Tofu is a white curd made from soy beans. The custom of making tofu originated in ancient China, and throughout Asia it's as important as any meat, commonly enjoyed as its substitute in omnivorous and vegetarian diets. Tofu is packed with protein, so it's a very healthy foodstuff. The bean curd that's made from soy beans is easier to digest for the human body than the beans themselves.
Tofu starts with soaking soy beans in water, then grinding, boiling and filtering. The result is soy milk, which can be enjoyed by itself. To make tofu, the milk is curdled with the addition of calcium sulphate. The curd is then transfered into square forms and pressed to squeeze out the liquid. The process is very much like making cheese.
Fresh tofu comes in three main varieties, which basically are the different moisture levels.
Silken tofu has the most water content. Its texture resembles custard, and it's commonly used in desserts and drinks. Try it as an alternative to dairy in smoothies.
Firm tofu has less water and springs back when pressed because the outside is relatively dry but the interior remains custard-like. Cut firm tofu into cubes and add to soups, rice or pasta dishes. The tofu will inevitably crumble in the latter two preparations, but if the tofu is squeezed by weighting down, it can be treated like extra-firm tofu. To weigh tofu, cut it into cubes, lay on a plate lined with paper towels and place a plate on top. Put a few heavy objects, like cans, on top of the plate and let it sit for 15 to 20 minutes. Repeat this process a couple of times until your tofu is as dry as you like it. Then you are ready to cook.
Extra-firm tofu has the least amount of liquid and has a texture that closely resembles cheese or protein. It's much more rubbery than firm tofu. This tofu can be deep-fried, which makes the texture even more like meat. It stands up to stir-frying better than firm tofu. You can bake, roast or grill it.