Sunday, January 16, 2011

Tofu - Soy food products

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 originated in the Han dynasty in ancient China. Li Shizhen in the Ming Dynasty described a method of making tofu in Bencao Gangmu. Tofu and its production technique were subsequently introduced into Korea and then Japan 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.
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.
The English word "tofu" comes from the Japanese tofu, which itself derives from the Chinese doufu from "bean" plus "curdled" or "fermented". The English term "bean curd(s)" for tofu has been used since at least 1840.
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.
Tofu originated in ancient China, 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.
In Asia, 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. The earliest document of tofu in Japan shows that the dish was served as an offering at the Kasuga Shrine in Nara in 1183. 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).
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.
There is a wide variety of tofu available in 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.
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 jia chang dou fu and ma po dou fu 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.
In Chinese cuisine, Douhua 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, douhua 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, sauteed 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, douhua is pronounced dau hu. 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.
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. 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 and yubu in Korea, 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 and is also popular in Korea, where it is called yubu chobap.
Soups, stews, and braised dishes
A rather famous hot Sichuan preparation using firm Asian tofu is mapo doufu. This involves braised tofu in a beef, chili, and a fermented bean paste sauce. In the Shanghai region it is called mala doufu.
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.
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 are rehydrated and enjoyed in savory 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, called sundubu, is used to make a thick stew called sundubu jjigae. Firm, diced tofu often features in the staple stews doenjang jjigae and kimchi jjigae.
As flavoring
Pickled tofu is commonly used in small amounts together with its soaking liquid to flavor 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.
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 (techniques to increase penetration of marinades are stabbing repeatedly with a fork or freezing and thawing prior to marinating). 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).
Tofu has also been fused into other cuisines in the west, for instance used in Indian-style curries.
Tofu and soy protein can be industrially processed to match the textures and flavors 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 non-animal protein.
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 3,000 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.

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