Soybean

Thomas Sorosiak. Cambridge World History of Food. Editor: Kenneth F Kiple & Kriemhild Conee Ornelas. Volume 1. Cambridge, UK: Cambridge University Press, 2000.

Description

The soybean plant belongs to the legume family (Leguminosae), the second largest family of flowering plants, with more than 14,000 species. Identifiable characteristics include a fruit located within a pod that dehisces along a seam from top to bottom. In the case of a soybean, the split takes place when the plant has matured and died to yield 2 to 4 seeds per pod that are easily removed without damage or loss.

The soybean’s size, shape, and color is determined by the variety. Soybeans range in size from small (1 centimeter [cm]) to large (3.5 cm), can be flattened or oblong, and are colored yellow, green, brown, or black. They are approximately 8 percent hull, 90 percent cotyledon, and 2 percent hypocotyl (Wolf and Cowan 1971).

Terminology

The terms “soy and “soya” are said to have derived from the Japanese word shoyu (or sho-yu) that designates a sauce made from salted beans. But the Japanese word may well have been inspired by the ancient Chinese name for the bean, which was sou. In Chinese, the word for soy sauce is jiangyou (or chiang-yiu). C. V. Piper and W. J. Morse (1923) have recorded more than 50 names for the soybean or its sauce in East Asia. In English the bean has been called soya bean, soya, soy, Chinese pea, Japanese pea, and Manchurian bean, to provide just a few of its appellations. For the purposes of this chapter, soya is used synonymously with the soybean and its many products.

Early History

Present-day soybean varieties (Glycine max), of which there are more than 20,000, can be traced to the wild soybean plant Glycine soja that grew in abundance in northeast China and Manchuria (Hymowitz and Newell 1981). Legends abound concerning the discovery and domestication of this food plant that today is the most widely used in the world (Toussaint-Samat 1993: 51). Around 2700 B.C., the legendary Chinese emperor Shen Nung is said to have ordered plants to be classified in terms of both food and medicinal value, and soybeans were among the five principal and sacred crops (Shih 1959). This dating squares nicely with the judgment of modern authorities on Asian plants that soybeans have been cultivated for at least 4,500 years (Herklots 1972). But there are other sources that indicate that the domesticated soybean (G. max) was introduced to China only around 1000 B.C. perhaps from the Jung people who lived in the northeast (Trager 1995).

The court poems of the Book of Odes, sixth century B.C., also indicate that the wild soybean came from northern China and that its cultivation began around the fifteenth century B.C. Confucius, who died in 479 B.C., left behind writings that mentioned at least 44 food plants used during Chou times; they included soybeans. But they do not seem to have been very popular in ancient times. Soybeans were said to cause flatulence and were viewed mostly as a food for the poor during years of bad harvests. Nonetheless, soybeans were recorded in the first century B.C. as one of the nine staples upon which the people of China depended, and certainly there were enough people. The first official census conducted in Han China at about that time counted 60 million people, and even if such a number seems implausibly high—especially in light of a census taken in A.D. 280 that showed only 16 million—it still suggests that Chinese agricultural policies were remarkably effective, both in feeding large numbers of people and, one suspects, in encouraging the growth of large numbers of people (Chang 1977: 71).The famine in China in the year A.D. 194 may have been the result of too many mouths to feed and thus responsible, at least partly, for the discrepancy in the two censuses. But in addition, famine forced the price of millet to skyrocket in relation to soybeans, resulting in an increased consumption of the latter—often in the form of bean conjee or gruel (Flannery 1969).

Early Dissemination

Because the wild soybean was sensitive as to the amount of daylight it required, and because the length of growing seasons varied from region to region, domestication involved much experimental planting and breeding to match different varieties with different areas. That this was done so successfully is a tribute to ancient Chinese farmers who, as noted, were doubtless impelled by an ever-increasing need to feed larger and larger populations of humans and animals. Soybeans ground into meal and then compressed into cakes became food for travelers and soldiers on the move who, in turn, widened knowledge of the plant.

Buddhist priests, however, were perhaps as instrumental as anyone in the domestication of the soybean and absolutely vital to its dissemination (Yong and Wood 1974). As vegetarians, they were always interested in new foods and drinks (such as tea, which they also nurtured to an early success in China). In their monasteries, they experimented with soybean cultivation and usage and found flour, milk, curd, and sauce made from soy all welcome additions to their regimes. As missionaries, they carried the soybean wherever they went, and in the sixth century A.D., they introduced it to Japan from Korea, which they had reached in the first century. Buddhism merged with the native Shinto religion, and the plant quickly became a staple in the Japanese diet.

Not only missionaries but also soldiers, merchants, and travelers helped introduce soybeans to Asian countries. The northern half of Vietnam had soybean food products as early as 200 B.C. During the sixth through the tenth centuries A.D., Thailand received soybeans from southwest China, and India was exposed to them during the twelfth century by traders from Pakistan.

