What kind of tomatoes are best for canning?
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i usually think of canned tomatoes as being used to preserve sauce or sauce tomatoes, as opposed to trying to preserve a slicing or salad tomatoe. As a result, I like to use nice roma, striped roman,etc for canning. Useful to note, however, that you can more easily freeze tomatoe sauce or cruches tomatoes with very little loss of flavor. It is one of the products where freezing is close to par with canning.
Ripe tomatoes either straight from the garden or farmer's market. I dehydrate tomatoes and store them in a closed container for use all year round. And I can pasta sauce (without meat) for use year round. My favorite recipe for sauce is http://www.animalvegetablemiracle.com/Tomato%20Sauce.pdf Canning tomatoes takes up too much shelf space and too many jars.
Here is some background on why not to buy commercially grown tomatoes - they are raised for shipping, not for taste. http://civileats.com/2011/05/17/why-the-modern-tomato-is-flawed-a-review-of-tomatoland/#more-12058
The best kind are called Roma (although there are many variations on this type). Sometimes they are called "paste" or "plum" tomatoes. They make good canners because they are meaty, as opposed to all juice. They do taste good fresh, however. Because of their structure, they keep their shape better than tomatoes grown strictly for eating. Any kind of tomato can be canned, in the event of a surplus. All that's needed is a bit of salt, unless the tomatoes are very low acid, in which case you may need to add a bit of lemon juice or vinegar. They should be peeled and heated (to bring up the juice) before canning. It's work, but then you have first rate canned tomatoes to use all year. If you don't raise them yourself, a good farm market should have "canning tomatoes" by the bushel.