Arikah Map

Tofu

TOFU can also be a military slang acronym, see FUBAR; it is also used as an acronym for top-posting
Tofu / Doufu / Bean curd
Tofu:Tofu-beijingchina
Seasoned tofu cubes in a Chinese dish
Burmese name
Tofu:Image:Bscript_pebya.png (pebya/péprā:) or Tofu:Image:Bscript_topu.png (tofu/tiuphü:)
Cambodian name
to hu
Chinese name
Chinese characters 豆腐 or 荳腐
Mandarin romanizations dòufǔ (Pinyin)
tou-fu (Wade-Giles)
Min Nan romanization tāu-hū (POJ)
Filipino name
tokwa
Indonesian name
tahu
Japanese name
Kanji 豆腐
Romaji tōfu
Korean name
Hangul 두부
Revised Romanization dubu
McCune-Reischauer tubu
Malaysian name
tauhu
Tamil name
tahu
Thai name
เต้าหู้ (IPA: [tâohûː])
Vietnamese name
Quốc Ngữ đậu phụ (đậu hũ)

Tofu, also called doufu (often in Chinese recipes) or bean curd (literal translation), is a food of Chinese origin, made by coagulating soy milk, and then pressing the resulting curds into blocks. The making of tofu from soy milk is similar to the technique of making cheese from milk. Wheat gluten, or seitan, in its steamed and fried forms, is often mistakenly called "tofu" in Asian or vegetarian dishes.


Contents

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 with their own soy milk, which is produced by soaking, grinding, boiling, and straining dried (or, more rarely, 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 [1]. The third type of coagulant, enzymes, is not yet used commercially but shows potential for producing both firm and "silken" tofu:

  1. Salt coagulants
    • Calcium sulfate (gypsum) and calcium chloride : 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, an important mineral for treating and preventing osteoporosis. As such, many tofu manufacturers choose to use this coagulant to be able to market their tofu as a good source of calcium.
    • Magnesium chloride: The coagulant used to make Japanese style tofu with 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 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.
  2. 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 inperceptable sour taste to the finished product. [2] Commonly used together with Calcium sulphate to give soft tofus a smooth tender texture.
  3. Enzyme coagulants
    • Among enzymes that have been shown to produce tofu are papain, and alkaline and neutral proteinases 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 celsius [3].

Contemporary tofu manufacturers may choose to use one or more of these coagulants, since they each play a role in producing a desired texture in the finished tofu[2]. Different textures result from different pore sizes and other microsopic features in tofus produced using each coagulant. The coagulant mixture is dissolved into water, and the solution is then stirred into boiled soy milk until the mixture curdles into a soft gel[1].

The curds are processed differently depending on the form of tofu that is being manufactured. For soft silken tofu (嫩豆腐; nèn doùfu) or tofu flower (豆花, dòuhuā) the soy milk is curdled directly in the tofu's selling package. For standard firm Asian tofu, the soy curd is cut and strained of excess liquid using cheese cloth or muslin and then lightly pressed to produce a soft cake. Firmer tofus, such as Asian dry tofu (荳乾) or Western types of tofu, are further pressed to remove even more liquid. The tofu curds are allowed to cool and become firm. The finished tofu can then be cut into pieces, flavoured or further processed.

Although tartness is sometimes desired in dessert tofu, the acid used in flavouring is usually not the primary coagulant since it is not desirable to the flavour or texture of the resulting tofu to add it in a sufficiently high concentration as to induce coagulation. A sour taste in tofu and a slight cloudiness in its storing liquid is also usually an indication of bacterial growth and, hence, spoilage.

Varieties

There is a wide variety of tofu available in the both western and eastern markets. Despite the daunting variety, tofu products can be split into two main categories: fresh tofu, which is produced directly from soy milk, and processed tofu, which is produced from fresh tofu. Tofu production also creates important side products which are often used in various cuisines.

Fresh tofu

Depending on the amount of water that is extracted from the tofu curds, fresh tofu can be divided into three main varieties.

Tofu:Silken tofu with soy sauce and a decorative carrot slice
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Silken tofu with soy sauce and a decorative carrot slice

Fresh tofu is usually sold completely immersed in water to maintain its moisture content. [6]

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 flavours [7].

Fermented

Flavoured

Tofu:Almond "tofu," which is not made of soy milk but rather from gelatin or agarose
Enlarge
Almond "tofu," which is not made of soy milk but rather from gelatin or agarose

Flavourants can be mixed directly into curdling soy milk while the tofu is being produced.

