Tofu

Tofu or bean curd is a food made by coagulating soy milk and then pressing the resulting curds into soft white blocks. It is of Chinese origin, and it is also a part of East Asian and Southeast Asian cuisine such as Chinese, Japanese, Korean, Indonesian, Vietnamese, and others. There are many different varieties of tofu, including fresh tofu and tofu that has been processed in some way. Tofu has very little flavor or smell on its own, so it can be used either in savory or sweet dishes, and it is often seasoned or marinated to suit the dish.

Tofu is thought to have originated in ancient China, during the Nara period. It also spread into other parts of East Asia as well. This spread likely coincided with the spread of Buddhism because it is an important source of protein in the vegetarian diet of East Asian Buddhism. Li Shizhen in the Ming Dynasty described a method of making tofu in Bencao Gangmu.

Tofu contains a low amount of calories, relatively large amount of iron, and little fat. Depending on the coagulant used in manufacturing, the tofu may also be high in calcium and/or magnesium.

Etymology

The English word "tofu" comes from the Japanese tōfu (), which itself derives from the Chinese ( or ) from "bean" () plus "curdled" or "fermented" ().

The English term "bean curd(s)" for tofu has been used since at least 1840.

Production

Tofu is made by coagulating soy milk and pressing the resulting curds. Although pre-made soy milk may be used, most tofu producers begin by making their own soy milk, which is produced by soaking, grinding, boiling and straining dried (or, less commonly, fresh) soybeans.

Coagulation of the protein and oil (emulsion) suspended in the boiled soy milk is the most important step in the production of tofu. This process is accomplished with the aid of coagulants. Two types of coagulants (salts and acids) are used commercially. The third type of coagulant, enzymes, is not yet used commercially but shows potential for producing both firm and "silken" tofu.

Salt coagulants

Calcium sulfate (gypsum): 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 no perceivable taste. Use of this coagulant also makes a 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 ( Traditional: 鹵水, 滷水; Simplified: 卤水) - Magnesium chloride and calcium chloride: Both of these salts have a high solubility rate 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 for 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 (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 a common coagulant for tofu in North America. Fresh clean sea water itself can also be used as a coagulant.

Acid coagulants

Glucono delta-lactone (GDL): A naturally occurring organic acid also used in cheese making, which produces a very fine textured tofu that is almost jelly-like. This coagulant is used especially for "silken" and softer tofus, and confers an almost imperceptible sour taste to the finished product. 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 efficacy 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.

Enzyme coagulants

Among enzymes that have been shown to produce tofu are papain, and alkaline and neutral proteases from microorganisms. In the case of papain, the enzyme to substrate ratio, by weight, was held constant at 1:400. An aliquot of 1% crude papain was added to "uncooked" soy milk at room temperature and heated to 90–100 °C. Its texture can be described as similar to that of very fine custard. In Japan and Korea, traditional soft tofu is made with seawater.

Douhua (, dòu huā or , dòufu huā in Chinese), or tofu brain ( or , dòufu naǒ in Chinese), often eaten as a dessert, but sometimes with salty pickles or hot sauce added instead, is another type of soft tofu with an even higher moisture content. Because it is nearly impossible to pick up this type of tofu with chopsticks, it is generally eaten with a spoon. With the addition of flavorings such as finely chopped spring onions, dried shrimp, soy sauce, chilli sauce, douhua is a popular breakfast dish across China. In Malaysia, douhua is usually served warm with white or dark (palm) sugar syrup, or served cold with longans.

Some variation exists among soft tofus. Black douhua () is a type of silken tofu made from plain black beans and soybeans, which is usually made into dòuhuā () rather than firm or dry tofu. The texture of black bean tofu is slightly more gelatinous than regular douhua and the color is greyish in tone. This type of tofu is eaten for the earthy "black bean taste." Edamame tofu is a Japanese variety of kinugoshi tōfu made from edamame (fresh green soybeans); it is pale green in color and often studded with whole edamame.

Firm tofu

Firm tofu (called lǎo dòufu in Chinese; , momendōfu in Japanese, lit. "cotton tofu"): Although drained and pressed, this form of fresh tofu still contains a great amount of moisture. It has the firmness of raw meat but bounces back readily when pressed. The texture of the inside of the tofu is similar to that of a firm custard. The skin of this form of tofu has the pattern of the muslin used to drain it and is slightly more resilient to damage than its inside. It can be picked up easily with chopsticks.

