Tofu/ja: Difference between revisions

== History ==

Tofu making was first recorded during the Chinese [[Han dynasty]] in 965 AD. Chinese legend ascribes its invention to Prince [[Liu An]] (179{{ndash}}122{{nbsp}}BC) of [[Anhui]] province. Tofu and its production technique were introduced to [[Japan]] during the [[Nara period]] (710{{ndash}}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 (nutrient)|protein]] in the [[Buddhist cuisine|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 food|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]] (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.

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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 [[Mongols|Mongolians]]. The primary evidence for this theory is the etymological similarity between the Chinese term ''rǔfǔ'' ({{lang|zh|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'' ({{lang|zh|豆腐}}, "beans curdled" ) or tofu. Although intriguing and possible, there is no evidence to substantiate this theory beyond academic speculation.

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===East Asia===

====China====

{{See also|List of Chinese inventions}}

A form of tofu may have been discovered during the [[Han dynasty]] (202&nbsp;BC{{snd}}AD 220), but it did not become a popular food in China until the [[Song dynasty]] (960–1279).

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====Japan====

[[File:TofuSeller1500.jpg|thumb|300px|Illustration of a tofu seller (right) and a ''[[sōmen]]'' seller (left) by [[Tosa Mitsunobu]], from the ''Songs of the Seventy-one Craftsmen'' (七十一番職人歌合 ''Shichijūichi-ban Shokunin [[Uta-awase]]''), a poetry anthology written around 1500]]

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Tofu was introduced to [[Japan]] by Zen Buddhist monks, who initially called it {{Nihongo|"Chinese curd"|唐符|tōfu}}. The earliest Japanese document concerning tofu refers to the dish being served as an offering at the [[Kasuga Shrine]] in [[Nara, Nara|Nara]] in 1183.

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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. A firm variation of tofu was introduced in [[Tosa Province]], today's [[Kōchi Prefecture|Kochi Prefecture]], by Mr. Park, the lord of Akizuki Castle and prisoner of war following the [[Japanese invasions of Korea (1592–1598)]] and he was given a town  and generous protection, and his family and subordinates ran many hard tofu shops and had a monopoly on them.  Gradually, production methods were devised to produce smooth tofu with a pleasant texture, and modern silken tofu was born. The book ''[[Tofu Hyakuchin]]'' ({{lang|ja|豆腐百珍}}), published in 1782 of the [[Edo period]], lists 100 recipes for cooking tofu.

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===Southeast Asia===

In Southeast Asia, tofu was introduced to the region by Chinese immigrants from [[Fujian|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-goaⁿ" respectively. In [[Indonesia]], [[Malaysia]], [[Singapore]], [[Thailand]], [[Cambodia]], [[Myanmar]], the [[Philippine]]s and [[Vietnam]], tofu is widely available and used in many local dishes.

Tofu is called ''tahu'' in Indonesia, and [[Indonesian cuisine|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 ''[[taho|tahô]]'' (soft tofu, from [[Hokkien in the Philippines|Philippine Hokkien]] 豆腐 "tāu-hū"), or as ''tokwa'' (dry, firm tofu that is usually fried, from [[Hokkien in the Philippines|Philippine Hokkien]] 豆干 "tāu-goaⁿ"), 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 City|Cebu]] or [[Kingdom of Tondo|Tondo]], but quickly spread to even remote native villages and islands.

=== Elsewhere ===

[[Benjamin Franklin]] 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 (merchant)|James Flint]] on the subject of how the Chinese converted callivances (soybeans) 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 Shizeng|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]] (''The Book of Tofu'', 1975).

== Production ==

  | header            = Making tofu

  | caption1          = Coagulated soy curds

  | caption2          = Curds in a tofu [[mold (cooking implement)|mold]]

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 ([[douhua]])

# The pressing of the soybean curds to form tofu cakes

It is similar to the production of dairy [[cheese]] by coagulating the milk of dairy animals to form curds and pressing and aging the curds to form cheese. Typical tofu-making procedures are cleaning, soaking, grinding beans in water, filtering, boiling, coagulation, and pressing.

