An opened tin of whole peeled plum tomatoes in their juice beside a glass jar of smooth red passata and a small bowl of crushed tomatoes on a wooden board, a wooden spoon, a sprig of basil and a halved fresh tomato at the edge

From Tin to Pan: A Cook's Guide to Tomatoes and Passata

October 1, 2026. Opened canned tomatoes moved to glass keep five to seven days in the refrigerator, the USDA FoodKeeper figure for high-acid canned foods. Frozen in a flat bag or an ice-cube tray, they stay safe indefinitely, and the USDA treats freezer times as a matter of quality only.

The ten answers below draw on the USDA, the FDA, the National Center for Home Food Preservation and the protected-origin records, and they run from the unopened tin to the pan. The Tinned Tomatoes and Passata complete guide is the long version.

1. How long do tinned tomatoes last unopened, and does the date matter?

Longer than the date says. Tomatoes are a high-acid canned food, and the USDA figure is that high-acid canned foods keep their best quality for 12 to 18 months, against 2 to 5 years for low-acid foods like meat, fish and most vegetables. The printed date is a best-quality date, not a safety date. An intact, undented, unrusted, unbulging tin stored in a cool, clean, dry place stays safe well past it. Passata in a jar is dated too; read that date the same way.

2. How long do they last once opened, and should they stay in the tin?

Into glass, and used within the week. The USDA FoodKeeper figure for opened high-acid canned foods, tomatoes included, is five to seven days in the refrigerator. The USDA's shelf-stable guidance also says to move opened canned food into glass or plastic for best quality, because food left in an open can may develop a metallic taste. Passata can stay in its jar with the lid on, and the same five-to-seven-day FoodKeeper figure is the closest guide for it.

3. Can I freeze leftover tinned tomatoes or passata?

Yes, and it solves the half-tin problem. The USDA treats freezer times as quality limits only; food kept constantly at 0°F stays safe indefinitely. Use frozen tomatoes while they still taste bright. Freeze in the portion you cook with: a half tin in a small container, passata in an ice-cube tray for the two tablespoons a pan sauce needs, tomato paste in tablespoon dabs on parchment and then bagged. A frozen whole tomato is best crushed into a sauce rather than left whole in a stew.

4. What is the difference between passata, purée, whole tomatoes and paste?

Water content and cooking, mostly. Passata di pomodoro is tomato passed through a sieve; the word comes from the Italian passare, to pass through. Tomato purée in the American sense is made from tomato liquid strained to exclude skins and seeds and then concentrated, and the US standard of identity puts it at 8 percent or more but less than 24 percent tomato soluble solids. Paste is what sits above that line. Canned whole tomatoes are cored, sealed in the container and heat-processed to prevent spoilage, with no cooking down. In the pan, the practical difference is time. As a cook's rule of thumb, whole tomatoes need twenty to thirty minutes and a spoon to break them down, passata makes a sauce in about ten, and paste works as a seasoning, fried briefly in the oil before any liquid goes in.

Form What it is Cooked down before packing Best for
Whole peeled Peeled, cored tomatoes, sealed and heat-processed No Long sauces, stews, shakshuka
Passata Tomatoes passed through a sieve Sieved, not concentrated to a paste; some, such as Masseria Mirogallo's, are blanched and jarred as is Fast sauces, pasta, a cooking base
Purée Strained tomato liquid, concentrated to 8 to under 24 percent solids Yes Body in soups and sauces
Paste Concentrated to 24 percent solids or more Yes, further Depth, fried in oil first

5. How do I know a San Marzano tin is the real thing?

The variety is real, and the label is the thing to read. The San Marzano fruit is long, 60 to 80 millimeters from stem to tip and often two-lobed, with a skin that comes away easily, and it is grown on irrigated plains of volcanic soil. Grown and processed in the Agro Sarnese-Nocerino, an area across parts of the provinces of Salerno, Naples and Avellino, the tinned tomatoes can be labeled Pomodoro San Marzano dell'Agro Sarnese-Nocerino and carry the protected designation of origin wording and logo, a status held since 1996. The name has also turned up outside the protected area: in 2015 Il Fatto Alimentare reported tins sold in the United States, printed in Italian with San Marzano Pomodori Pelati, that held tomatoes grown in the United States, with the origin in small type. The tests are the DOP wording and logo, the full protected name, and peeled tomatoes, the form the protected specification names. A tin of San Marzano-style crushed tomatoes is not the protected product, whatever the name on it.

6. Why is there citric acid, salt or calcium chloride in my tinned tomatoes?

Each one has a job, and only one of them is there to season. Citric acid is acidity control. The line that separates safe canning methods is pH 4.6: foods at or below it can be canned in a boiling-water bath, foods above it need pressure sterilization at 240 to 250 degrees Fahrenheit, about 116 to 121 Celsius, because the spores of Clostridium botulinum are very hard to destroy at boiling temperature. Some tomatoes are now known to sit slightly above that line, so the National Center for Home Food Preservation directs home canners to add a tablespoon of bottled lemon juice or a quarter teaspoon of citric acid to every pint, and says the acid cannot be reduced to taste. The US standard for commercially canned tomatoes likewise permits organic acids for the purpose of acidification, the job citric acid does on a label.