Recent History and Dissemination

The Portuguese began trading in East Asia during the sixteenth century, as did the Spanish and later the Dutch. Yet the soybean was not known in Europe until the end of the seventeenth century when Engel-bert Kaempfer published his Geschichte und Beschreibung von Japan, an account of his visit to that country during the years 1692-4 as a guest of the Dutch East India Company. He wrote of the bean that the Japanese prized and used in so many different ways, and in 1712, he attempted, not very successfully as it turned out, to introduce this miracle plant to Europe. Its products simply did not fit into the various cuisines of the continent, which, in any event, were only then in the process of fully utilizing the relatively new American plants, such as maize and potatoes.

The botanists, however, were thrilled to have a new plant to study and classify, and Carolus Linnaeus, who described the soybean, gave it the name Glycine max. Glycine is the Greek word for “sweet,” and “max” presumably refers to the large nodules on the root system, although other sources suggest that the word max is actually the result of a Portuguese transcription of the Persian name for the plant (Toussaint-Samat 1992: 52).

Because of scientific interest, the soybean was shuttled about the Continent during the eighteenth century for experimental purposes. In 1765, soybean seeds reached the American colonies with a sailor named Samuel Bowen, who was serving aboard an East India Company ship that had just visited China. Bowen did not return to the sea but instead acquired land in Savannah, Georgia, where he planted soybeans and processed his first crop into Chinese vetch, soy sauce, and a starchy substance incorrectly called sago. In North America as in Europe, however, soybean products did not go well with the various cuisines, and the bean remained little more than a curiosity until the twentieth century, despite efforts to reintroduce it.

By the mid-nineteenth century, the soybean was being rapidly disseminated around the globe as trade, imperialism, clipper ships, and then steamships all joined to knit the world more closely together. The expedition of Commodore Matthew Perry that opened Japan to trade in 1853-4 returned to the United States with the “Japan pea”—actually 2 soybean varieties that were subsequently distributed by the U.S. Commissioner of Patents to farmers for planting. But lacking knowledge of and experience with the plant, the recipients were apparently not successful in its cultivation.

During the American Civil War, when shipping was disrupted, soybeans were frequently substituted for coffee, especially by soldiers of the Union army (Crane 1933: 270). Interest also arose in soybean cultivation as a forage plant, and the Patent Office and the new Department of Agriculture (USDA) encouraged experimental planting. The USDA’s role in promoting agricultural research, regulating the industry, and serving as an information generator for farmers proved invaluable to all farmers and certainly to those growing soybeans for the first time (Arntzen and Ritter 1994: 466).

There were 2 stages in processing the soybean plant as a forage crop or hay. The first was to cut the plants just before the leaves turned yellow but after the pods, containing semiripened seeds, had formed, thereby increasing the plants’ protein value. In the second stage, the plants were windrowed and left to dry for a day or two, after which the windrows were raked into bunches and dried for another three or four days. Lastly, the bunches were stacked in barns right side up. The average yield of hay using this method was approximately 4 tons an acre, with a protein content of close to 11 percent.

In harvesting the soybean plant for silage, the process called for cutting the plants earlier – when their seedpods contained premature green seeds. These were made into bundles of about 25 pounds each, then stored in barns until needed. This method traded some protein content for less leaf loss during harvesting.

Soybean plants, processed by either of these methods, lowered the cost of feeding livestock by replacing the more expensive grass hay and corn. Even a combination of soybean hay or silage and traditional feeds resulted in considerably reduced feed costs and supplied more protein than hay or corn alone could deliver.

At the turn of the twentieth century, the population of the United States was swelling with immigrants, and significant technological advances were spinning out of an ever-accelerating industrial process. An increased demand for food spurred soybean cultivation, and processing was facilitated by electric motors to power grinding equipment that made soybean meal more quickly and efficiently than ever before. Mechanized farm implements encouraged the planting of still more land in soybeans, while lowering the costs of harvesting.

The result was that soybeans produced in the United States became competitive with those grown in East Asia, despite the Asian application of very cheap labor. By 1911, the U.S. industry not only processed soybean meal into cakes for livestock feed but also began to press the beans into oil, as China was already doing. Indeed, the high oil content of the soybean (about 20 percent) was arousing substantial commercial interest.

Previously, a shortage of soybeans in the United States and the predominance of cottonseed oil (then called Wesson Oil after David Wesson, who, in 1899, developed a method for clarifying it) had retarded the development of soybean oil. But in 1915, cottonseed oil became scarce because the U.S. cotton was infested with boll weevils, and this in turn led to the processing of soy oil for human consumption. Cottonseed- processing plants quickly became soybean-processing plants, because the presses and other equipment worked equally well with soybeans. Moreover, a new method was discovered for extracting the oil by first grinding the beans, then soaking them in a solution of benzol, naphtha, and ether, which for every bushel (60 lbs.) of soybeans yielded 10.5 pounds of oil and 48 pounds of meal. Thus, soybean oil was efficiently produced at a time when World War I was creating more demand for oils.

