History of Soy Sprouts
by William Shurtleff and Akiko Aoyagi
A Chapter from the Unpublished Manuscript, History of Soybeans and
Soyfoods, 1100 B.C. to the 1980s
©Copyright 2004 Soyfoods Center, Lafayette, California
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When people speak of "bean sprouts," they are generally referring to the sprouts of the mung bean (Vigna radiata , called green gram in India), which are more widely used than soy sprouts. The latter, however, are also quite popular, having more protein than any other sprout plus an appealing nutty savor and crunch. Traditionally in most countries small-seeded soybeans have been considered the best for sprouting. They have a relatively thicker seed coat than large-seeded soybeans and thus have a higher rate of germination. Larger soybeans with their thinner seed coats crack more easily and then often fail to sprout. Moreover, small-seeded soybeans seem to give sprouts with the best texture and a bland flavor. The sprouting process typically takes 4-5 days, by which time the sprout (radicle) should be about 1 inch long. One pound of dry beans yields about 8-10 pounds of sprouts. Soy sprouts must be cooked (parboiled for 10 minutes or fried for 6-7) before they are consumed to destroy trypsin inhibitors and improve their flavor. This cooking, unfortunately, also destroys some of their vitamin C.
Etymology . In ancient times, from the third century AD, soy sprouts were called dadou huang chüan , literally "soybean yellow curls" or "yellow rolls." These were actually fresh soy sprouts which were dried, then generally used medicinally. By AD 659 we see reference to "fresh soy sprouts" ( nieh sheng ), then by the Sung dynasty (960-1127) to dried soy sprouts as huang chuan p'i ("sprout curl skins"). By the Ming?? dynasty (1368-1662) the two terms now most widely used to refer to soy sprouts, douya ("bean sprouts") and huang douya ("yellow bean sprouts") had been introduced. Today in Canton, soy sprouts may be called dou-miao sp??("bean seedling"). They are occasionally called tou-ya ts'ai ("bean sprout vegetable") in contrast with mung bean sprouts (ya ts'ai)??.
In Korea soy sprouts are called kongnamul, in Japanese daizu no moyashi ("sprouts of soybean"), in Indonesian taugé kedele ("soybean sprouts"), in Malaysian tau geh ("sprouts"), in Vietnamese gia dau nanh, and in Filipino tauge .
In English, soy sprouts have been known by many names: "bean sprouts" (Stuart 1911; Shih 1918), "soy-bean sprouts" (Morse 1918a; McCay et al. 1945), "soy bean sprouts" (Adolph 1922), "soybean sprouts" (Piper and Morse 1923; Horvath 1927; Chen 1956), "sprouted soy beans" (McCay 1943), and "sprouted soybeans" (Burkholder and McVeigh 1945; Jones 1963). The term "soy sprouts" was first used by Lager and by Faulkner and Simpson in 1945, and thereafter by many researchers and writers including Munn (1946) and Van Duyne (1950). More recently the term "germinated soybeans" has come to be used for its conciseness in the phrase "immature, mature, and germinated soybeans," used to compare the properties of these three whole-soybean products (Rackis 1978; Bau and Debry 1979). It is unlikely that this term will ever be used much in common parlance.
Soy sprouts are known as graines de soja germinees in French, as Sojasprossen or Sojakeimlinge in German, and as germinados de soya in Spanish.
HISTORY OF SOY SPROUTS IN EAST ASIA
In most parts of East Asia, except Korea, soy sprouts are the second most widely used sprout, after mung bean sprouts. In Korea they are the most popular sprout.
