How long does opened tomato paste last in the fridge?

The short version: opened tomato paste kept covered in the fridge is generally good for about a week, sometimes a little longer if it was transferred out of the can. That number matters less than the reason most tomato paste never gets the chance to reach it — a can is built for a dish that uses the whole thing, but very few recipes actually call for the whole thing.

The real problem is rarely the paste itself

Tomato paste is sold in a size built for restaurant cooking, not a two-tablespoon addition to a Tuesday sauce. A standard small can holds roughly six tablespoons; most recipes that call for tomato paste at all ask for one or two of them. That leaves a can that is mostly still full, no longer sealed, and with no obvious next use — exactly the shape of ingredient that ends up pushed to the back of a shelf rather than thrown away or used up, because throwing away something you just opened feels wasteful and there is no plan for using the rest.

Can, jar, or tube — the container changes the rules

A metal can was never meant to store food after opening. Once it is open, the exposed metal can react with the paste's acidity and give it a faint tinny taste over a few days, so the standard advice is to spoon the leftover out of the can entirely and into a small glass or plastic container with a tight lid, rather than leaving it in the can with foil over the top. A jar of tomato paste does not have that problem and can simply be resealed. A squeezable tube, common in Europe as double- or triple-concentrated paste, is built differently again — the opening is small, air exposure per use is minimal, and a tube typically keeps considerably longer in the fridge than a can or jar does, closer to several weeks than one.

What actually happens once it is open

Tomato paste is naturally acidic, which slows down a lot of the bacteria that spoil less acidic foods quickly, but acidity is not a preservative on its own, and paste is thick, moist and nutrient-dense enough for mould to take hold on the surface if it sits for too long. Kept cold, tightly sealed, and spooned out with a clean utensil each time rather than a used cooking spoon, a week is a reasonable planning window for a can or jar. Past that point the paste itself may still look fine while the odds of surface mould keep climbing, which is the main reason the freezer suits it better than the fridge for anything you will not use again within a few days.

Freezing is where tomato paste actually does well

Because a recipe only ever needs a spoonful, freezing it in spoonful-sized portions solves the underlying problem rather than just delaying it. Drop tablespoon-sized dollops onto a lined tray, freeze until solid, then transfer the frozen dollops into a bag or container — from that point on, a recipe that needs tomato paste needs one frozen spoonful straight from the freezer, no thawing, no half-used jar taking up fridge space in between. An ice cube tray works the same way if the portions suit your recipes. Frozen this way, tomato paste holds up well for months, which turns a can that would otherwise be used once and forgotten into a spoonful of concentrate on hand for the next several dishes that need one.

What spoilage looks like

• Mould on the surface, often a fuzzy grey, white or greenish patch. Because tomato paste is a paste rather than a solid food, mould can send threads through it that are invisible from the top, so the usual advice with a thick, moist paste is to discard the batch rather than scrape the visible spot off and keep the rest.
• A noticeably darker colour or a dry, cracked skin on top where it has been exposed to air repeatedly — a sign it has dried out and oxidised rather than an immediate safety issue, but a fair reason to use it up rather than keep it going.
• Any fermented, sharply sour or off smell that is not the paste's normal tangy, concentrated tomato scent.
• A can that has bulged or domed at the ends before it was even opened — a sign of gas building up inside a sealed can, and reason to discard it unopened rather than taste it to check.

The thing that actually helps

The habit that closes the gap is the same one that helps with any ingredient a recipe only partly uses: note what is left and where it went, rather than trusting memory to surface it again before it turns. This is close to what Munch's opened-item tracking is for — a can or jar you log keeps its own storage location and its own countdown once marked opened, visible to the rest of the household, so half a can of tomato paste shows up as something to use rather than quietly ages out at the back of a shelf.