Tofu
Tofu 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 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 providing a rich source of protein. Cultivation of tofu has one of the lowest needs for land use and emits some of the lowest amounts of greenhouse gas emissions per gram of edible protein of any food.
Etymology
The English word "tofu" comes from Japanese tōfu. The Japanese tofu, in turn, is a borrowing of Chinese 豆腐 '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" for tofu has been used in the United States since at least 1840.
History
Tofu making was first recorded during the Chinese Han dynasty. Chinese legend ascribes its invention to Prince Liu An of Anhui province. Tofu and its production technique were introduced to Japan during the Nara period 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.Theories of origin
The most commonly held of the three theories of tofu's origin maintains that tofu was discovered by Liu An, 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, which literally means "milk curdled", used during Sui dynasty, for dishes with a consistency like yogurt or soft cheese, later influenced by Mongolian milk products and methods of production, and the term dòufu or tofu. Although intriguing and possible, there is no evidence to substantiate this theory beyond academic speculation.
East Asia
China
A form of tofu may have been discovered during the Han dynasty, but it did not become a popular food in China until the Song dynasty.In China, tofu was traditionally eaten at the graves of deceased relatives. Ghosts were said to have long since lost their chins and jaws, so only tofu was soft enough for them to eat. Before the advent of refrigeration in China, tofu was usually sold only in the winter because it did not spoil easily in cold weather. In the warmer months, once made, tofu would spoil if left for more than a day.
Japan
Tofu was introduced to Japan by Zen Buddhist monks, who initially called it "Chinese curd". The earliest Japanese document concerning tofu refers to the dish being served as an offering at the Kasuga Shrine in Nara in 1183.The tofu that was introduced from China is thought to have originally been hard tofu such as island tofu from Okinawa, hard tofu from Hakusan City in Ishikawa Prefecture, Gokayama City in Toyama Prefecture, and Iya region in Tokushima Prefecture. Gradually, production methods were devised to produce smooth tofu with a pleasant texture, and modern silken tofu was born. The book Tofu Hyakuchin, published in 1782 of the Edo period, lists 100 recipes for cooking tofu.
Southeast Asia
In Southeast Asia, tofu was introduced to the region by Chinese immigrants from Fujian province, as evidenced by many countries in Southeast Asia referring to tofu using the Min Nan Chinese word for either soft or firm tofu, or tāu-hū or tāu-koaⁿ respectively. In Indonesia, Malaysia, Singapore, Thailand, Cambodia, Myanmar, the Philippines and Vietnam, tofu is widely available and used in many local dishes.Tofu is called tahu in Indonesia, and Indonesian dishes such as tahu sumbat, taugeh tahu, asinan, siomay and some curries, often add slices of tofu. Tahu goreng, tahu isi and tahu sumedang are popular fried tofu snacks.
Tofu is called tauhu in Malaysia and Singapore. Malaysian and Singaporean Indians use tofu in their cuisine, such as in Indian mee goreng, and rojak pasembor. Peranakan cuisine often uses tofu, as in Penang curry noodles and laksa. Indonesia, Thailand, Malaysia, and the Philippines are major producers of tofu and have plants in many municipalities.
Tofu in the Philippines is widely eaten as the breakfast snack tahô, or as tokwa, which is a staple alternative to meat in main meals and in numerous regional dishes. Tofu was introduced to the archipelago in the 10th to 13th centuries by Song dynasty Chinese mariners and merchants, along with many other foods that became staples of the Philippine diet. The use and production of tofu were first limited to urban centers with influential Chinese minorities, such as Cebu or Tondo, but quickly spread to even remote native villages and islands.
Elsewhere
was the first American to mention tofu, in a 1770 letter to John Bartram. Franklin, who encountered it during a trip to London, included a few soybeans and referred to it as "cheese" from China. In 1770, Franklin also corresponded with James Flint on the subject of how the Chinese converted callivances into tofu. Flint's writing "Towfu" in his letter is the earliest documented use of "tofu" in the English language. The first tofu company in the United States was established in 1878. In 1908, Li Yuying, a Chinese anarchist and a vegetarian with a French degree in agriculture and biology, opened a soy factory, the Usine de la Caséo-Sojaïne. This was the world's first soy dairy and the first factory in France to manufacture and sell beancurd.However, tofu was not well known to most Westerners before the middle of the 20th century, when it was popularized in the United States by William Shurtleff and Akiko Aoyagi.
Production
Regardless of the product or scale of the production, the production of tofu essentially consists of:- The preparation of soy milk
- The coagulation of the soy milk to form curds
- The pressing of the soybean curds to form tofu cakes
Coagulation of the protein and oil suspended in boiled soy milk is the most important step in the production of tofu. Salts or acids are commonly used as coagulants. Many variables affect the process, including the variety and percentage of protein in the soybeans used, slurry cooking temperature and coagulation temperature.
Soybean proteins are mainly composed of 7S and 11S proteins. The negative surface charges on these globulins usually cause them to repel each other. Heating soy milk denatures the proteins and exposes hydrophobic groups normally oriented toward the inside of the globulin structure. Cations from coagulants bind the negatively charged groups. As the net charges of the protein molecules are neutralized, attractive hydrophobic interactions dominate over repulsive electrostatic charges, and protein aggregates are formed.
Salt coagulants
is the traditional and most widely used coagulant to produce Chinese-style tofu, it produces a tofu that is tender but slightly brittle in texture. The coagulant itself has very little noticeable taste. Also known as gypsum, calcium sulfate is quarried from geological deposits, and no chemical processing or refining is needed, making it the cheapest coagulant used in tofu production. When used in production, the coagulation reaction is slower due to its low solubility, forming a smooth, more gelatinous tofu with relatively high water content and soft texture. Use of this coagulant also makes tofu that is rich in calcium. As such, many tofu manufacturers choose to use this coagulant to be able to market their tofu as a good source of dietary calcium.Chloride-type nigari salts or lushui may also be used. Magnesium chloride and calcium chloride are highly soluble in water and affect soy protein in the same way, whereas gypsum is only very slightly soluble in water and acts differently in soy protein precipitation, the basis of tofu formation. These are the coagulants used to make tofu with a smooth and tender texture. In Japan, a white powder called nigari, which consists primarily of magnesium chloride, is produced from seawater after the sodium chloride is removed and the water evaporated. Depending on its production method, nigari/lushui may also contain small quantities of magnesium sulfate, potassium chloride, calcium chloride, and trace amounts of other naturally occurring salts. Although the term nigari is derived from nigai, the Japanese word for "bitter", both nigari and pure magnesium chloride impart very little perceivable taste to the finished tofu. Calcium chloride is not found in seawater in significant quantities and therefore is not regarded as nigari. It is used extensively in the United States due to its flavor and low cost. Fresh clean seawater itself can also be used as a coagulant.