The oldest methods of preparing green, immature soybeans for consumption was by roasting or by soaking, grinding, and cooking (Toussaint-Samat 1993). Mature soybeans were processed in much the same manner but with a longer cooking time.
Soybeans, paradoxically, have a very bland taste, which probably inspired the development of flavorful fermented soy products. Such soy processing began in China during the Chou dynasty (1122-246 B. C.) and subsequently spread to other areas of the Far East.
One of the first of these products, and the best known to Westerners, is shoyu or soy sauce - a dark brown liquid used extensively in Chinese food preparation - that is obtained by fermenting a combination of soybeans and wheat. The original process entailed first boiling soybeans with koji (Aspergillus oryzae) which, in this case, was a mold skimmed from the surface of cooked wheat that had cooled and fermented. Soy sauce has a salty taste and a subtle, but tantalizing, aroma that goes well with rice dishes.
Another product is soy paste, produced in a process similar to that which yields soy sauce, except that the koji is derived from barley or rice. Soy paste is also Chinese in origin and evolved from a paste of fish puree called jiang that was used before soya became popular. By the time of the Han dynasty in the third century, soy paste had become the important ingredient in jiang. Two or three centuries later, the Koreans were producing soy paste and the Japanese got the recipe from them. Today there are numerous such pastes, called miso, in everyday use in Japan. The color can vary, depending on the soybean-to-rice or barley ratio. The greater the amount of rice used, the lighter (and sweeter) the product. In the past, soy paste was stored in earthen jars for up to a year, which was said to improve the flavor.
Tempeh kedlee is a third soy product primarily confined to Indonesia, where more than half of the soybeans produced are devoted to it. It has a fine flavor, but not the longevity of other soy products. Also Indonesian in origin is ontjom, made by combining the residue of soybean milk with peanuts and allowing the mixture to ferment. The result is a kind of soy sauce with a nutlike flavor.
Still another product that originated in Indonesia (and Thailand as well) is tao tjo, made by combining cooked soybeans and roasted rice flour with koji. After about four days, a fungus covers the solution, whereupon the mixture is dried in the sun, then soaked in brine. A few days later, sugar and rice yeast are added and the sun, once again, is employed to dry the combined beans and flour. The end product is a sweet soy sauce to accompany vegetable, meat, or fish dishes.
A final Indonesian contribution is ketjab, in which bacteria are combined with cooked black beans, fermented, and then placed in salt brine for a week or so. The beans are drained and the residue is cooked several times. The extract that remains is sweetened with sugar and permitted to evaporate further.
A sixth soy product is natto, a gray-colored liquid with a strong, musty flavor, produced in Japan by wrapping cooked soybeans in rice straw and allowing the whole to ferment. The taste is something of an acquired one for Westerners and varies depending on locale.
Buddhist monks first developed hamanatto in their monasteries. This is still another fermented soy product, obtained in an elaborate procedure employed by the monks that began with soaking whole soybeans for up to 4 hours, then steaming them for 10 hours. Afterward, the beans were covered with koji and left to ferment for 20 hours, during which time a green mold developed to cover the beans. Next, they were dried in the sun to lower their moisture content, then placed in wooden buckets with strips of ginger on the bottom. After a year, the soybeans were once more dried in sun - this time until they turned black. The final product was a soybean sauce with a very sweet flavor and a pleasant aroma.
The major Korean contribution to soy products of the world is kochu chang, made by mashing boiled soybeans and beginning their fermentation with the addition of a bit of a previous batch, much like starter dough. This mixture was then placed in a sack and hung to dry in the sun for a couple of months, after which time the fermented mash was pulverized and mixed with salt and water. The final step was to put the mixture in an earthen jar to age for three months or so. After chilli peppers reached the East in the sixteenth century, they were added to the mash for additional flavor.
In addition to these sauces, soybeans have been processed by the Chinese and others of the Far East into bean curd, soybean milk, and bean bran. Soybean curd or tou-fu is made by wet-grinding the beans into a thin mixture that is strained, then coagulated with gypsum, which causes the proteins to precipitate. The mixture is strained a last time to become bean curd and soy milk, respectively. Bean curd thus provides the Asians with flour and milk, both very important foods in everyday life. The curd itself is often served with rice, meats, vegetables, and fish. It is also added to soups, mashed for making breads and cakes, and deep-fried.
Soybean milk - a vegetable milk - is obviously of considerable importance in a region of the world where little cattle raising takes place and where the human population seems to be uniformly lactose intolerant. In addition to serving as a beverage in its own right, soy milk is processed as a soft drink (Trager 1995).
The sprouts of soybean and mung beans (Phaseo-lus aureus) serve as an instant vegetable high in vitamin C and are also blanched and processed into cellophane noodles. Soybean sprouts are traditionally eaten on the Chinese New Year. Finally, young soybean pods are eaten boiled or roasted as a snack with soy sauce or sesame oil.
Nutrition
East Asians have long been dependent on soybeans for corrections of nutritional deficiencies. Soy sauces and other typical soy products are all concentrates of the B vitamins and contain significant amounts of the minerals calcium, iron, magnesium, phosphorous, and zinc. In addition, as we have already noted, they yield a very high quality protein, as well as important lipids, carbohydrates, and fiber.
Soy protein is also important nutritionally because of the ways in which it is employed in other food products for purposes of emulsion formation, promotion of fat and water absorption, and texture and color control. Foods benefiting from soy protein include bologna, frankfurters, breads, soups, cakes, pasta, gravies, whipped toppings, and simulated meats, vegetables, and fruits (Wolf and Cowan 1971: 52).
Soy flour usage, however, has not lived up to earlier expectations. The flour does have a nutty taste and very fragrant aroma; sweetened with sugar, it is baked into breads, muffins, cakes, cookies, and the like (Piper and Morse 1923). But unfortunately, it has a limited shelf life, which discourages production in large quantities.
It would not do to end this section on the nutritional value of soybeans without noting that they also contain various potentially toxic substances that can inhibit growth, reduce the absorption of fats, enlarge the pancreas, and decrease the energy yield of the diet (Norman 1978: 227). Among these antinutritional agents are trypsin, phytic acid, hemagglutinin, saponin, and phenolic constituents. Fortunately, the process of cooking eliminates the toxicity of soybeans.
Thomas Sorosiak
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World History