Some places in Japan, a very firm type of momendofu is eaten, called ishi-douhu{石豆腐 (literally stone tofu)} in a part of Ishikawa, or iwa-douhu{岩豆腐 (literally rock-tofu)} in Gokayama, Toyama and Iya, Tokushima. Some of these tofu are able to be tied by rope for carrying, because of their firmness. These types of firm tofu are produced by using seawater instead of nigari (magnesium chloride), or using concentrated soy milk. Some of them are squeezed of excess moisture using heavy weights. These products are produced in areas where the travel is inconvenient, such as remote islands, mountain villages, heavy snowfall areas, and so on.

Chinese "dry tofu"

Dòu gān (, literally "dry tofu" in Chinese) has not, despite its name, actually been dried but is rather an extra firm variety of tofu with a large amount of liquid pressed out of it. Dòu gān contains the least amount of moisture of all fresh tofu and has the firmness of fully cooked meat and a somewhat rubbery feel similar to that of paneer. When sliced thinly, this tofu can be crumbled easily. The skin of this form of tofu has the pattern of the muslin used to drain and press it. Western firm tofu is milled and reformed after the pressing and sometimes lacks the skin with its cloth patterning. One variety of dried tofu is pressed especially flat and sliced into long strings with a cross section smaller than 2 mm × 2 mm. Shredded dried tofu (, dòu gān sī in Chinese, or simply , gān sī), which looks like loose cooked noodles, can be served cold, stir-fried, or similar in style to Japanese aburaage.

Processed tofu

Many forms of processed tofus exist, due to the varied ways in which fresh tofu can be used. Some of these techniques likely originate from the need to preserve tofu before the days of refrigeration, or to increase its shelf life and longevity. Other production techniques are employed to create tofus with unique textures and flavors.

Fermented

Pickled tofu ( in Chinese, pinyin: dòufu rǔ, lit. "tofu dairy," or ; chao in Vietnamese): Also called "preserved tofu" or "fermented tofu," this food consists of cubes of dried tofu that have been allowed to fully air-dry under hay and slowly ferment from aerial bacteria. And in Japan, pickled tofu with miso paste is called 'tofu no misodzuke', which is a traditional preserved food in Kumamoto. In Okinawa, there is a pickled and fermented tofu called tofuyo. It is made from 'Shima-doufu' (an Okinawan variety of large & firm tofu).It is fermented, and matured with koji mold, red koji mold, and awamori. Stinky tofu ( in Chinese, Pinyin: chòu dòufu): A soft tofu that has been fermented in a unique vegetable and fish brine.

Fried

With the exception of the softest tofus, all forms of tofu can be fried. Thin and soft varieties of tofu are deep fried in oil until they are light and airy in their core ( dòupào, 豆腐泡 doufupao, 油豆腐 youdoufu, or doubu in Chinese, literally "bean bubble," describing the shape of the fried tofu as a bubble).

Tofus such as firm Asian and dòu gān (Chinese dry tofu), with their lower moisture content, are cut into bite-sized cubes or triangles and deep fried until they develop a golden-brown, crispy surface ( in Chinese, zhà dòufu, lit. "fried tofu"). These may be eaten on their own or with a light sauce, or further cooked in liquids; they are also added to hot pot dishes or included as part of the vegetarian dish called luohan zhai.

Aburaage (油揚げ): Japanese thin fried tofu for Inari-sushi.

Atsuage (厚揚げ): The thicker variety of fried tofu. It is also called namaage (生揚げ).

Frozen

Thousand layer tofu ( in Chinese, literally "thousand layer tofu" or "frozen tofu"): By freezing tofu, the large ice crystals that develop within the tofu result in the formation of large cavities that appear to be layered. The frozen tofu takes on a yellowish hue in the freezing process. Thousand layer tofu is commonly made at home from Asian soft tofu though it is also commercially sold as a specialty in parts of Taiwan. This tofu is defrosted, and sometimes pressed to remove moisture, prior to use. Koyadofu (kōyadōfu, in Japanese): The name comes from Mount Koya, a center of Japanese Buddhism famed for its shōjin ryōri, or traditional Buddhist vegetarian cuisine. It is sold in freeze-dried blocks or cubes in Japanese markets. It must be soaked in water before eating, and is typically simmered in dashi, sake or mirin and soy sauce. In shōjin ryōri, vegetarian kombu dashi, made from seaweed, is used. When prepared in the usual manner, it has a spongy texture and mild sweet and savory flavor. A similar form of freeze-dried tofu, in smaller pieces, is found in instant soups (such as miso soup), in which the toppings are freeze-dried and stored in sealed pouches. Tofu is also a main dish, especially this type which is commonly used and is in high demand in eastern Asia.

