How to Can Tomatoes Safely
Can tomatoes safely by adding acid (bottled lemon juice or citric acid) to each jar, as tested recipes require, then processing in a water-bath canner (or pressure canner) for the specified time. Tomatoes are borderline-acid, so acidification is essential.
Tomatoes feel acidic, but they sit right on the borderline that decides safe canning, and modern varieties can fall on the low-acid side. That is why safe tomato canning has one non-negotiable step: adding acid.
Why acidification matters
Safe water-bath canning relies on the food being high-acid enough to prevent botulism. Tomatoes hover near the cutoff, so adding a measured amount of acid guarantees they are in the safe range. Skipping it, or guessing, is exactly the kind of shortcut that makes home canning unsafe.
The process
- Prepare tomatoes per a tested recipe (whole, crushed, juice, sauce).
- Add the specified acid to each jar.
- Fill to headspace, wipe rims, apply lids.
- Process in a water-bath canner (or pressure canner if the recipe gives that option) for the tested time and your altitude.
- Cool and check seals.
Making sauce first? See tomato sauce with a food mill, and the general method in how to water-bath can.
- National Center for Home Food Preservation (NCHFP) — tested home-preservation methods and the USDA Complete Guide to Home Canning
- USDA Food Safety and Inspection Service (FSIS)
- U.S. Food & Drug Administration (FDA) — Food
- FoodSafety.gov
Frequently asked questions
Why do you add lemon juice or citric acid to canned tomatoes?
Tomatoes are borderline in acidity, and modern varieties can be low-acid. Adding a tested amount of bottled lemon juice or citric acid ensures they are acidic enough to can safely.
Can I water-bath can tomatoes?
Yes, once properly acidified, following a tested recipe. Some tomato products may specify a pressure-canning option instead; follow the recipe for your product.
Do I have to acidify even ripe garden tomatoes?
Yes. You cannot judge acidity by taste, and it varies by variety and ripeness. Always add the tested amount of acid regardless of how the tomatoes taste.