three times a year so have seen a lot of use.

The manufactures made a bit of a change realizing folks were reusing the jars for home canning although I think a more likely explanation was to cut down production costs.  They have gone to a smaller mouth, thinner thread on some of their sauces so the mason rings will not fit even though the jars continue to be embossed with 'Atlas mason'.  If you are buying commercial sauces specifically for the purpose of reusing them for home canning, take a mason jar ring with you.  Avoid any sauce with the thinner lid fitting the thinner rims.  Jars that can be repurposed for home canning will have a lid with a band the same depth as a mason jar ring.

The jars pictured have been in service for about 10 years without a problem.  I've had no more breakage than using regular mason jars which is minimal to begin with.  The risk of any scratches in the jar are minimal because any frugal homemaker would use a spatula not a knife to get the last remains from the jar.  The jars are 750 ml rather than 500 ml or a L which is an off size for home canning jars.  In this case the jars are processed to the next largest size so I processed according to the 1 L size (20 minutes at 10 lb pressure).

I canned the second batch of tomato purée in 1 - L mason jars.  While this is a new product in the pantry, it will be one that graces the shelves from now on.   Something tells me I did not can enough of it!

Tomatoes and tomato products tend to separate during storage due to the release of the enzyme pectase (pectinesterase) that is released when the tomato is cut.  A special process is used to prepare the tomato purée to prevent it from separating. This involves heating a small amount of the purée quickly over high heat then slowly adding in the remainder of the purée in small amounts while continuing to cook.  I started with about 750 ml of the purée.  Once that came to a boil I stirred in about 500 ml of the raw purée.  I continued in this fashion until all the purée had been added and was fully cooked then boiled the purée down a bit to get the right consistency.  The result was a beautiful tomato purée ready for the pantry and doesn't it just look lovely?