Byproducts of tofu production

Tofu production creates some edible byproducts. Food products are made from the protein-oil film, or "skin," which forms over the surface of boiling soy milk in an open shallow pan. The leftover solids from pressing soy milk are called okara.

Tofu skin

Tofu skin is produced through the boiling of soy milk, in an open shallow pan, thus producing a film or skin composed primarily of a soy protein-lipid complex on the liquid surface. The films are collected and dried into yellowish sheets known as soy milk skin (, fǔ pí in Chinese; , yuba in Japanese). Its approximate composition is : 50–55% protein, 24–26% lipids (fat), 12% carbohydrate, 3% ash, and 9% moisture.

The skin can also be bunched up to stick form and dried into something known as "tofu bamboo" (, fǔ zhú in Chinese; phù trúc in Vietnamese; kusatake, Japanese), or myriad other forms. Since tofu skin has a soft yet rubbery texture, it is folded or shaped into different forms and cooked further to imitate meat in vegan cuisine.

Some factories dedicate production to tofu skin and other soy membrane products.

Okara

(, xuě huā caì, lit. "snowflake vegetable"; , dòufu zhā, lit. "tofu sediment/residue"; kongbiji, 콩비지 in Korean), sometimes known in the west as "soy pulp" or "tofu lees", is the fibre, protein, and starch left over when soy milk has been extracted from ground soaked soybeans. Although it is mainly used as animal feed in most tofu producing cultures, it is sometimes used in Japanese and Korean cuisines. It is also an ingredient for vegetarian burgers produced in many western nations.

Non-tofu "tofus"

Due to their Asian origins and their textures, many food items are called "tofu" even though their production processes are not technically similar. For instance, many sweet almond tofus are actually gelatinous desserts made from agar or gelatin and whitened with milk or coconut milk more similar to Japanese anmitsu. As well, some foods such as Burmese tofu are not coagulated from the "milk" of the legume but rather set in a manner similar to soft polenta, Korean muk, or the jidou liangfen of Yunnan province of Southwest China.

Burmese tofu

Burmese tofu (to hpu in Burmese) is a type of legume product made from besan (chana dal) flour the Shan variety uses yellow split pea flour instead. Both types are yellow in color and generally found only in Myanmar, though the Burman variety is also available in some overseas restaurants serving Burmese cuisine.

Burmese tofu may be fried as fritters cut in rectangular or triangular shapes. Rice tofu, called hsan to hpu (or hsan ta hpo in Shan regions) is made from rice flour (called hsan hmont or mont hmont) and is white in color, with the same consistency as yellow Burmese tofu when set. It is eaten as a salad in the same manner as yellow tofu.

Preparation

Tofu has very little flavor or smell on its own. Consequently tofu can be prepared either in savory or sweet dishes, acting as a bland background for presenting the flavors of the other ingredients used. As a method of flavoring it is often marinated in soy sauce, chilis, sesame oil, etc.

Eastern methods

In Asian cooking, tofu is eaten in myriad ways, including raw, stewed, stir-fried, in soup, cooked in sauce, or stuffed with fillings. The idea of using tofu as a meat substitute is not common in East Asia. Many Chinese tofu dishes such as jiā cháng dòu fǔ (家常豆腐)and má pó dòu fú (麻婆豆腐) include meat.

Lightly flavored

In Japan, a common lunch in the summer months is hiyayakko (), silken or firm Asian tofu served with freshly grated ginger, green onions, and/or katsuobushi shavings with soy sauce. In the winter, tofu is frequently eaten as yudofu, which is simmered in a claypot with some vegetables(ex:chinese cabbage, green onion etc.) using konbudashi.

, Hong Kong.]] In Chinese cuisine, Dòuhuā () is served with toppings like boiled peanuts, azuki beans, cooked oatmeal, tapioca, mung beans and a syrup flavored with ginger or almond. During the summer, dòuhuā is served with crushed ice; in the winter, it is served warm. And also,many parts of China, fresh tofu is similarly eaten with soy sauce or further flavored with katsuobushi shavings, century eggs (), and sesame seed oil.

In Korean cuisine, dubu gui () consists of pan fried cubes of firm tofu, seasoned with soy sauce, garlic, and other ingredients. Cubes of cold, uncooked firm tofu seasoned with soy sauce, scallions, and ginger, prepared in a manner similar to the Japanese hiyayakko, are also enjoyed. The popular bar food, or anju (), called dubu kimchi (), features boiled, firm tofu served in rectangular slices around the edges of a plate with pan fried, sautéed or freshly mixed kimchi () in the middle.

