That last part is the bit worth reading on.
Opened tofu
Water-packed tofu is sold sitting in water, and it wants to stay that way. Drain the packet liquid, put the block in a container, cover it with fresh cold water, and seal it. Change the water every day. It keeps three to four days like that.
Left uncovered in the fridge it dries at the edges and picks up whatever else is in there — tofu is bland and absorbent, which is the whole reason we marinate it, and it works just as well on last night's onions.
Shelf-stable silken tofu in a carton is a different product. It lives in the cupboard until you open it, then behaves like any other opened tofu: fridge, covered, a few days.
Cooked tofu
Three to four days in an airtight container, same as most cooked food.
It does change. Crisped tofu goes soft in the fridge because the crust reabsorbs moisture from the sauce around it — which is why Tofu 'Chicken' with Spinach Sauce is packed with the sauce separate from the tofu across its five meal-prep containers. Reheat crisped tofu in a dry pan rather than a microwave if you want any of the texture back.
How to tell it has gone
Trust your nose first. Fresh tofu smells of almost nothing. Off tofu smells sour or faintly like old milk, and that is the reliable signal.
Then look and touch: a slippery or slimy film on the surface, any darkening or yellowing, or a sour taste. Any of those and it goes in the bin. This is not a "cut off the bad bit" ingredient.
If you are unsure, throw it out. A block of tofu costs less than a bad evening.
Freezing changes it, and that is often the point
Frozen tofu keeps around three months before the quality drops. But freezing does something to tofu that it does not do to most food, and it is worth knowing on purpose rather than discovering by accident.
Tofu is mostly water held in a protein mesh. Freeze it and that water forms ice crystals that push the mesh apart. Thaw it and the water drains out, leaving a structure that is spongier, chewier and far more absorbent than it went in.
Which is why several of our recipes ask for it deliberately. Marry Me Tofu in Creamy Tuscan Sauce freezes overnight, thaws, then tears the block by hand — the ragged edges hold the sauce where a clean-cut cube does not. Tofu Butter Chicken offers freezing as the direct alternative to pressing, because both do the same job of getting the water out. And Greek Tofu Salad freezes or presses before the marinade, because water still in the block is water that is not marinade.
Thaw it in the fridge, then squeeze it gently — a surprising amount of liquid comes out, and that is the space the marinade goes into.
If you want tofu to stay silky rather than chewy, do not freeze it. There is no undoing it.
