Avoid overripe tomatoes. Freezing is a safe, easy alternative to home canning. Frozen tomatoes and tomato products do not need added acid.
Tomatoes are the most widely home-canned product in the United States.
They also are one of the most commonly spoiled home-canned products. The canning processes recommended in this fact sheet are the result of USDA research on safe home-canning procedures for tomatoes and tomato products. When this happens, the product must be canned in a pressure canner as a low-acid product or acidified to a pH of 4.6 or lower with lemon juice or citric acid. Research has found several conditions that can reduce the acidity of tomatoes. These include decay or damage caused by bruises, cracks, blossom end rot or Insects, and overripening.