In the Philippines, the sweet delicacy taho is made of fresh tofu with brown sugar syrup and sago. The Malaysian version of taho or douhua is called tofufa. Warm soft tofu is served in 'slices' (due to being scooped using a flat spoon from a wooden bucket) in a bowl with either pandan-flavored sugar syrup or palm sugar syrup.

In Vietnam, dòuhuā is pronounced đậu hủ. This variety of soft tofu is made and carried around in an earthenware jar. It is served by being scooped into a bowl with a very shallow and flat spoon, and eaten with either powdered sugar and lime juice or with a ginger-flavored syrup. It is generally eaten hot, even during summer.

Fried

A common cooking technique in many parts of East and Southeast Asia involves deep frying tofu in vegetable oil, sunflower oil, and canola oil to varied results. In Indonesia it is usually fried in palm oil. Although tofu is often sold preprocessed into fried items, pre-fried tofu is seldom eaten directly and requires additional cooking. Depending on the type of tofu used, the texture of deep fried tofu may range from crispy on the outside and custardy on the inside, to puffed up like a plain doughnut. The former is usually eaten plain in Chinese cuisine with garlic soy sauce, while the latter is either stuffed with fish paste or cooked in soups. although little else is known about the exact historic origins of tofu and its method of production. While there are many theories regarding tofu's origins, historical information is scarce enough as to relegate the status of most theories to either speculation or legend. Like the origins of cheese and butter, the exact origin of tofu production may never be known or proven.

What is known is that tofu production is an ancient technique. Tofu was widely consumed in ancient China, and techniques for its production and preparation were eventually spread to many other parts of Asia.

Three theories of origin

The most commonly held of the three theories of tofu's origin maintains that tofu was invented in northern China around 164 BC by Lord Liu An, a Han Dynasty prince. Although this is possible, the paucity of concrete information about this period makes it difficult to conclusively determine whether Liu An invented the method for making tofu. Furthermore, in Chinese history, important inventions were often attributed to important leaders and figures of the time.

Another theory states 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 likely have contained calcium and magnesium salts, allowing the soy mixture to curdle and produce a tofu-like gel. This may have possibly been the way that tofu was discovered, since soy milk has been eaten as a savory soup in ancient as well as modern times. Its technical plausibility notwithstanding, there is little evidence to prove or disprove that tofu production originated in this way. The book Tofu Hyakuchin (), published in the Edo period, lists 100 recipes for cooking tofu.

The rise in acceptance of tofu likely coincided with that of Buddhism as it is an important source of proteins in the religion's vegetarian diet. Since then, tofu has become a staple in many countries, including Vietnam, Thailand, and Korea, with subtle regional variations in production methods, texture, flavor, and usage.

Tofu is so highly esteemed in Korean culture that the menus of many Korean restaurants are based almost entirely on tofu, including some which feature only sundubu jjigae (a stew made with soft tofu) and gochujang (red chili paste).

Tofu in the Philippines is essential to the daily diet, as taho, widely eaten as breakfast, or tokwa (a dry fried variation), which is a staple or alternative to meat in main meals, and in numerous regional dishes. Tofu was introduced to the archipelago in the 10-13th centuries by Song Chinese mariners and merchants, along with many different foods which had become staples of the Filipino diet. The use and production of Tofu were first limited to urban centers with influential Chinese minorities, such as Tondo or Cebu, but were quickly spread to even remote native villages and islands, long before the Spanish arrival in the 17th century.

In Malaysia, Singapore, Thailand and Indonesia, tofu or tahu is widely available and used in many Malay dishes such as sayur goreng, masak lodeh, tahu sumbat, rojak, pecal, gado-gado, lontong and some curries. The Malaysian and Singaporean Indians use tofu in their cuisine such as Indian mee goreng and rojak pasembor. The makers of tofu in these countries were originally the Chinese but tofu now is made by non-Chinese as well.

In the West

The first tofu company in the USA was established in 1878. However tofu was not well known to most Westerners before the middle of the 20th century. With increased cultural contact between the West and Asia and growing interest in vegetarianism, knowledge of tofu has become widespread. Numerous types of pre-flavored tofu can be found in many supermarket chains throughout the West.

Nutrition and health information

Protein

Tofu is relatively high in protein, about 10.7% for firm tofu and 5.3% for soft "silken" tofu with about 5% and 2% fat respectively as a percentage of weight.