Fried

Frozen

Tofu:Thawed and sliced frozen tofu
Enlarge
Thawed and sliced frozen tofu

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 is called okara.

Yuba

Boiling of soy milk, in an open shallow pan , produces a film or skin composed primarily of a soy protein-lipid complex on the liquid surface [6]. The films are collected and dried into yellowish sheets known as yuba or soy milk skin (腐皮, fǔ pí in Chinese; 湯葉, yuba in Japanese). Its approximate composition is : 50–55% protein, 24–26% lipids (fat), 12% carbohydrate, 3% ash, and 9% moisture.[2]

The yuba can also be bunched up to stick form and dried into something known as "tofu bamboo" (腐竹, fǔ zhú in Chinese; kusatake, Japanese), or a myriad of 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 vegetarian cuisine.

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

Okara

Okara (雪花菜, xuě huā caì, lit. "snowflake vegetable"; 豆腐渣, doùfu zhā, lit. "tofu sediment/residue"; kongbiji in Korean), sometimes known in the west as soy pulp, is the fibre, protein, and starch left over when soy milk has been extracted from ground soaked soybeans [6]. 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. Okara is rarely seen or used in Chinese cuisine.

Tofu made from other legumes

Preparation

Tofu has very little flavour or smell on its own. As such, tofu can be prepared either in savoury or sweet dishes, acting as a canvas for presenting the flavours of the other ingredients used.

Western methods

Generally, the firmer styles of tofu are used for kebabs, mock meats, and dishes requiring a consistency that holds together, while the softer styles can be used for desserts, soups, shakes, and sauces.

Firm western tofus can be barbecued since they will hold together on a barbecue grill. These types of tofu are usually marinated overnight as the marinade does not easily penetrate the entire block of tofu. Grated firm western tofu is sometimes used in conjunction with TVP as a meat substitute. Softer tofus are sometimes used as a dairy free or low calorie filler. Silken tofu may be used to replace cheese in certain dishes (such as lasagna).

The versatility of tofu and soy protein can be industrially processed to match the textures and flavoured to the likes of cheese, pudding, eggs, bacon, etc. Tofu's texture can also be altered by freezing, pureeing, and cooking. In the Americas, Europe, Australia and New Zealand, tofu is frequently associated with vegetarianism and veganism as it is a source of high quality non-animal protein.

Eastern methods

In Asian cooking, tofu is eaten in a myriad of ways, including raw, stewed, stir-fried, in soup, cooked in sauce, or stuffed with fillings.

Lightly flavoured

The light greenish "bean" smell of tofu is much enjoyed in East Asian cuisines and fresh tofu is often eaten plain or simply flavoured.

In Japan, a common lunch in the summer months is hiyayakko (冷奴), silken or firm Asian tofu served with freshly grated ginger, scallions, and soy sauce. In many parts of China, fresh tofu is similarly eaten with soy sauce or further flavoured with katsuobushi shavings, century eggs (皮蛋), and sesame seed oil.

Tofu:Dòuhuā (豆花), is a soft tofu dish. The fresh tofu is served warm and here dressed with sweet syrup. Lamma Island, Hong Kong.
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Dòuhuā (豆花), is a soft tofu dish. The fresh tofu is served warm and here dressed with sweet syrup. Lamma Island, Hong Kong.

Dòuhuā (豆花) 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. [9]

In Korean cuisine, dubu jorim consists of cubes of firm tofu that are pan fried and seasoned with soy sauce, garlic, and other ingredients. Cubes of cold, uncooked tofu seasoned with soy sauce, scallions, and ginger, prepared in a manner similar to the Japanese hiyayakkoare also enjoyed.

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. 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[9]. In Japan, cubes of lightly coated and fried tofu topped with a kombu dashi-based sauce are called agedashi-dofu (揚げ出し豆腐). Soft tofu that has been thinly sliced and deep fried, known as aburage in Japan, is commonly blanched, seasoned with soy sauce and mirin and served in dishes such as kitsune udon. Aburage is sometimes also cut open to form a pocket and stuffed with sushi rice; this dish is called inarizushi (稲荷寿司) .

Soups, stews, and braised dishes

A rather famous hot Sichuan preparation using firm Asian tofu is mápó dòufu (麻婆豆腐). This involves braised tofu in a pork, chili, and a fermented bean paste sauce. In the Shanghai region it is called málà dòufu (麻辣豆腐).

