How to make tofu (Milking the Soy Bean, Part 2)
In Part 1, I showed you how to make your own pure, unadulterated soy milk. Now let's turn this into tofu（豆腐). Tofu is soy milk that has been coagulated with the addition of a harmless chemical. (Incidentally the kanji characters for tofu literally mean fermented beans, but tofu is not fermented in any way - at least as it's made currently.)
As I've mentioned before, I turn most of the soy milk I make into tofu, because while I like soy milk well enough, I just love good, fresh, creamy tofu. Yes it is bland, but there is beauty in that blandness. I love the beany taste of tofu that totally lacks the rather grassy taste of that is prevalent in soy milk.
A word of warning before you proceed. For some reason, tofu comes out a bit different every time I make it. Sometimes it's rather grainy, sometimes the curds are big and creamy. Sometimes the tofu is sort of hard and small, other times it's moist. Occasionally the tofu simply falls apart. I think this has to do with the beans, the temperature of the soy milk, and so on. I'm still trying to figure out what exactly causes the differences. Whatever the outcome though, homemade tofu is still really delicious, so don't be afraid of giving this a try.
The equipment and ingredients
In addition to the equipment you need for making the soy milk, you will need the following for creating tofu:
1. A coagulant: nigari, magnesium chloride or calcium sulfate (gypsum)
Here's where it starts to get scientific! Nigari a.k.a. bitter salt is the tofu coagulant that is most commonly used in Japan; it's magnesium chloride with other trace minerals. Another coagulant is gypsum or calcium sulfate, which is more commonly used in China. You can get pure magnesium chloride or calcium sulfate from health food stores or pharmacies, and nigari is available from some health food stores or by mail order.
Recently nigari has been touted as a health and weight loss supplement (don't ask me why, or whether the claims made are true). However, I have found that the nigari sold as a health supplement doesn't seem to have the same coagulating potency as the nigari sold specifically for making tofu. So for foolproof tofu, buy nigari from tofu and soy milk making oriented sources.
Nigari is available either in concentrated liquid form, or more commonly in powdered or flaked form. I'll give instructions for making tofu with powdered nigari, which is easy to handle.
2. A box of some kind with drainage holes, or another porous mold
If you want to make square tofu, you will need a square shaped box. I have this rather sleek looking stainless steel model from Japan:
It has holes on all sides and the bottom, and the bottom is raised on two feet so that it can drain free. It also has a solid sheet of stainless steel that fits in the box and acts as a weight. (Update: See where and how to purchase a stainless steel tofu mold very similar to this one at the bottom of this article.)
But previously I have used a plastic Tupperware-type storage box with holes poked through the sides and the bottom with a drill. That worked just as well. For the amount of soy milk in the recipe following, a box that is about 15cm wide x 20cm long x 15 cm deep (6 inches x 8 inches x 6 inches) is ideal. You can also purchase square tofu molds from mailorder sources.
Incidentally, you may see instructions on some sites for making a wooden tofu mold. If you decide to do this, be very careful what kind of wood you use, and what kind of screws. Remember that the mold will be totally soaked, so if you're not careful the screws will turn rusty or the wood will warp - and if it's not dried enough between uses it may even start sprouting the kind of "mold" we don't want. Generally I much prefer easy-to-clean plastic or stainless steel molds.
If you aren't concerned with making your tofu square - for instance if you primarily use your tofu mashed up into other ingredients - you can use any container with drainage holes in it. I've made little round ones in tea strainers for example. A smallish fine-mesh sieve lined with a cotton cloth works very well.
3. Cotton muslin, cheesecloth or other porous fabric
This is to line your mold with. For my square stainless steel mold I have two long, narrow strips of cotton; one is about the width of the narrow end of the rectangle, and the other the width of the wide end. For making tofu in a small sieve, I just use a plain cotton handkerchief.
4. Optional: a thermometer
The ideal temperature of the soy milk for making tofu seems to be around 75°C / 165°F. If you want to have more control over the results, use a food thermometer to measure the temperature.
Momen or Kinugoshi?
You may have seen two types of tofu in stores: momen, or firm, and kinugoshi, or silken. Momen means a type of cotton, and kinu is the word for silk; kinugoshi means "strained through silk". In actuality, the difference between the two types is how much the water is drained from the tofu. Kinugoshi is softer because it has more water in it. However, obtaining that smooth, silky texture is rather difficult at home, so my instructions are for making momen type (firm) tofu.
Let's make tofu
Follow the instructions for making soy milk, but instead of putting the strained milk someplace where it can cool down, put it back into a clean pot on the stove on the lowest heat. It should not boil, but just stay hot. If you are using previously made soy milk, heat it up so that it's hot but not boiling. Use a thermometer if you want to be precise - it should be around 75°C / 165°F.
Once you have strained out all the milk, make your nigari mixture by dissolving 4 teaspoons of powdered nigari in a cup of lukewarm water until the powder is dissolved. (This amount is for the soy milk created from 500g / about 1 lb of dry soy beans, as described in Part 1.) Stirring the warm soy milk, add the nigari liquid in stages, stirring then waiting a bit between additions. As soon as the curd starts to separate from the liquid, stop adding. It should look sort of like this:
The reason you don't want to add all the nigari at once is because it has a slightly bitter taste, so you want to add a little as possible while still achieving a good degree of coagulation. Most of the time though, the entire amount can be added.