China . Soy sprouts almost certainly originated in China. In ancient times, they were generally dried, then used medicinally. The earliest known reference to dried soy sprouts appears in the Wu Shih Pen Ts'ao , a materia medica written by Wu P'u during the third century AD; it says: "Dried soy sprouts come from the first yellow shoots the soybean plant pushes up from the earth." The Shen Nung Pen Ts'ao Ching , a materia medica (author unknown) written between the third and fifth centuries AD, states that "Dried soy sprouts have a pleasant taste and a tranquil or uniform effect upon the human system" (Wu 1848). The Ming I Pieh Lu , written by T'ao Hung-ching in the early sixth century, made the first mention of black soybean sprouts. As discussed in Chapter 8, the Chinese have long considered black soybeans to have special medicinal value. "Black soybeans are used to make sprouts. When the sprouts are five inches long, dry them. They are called `yellow curls.' After boiling, take as required." The T'ang pen-ts'ao chu , one of the most important materia medica of the T'ang dynastic, written by Su Kung in AD 659, stated that "Soybeans were used to grow sprouts, called `soy sprouts' or `fresh sprouts' (nieh shêng). When these sprouts are dried they are called `yellow curls' (huang chuan). They are used for food." The Shih-liao pen-ts'ao , a T'ang materia medica by Meng Shen (650-700) states: "Soy sprouts [ chüan nien , literally "curls sprouts"] are five fen ?? in length. They are used as a remedy for purifying the blood of married women, and are considered very good." Dried soy sprouts were also mentioned in another important T'ang dynasty materia medica, the Pen-ts'ao shih-i by Ch'en Ts'ang-ch'i, written in 739.
During the Sung dynastic (960-1127) reference to soy sprouts appeared in many works, including the Tung-ching meng-hua lu by Meng Yuan-lao (1147; "Every day they sell . . . sprouting soybeans"), the T'ung chih by Cheng Ch'iao (1150; "The herbals call soy sprouts `yellow curls' or `curled shoots'"). The T'u-ching pen-ts'ao of this period repeated earlier information but added: "Soy sprouts . . . are grown everywhere in the vicinity of Tai-shan mountain . . . Dried soy sprouts are also called huang chuan p'i ("sprouts curl skins") by the Medical Prescription Books (Fang Shu). At present, the sprouts are generally given to women after childbirth to purify their milk and increase their strength" (Wu 1848).
The famous materia medica Pen-t'sao kang-mu by Li Shih-chen (1578-97) had a long section on soy sprouts. After quoting the information on soy sprouts from the sixth century Ming-i pieh-lu , Li described how to make soy sprouts: "On a `water day' soak black soybeans in clear water, and after the sprouts have grown, take off the hulls and dry the sprouts in the shade." Commenting on this passage, Stuart (1911) said of black soy sprouts: "Their medical properties are considered to be laxative, resolvent, and constructive. They are reputed to have a special influence upon the growth of the hair, and to be curative in ascites and rheumatism."
During the Ming dynasty?? (1368-1662) Ming Chen-i wrote a rhythmic prose piece ( Fu ) entitled "Soy Sprout Poem" ( Tou-ya Fu ), which runs as follows (Wu 1848):
We have other things which are like the frozen flesh of jadelike mixture. The seed does not enter the foul earth. The root needs no support to hold this plant erect. The golden sprouts are one inch long. The pearly kernels are doubly prolific. There are some variegated green or blue, but none vermilion or crimson. In the white dragon's hair the spring silkworms hibernate. These words are quite true and really, the soybean deserves this description.