[[wikt:coagulation|Coagulation]] of the protein and oil ([[emulsion]]) suspended in boiled soy milk is the most important step in the production of tofu. This process is accomplished with the aid of coagulants. Coagulation depends on complex interactions. There are many variables including the variety and percentage of protein in the soybeans used, slurry cooking temperature, coagulation temperature, and other factors.

Soybean proteins are mainly composed of 7S and 11S proteins. The negative surface charges on these [[globulin]]s 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 effect|hydrophobic interactions]] dominate over repulsive electrostatic charges, and [[protein aggregates]] are formed.

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=== Salt coagulants ===

  | header            = Tofu tools

  | caption1          = ''Dubu-teul'' ('tofu mold') from [[Korea]]

  | caption2          = ''Dubu-kal'' ('tofu knife') from Korea

* '''[[Calcium sulfate]]''' ([[gypsum]]) ({{lang-zh|links=no|c=石膏|p=shígāo}}) – 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 is tasteless. 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#Nutrition|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''' (Traditional: 鹵水, 滷水; Simplified: 卤水; Pinyin: lǔshuǐ) – [[Magnesium chloride]] and [[calcium chloride]]: Both of these salts 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 [[Sea water|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]] (Epsom salt), [[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", neither ''nigari'' nor pure magnesium chloride imparts a 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.

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=== Acid coagulants ===

* '''[[Glucono delta-lactone]]''' (GDL): A naturally occurring organic acid also used in [[cheesemaking]], this coagulant produces a very fine textured tofu that is almost jelly-like. It is used especially for "silken" and softer tofus and confers a faint sour taste to the finished product. GDL is derived from glucose and takes the form of a white powder at room temperature. Its molecular structure contains a six-membered [[Heterocyclic compound|heterocyclic]] ring that is hydrolyzed upon contact with water, slowly converting GDL to gluconic acid. forming a single, smooth gel that is free of air gaps and that resists breaking during transportation. Using GDL as a coagulant, silken tofu can be formed directly in its container, as it does not require pressing. This acid coagulant is also commonly used together with calcium sulfate to give soft tofu a smooth, tender texture.

* Other edible acids: Though they can affect the taste of the tofu more, and vary in density and texture, acids such as [[acetic acid]] ([[vinegar]]) and [[citric acid]] (such as lemon juice), can also be used to coagulate soy milk and produce tofu.

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=== Enzyme coagulants ===

* Among [[enzymes]] that have been shown to produce tofu are [[papain]], and alkaline and neutral [[protease]]s from microorganisms. Papain, moreover, has been studied as a gelling agent to produce "instant tofu" from soy protein isolate and soy glycinin (11S) protein.

The curds are processed differently depending on the form of tofu that is being manufactured. For soft silken tofu ({{lang|zh|[[wikt:嫩|嫩]][[wikt:豆|豆]][[wikt:腐|腐]]}}; ''nèndòufu'' in Chinese or {{lang|ja|絹漉し豆腐}} ''kinugoshi-dōfu'' in Japanese) or tofu pudding ({{lang|zh|[[wikt:豆|豆]][[wikt:花|花]]}}, ''dòuhuā'' or 豆腐花, ''dòufuhuā'' in Chinese, or {{lang|ja|おぼろ豆腐}} ''Oboro-dōfu'' in Japanese) the soy milk is curdled directly in the tofu's final packaging. For standard firm East Asian tofu, the soy curd is cut and strained of excess liquid using [[cheesecloth]] or [[muslin]] and then lightly pressed to produce a soft cake. Firmer tofus, such as East Asian dry tofu ({{lang|zh|[[wikt:豆|豆]][[wikt:干|干]]}} in Chinese or {{lang|ja|凍み豆腐}} ''Shimi-dōfu'' in Japanese) or Western types of tofu, are further pressed to remove even more liquid. In Vietnam, the curd is strained and molded in a square mold, and the end product is called ''đậu khuôn'' (molded bean) or ''đậu phụ'' (one of the Vietnamese ways to pronounce the Chinese ''dòufu''). The tofu curds are allowed to cool and become firm. The finished tofu can then be cut into pieces, flavored or further processed.