How long does opened tofu last in the fridge?

The short version: opened tofu, kept submerged in fresh water in a sealed container and refrigerated properly, is commonly good for somewhere around three to five days, and the date printed on the package has very little to do with that number. Tofu is one of the clearer cases of a food sold under two entirely different date systems depending on how it is packaged, and the confusion that causes is exactly why an opened block gets forgotten and wasted more often than it should.

Why tofu's date is confusing before you even open it

Silken tofu often comes in an aseptic carton that sits on an unrefrigerated shelf for months — the packaging is sterilised and sealed the way a carton of stock is, so the printed date really is describing a long, stable, unopened shelf life. Fresh tofu, the kind sold in a tub of water in the refrigerated case, is a different product wearing a similar shape. It was never sterile to begin with, it has been sitting in water since it was made, and the date on it describes a much shorter, refrigerated, unopened window. People generalise from one to the other — "tofu keeps forever, it doesn't even need the fridge" — because they last bought the aseptic carton, and that assumption stops being true the moment the product in front of them is the fridge kind.

Either way, once you cut the seal, both kinds are now a wet, protein-rich, near-neutral food sitting in room-temperature water for the time it takes you to open it, drain it and use some. That is a good environment for bacteria regardless of which date system was printed on the package to begin with, which is why the opened-tofu clock has almost nothing to do with either date and needs to be tracked on its own.

What actually decides how long it keeps once opened

Whether it stays submerged. A block sitting exposed to air in the fridge dries and skins over at the surface, and that dried surface is also where bacteria concentrate. Leftover tofu kept covered in fresh water in a sealed container keeps noticeably longer than the same block wrapped loosely in its original packaging.

Whether the water gets changed. The water a block sits in is not neutral once it has been standing for a day — it is slowly picking up whatever came off the surface of the tofu. Changing it daily, or at least every other day, resets that and is the single habit that buys the most extra time for the least effort.

Temperature and placement. The same rule that applies to milk applies here: the fridge door swings warmer every time it opens, so a tub of tofu kept there ages faster than the same tub kept on a middle shelf toward the back.

Firm versus silken. Firm and extra-firm tofu, with less exposed surface relative to their density and a lower water content, tend to hold up a little longer than silken, which is soft enough that its surface degrades faster and shows sliminess sooner.

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

How to judge it yourself, in ten seconds

Tofu on its own barely smells like anything, which is exactly what makes a change in smell such a reliable signal.

• Smell first. Fresh tofu smells faintly of soybeans and clean water, or close to nothing at all. A sour, sharp or ammonia-like smell means stop — that is not a smell fresh tofu ever has.
• Check the water before the block. Cloudy, milky or stringy water is often the earliest sign, showing up before the tofu itself smells or looks any different. Clear water is a genuinely good sign.
• Touch it. A slimy or sticky film on the surface is one of the most reliable tells for tofu specifically, more so than for most other fridge foods, and it is easy to check with a finger before you even cut into it.
• Look for discolouration. Fresh tofu is an even white or off-white. Yellowing, pink or grey patches, or a surface that looks noticeably different from the inside once you cut it, are signs to stop rather than push through.

One thing worth knowing: freezing changes tofu's texture permanently, turning it spongier and chewier as the water inside forms ice crystals and forces its way out of the structure. That is not a spoilage sign in food you freeze on purpose — it is actually a texture some cooks freeze tofu specifically to get, since it soaks up marinade and sauce far better afterwards. It only becomes a problem if you are trying to judge an already-thawed block by how a fresh one is supposed to look and feel.

The thing that actually helps

An opened tub of tofu gives you almost none of the usual cues. It does not wilt like a vegetable or discolour the way meat does in the first day or two, so by the time it is obviously off, it has usually been off for a while. The single most useful habit is the same low-tech one that works everywhere else in the fridge: the day you open it, write that date on the container, or note it somewhere you will actually see it before you cook. "Opened Tuesday, it's now Sunday" is a decision you can make in a second. A tub with no marking on it is a guess, and guesses about a food with almost no smell of its own tend to go the wrong way.

This is close to what Munch is built to do without you having to remember it: marking an item opened switches it onto its own, separate 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 the tub someone else opened on Tuesday still reads as five days old to whoever finds it on Sunday, instead of being a silent guess for whoever opens the fridge next.