Publications on soy sprouts increased during the 20th century. Li and Grandvoinnet (1912) praised sprouts since "They don't ever touch the earth or manure. In China bouillon is prepared with soy sprouts, which replaces to good advantage meat bouillons." The first detailed information on making soy sprouts in China was published by Shih in 1918. He noted that the two main types of soybeans used to make soy sprouts were the "sprout bean," which yielded "yellow bean sprouts" (huang tou-ya) and the "green bean," which yielded "green bean sprouts" (ch'ing tou-ya). These two types of soybeans are smaller than most soybeans. The well-washed beans were poured into a large vessel about 36 inches deep and 18 inches in diameter, and having a small draining hole in the bottom. The vessel was covered with a straw lid to keep out the light. The beans must be rinsed at least three times a day in summer and twice in winter. They were kept in the vessel to sprout about 3 days in summer and 15 days in winter; then they were ready to sell in the marketplace. They were boiled with salt, soy oil, or rapeseed oil and soybean jiang (like miso). They were eaten as a common vegetable throughout the year. In 1920 Adolph and Wu gave the first known analysis from China of soy sprouts; they contained 87.9% moisture and 5.7% protein. In 1922 he noted that soybeans were very widely consumed in China, usually cooked in oil to "produce a dish which appeals very strongly to the taste of Americans in China. It is strongly recommended for use as a vegetable on the American table." In 1929 Chung and Ripperton in Hawaii stated that in the market, Chinese soy sprouts were kept submerged in water to retain their crispness and succulency. Photographs from the 1930's, however, generally show them stored in woven bamboo baskets, not immersed in water. In 1931 Morse noted that in many parts of China small soybean plants, when 3-4 inches high (thinnings), were used as greens (Dorsett and Morse 1928-31). The English physician Gray (1936) wrote from China: "Soy sprouts make a very favorite dish among the Chinese. In every town in village throughout China more especially in the northern half [where the cold, dry climate yields few winter vegetables], one sees tubs of tender white-stalked, yellowish-tipped sprouts being hawked for sale and finding ready purchasers." In 1938 Kung, Yeh, and Adolph (Ref??) found the calcium of soy sprouts to be utilized only about half as efficiently (by humans??) as the calcium of various green leaves.
Soy sprouts are said to be sold more widely during the winter months, when fresh vegetables are scarce, and when they are easier to grow and keep without refrigeration and spoilage. Cabbage is the only other vegetable readily available in the markets from November through April. Indeed soy sprouts bridge the gap between legumes and vegetables.
Soy sprouts are grown in either of three ways in China: in 36-inch deep earthenware pots; in 30-inch-diameter, 10-inch deep woven bamboo baskets from which they are sold directly at the market (see Smith 1949 for a photo of soy sprouts sold this way in Guangzhou/Canton); or in wooden boxes, with a straw mat bottom and top, starting with a 3-inch deep layer of soaked beans. The sprouts are rinsed with water 3-4 times a day, and take 10-14 days in winter, 4-5 days in summer to reach maturity (H.L. Wang et al. 1977; Guo 1983). They are sold by weight. Shurtleff (1983b) reported seeing soy sprouts sold in Henan outdoor market in warm July weather; two wicker baskets (each 18 inches in diameter and 14 inches deep) full of soy sprouts were sold next to five baskets of mung bean sprouts.
Soy sprouts keep longest in a brown paper bag, placed inside a plastic bag. Fat and succulent white sprouts are considered best. In China soy sprouts are typically cooked in either of three ways: stir-fried in a wok with meat and vegetables, parboiled for 1-2 minutes then used in cooked salad-like dishes, or added to soups (Lin 1976).
Korea . Although soy sprouts are more extensively used in Korea than in any other country, very little?? is known of their history. They have long been made from special varieties of small-seeded soybeans that give a good texture and bland flavor. In 1931 Morse mentioned that the sprouts were grown in nearly spherical earthenware pots and sold from these same pots. They were also occasionally grown on 12- by 18-inch flats, covered with burlap, and sprouted at 21*C (70*F) for 10-12 days. In some cases the sprouts were grown to 11 inches long, then the roots were trimmed before sale (Dorsett and Morse 1928-31). Smith (1949) wrote that soy sprouts
are much in demand, especially during the winter months. They are used in combination with meat, Chinese cabbage, spinach, turnips, soups, and other cooked dishes . . . They supply much-needed vitamins to the Korean's usual polished rice diet. In some instances the beans are left on the sprouts, in others they are removed. The beans are sprouted in central places and usually peddled in two-wheeled, man-drawn carts.
In 1978 Wang and Lee reported on the dramatic increases in vitamins B-1, B-2, and C during sprouting, these values reaching their peak after 7 days at 18-20*C. Today the most popular Korean soy sprout recipes are Clear-and-Hot Soy Sprout Soup ( Kongnamul Kuk ), Cooked Soy Sprout Salad ( Kongnamul ), and Soy Sprouts Atop Rice ( Kongnamul Pap ). In 1980, some 40,000 tons of dry soybeans were made into sprouts in Korea, which accounted for 12.5% of all Korean soyfood consumption.
