When canning tomatoes safely at home, be sure to use tested canning recipes that add citric acid, vinegar or lemon juice. Tomatoes are a medium-acid food with a pH in the range of 4.5–5.2. You must use a tested canning recipe that has determined the amount of acid to add in order to increase the acidity by lowering the pH to a safe level ...
Read the Is there a decent jar/can tomato sauce without citric acid or spices? discussion from the Chowhound General Discussion, Pasta Sauce food community. Join the discussion today.
Sorting Out Tomato Canning Directions. Elizabeth L. Andress, Ph.D. National Center for Home Food Preservation June 2010. Just as the varieties of tomatoes in the markets keep changing and increasing in number, it is important to remember we have variety in the directions for canning tomatoes.
Most canned tomatoes also have citric acid in them, which is usually GMO corn based…. so know what you are getting with your tomatoes. We use the Bio Nature tomatoes in the glass jar.
Even the best quality canned tomatoes often have citric acid added because the acidity in tomatoes by themselves is not enough for long term storage in a normal canning process. Some low quality brands may add more citric acid than necessary in order to add some flavor, they also add water, sugar and salt to make up for the lack of good tomatoes.
Citric acid is sold under various brand names such as Ball, Mrs Wages, and many, many other brand names. It’s good for those who don’t want the taste of either vinegar or lemon in their canned goods. Citric acid lowers the pH without changing the tomato flavor like lemon juice.”  Ball Citric Acid product description. Accessed March 2015.
An important canning safety tip. Tomatoes can only be preserved in a waterbath canner if there’s added acidity. For recipes like tomato salsa that’s done by adding vinegar (5%). For canning tomato sauce that’s done by adding citric acid.
In the past, tomatoes were considered a high-acid food, which suggested that they could be canned without any supplemental acid. However, we now understand that the acidity of a tomato depends on its variety and its ripeness, which makes it impossible to know for sure if it is high- or low-acid.
So I looked on Amazon for a tomato paste without citric acid and ordered this for her. At first she said the 12 cans were enough for 20 years, but then she tried it and said it tastes much better than the other tomato pastes she's been using. Now she says it won't take long to use them all up; she uses it to make tomato soup, for example.
My dude and I bought a pressure canner with the knowledge we could can low acid foods (green beans) and questionably acidic foods (tomatoes) without the use of additional acid such as lemon juice or citric acid.