None of these lessons in supply and demand were lost on southern farmers, who began to plant soybeans on land barren because of the boll weevil. The USDA also encouraged soybean cultivation in the states of the Midwest. In 1922, a soybean-processing plant was opened in Decatur, Illinois. To ensure a steady soybean supply, the “Peoria Plan” was developed to guarantee Illinois farmers a base price of $1.35 a bushel (Smith and Circle 1972). In addition, farmers throughout the nation were given an inducement to grow soybeans with the passage, in 1923, of the Smoot-Hawley Tariff, which placed import duties of 2 cents per pound on soybeans, 3.5 cents per pound on soybean oil, and $6.00 per ton on soybean meal.

Soybeans became the nation’s “Cinderella” crop in the 1920s. Demand was high for soybean cakes, which continued to provide farmers with a high-protein, low-cost animal feed. But it was demand for soybean oil that stimulated still more production; soybeans yielded oil valued at 20 cents per pound, or $400.00 per ton, as opposed to meal worth only $20.00 a ton. Research supported by the processing plants helped plant breeders develop new soybean varieties with higher oil contents.

During the 1920s, this oil went into numerous industrial products, among them soaps, paints and varnishes, linoleum, ink, glycerin, explosives, celluloid, and a substitute for rubber. Moreover, the low cost of soybean production stimulated research to discover still more industrial uses. Yet, soybeans remained an underused food resource because of their relatively high saturated fat content, which made the oil solidify, as well as their high percentage of bad-tasting linolenic acid.

It was during the 1930s that research on soybean oil refinement, flavor reversion, and especially hydrogenation ultimately resolved these problems and opened the way for soybeans to be employed in food products (Toussaint-Samat 1993). Increasingly, the oil found its way into shortenings, margarine, salad dressings, and, of course, cooking oils. In fact, during the Great Depression years, soybean oil was well on its way to becoming the most important food oil in the United States, a status it achieved after World War II and never relinquished.

It is interesting to note that during that war, the only survival rations issued to Japanese soldiers had consisted of bags of soy flour, perhaps illustrative of the fact that despite the growing use of soybeans in the United States, they were still an Asian resource. Following the war, soybeans became the world’s most important crop, not because of the Asian influence but because of productivity. Initially, much of the postwar surge of U.S. interest was due to the ability of soybeans to regenerate the soil when planted in rotation with corn (Pepper 1994: 193). During the war, soy margarine had replaced butter on most tables, a use that continued after 1945.

Making a transition to soybeans from a previous concentration on corn, wheat, cotton, or tobacco was scarcely a hardship for farmers because surpluses of these latter crops existed, and because with the passage of the Agriculture Adjustment Act in 1933, restrictions had been placed on the amount of acreage that could be devoted to them. Meanwhile, the government was promoting soybean products by, among other things, organizing the Regional Soybean Industrial Products Laboratory in 1938.

And once again research found industrial applications for soybeans – this time for using soy protein in the paper industry and for making plastics from oilcake residue in the automobile industry. At the same time, world food requirements in the 1950s increased demand for soy protein for both humans and domesticated animals. During this decade, American farmers responded by producing an annual average of 300 million bushels of soybeans for industrial and food use. In the process, the United States, which prior to World War II had been the world’s biggest importer of fats, became its greatest exporter, accounting for fully 75 percent of the world’s soybean crop.

Because of plant breeding, the soybean—once a subtropical plant—moved north as far as 52 degrees, and soybean fields became familiar sights from Minnesota to the Deep South. Soybean meal processed in the northern states was carried by rail to barges on the Mississippi River that transported it to New Orleans for shipment to world markets (Forrestal 1982).

In addition to the ease of bulk transportation, soybeans lend themselves to handling in many other ways. They can withstand long storage and shipment over long distances; they are easily harvested in an entirely mechanical procedure; and a growing season of only 15 weeks makes it easy to adjust production to world market demand. In short, as one food author has pointed out, supply can be virtually guaranteed, and if there is overproduction, there is no need to destroy the surplus (Toussaint-Samat 1993).

The people of Far Eastern countries receive, on average, about 12 percent of their protein requirements from soybean products. But despite the high protein content of the soybean and the high quality of that protein, attempts to introduce soya to many poor regions of the world, such as India, Africa, and Latin America, have historically met with little success, with southern South America a notable exception. For example, in Mexico in the 1940s the National Indian Institute handed out soybeans to the impoverished Otomi Indians living in the Mezquital valley. Although the legume flourished in the arid soil, the experiment failed when Otomi women were unable to hand-grind the soybeans to make a decent tortilla (Granberg 1970).

International efforts, however, continue to increase consumption, particularly in the soybean fortification of cereals on which many people rely. All of these cereals—rice, maize, barley, wheat, and rye—yield a protein that is incomplete, meaning that it does not contain all of the essential amino acids. Yet what they lack, soybeans contain, and soybeans are also high in the B vitamins, along with vitamin E, phosphorous, and iron.Thus, in cases where soya is used to supplement other cereals, as in Golden Elbow or Vitalia macaroni, Kupagani biscuits, ProNutro cereal, and Cerealina, the consumer receives a whole protein equal to that provided by meat, fish, and dairy products (Fortified foods 1970).

Processing, Preparation, and Products

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 (Phaseolus aureus) serve as an instant vegetable high in vita-min 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.