I spent a couple of hours researching the manufacture of tofu. I like bullets, so here’s the process. Some endnotes are given for those interested.
- Start with dried soybeans
- Soak for many, many hours
- Grind beans into a paste
- Boil the paste with water
- Strain out the liquid, discarding the solids (okara) (1)
- Heat the liquid and add a coagulant (commonly, calcium chloride) (2)
- Strain out the solids, or curds, and discard the liquids (3)
- Put the solids into a mold
- Press the solids until a solid, yet soft, block has been formed
Here’s a great little YouTube video on the process:
(1) Okara is mostly fiber and some protein. It is used in Japanese, Korean, and Chinese cuisine, but mainly for animal consumption.
(2) Calcium chloride adds a significant amount of calcium to tofu, making it a source of calcium comparable to milk. Tofu seems to be not quite as good a source for calcium as milk, but close – about 70% by volume. Manufacturing techniques vary and could raise or decrease that figure. Not all tofu is made with calcium chloride.
(3) These soy curds are rich in protein, with some fat and carbohydrate. Since this is what tofu is made of, tofu is mainly water (84% by weight), protein, fat, and carbohydrate.