Is it Safe to Can “Low Acid” Tomatoes?

This question is asked frequently. It is safe to use tomatoes described as “low acid” in canning. Follow the same procedures as with regular tomatoes. When canning tomatoes, they must be acidified with either bottled lemon juice, citric acid, or vinegar with 5% acidity.

According to Kansas State University Extension Horticulture:

“Flavor in tomatoes is a complicated process. Flavor is regulated by the balance of acid, sweetness (or sugar), and some 37 other compounds found in tomatoes that are known to have a taste or flavor. Slight differences in any of the flavor compounds and differences among the balance of these compounds can make pronounced differences in taste. As the tomato ripens, some of the acidic flavor is replaced so that it becomes milder in flavor.

It has been shown, in several USDA tests, however, that tomato acidity varies very little among tomato varieties. There is some decline in acidity when the tomatoes reach a very complete ripeness‑‑approaching overripe.

In flavor evaluations of tomatoes, we asked 50 people to rate over 20 varieties of tomatoes for flavor (including sweetness and acidity), texture (firmness or softness), as well as visual appearance. We asked them to rate these factors on a 1 to 10 scale. It was interesting to note that there were ranges for all these factors from 2 to 10. What one person reacted to with a low rating, another reacted with a high rating. As we began to look at the results, there was much more variability among the raters than there was among the tomatoes.”

More information can be found at:

• The Influence of Different Tomato Varieties on Acidity as it Relates to Home Canning – Journal of Extension
• Acidifying Tomatoes When Canning – National Center for Home Food Preservation
• Preserving Tomatoes pdf – Kansas State University Extension