Understanding tofu
What it is, what is in it, how long it keeps, and honest answers to the questions people ask before they are willing to cook it again.
What tofu actually is
Soybeans are soaked, ground with water and strained to make soy milk. A coagulant is added, usually a calcium or magnesium salt, and the milk separates into curds and whey in the same way milk does when you make fresh cheese. The curds are pressed into blocks. How hard they are pressed, and for how long, is the entire difference between silken tofu and super-firm tofu.
That is the whole process. Three ingredients in most cases: soybeans, water and a coagulant. It has been made this way for roughly two thousand years, which is worth knowing if you have absorbed the idea that tofu is a modern processed product invented to replace meat.
The firmness scale matters more than any other label on the package, and it is covered in detail in the tofu types guide.
Everything the supermarket does not stock
The six firmness words on an American package describe one narrow product. Yuba, aburaage, atsuage, koyadofu, doufu gan and fermented bean curd are separate ingredients with separate uses, and a great many of the dishes people associate with tofu were built around one of those rather than around a water-packed block.
The nutrition question
Tofu is a complete protein, which means it contains all nine essential amino acids. The amount per serving varies considerably by firmness, because firmness is mostly a measure of how much water was pressed out. Super-firm tofu can carry roughly double the protein per hundred grams of a silken block, simply because there is more tofu and less water in the same weight.
Calcium depends on the coagulant used, which is why two packages with near-identical ingredient lists can differ several-fold on that line. If calcium matters to you, the label is the only reliable guide.
The soy question
This is the question that stops people from eating tofu more often than taste does, and it deserves a careful answer rather than a reassuring one. Soy contains isoflavones, which are plant compounds that can bind weakly to estrogen receptors. That fact is not in dispute. What that means for human health has been studied extensively and the picture is more settled than most internet arguments suggest, though there are real limits to what the research can tell you.
The page below lays out what the evidence supports, where it is mixed, and which claims on both sides go further than the data allows. It is written to be read by someone who is skeptical rather than someone looking for permission.
Soy, hormones and the questions people actually ask →
Nothing on this site is medical advice. If you have a specific health condition, a thyroid diagnosis, a soy allergy, or you are managing a hormone-sensitive illness, that conversation belongs with your doctor rather than with a cooking website.
Storage and shelf life
An unopened block keeps for weeks in the fridge and considerably longer in the freezer. An opened block is a different problem: it needs to be covered in fresh water, that water needs changing, and there is a limit to how long that holds. Knowing when tofu has turned is straightforward once you know what to look for, and it is not subtle.
Freezing deserves a mention here as well, because it is both a storage strategy and a texture technique. A block frozen for convenience comes out of the freezer better than it went in, which is unusual for any food.
If you eat meat
Most tofu writing is aimed at people who have already stopped eating meat, which makes it useless to everyone else. It compares tofu to chicken, loses that comparison, and then argues that you should not mind.
A more useful framing is that tofu is a firm savory protein that carries sauce unusually well, cooks in fifteen minutes, keeps in the fridge unopened for weeks, and costs less than most animal protein. Those are the reasons to keep it in the rotation. None of them require you to give anything up.
A note on how this site handles claims
Cooking advice here comes from repeatable kitchen results and is written as such. Anything touching health is written more cautiously, with the uncertainty stated rather than smoothed over, and with the reader pointed toward the underlying evidence where that is useful.
Where a claim is contested, this site says so instead of picking whichever version makes tofu sound better. That applies to protein content, to soy and hormones, and to the frequent suggestion that tofu is a straightforward substitute for meat, which it is not.
Corrections are welcome and get made. The contact page is the way to send one.