Tofu

Tofu (Japanese: 豆腐, Hepburn: Tōfu; Korean: 두부; RR: dubu, Chinese: 豆腐; pinyin: dòufu) or bean curd is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness: silken, soft, firm, and extra (or super) firm. It originated in China and has been consumed for over 2,000 years. Tofu is a traditional component of many East Asian and Southeast Asian cuisines; in modern Western cooking, it is often used as a meat substitute.

Nutritionally, tofu is low in calories, while containing a relatively large amount of protein. It is a high and reliable source of iron, and can have a high calcium or magnesium content depending on the coagulants (e.g. calcium chloride, calcium sulfate, magnesium sulfate) used in manufacturing. Cultivation of tofu, as a protein-rich food source, has one of the lowest needs for land use (1.3 m²/ 1000 kcal) and emits some of the lowest amount of greenhouse gas emissions (1.6 kg CO₂/ 100 g protein).

The English word "tofu" comes from Japanese tōfu (豆腐). The Japanese tofu, in turn, is a borrowing of Chinese 豆腐 (Mandarin: dòufǔ; tou4-fu) 'bean curd, bean ferment'.

The earliest documentation of the word in English is in the 1704 translation of Domingo Fernández Navarrete's A Collection of Voyages and Travels, that describes how tofu was made. The word towfu also appears in a 1770 letter from the English merchant James Flint to Benjamin Franklin. The term "bean curd(s)" for tofu has been used in the United States since at least 1840.

Tofu making was first recorded during the Chinese Han dynasty. Chinese legend ascribes its invention to Prince Liu An (179–122 BC) of Anhui province. Tofu and its production technique were introduced to Japan during the Nara period (710–794) but there are no clear records; tofu first appeared on record in 965 AD. Some scholars believe tofu arrived in Vietnam during the 10th and 11th centuries. It spread to other parts of Southeast Asia as well. This probably coincided with the spread of Buddhism as it is an important source of protein in the vegetarian diet of East Asian Buddhism. Li Shizhen, during the Ming dynasty, described a method of making tofu in the Compendium of Materia Medica. Since then, tofu has become a staple in many countries, including Vietnam, Thailand, and Korea, with regional variations in production methods, texture, flavor, and usage.

The most commonly held of the three theories of tofu's origin maintains that tofu was discovered by Liu An (179–122 BC), a Han dynasty prince. While plausible, the paucity of reliable sources for this period makes this difficult to conclusively determine. In Chinese history, important inventions were frequently attributed to important leaders and figures of the time. In 1960, a stone mural unearthed from an Eastern Han dynasty tomb provided support for the theory of the Han origin of tofu; however some scholars maintain that tofu during the Han dynasty was rudimentary and lacked the firmness and taste for it to be considered as tofu.

Another theory suggests that the production method for tofu was discovered accidentally when a slurry of boiled, ground soybeans was mixed with impure sea salt. Such sea salt would probably have contained calcium and magnesium salts, allowing the soy mixture to curdle and produce a tofu-like gel.

The last group of theories maintains that the ancient Chinese learned the method for curdling soy milk by emulating the milk curdling techniques of the Mongolians. The primary evidence for this theory is the etymological similarity between the Chinese term rǔfǔ (乳腐), which literally means "milk curdled", used during Sui dynasty (AD 581–618), for dishes with a consistency like yogurt or soft cheese, later influenced by Mongolian milk products and methods of production, and the term dòufu (豆腐, "beans curdled" ) or tofu. Although intriguing and possible, there is no evidence to substantiate this theory beyond academic speculation.