Dried tofu is usually not eaten raw but first stewed in a mixture of soy sauce and spices. Some types of dried tofu are preseasoned with special blends of spices, so that the tofu may either be called "five spice tofu" (五香豆腐) or "soy sauce stewed tofu" (鹵水豆腐). Dried tofu is typically served thinly sliced with chopped green onions or with slices of meat for added flavor. Most dried tofu is sold after it has been fried or pre-stewed by tofu vendors[9].

Soft tofu can also be broken up or mashed and mixed with raw ingredients prior to being cooked. For example, Japanese ganmodoki is a mixture of chopped vegetables and mashed tofu. The mixture is bound together with starch and deep fried. Chinese families sometimes make a steamed meatloaf or meatball dish from equal parts of coarsely mashed tofu and ground pork. In India, tofu is also used as a low fat replacement for paneer providing the same texture with similar taste.

Tofu bamboos are often used in lamb stew or in a dessert soup. Tofu skins are often used as wrappers in dim sum. Freeze-dried tofu and frozen tofu is rehydrated enjoyed in savoury soups. These products are often taken along on camping trips since a small bag of these dried tofu can provide protein for many days.

In Korean cuisine, soft tofu (sundubu in Korean) is used to make a thick soup called sundubu jjigae (순두부 찌개).

As flavouring

Pickled tofu is commonly used in small amounts together with its soaking liquid to flavour stir-fried or braised vegetable dishes (particularly leafy green vegetables like water spinach). It is often eaten directly as a condiment with rice or congee.

History

Very little 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 prince during the Han Dynasty. Although this is possible, the paucity of concrete information about this period makes it difficult to conclusively determine whether or not 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.[5] [6]

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.1 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. Despite its technical plausibility, there is little evidence to prove or disprove that tofu production originated in this way.[5]

The last group of theories maintains that the ancient Chinese learned the method for the curdling of soy milk by emulating the milk curdling techniques of the Mongolians or East Indians. For, despite their advancement, no technology or knowledge of culturing and processing milk products existed within ancient Chinese society. The primary evidence for this theory lies with the etymological similarity between the Chinese term for Mongolian fermented milk (rufu, which literally means "milk spoiled") and the term doufu or tofu. Although intriguing and possible, there is no evidence to substantiate this theory beyond the point of academic speculation.[5]

Established history of tofu

Although its development likely preceded Liu An, tofu is known to have been a commonly produced and consumed food item in China by the 2nd century BC. Although the varieties of tofu produced in ancient times may not have been identical to those of today, descriptions from writings and poetry of the Song and Yuan Dynasty show that the production technique for tofu had already been standardized by then, to the extent that they would be similar to tofu of contemporary times.

Tofu and its production technique were subsequently introduced into Japan in the Nara period (late eighth century) as well as other parts of East Asia. This spread likely coincided with the spread of Buddhism as it is an important source of proteins in the religion's vegetarian diet.[6] Since then, tofu has become a staple in many countries, including Vietnam, Thailand, and Korea, with subtle regional variations in production methods, texture, flavour, and usage.

Tofu was not well known to most Westerners before the middle of the 20th century. However, with increased cultural contact and an interest in vegetarianism, tofu has become a more familiar product to Westerners.

Nutrition and health information

Tofu is low in calories, contains beneficial amounts of iron (especially important for women of child bearing age) and has no cholesterol (a risk factor for heart disease). Depending on the coagulant used in manufacturing, the tofu may also be high in calcium (important for bone development and maintenance) and magnesium (especially important for athletes).

Protein

Tofu is relatively high in protein, about 10.7% for firm tofu and 5.3% for soft "silken" tofu with about 2% and 1% fat respectively as a percentage of weight.3

In 1995, the New England Journal of Medicine (Vol. 333, No. 5) published a report from the University of Kentucky entitled, "Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids." It was financed by the PTI division of DuPont,"The Solae Co."[3] St. Louis, Missouri. This meta-analysis 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) adsorbed 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." One serving, (1 cup or 240 mL) of soy milk, for instance, contains 6 or 7 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 cast doubt on the FDA allowed "Heart Healthy" claim for soy protein.[4] Among the conclusions the authors state, "In contrast, soy products such as tofu, soy butter, soy nuts, or some soy burgers should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat. Using these and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health."[5]

Isoflavones

Soy isoflavones have not been shown to reduce post menopause "hot flashes" in women and the efficacy and safety of isoflavones to help prevent cancers of the breast, uterus or prostate is in question. Thus, soy isoflavone supplements in food or pills is not recommended. The original paper is in the journal Circulation: January 17, 2006. [6]

A study done by the Pacific Health Research Institute followed over 3000 Japanese men between 1965 and 1999, which showed a positive correlation between brain atrophy and consumption of tofu. [7]. Nevertheless, this is a single study and by itself, does not show conclusively that soy isoflavones causes brain atrophy.

