| Tofu / Doufu / Bean curd | |
|---|---|
| Burmese name | |
| (pebya/péprā:) or Bscript_topu.png (tofu/tiuphü:) | |
| Cambodian name | |
| to hu | |
| Chinese name | |
| Chinese characters | or |
| Mandarin romanizations | dòufǔ (Pinyin) tou-fu (Wade-Giles) |
| Cantonese romanization | daau6 fu6 (Jyutping) |
| Filipino name | |
| tokwa | |
| Indonesian name | |
| tahu | |
| Japanese name | |
| Kanji | |
| Romaji | tōfu |
| Korean name | |
| Hangul | |
| Revised Romanization | dubu |
| McCune-Reischauer | tubu |
| Malaysian name | |
| tauhu | |
| Tamil name | |
| tahu | |
| Thai name | |
| (tauhu) | |
| Vietnamese name | |
| Quốc Ngữ | |
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.
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 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. The third type of coagulant, enzymes, is not yet used commercially but shows potential for producing both firm and “silken” tofu:
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. 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.
The curds are processed differently depending on the form of tofu that is being manufactured. For soft silken tofu (; nèn doùfu) or tofu flower (, 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 () 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.
The tofu skin can also be bunched up to stick form and dried into something known as “tofu bamboo” (, 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.
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 conjuction with TVP as a meat substitute. Softer tofus are sometimes used as a dairy free or low calorie filler.
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.
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. 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. In Japan, cubes of lightly coated and fried tofu topped with a kombu dashi-based sauce are called agedashi-dofu (). 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 () .
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.
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” () or “soy sauce stewed tofu” (). 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.
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.
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 (). 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 hiyayakko (described earlier) are also enjoyed.
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.
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. Despite its technical plausibility, there is little evidence to prove or disprove that tofu production originated in this way.
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.
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. 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.
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.
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."* 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. The panel found that 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. 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."[http://circ.ahajournals.org/cgi/content/full/113/7/1034#SEC5
The original paper is in the journal Circulation: January 17, 2006.*
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. *. 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." *
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 open air 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.
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