Japan . Soy sprouts are not widely used in Japan and very little is known of their history. They were probably introduced to Japan by Buddhist monks more than a thousand years ago. Watanabe et al. (1971) stated that 5,000 tons of soybeans (or was it soy sprouts??) were used in Japan each year, and that large seeded soybeans were considered to make the best sprouts. He also gave a nutritional comparison of soy and mung bean sprouts. Since the Japanese government keeps no separate figures on soy sprout production, little is known of the size of the industry. In 1980 the largest manufacturer of soy sprouts, Kanto Moyashi, grew some 10 tonnes of them daily. The main use of soy sprouts in Japanese cookery is in vinegared salads and sauteed preparations.
Other East Asia . Soy sprouts have long been used on a limited scale throughout Southeast Asia. Ochse (1931) reported that in Indonesia soy sprouts were sometimes fermented to make ketjambah kedele ; they were cooked and eaten as petjel with ganteng rice (defs??). Stahel (1946b) said that in Indonesia soy sprouts (called toklan or taoge ) were one of the ingredients in every Rijst-tafel (Rice Table). In Malaysia, according to Ng (1979) soy sprouts are grown in deep, round tin containers with a perforated bottom. They are cooked with meats, prawns, and pressed tofu, or used in meat-and-vegetable fillings for pressed tofu.
HISTORY OF SOY SPROUTS IN EUROPE
Compared with the United States, surprisingly little work has been done with soy sprouts in Europe. The earliest known reference was a detailed report by Schulze in 1889 "On Some Nitrogen-Containing Constituents in Soy Sprouts (or Etiolated Soy Shoots; Keimlinge von Soja )." Actually this research was directed at soybeans germinating in a field rather than sprouts for food use. These sprouts were reported to contain as much as 7-8% of asparagine, as well as leucine (both amino acids), choline, and perhaps a little arginine (defs??), all of which were extracted and analyzed. The first known reference to soy sprouts for food use was by Li Yu-ying in 1910 and 1912. In his book on soyfoods in Chinese in 1910, he recommended their use to Chinese in place of lettuce in salads. By late 1910 or early 1911, he was making soy sprouts in his soyfoods plant near Paris; these were first commercial soy sprouts in the Western world. In Le Soya (1912) he and Grandvoinnet discussed soy sprouts in China and gave the world's first nutritional analysis of soy sprouts, comparing them with mung bean sprouts. In 1916 Rouest wrote that Li's Parisienne clientele liked his soy sprouts the best of all his soyfoods, and they were widely sold daily in the markets in Paris and of the suburbs. In 1912 N. Bergey was granted a French patent (No. 452,082; Feb. 26) for toasting soy sprouts, then grinding them to a powder. In 1914 Mollieux, in France, published a 3-page study "On the Composition and Food Value of Fresh Soy Bean Sprouts." He found them to contain 93.4% water and 2.3% protein. The next published report on soy sprouts was in 1979 by Bau and Debry, who reported that the trypsin inhibitor activity of soybeans was reduced by 30% during sprouting and that the vitamin C content increased from 0 to 25 mg/100 gm. The only known commercial producer of soy sprouts in Europe in 1982 was Portman Soyfoods in Amsterdam, however there were probably other small Chinese and Korean producers in cities with large East Asian populations.
HISTORY OF SOY SPROUTS IN THE UNITED STATES
Early Developments (1896-1939) . The earliest known reference to soy sprouts in the US or in English was by Trimble in 1896. He summarized the study on "etiolated soja shoots" done by Schulze in Germany in 1889; no mention was made of their use for food. Serious interest in soy sprouts for food use began during World War I, with four reports appearing in 1918. Morse (1918a) described their use in China and their potential as a home winter vegetable. "It is quite possible that sprouted soy beans utilized in various vegetable dishes would appeal to the American taste," he concluded. Jordan (1918) gave detailed instructions for sprouting soybeans on boards of trays lined with damp cloths, noting that they should be ready in 3-6 days, depending on the temperature, and should be harvested before they develop lateral or side roots. After being immersed in boiling water for one minute, they are "ready to serve as a salad with French dressing, or as a regular vegetable dish with meat gravy or soy sauce. The sprouts are also good in meat stews or chop suey. It is in the latter dish that they are often found. When added to other dishes, they should be cooked with them for about five minutes." Shih (1918), writing in English from China, described the basic method of preparation and ways of serving, as mentioned earlier. Itano (1918) described a method of preparation similar to Shih's and suggested that sprouts be "boiled and served as a hot vegetable or as a cold salad."
