How long does opened tempeh last in the fridge?

The short version: opened tempeh, wrapped tightly and kept cold, is commonly good for somewhere around three to five days, sometimes closer to a week if it is well sealed and undisturbed. The number matters less here than the method, though, because tempeh breaks the one test most people fall back on for everything else in the fridge — looking for mould — and that is exactly why it gets thrown out too early, or eaten too late.

Why the usual test does not work on tempeh

Tempeh is fermented soybeans held together by a living mould culture, usually Rhizopus, grown on purpose over a day or two until its white threads bind the beans into a firm cake. That white, faintly fuzzy coating is not contamination. It is the product working as intended, and a block with none of it at all is usually the less typical one. This is the opposite of almost every other food people keep in a fridge, where any fuzz at all means stop.

The result is that the one instinct that protects you with bread, cheese or leftovers — "does it look like something is growing on it" — is unusable here, because something is always growing on it, by design. Judging opened tempeh means learning what its normal, expected mould looks like well enough to notice when something else has joined it.

What actually decides how long it keeps once opened

How tightly it is wrapped. An open face exposed to fridge air dries out, hardens and starts picking up moisture from condensation as the fridge cycles — both of which shorten its life. Pressing the wrap directly against the cut surface, or moving the piece into a small sealed container, slows both.

Temperature and placement. The same rule that applies everywhere else in the fridge applies here: a middle shelf toward the back stays colder and more stable than the door, which swings warmer every time it opens.

Whether it has been frozen. Tempeh freezes unusually well for a fresh food, because fermentation has already made it a fairly stable product before it ever reaches your fridge. A block you are not going to use within a few days keeps far longer cut into portions and frozen than left opened in the fridge hoping to get to it.

Cooked versus raw. Tempeh that has gone into a finished dish follows the ordinary cooked-leftovers timeline, not the raw-block one — it is sitting in sauce or oil at that point, and should be judged the way you would judge any other cooked leftover.

How to judge it yourself, in ten seconds

The trick is knowing what tempeh's normal mould looks and smells like, so a departure from it actually registers.

• Smell first. Fresh tempeh smells mild, earthy and a little nutty or mushroom-like — that smell comes from the same fermentation that made the mould. A strong ammonia smell, or anything sharply sour, is the clearest sign to stop.
• Check the colour of the fuzz. Its normal coating is white to grey, sometimes with black or grey speckling as the mould matures further — that speckling alone is not a bad sign. Colour outside that range — green, pink, orange or a fuzz that is noticeably darker or wetter-looking in patches than the rest of the block — is not the tempeh's own culture and is the sign to stop.
• Touch it. Fresh tempeh is firm and dry to the touch. Sliminess, stickiness or a soft, mushy patch is a texture change the mould culture does not normally produce.
• Look at the bean structure. The beans should still be visible and distinct under the white webbing. A block that has gone soft and uniform, with the beans no longer holding their shape, has moved past where the culture is doing something useful.

None of this is a substitute for official food-safety guidance where the two disagree — when in doubt about a specific block, that guidance and your own judgement come first. But knowing that white and grey are the normal palette, and that black speckling on its own is not automatically bad, is the piece of information most people are simply never given, and it is the difference between throwing out a perfectly good block on sight and actually using it.

The thing that actually helps

Because the visual test is unreliable here, the date you opened the package is doing more work than usual — it is the one piece of information that does not depend on reading a mould pattern correctly. Writing that date on the wrapper, or noting it somewhere you will see before you cook, turns "is this still the good kind of fuzzy" into a much smaller question: how many days has it actually been.

This is close to what Munch is built to do without you having to remember it yourself: marking an item opened switches it onto its own countdown from that day rather than the original unopened date, the batch stays tied to where it actually lives in the fridge, and everyone in the household sees the same real age for it — so a block someone else opened on Tuesday still reads as four days old to whoever finds it on Saturday, instead of a silent guess.