How Long Does Tomato Paste Last After Opening?

Why opened tomato paste fades fast

Tomato paste is a concentrated product — most of the water has already been driven off during reduction — so what spoils it after opening isn't moisture, it's air contact. Exposed paste oxidizes at the surface, darkening and picking up a slightly metallic or flat taste well before it becomes unsafe to eat. That's why the useful shelf clock for opened paste is a flavour clock, not strictly a safety one, though a jar left too long can eventually grow visible mould and should be discarded at that point.

Glass jars and tins behave a little differently once opened. A jar can be resealed with its own lid; a tin cannot, so its contents are best transferred to a clean container with a tight lid rather than left in the can, where the exposed metal edge and the paste both degrade faster.

The oil-cap trick for glass jars

Smoothing the top of the paste flat and pouring a thin film of oil over it — a few millimetres is enough — creates a barrier that slows oxidation noticeably, which is why the practice shows up across Mediterranean kitchens for jarred pastes, preserves and pestos alike. It works best in a glass jar with a proper lid rather than a tin, since the jar can go straight back into the fridge sealed. This isn't a substitute for using the paste within about a week; it simply buys a few extra days of good colour and flavour at the edges.

Freezing in portions instead of stretching the fridge window

For any kitchen that doesn't turn over a full jar or tin within a week, freezing beats refrigeration outright — tomato paste freezes cleanly and doesn't separate badly on thawing. The common method is spooning tablespoon-sized portions onto a lined tray, freezing them solid, then bagging the frozen dollops so single portions can be pulled straight into a sauce or braise without defrosting the whole batch first.

This portioning habit matters more in foodservice than it looks: a kitchen using Tomato Paste as a base for shakshuka, stews or a sauce and only needing a spoonful at a time avoids opening — and then wasting — a fresh jar for every small dish. See how kitchens portion tomato paste from large tins for par-level planning across a busy station.

Signs it's gone off — and general dry-goods storage

Watch for a sour or fermented smell, visible mould on the surface, or a colour shift beyond the normal darkening at the edges — any of those means the jar should be discarded rather than skimmed and kept. Short of that, ordinary browning at the surface is a flavour issue, not a safety one, and paste that's simply a bit duller in colour is still fine to cook with once the discoloured layer is removed.

Unopened cases keep well at normal room temperature; our dry storage guidance covers the temperature and humidity range that keeps a pantry of canned and jarred goods, tomato paste included, at its best before a case is even opened.