In 1922 Adolph, writing from China, said that Americans living in China liked stir-fried soy sprouts, and they probably would go over well in America. In 1923 Piper and Morse included one page of detailed information about soy sprouts, including a photograph taken before 1918 showing how they were sold in China in woven bamboo baskets, a description of how they were made and served in China (adopted from Shih 1918), and, most important, nine Western-style soy sprout recipes, the first such recipes to be published in any European language. Horvath (1927), after a review of earlier literature and a discussion of soy sprouts in China, mentioned for the first time that, based on experiments done in Europe on other germinating seeds, soy sprouts probably developed a large amount of vitamin C during sprouting. According to Hardenburg (1928) "Perhaps the most common use of the soybean as human food in America is in the form of sprouts, familiar to many patrons of the chop suey restaurants . . . the soybean and mung bean are both extensively used in chop suey trade." From this statement it is clear that soy sprouts were being produced by this time (and probably since at least the late 1900s) by Chinese sprout shops and/or chop suey restaurants.
In 1933 Morse reported that "Small-seeded varieties of soybeans especially desirable for sprouts have recently been introduced [to the US] from the Orient and tests indicate that a product superior to mung bean sprouts can be produced in the United States." This key concept, unfortunately, lay dormant until the 1980s. In 1936 Lager was selling soy sprouts at her House of Better Living in Los Angeles; they were probably canned, since they were also sold via her mail order catalog. Information on soy sprouts was given in USDA Leaflet No. 166 (Whiteman and Keyt 1938) and recipes for sprouting soybeans at home and cooking with them (Sprouts with Rice) were presented in Jethro Kloss' Back to Eden (1939).
World War II and the 1940s . There was an almost astonishing growth of interest in soy sprouts in America during World War II, when they were taken out of the Chinese markets and chop suey or chow mein dishes in Chinese restaurants, and placed on American tables as an excellent wartime meat substitute and a rich source of protein and vitamins B and C. The leading center of research on soy sprouts during this period was Cornell University, where Dr. Clive McCay and other members of the School of Nutrition worked closely with the Soybean Committee of the New York State Emergency Food Commission, headed by Jeanette McCay (see Chapter 42). Starting in the early 1940s two Chinese graduate students in Nutrition at Cornell, Peng-chen Hsu and Stella Y.Y. Cheng, began studying sprouting methods and increases in vitamins B and C in soy sprouts. With one of his students, Professor McCay visited New York's Chinatown to do the first known study by a Westerner of the traditional methods of producing and handling soy sprouts. Back at Cornell they started work on large scale soy sprout production. They developed an automatic watering device (a "tipping bucket") in the nutrition laboratory that rinsed 100-pound batches of sprouting soybeans with a hopperful of water every 3 hours day and night. These sprouts were sold for about 10 cents a pound at the local Ithaca Co-op food store and the university meat shop; and they were served at the Cornell home economics cafeteria. A steady little business was developed in the spring of 1943, the first Caucasian soy sprouts plant in the West. To answer many enquiries on how to use soy sprouts, several mimeographed sheets were issued containing sprouting instructions and recipes. In the earliest of these (April 1943) entitled "Sprouted Soy Beans," Clive McCay, always gifted with the turn of phrase, started by noting:
Our daily paper would surprise us if it carried an ad: `Wanted, a vegetable that will grow in any climate, rivals meat in nutritional value, matures in three to five days, may be planted any day in the year, requires neither soil nor sunshine, rivals tomatoes in vitamin C, has no waste, can be cooked with as little fuel and as quickly as a pork chop.' The Chinese discovered this vegetable centuries ago in sprouted soy beans. Today they are an important food for many millions.
