Pressure Canning Tomatoes

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Pressure canning tomatoes is safe and fast if you use a USDA-tested procedure and still add acid to every jar. Per the National Center for Home Food Preservation (NCHFP), crushed tomatoes take 20 minutes at 6 psi in a dial-gauge canner (5 psi in a weighted-gauge canner) at low elevation, or 15 minutes at 11 psi (10 psi weighted). Pints and quarts take the same time.

The acid step is the part people skip. The NCHFP says the pressure options for tomatoes "were not developed for tomatoes without added acid." So bottled lemon juice or citric acid goes into every jar, whether you use a pressure canner or a boiling water bath.

Everything below comes from the NCHFP tomato pages, which are adapted from the USDA Complete Guide to Home Canning (2015). Don't change jar sizes, headspace or ingredients.

Why Tomatoes Need Acid Even in a Pressure Canner

Most fresh vegetables are low-acid, but tomatoes sit on the line. The USDA says some tomatoes have pH values slightly above 4.6, the cutoff for safe boiling water canning. Once acidified, they're acid foods.

The USDA tested both processes on acidified tomatoes. The NCHFP calls the boiling water and pressure options "equal processes with different time/temperature combinations." The pressure option is just a shortcut with the same recipe. It isn't a way to skip the lemon juice.

Acid per jar (NCHFP)

Add the acid straight to the jar before you fill it. The NCHFP says vinegar may cause undesirable flavor changes, and you can add a little sugar to offset the sour taste. Don't leave the acid out.

Pressure Canning Times for Tomatoes (NCHFP)

Several tomato products give you a choice of pressures. Higher pressure means a shorter time. Pick one row and stick to it.

Dial-gauge pressure canner

All times apply to pints or quarts.

Weighted-gauge pressure canner

Yes, the 1-minute row for water-packed tomatoes is real. It's in the USDA guide. As with every row, timing starts only after the canner has vented for 10 minutes and come up to pressure.

The NCHFP tables stop at 8,000 feet for dial gauges. If you live higher, ask your county extension office. Our pressure canning altitude chart explains how the bands work, and the calculator gives your setting.

How Many Tomatoes You Need

From the NCHFP recipe pages:

Use firm, disease-free, ideally vine-ripened tomatoes. The NCHFP warns against canning tomatoes from dead or frost-killed vines.

Step-by-Step: Crushed Tomatoes in a Pressure Canner

Crushed tomatoes are the most useful style for soups, stews and sauces, and the NCHFP calls them "a high-quality product." Here's the tested procedure.

1. Peel. Wash the tomatoes and dip them in boiling water for 30 to 60 seconds, until the skins split. Dip them in cold water, slip off the skins and remove the cores. Trim bruised or discolored spots, then quarter them.
2. Start the crush. Heat about one-sixth of the quarters quickly in a large pot, crushing them with a wooden mallet or spoon as you add them so they release juice.
3. Add the rest. Once that batch boils, gradually add the remaining quarters, stirring constantly. They don't need crushing; they soften as they heat.
4. Boil gently for 5 minutes after all the tomatoes are in.
5. Acidify the jars. Put 1 tablespoon of bottled lemon juice or ¼ teaspoon of citric acid in each pint jar, or double that in each quart.
6. Salt is optional. Add up to 1 teaspoon per quart if you like.
7. Fill the jars right away with hot tomatoes, leaving ½ inch of headspace. Wipe the rims and put on the lids.
8. Load the canner with the rack and 2 to 3 inches of hot water, or the amount your manual specifies. Lock the lid.
9. Vent for 10 minutes with the weight off or the petcock open.
10. Pressurize to the pressure you chose from the tables above.
11. Time it: 20 minutes at the lower pressure or 15 minutes at the higher one. If the pressure drops below your target, bring it back up and restart the full time.
12. Let the canner cool on its own. Remove the weight, wait 10 minutes and open the lid away from you.
13. Cool the jars 1 inch apart for 12 to 24 hours, then check the seals.

New to the canner itself? Our beginner's guide to using a pressure canner walks through venting and cool-down in detail.

Whole or Halved Tomatoes: Three Packs

The NCHFP has three procedures for whole or halved tomatoes. All three start the same way: peel, core, leave whole or halve, and add the acid and optional salt to the jars.