Turn off the heat, and put a tight fitting lid on the pot. Leave for at least 15 minutes, then take a look, stirring very gently to see the state of the curds. They should be fairly big and totally separated from the yellowish liquid. If the white particles are still very small and floating all around in the liquid, add the rest of the nigari liquid if you have some left, or make up an additional teaspoonful's worth of powder and water. Stir in, and put the lid back on for an additional 10-15 minutes.
In the meantime, prepare your mold by lining them with clean white cloths that have been moistened with water and then wrung out. Here I have lined my square mold with the two narrow strips of cloth described in the Equipment section.
Look in the tofu pot again. The white curd will have settled on the bottom and all you will see is yellowish liquid. I like to scoop most of this off first. Sink a small sieve into the pot to prevent yourself from scooping up the tofu curds, and ladle out the liquid.
After you've scooped off most of the liquid, you will be left with mostly curd, which looks like this:
Put your mold in the sink or over a container large enough to catch the liquid that will be strained out, and scoop the curds into it. Here I'm pouring the curd into the square mold:
In the photo below I've shown an alternate "mold" you can use, if you don't have a square one. It's a small sieve (the same one I used for scooping out the liquid actually), lined with a large cotton napkin. You'll get a round shaped tofu of course, but it will taste the same as a square one!
Keep filling the mold you may need to wait for some of the liquid to drain out a bit before adding more. Once you fill up the mold, the resulting tofu will be about half the size of the mold once it's been pressed.
Once you've added all the curd, fold the cloth over to cover.
Then, put some kind of weight on top, to help to press out the liquid. My mold had a lid of sorts which has some weight, plus I can press down gently on the handle.
For my improvised round sieve/mold, I've put a bowl filled with some water on top of the cloth-covered tofu. The weight of the bowl will help to press out the water.
Leave the tofu like this for a while, at least 15 minutes or so. You can very gently press down if you like, but generally time and gravity will do its work for you.
Take the lid or weight off and gently poke the tofu. It should feel firm enough to hold together.
Fill a large bowl with water, and put your mold into it, Invert gently so that the tofu falls out.
Carefully peel off the cloth. There's your tofu!
The final step is to de-bitter the tofu. As I've mentioned above nigari has a bitter taste, and you want to wash this out. (The bitterness is very subtle, so try tasting a bit of the drained tofu first. If you don't detect any bitterness you can skip this step.) The easiest way to de-bitter tofu is under running water. Put a sieve (I've used that same trusty little one again) over the bowl holding the tofu, and run a slow stream of tap water over it. The sieve will break up the water enough so that it doesn't cause the tofu to crumble. Leave like this for about 20-30 minutes.
You can see some odd looking scraggly pieces of tofu in the picture. That's what came out of the sieve-mold, because I put most of the curd into my square mold. If I had put all the curd into the sieve I would have gotten a round tofu. The point here is, if you end up with bits and pieces of tofu, don't despair and throw them out - they're still useful!
Finally, it's time to store your tofu. Tofu tastes best a few hours after it's been made. If you make your tofu on a Saturday morning, it will be at peak eating for dinner. Take it out of the water carefully. Here is my gorgeous tofu nestled in an Ikea plastic container.
If you intend to eat the tofu on the same day (and, why wouldn't you want to?) don't put any water in the container. Put on an airtight lid, and store in the refrigerator until ready to eat. If you will keep the tofu for more than a day, put in enough water to cover the tofu. However, home made tofu should not be kept more than a couple of days - remember this is totally preservative-free.
So there you have it: homemade tofu. I've tried to explain every step of the process so it may look complicated, but it really isn't. From start to finish, making tofu requires about 90 minutes, though much of that time is waiting for things to happen. If you're making soy milk on the same day, add another hour. This is a great weekend-morning type of project. You'll get rather wet and messy, so put on a big apron or old clothes and have fun!
Now, what to do with that leftover fiber or okara? Read on...
Update: Where to purchase a stainless steel tofu mold/press similar to the one I have
Just Hungry reader Bharati found a very similar tofu press to the one I have for sale and kindly shared the information. It's made of stainless steel, and according to the description it can make a block of tofu that's the size of about 2 blocks of commercially made tofu at once. The mold comes with a cloth liner and a strainer bag. Here it is on the Rakuten shopping site; and here it is on Amazon Japan.
The Amazon seller does not ship this item overseas, so to purchase it, you will need to have a friend in Japan who can send it to you or sign up with a shipping agent who can receive your packages in Japan for you and then send it along to you for a small fee. A list of overseas shipping agents is on this page. (Correction from previous edit: The Rakuten seller seems to ship overseas - if in doubt ask them first!)
One final note: This page, more than any other on this site, has been plagiarized by several unscrupulous sites. This is the original page, produced by hours and hours of experimentation on my part. Accept no substitutes!