This study by L.R. White, et al., from the National Institute of Aging, NIH, was rejected as not credible by the Food and Drug Administration when it issued its 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." [8]

Sales and distribution

In the West, tofu can be obtained in Asian markets, farmers' markets, and health food stores. Depending on its local popularity, many grocery stores also stock tofu. The largest provider of tofu products in the United States is Hong Kong-based Vitasoy, which also manufactures the brands Nasoya and Azumaya. Another major brand is Mori-Nu (Morinaga Nutritional Foods), a subsidiary of Morinaga Milk Company of Japan, which pioneered the sale of shelf-stable, aseptically packaged tofu.

In the East, tofu may be produced locally by relatively small vendors 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. Most silken and flavoured tofus are produced by large factories. This is due to the fact that such factories have the facilities to meet the required sanitary conditions for production of these forms of tofu on a large scale. In Chinese supermarkets, tofu can be found in many different flavours and grades of consistency.

Etymology

The English word "tofu" comes from the Japanese tōfu (豆腐),5 which itself derives from the Chinese dòufu (豆腐 or 荳腐). Although in both languages the characters together translate as "bean curd," the literal meaning of the individual characters is "bean" (豆) and "curdled" (腐).

Choosing Tofu

Unless one purchases it in sterilized containers, tofu does require some choosing when purchasing and some care while storing:

Miscellaneous

Myths

The Chinese have a myth that if one eats tofu, one should not eat or drink honey for fear that this might cause death.[citation needed]

Notes

</div>
Korean sundubu (soft tofu) is still produced in a similar manner, traditionally using seawater as a coagulant.
</div>
Volume 333, no 5, from the University of Kentucky entitled "Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids." It was financed by the PTI division of DuPont,"The Solae Co.", St. Louis.
</div>
Ang.
</div>
Sacks, Doheny.
</div>
American Heritage Dictionary.

References

  1. ^ a b Berk, Zeki. (1992). "Tofu". Chapter 9.5. Technology of Production of Edible Flours and Protein Products from Soybeans.. FAO Agricultural Services Bulletin No.97. ISBN 92-5-103118-5
  2. ^ a b Guo S.-T. and Ono T. (2005). The Role of Composition and Content of Protein Particles in Soymilk on Tofu Curding Glucono-d-lactone or Calcium Sulfate. Journal of Food Science 70 (4): 258–262.
  3. ^ Liu, KeShun. (1997). Soybeans: Chemistry, Technology, and Utilization
  4. ^ a b Shurtleff, William and Aoyagi, Akiko. (2000). Tofu & Soymilk Production: The Book of Tofu Vol. II, 3rd edition. Soyfoods Center. ISBN 1-928914-05-5.
  5. ^ a b c d e Shurtleff, William and Aoyagi, Akiko. (2004). History of Tofu. A Special Report on The History of Traditional Non-Fermented Soyfoods (unpublished manuscript) Soyfoods Center website
  6. ^ a b c d e f 森井源一 and 一志治夫. (2004). 豆腐道:嵯峨豆腐「森嘉」五代目. 新潮社. ISBN 4-10-471901-3
  7. ^ a b c Shurtleff, William and Aoyagi, Akiko. (2004). History of Fermented Tofu A Special Report on The History of Traditional Fermented Soyfoods (unpublished manuscript) Soyfoods Center website
  8. ^ The Hwang Ryh Shang Company of Taiwan, a major producer of pickled tofu, mislabels this ingredient as "red date" (jujube) on the English-language list of ingredients on its product labels[1], although the Chinese list of ingredients on the same product lists 紅糟 (red yeast rice).
  9. ^ a b c 夏威廉 and 青柳昭子. (2005). 豆腐之書. 柿子文化. ISBN 986-81319-1-X
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