• Packed in water: For a raw pack, fill jars with raw tomatoes and cover with boiling water. For a hot pack, cover the tomatoes with water in a pot, boil gently for 5 minutes, then fill and cover with the cooking liquid. Leave ½ inch of headspace either way. This is the shortest process.
• Packed in tomato juice: Same idea, but the covering liquid is hot tomato juice. The process is longer: 40 minutes at the lower pressure or 25 at the higher one.
• Raw pack without added liquid: Pack raw tomatoes and press them down until the spaces between them fill with juice, leaving ½ inch of headspace. Same times as the juice pack.

The water pack is fastest, but the juice and no-liquid packs give a richer tomato with less water in the jar.

Tomato Juice and Tomato Sauce

Tomato juice: To keep the juice from separating, the NCHFP says to cut about 1 pound of tomatoes at a time into a saucepan and heat it to boiling while crushing. Keep adding and crushing quarters so the mixture boils constantly, then simmer for 5 minutes. Press through a sieve or food mill, reheat to boiling and fill the jars, with the acid already added, leaving ½ inch of headspace.

Standard tomato sauce: Prepare and press the tomatoes as for juice. Simmer in a wide pan until the volume drops by about one-third for thin sauce or one-half for thick sauce. Acidify the jars and fill with ¼ inch of headspace, which is less than the other styles.

This is plain tomato sauce. If you want to add onions, garlic, peppers or meat, that's a different, low-acid product with its own tested recipe. See our guide to canning spaghetti sauce.

Tomato Mixtures That Are Pressure-Canner Only

A few USDA tomato recipes mix in other vegetables or meat and have only pressure canner processes. The NCHFP says tomatoes with okra or zucchini and both spaghetti sauces are low-acid foods that don't need the added lemon juice or citric acid when processed as directed. Mexican tomato sauce already includes vinegar in its ingredient list. Follow each recipe exactly.

These run at the standard low-acid pressures: 11 psi in a dial-gauge canner at 0–2,000 feet (12, 13 and 14 psi in the higher bands), or 10 psi in a weighted-gauge canner at 0–1,000 feet and 15 psi above that. For tomatoes with okra or zucchini, the NCHFP uses about 3 pounds of tomatoes per pound of okra or zucchini, and allows four or five pearl onions or two onion slices per jar.

Pressure Canner or Water Bath?

Both are safe for acidified tomatoes. The NCHFP gives boiling water times too. For crushed tomatoes at 0–1,000 feet, that's 35 minutes for pints and 45 for quarts, and the times climb with elevation.

A pressure canner wins on time at the processing stage, especially for the longer packs. Whole tomatoes in juice take 85 minutes in boiling water at low elevation, against 25 to 40 minutes under pressure. The canner does take longer to heat, vent and cool down. Our comparison of pressure canning vs water bath canning goes through the trade-offs.

Common Mistakes With Canned Tomatoes

• Skipping the acid because you're pressure canning. The pressure options assume added acid. Leave it out and the process isn't tested.
• Using fresh lemons. The NCHFP specifies bottled lemon juice, which has a consistent acidity.
• Adding onions, peppers or herbs to plain tomatoes. That turns them into a mixed, low-acid product. Use a tested recipe such as spaghetti sauce or salsa instead.
• Mixing pressure and time rows. If you choose 6 psi, you need the 20-minute (or 15-minute) time that goes with it, not the shorter one for 11 psi.
• Using 15 psi above 1,000 feet in a weighted canner. The NCHFP marks that option "Not recommended." Use the 10 psi row, which already accounts for elevation.
• Canning from frost-killed vines. The NCHFP rules these out.
• Too much or too little headspace. It's ½ inch for most styles and ¼ inch for sauce.

Storing and Opening Your Tomatoes

Remove the bands after 12 to 24 hours, check that each lid is concave and holds, then label the jars. The USDA says to store them below 95°F (35°C), ideally at 50 to 70°F (10 to 21°C).

Don't taste anything from a jar with a bulging or unsealed lid, spurting liquid, an off smell or mold. The USDA treats suspect low-acid foods, including tomatoes, as if they contain botulinum toxin. Our botulism safety guide explains how to dispose of them.

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