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.
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 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.
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.
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.
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.
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.
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.
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.
Reference : http://en.wikipedia.org/wiki/Tofu