Safe Preserving: Lots of Tomatoes to Can!

I have a bounty of garden tomatoes to can.  How do I know whether to pressure can them or can them in a boiling water canner?

canned tomatoes

There are lots of great things to be said for home-canned tomatoes: the flavor can’t be beat, canned tomatoes are a versatile pantry item, working well in so many family-favorite dishes, and even the canning process offers lots of options.  Safe, research-tested home-canned tomato recipes offer options for processing in either a boiling water canner or a pressure canner (dial or weighted gauge).  So how do you know which process to choose?

Consider the type of canner you have and the amount of time you are able to spend.  Most any deep pot that is fitted with a rack in the bottom and a tight-fitting lid can be used as a boiling water canner.  The pot must be deep enough so that when the canning jars are placed in the canner, water covers the jars by 1 to 2 inches.  Safe recommendations now allow for using an atmospheric steam canner in place of a boiling water canner.  Contact your local Winnebago County Extension office at (920) 232-1973 for more information.

pressure canner may be of one of two types, a dial gauge or a weighted gauge.  A pressure canner operates at temperatures above the boiling point of water, generally 240°F to 250°F, so processing times can be significantly shorter – although you must still allow for time to vent the canner (10 minutes) and for the canner to cool down (de-pressurize), all of which adds to the time allocated for pressure canning.

Let’s look at an example of choices that you have.

Tomatoes – Whole or Halves, Raw Pack without Added Liquid
Boiling water canner 0-1,000 feet elevation
 Pints or quarts 85 minutes*
Dial gauge canner 0-2,000 feet elevation
Pints 40 minutes at 6 lbs.
Pints or quarts** 25 minutes at 11 lbs.
Weighted gauge canner 0-1,000 feet elevation
Pints 40 minutes at 5 lbs.
Pints or quarts** 25 minutes at 10 lbs.

*ADD 5 minutes for elevations over 1,000 feet.  Check elevation using the online application.

**Safe modification from published recipe.  Pressure canners are most commonly operated at 11 lbs (psi) for a dial gauge, or 10-15 lbs (psi) for a weighted gauge.  Processing pints at the higher pressure used for quarts is perfectly safe, and often easier to do.

Even if you add in the additional time needed to process tomatoes in a pressure canner: venting (10 minutes), pressurizing the canner (~5  minutes), and cooling (~30 minutes), the total time required may be less in a pressure canner than a boiling water canner.  The choice of canning method is up to you.  Just be sure to choose a research-tested and up-to-date recipe, which includes adding acid to tomato products.

Safe methods of preserving tomatoes do not include open kettle canning (putting hot tomatoes in a jar and sealing – no heat processing), oven canning, or dish washer canning.  Remember to always follow a research-tested and up to date recipe in order to safely preserve the bounty of your garden.

Safe preserving!

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