In 1995, a report from the University of Kentucky, financed by The Solae Company St. Louis, Missouri (the PTI division of DuPont), concluded that soy protein is correlated with significant decreases in serum cholesterol, Low Density Lipoprotein LDL (bad cholesterol) and triglyceride concentrations. However, High Density Lipoprotein HDL (good cholesterol) did not increase. Soy phytoestrogens (isoflavones: genistein and daidzein) absorbed onto the soy protein were suggested as the agent reducing serum cholesterol levels. On the basis of this research, PTI, in 1998, filed a petition with Food and Drug Administration for a health claim that soy protein may reduce cholesterol and the risk of heart disease.

The FDA granted this health claim for soy: "25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease." For instance, 100 grams of firm tofu contains 15.78 grams of soy protein. In January 2006, an American Heart Association review (in the journal Circulation) of a decade-long study of soy protein benefits showed only a minimal decrease in cholesterol levels, but it compared favorably against animal protein sources.

Isoflavones

Soy isoflavones have not been shown to reduce post menopause hot flashes in women or to help prevent cancers of the breast, uterus or prostate. Thus, soy isoflavone supplements in food or pills are not recommended.

A study done by the Pacific Health Research Institute followed over 3000 Japanese men between 1965 and 1999, which showed a positive correlation between cerebral atrophy and consumption of tofu. According to the Alzheimer's Research Trust, more research is needed.

Health issues

High consumption of tofu has been linked with dementia in older age groups in more than one study, whereas in younger and middle-age age groups it might actually protect the brain. It has been stressed that there is no evidence that eating tofu in moderation can cause any problems, and that further research is needed to confirm both the negative as well as the positive effects.

Sales and distribution

In many countries in the West, tofu can be obtained in Asian markets, farmers' markets, and health food stores. It is also increasingly available in supermarkets, especially in larger branches, and in metropolitan areas. The largest provider of tofu products in the United States is House Foods America Corp, a subsidiary of Japanese company House Foods Corp ().

House Foods America Corp. has tofu plants in California and New Jersey with a combined capacity of manufacturing 350,000 pieces of tofu per day. Other major brands are Vitasoy, a subsidiary of a Hong Kong based company, which also manufactures the brands Nasoya and Azumaya; and Mori-Nu (Morinaga Nutritional Foods), a subsidiary of Morinaga Milk Industry (森永乳業) of Japan, which pioneered the sale of shelf-stable, aseptically packaged tofu.

Fresh local tofu varieties are often available in Western areas with high concentrations of Asian populations.

In the East, tofu may be produced locally by relatively small vendors in the form of 2'x2'x2" block, then cut into 2"x2"x2" pieces when sold; or distributed widely by large national brands. Fresh tofu is usually bought from local vendors and is sold directly from large bins or pots at street markets. Asian firm tofu and "tofu flower" are commonly sold in this manner and are usually no more than a few hours old. Tofu that is sold by large manufacturers often comes packaged in sealed plastic cartons or tubes, and may be at most two weeks old. In Chinese supermarkets, tofu can be found in many different flavors and grades of consistency.

Most silken and flavored tofus are produced by large factories, which have the facilities to meet the required sanitary conditions for production of these forms of tofu on a large scale. In Japan, silken tofu is made daily without preservatives and is considered unsellable if it sits unsold in the supermarket for 2 days.

See also

Tempeh

Soy milk

Soybean

Douhua

Femarelle (DT56a)

Buddhist cuisine

Chinese cuisine

Filipino cuisine

Indonesian cuisine

Japanese cuisine

Korean cuisine

Vegetarian cuisine

Vietnamese cuisine

Los Angeles Tofu Festival

Notes

References

. . . . . . (In Chinese.) . . .

Du Bois, Christine M.; Tan, Chee-Beng. Mintz, Sidney Wilfred (2008), The World of Soy, University of Illinois Press, ISBN 0-252-03341-8

Knopper, Melissa. (Jan 2002), The joy of soy, The Rotarian, Vol. 180, No. 1, p. 16, ISSN 0035-838X

External links

The Oxford companion to food Alan Davidson,Tom Jaine

Community scale manufacture of organic nigari tofu - Arcata, California, USA

Large scale manufacture of Shan tofu (video) - Inle Lake, Myanmar

* Category:Soy products Category:Meat substitutes Category:Chinese ingredients Category:Indonesian cuisine Category:Japanese cuisine Category:Japanese cuisine terms Category:Korean cuisine Category:Vegan cuisine Category:Vietnamese cuisine