McCay recommended that the beans be sprouted in a flower pot with a hole in the bottom. Also in 1943 Christine A. Heller at Cornell wrote a 6-page leaflet "Cooking With Soy Bean Sprouts" and McCay and Heller wrote an article for Soybean Digest entitled "Soy Sprouts," with sprouting instructions and recipe suggestions.
The Soybean Committee of the New York State Emergency Food Commission had been established by governor Thomas Dewey in May 1943; it set to work immediately and sprouts were one of the foods it focused on. In June 1943 governor and Mrs. Dewey hosted a soyfoods luncheon at their Executive Mansion in New York to mark the beginning of their campaign to introduce soyfoods. State and national media gave the event extensive coverage. A soy sprout salad was part of the menu. Dr. McCay discussed his group's work on soy sprouts, repeating his catchy story about "Wanted: A vegetable that will grow in any climate . . . " The event was a great success, the reporters being most favorably impressed. On 19 July 1943 a major article appeared in Life magazine with photographs of the governor's luncheon and closeups of McCay's method for growing soy sprouts at home, this time using an inverted jar with gauze over the mouth. In the September 1943 issue of Readers Digest Hodges' "Are You Neglecting the Wonder Bean?" also discussed soy sprouts in a very favorable light. The Food Commission sent out information on soy sprouts (and other soyfoods) to some 300,000 people who wrote asking for it. In early 1944 McCay and Heller wrote an expanded (16-page) booklet "Sprouted Soy Beans;" it was published and widely distributed free of charge by the Food Commission. Also in 1944 Y-Y Stella Cheng finished her PhD thesis on The Effect of Sprouting on the Nutritive Value of Soybeans: The Ascorbic Acid Content and the Protein Quality . This was the world's first doctoral dissertation on soy sprouts and one of the first studies on increases in their vitamin C. At about the same time a poster was printed showing the steps in sprouting soybeans, based on Clive's investigations. Then in February 1945 the Soybean Committee and Cornell University published an excellent 65-page booklet titled "Soybeans," which contained six pages of information on soy sprouts, including details on nutritional values; substantial production of vitamin C plus a fourfold increase in riboflavin and a doubling of niacin were reported (Soybean Committee 1945). In 1945 Lee and Whitcombe at Cornell found that soy sprouts lost 50% of their vitamin C during blanching and 70% during blanching, freezing, and subsequent cooking. Light was found to increase the vitamin C content of soy sprouts considerably. In 1946 Munn of Cornell's New York State Agricultural Experiment Station published a technical article on "Producing Soy Sprouts," and in 1950 C.H. Wu published a MSc thesis at Cornell on the palatability and food value of soybeans after sprouting and cooking.
By 1943 other universities and agricultural experiment stations had joined Cornell in taking a serious interest in soy sprouts. Bulletins containing basic information or original research were published at the University of Michigan (Beeskow 1943, 1944), Columbia University (Trelease and Trelease 1943), Maryland Agricultural Experiment Station (Walls 1943), University of Nebraska (Stanek 1943 Ref??), and University of Illinois (Faulkner and Simpson 1945; Van Duyne 1950); they found that black soybeans seemed to produce the most tender sprouts.
From 1944 numerous nutritional studies were done on soy sprouts on the changes in nutrient composition during sprouting; these included publications by Block and Bolling (1944 Ref??), French et al. (1944), Everson et al. (1944), Burkholder and McVeigh (1945), Desikachar and De (1947; they found no change in trypsin inhibitor content during sprouting), and several others. Although USDA did little to promote soy sprouts (feeling that there were simpler ways to introduce soyfoods into the American diet), they were discussed by Drown (1943) in a USDA publication on soyfoods. The military, however, took an interest in them as a way of supplying personnel in remote regions with fresh vegetables. Canadian troops stationed in the Arctic used soy sprouts as a fresh vegetable year round (Hodges 1943a,b).