Calcium chloride is a firming agent that keeps whole and diced tomatoes from collapsing in the tin. The US standard for canned tomatoes permits calcium salts for firming, with a higher limit for diced, sliced and wedged styles, and the standard for purée and paste does not list them at all. Firmed diced tomatoes can hold their shape in a sauce, so whole tomatoes crushed by hand suit a smooth one. Salt is the one that seasons, and the label says whether it is there.

7. What does the research say about tinned tomatoes and health?

The research here centers on lycopene, the red pigment in tomatoes. Lycopene is concentrated in tomato paste: the USDA database lists about 28.8 milligrams per 100 grams of canned tomato paste. Research also suggests it is more available to the body from paste than from fresh tomato. In a 1997 study in the American Journal of Clinical Nutrition, volunteers given the same dose of lycopene as tomato paste or as fresh tomatoes, each with oil, showed 2.5 times the peak lycopene concentration and 3.8 times the area under the curve in the chylomicron fraction of their blood after the paste. The FDA reviewed health-claim petitions in 2005 and found no credible evidence that lycopene, as a food ingredient, a component of food or a supplement, reduces the risk of any of the cancers it examined, and the European Food Safety Authority found in 2011 that a cause-and-effect link between lycopene and protection from oxidative damage had not been established. The USDA database lists canned tomatoes with no salt added as their own entry, and a passata or whole tomato with no added salt lets the cook do the seasoning.

8. What about BPA in the can lining?

Cans are lined with a protective coating to keep food off the metal, and BPA, which the FDA says has been used in food packaging since the 1960s, has been one of the materials in those linings. The FDA's stated position is that BPA is safe at the current levels occurring in foods and that the available information continues to support its approved uses in food packaging. The agency's 2012 and 2013 amendments, on baby bottles, sippy cups and infant formula packaging, were based on those uses having been abandoned, not on a safety finding.

Europe went further. In April 2023 the European Food Safety Authority's re-evaluation set a tolerable daily intake for BPA of 0.2 nanograms per kilogram of body weight per day, against a previous temporary level of 4 micrograms, a cut of about 20,000 times. The European Commission then adopted a ban on BPA in food contact materials, the coating on metal cans included, in December 2024, with an 18-month phase-out for most products and very limited exceptions where no alternatives exist.

9. Why does my sauce taste sharp or metallic, and how do I fix it?

Sharpness and a metallic edge are separate problems. For sharpness, salt first. Then, in order: cook it longer, add fat (a spoon of olive oil or butter at the end), add a pinch of sugar only if the fat has not done it, and use a pinch of baking soda only as a last resort. The Fixing a Dish from the Shelf guide walks through the same levers. For a metallic taste in leftovers, the USDA advice from answer two applies: move opened canned food out of the can and into glass or plastic.

10. Can I use passata instead of tinned tomatoes, or fresh instead of either?

Yes to both, measured by weight. As a cook's rule of thumb, passata, crushed and whole tinned tomatoes swap gram for gram, so 400 grams of passata stands in for a 400 gram tin of whole tomatoes, and the sauce comes together faster. Paste is not a substitute for any of them; two tablespoons of paste stirred into 350 grams of water makes a thin purée, and it tastes cooked, because it is. Fresh tomatoes are worth the swap in season: about 500 to 600 grams of ripe plum tomatoes, peeled and seeded, cooks down to the equivalent of one tin. These are kitchen ratios, not regulation, and a sauce forgives a ten percent error either way.

Recipe calls for Use instead Amount Adjust
400 g tin whole tomatoes Crushed tomatoes 400 g Nothing; slightly less cooking time
400 g tin whole tomatoes Passata 400 g Weight for weight; a faster sauce
400 g tin whole tomatoes Fresh plum tomatoes, peeled and seeded 500 to 600 g In season only; cook down 10 minutes longer
400 g passata Whole tomatoes, hand-crushed 400 g tin Cook longer to break them down
2 tbsp tomato paste Passata, reduced 150 g simmered to 2 tbsp Fry in oil once reduced

Four tomatoes to reach for

I Contadini whole peeled tomatoes (shop I Contadini whole peeled tomatoes) come from Puglia, hand-picked, briefly heated, peeled, jarred by hand and pasteurized, and the I Contadini producer guide tells the producer's story. They are the whole tomato for a long sauce, packed in water. The jar holds 19.4 ounces, about 550 grams, so the ratios in answer ten, written for a 400 gram tin, scale up by a little over a third. The Puglia on a Plate guide covers the region they come from.

The same producer's La Rustica passata (shop La Rustica passata), made in Salento from tomatoes processed within a day of picking, is a jar for the ten-minute sauce. Masseria Mirogallo's passata (shop Masseria Mirogallo passata) is made from tomatoes blanched in boiling water and passed through a sieve, and it suits pasta or a cooking base. Gentile's yellow Piennolo tomatoes (shop Gentile yellow Piennolo tomatoes) are the jar for a sauce that should be gold rather than red; the product page describes them as small, sweet tomatoes grown in volcanic soil near Mount Vesuvius.

Any of the four makes a plain sauce, and the pasta shapes guide matches the shape to it. For depth, melt a fillet or two of anchovy into the oil first, a trick the anchovies complete guide covers. The shop is at 263 Josephine Street in Cherry Creek, Denver, and products ship nationwide from theambrosianpantry.com.

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