Tofu

Tofu's origins remain contested, but its mechanism is clear: coagulate soy milk with mineral salts, and the proteins form a soft curd. The process mirrors cheese-making, and some scholars suggest Chinese observers learned the principle from Central Asian herders who curdled animal milk. What is certain is that by the Han Dynasty (206 BCE - 220 CE), soy processing had advanced to the point where bean curd production became possible.

The legend attributes invention to Liu An, Prince of Huainan, around 164 BCE. In his alchemical laboratory, seeking elixirs of immortality, he supposedly combined ground soybeans with nigari—the bittern liquid remaining after sea salt crystallizes. The resulting curd was not eternal life but was nutritious, storable, and economical. Whether Liu An actually made this discovery remains unprovable; the attribution first appears 1,000 years later in Song Dynasty writings.

More plausibly, tofu emerged from incremental improvements in soybean processing. Soaking beans, grinding them, boiling the slurry, and straining out fiber produces soy milk—a process documented earlier than tofu itself. Adding coagulants to soy milk is a small step once you understand that proteins can aggregate. Calcium sulfate (gypsum), magnesium chloride (nigari), or even acidic substances trigger coagulation.

The adjacent possible included both the knowledge and the motivation. Soybeans were a staple crop in northern China. Buddhist dietary restrictions, spreading through China from the 1st century CE, created demand for protein alternatives to meat. Tofu provided complete protein—all essential amino acids—in a form that satisfied religious requirements and stored well.

Geographic factors shaped regional variations. Soft silken tofu dominated southern Chinese cuisine; firmer pressed varieties suited northern cooking styles. Japan received tofu via Buddhist monks around the 8th century CE, developing its own tradition. Korea, Southeast Asia, and eventually global markets each adapted the basic technology to local tastes.

The process itself is forgiving: vary the coagulant, pressing time, or water content and you get different textures. This flexibility allowed tofu to fill multiple culinary niches, from soup to stir-fry to dessert, spreading wherever soybeans grew and protein was needed.