Tofu

When calcium sulfate (3 g salt/kg milk) is added to soy milk at 65 °C, a gel (called soy curd ) slowly precipitates. The curd is separated from excess fluid by gentle squeezing in a special wooden filter box. A washing procedure then follows. The water content of the product is about 88%. Tofu contains 55% protein and 28% fat dry weight. In China and some other Asian countries, tofu is the largest source of food protein. It is 

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Tofu. Tofu is prepared by adding a coagulant such as calcium sulfate to soymilk to precipitate the protein and oil into a gelatinous curd. The curd is then separated from the soluble portion (whey), pressed, and washed to yield a market-ready product. Tofu, a traditional food in Japan (90), was populari2ed in the United States in the late 1970s and is available in many U.S. supermarkets. 

W. Shuideff and A. Aoyagi, The Book of Tofu, Vol. 2, Tofu and Sojmilk Production, New-Age Poods Study Center, Lafayette, Calif., 1979, 336 pp. 

Cheese. The evolution of imitation cheese has come from the substitution of milk components ia the development of filled and nondairy cheese and development of a synthetic cheese based on the Chinese food sufu, a form of tofu, which is based on soybean curd. 

Soybean-Based Cheese. In tofu cheese manufacture, the soybeans are cooked to give soy milk, then formed into a curd using calcium sulfate, and pressed to give tofu. The tofu is inoculated y ctinomucor elegans fermented, salted, and aged to form sufu (soft cheese) (17). This product is widely used ia the Orient and is gaining acceptance ia the United States. 

The effects of phytoestrogens on cognitive function have also been investigated in humans. However, the results of these studies were inconclusive. White et al, (2000) concluded that tofu consumption in midlife was associated with diminished cognitive function later in life. In contrast. File et al. (2001) reported that short-term consumption of high levels of isoflavones (100 mg/day) may improve memory. 

Brain aging and midlife tofu consumption. J Am Coll Nutr. 19 242-55. 

Herbal products used for the relief of menopausal symptoms are purported to act by a number of different mechanisms. Phytoestrogens are plant sterols that are structurally similar to human and animal estrogen. Soy protein is a common source of phytoestrogens and can be found in products such as tofu, soy milk, soy flour, and tempeh. Various studies have demonstrated conflicting results as to the efficacy of... 

A ounces cheddar cheese 1 / ounces jack cheese 1 A ounces Swiss cheese 1 A ounces part-skim mozzarella 4 tablespoonfuls grated Parmesan cheese 8 ounces tofu... 

Uses of Soybeans as Foods in the West with Emphasis on Tofu and Tempeh... 

Soybeans have been used as food in the Orient since ancient times and various methods have been developed to make soybeans as palatable as possible. In recent years, a large number of these simply processed soyfoods are emerging in the West. Tofu and tempeh are the most popular and have the fastest growth rate of any soyfood in America. Tofu is made by coagulating the protein with a calcium or magnesium salt from a hot-water extracted, protein-oil emulsion of whole soybeans. 

It is a highly hydrated gelatinous product with a bland taste. The texture characteristics of the curds vary from soft to firm, depending on the processing conditions. Thus, tofu can be easily incorporated with other foodstuffs and used in nearly every culinary context from salad to dessert and from breakfast foods to dinner entrees. Tempeh is made by fermenting cooked soybeans with a mold, Rhizopus oligosporus. 

Based on processing technology, the soybean foods that have been consumed in East Asia may be classified into two general types non-fermented and fermented (2-8) as shown in Table I. Names of these foods and the details of preparing and serving such foods may vary from country to country. Among them, soybean curd (tofu) and soy sauce have been the most widely consumed in the Orient. 

Soybean curd (tofu) White or pale yellow curd cubes coagulated from soybean milk. Served as main dish with or without further cooking. 

Tofu has long been a source of protein in the Orient. It has much the same importance to the people of the Orient that meats, eggs and cheese have for the people in Western Countries. Tofu is usually sold in the form of a wet cake with a creamy-white color, smooth custard-like texture and a bland taste. It is highly hydrated and, depending on the water content, tofu products with different characteristics can be produced. The typical oriental type of tofu has a water content about 85%. Japanese prefer tofu having a smooth, fragile texture that contains about 88% water. The Chinese, on the other hand, produce many types of firm products with a chewy meatlike texture and a water content as low as 50-60%. Western consumers like tofu with a firm texture therefore, tofu found in the U.S. supermarkets contains 75-80% water. 

Because of its fine texture, bland taste and light color, tofu has been used in nearly every culinary context desserts, salads, breakfast foods, dinner entrees and burgers. It can be cooked simply with desired flavoring agents or it can be easily incorporated with other foodstuffs. 

Three main steps are involved in making tofu (Figure 1) Preparation of soybean milk, coagulation of protein, and formation of tofu cakes in a mold. By experience, the Orientals have found that the most suitable ratio of water (including that absorbed during soaking) to dry soybeans is 8 1 to 10 1. Watanabe et al (15)... 

Figure 3. Relationship of concentration and type of coagulant to the texture characteristics of tofu ( 13) ...

Thus, many factors affect the final product. By knowing the effects that each factor produces, one can choose and establish a set of conditions to reproduce the desired type of tofu. 

Table II. Protein to Oil Ratio of Tofu and Soymilk as Affected by Protein and Oil Content of Soybeans (14)...

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