Most of the soyfoods cookbooks published during the war had long sections on soy sprouts (Heller and McCarthy 1944; Lager 1945). They generally advised boiling or steaming the sprouts for 7-15 minutes before serving to remove the raw beany flavor. Some advised grinding the sprouts in a food chopper for use in casseroles, curries, stews, etc. Even well-known nutritionists such as Dr. Frances Pottenger, Jr. of southern California helped promote the use of soy sprouts.
Little is known about commercial production of soy sprouts during the war. McCay and Heller (1943) wrote: "Soybean sprouts can be seen any day in the markets of New York's Chinatown. They are produced in the local cellars and sold from bins or barrels like other vegetables." Trelease and Trelease (1943) reported that there were six firms, all apparently run by East Asian-Americans, in New York City making both soy and mung sprouts. There were probably one or more similar operations plus a number of restaurants that made soy sprouts in cities with large Korean- or Chinese-American populations. It would not be surprising to learn that such businesses had been making soy sprouts in the US since the late 1900s, although no known records exist. By 1944 La Choy Food Products in Ohio was making soy sprouts. Lager (1945) noted that "Already progressive merchants are selling soy sprouts," and Morse and Cartter (1952) reported that during the 1940s a number of companies had successfully canned soy sprouts.
1950-1969 . There was very little interest in or research on soy sprouts during the 1950s. However Smith and Van Duyne (1950) gave a nice review of work to date, and Chen (1956) gave 11 recipes plus home and commercial sprouting techniques. Nutritional studies were done by Sugimoto (1954 Ref??), McKinney et al. (1956, at the USDA/NRRC in Peoria, Illinois), and Weakley and McKinney (1957 Ref??),
Starting in the mid-1960s there was a great wave of interest in America in sprouts, especially among young people interested in natural foods, food self sufficiency, vegetarian diets, etc. Many people started to make their own sprouts at home. While alfalfa, mung, and wheat were the most popular seeds for sprouting, soy was also fairly widely used. But a lack of good methods for sprouting soybeans and the fact that they could not be eaten raw limited their popularity. D.V.G. Jones in The Soybean Cookbook (1963) gave a nice section on "Sprouted Soybeans" with 19 recipes. Standal (1967) gave the amino acid composition of soy sprouts and found that there was no change in composition during sprouting.
1970-1982 . The 1970s and early 1980s saw a rebirth of interest in soy sprouts. Most of the published research concerned their nutritional value and biochemical changes taking place during sprouting. Major findings included the following. Soy sprouts have twice the protein content of most other sprouts (Leung et al. 1972; Rackis 1978). There is probably a reduction of soybean trypsin inhibitor activity during sprouting. Bates et al. (1977) reported a 70% decrease in activity after 4 days, Bau and Debry (1979) found a 30% reduction after 3 days, but Collins and Sanders (1976 Ref??) reported only very little decrease. It has been speculated that internal heat generated during sprouting may cause some of the decrease. This reduction is probably of little practical significance since the sprouts must still be cooked to give them their best flavor and texture. The protein quality of soy sprouts, based on contradictory data in various studies, is probably not significantly different from that in whole dry soybeans. Bates et al. (1977) found that the PER (Protein Efficiency Ratio) of whole dry soybeans, soy sprouts, and fresh green soybeans were 2.11, 2.02, and 2.05 respectively. They and Bau and Debry (1979) reported little change in amino acid composition during sprouting. Bates and Matthews (1975) reported that the ascorbic acid (vitamin C) content of soybeans increased from 2 to 11 mg/100 gm during sprouting, and that the beta-carotene content increased from 0.12 to 0.20 mg/100 mg. Bau and Debry (1979) found that ascorbic acid content increased from 0-25 mg/100 gm. However appreciable amounts of both are destroyed during cooking (estimated 50% of the ascorbic acid) to maximize protein quality and organoleptic acceptability, an unavoidable tradeoff. Hofsten (1979) reported large increases in vitamin B-12 during sprouting, but did not give specific figures for soy sprouts. More research is needed on this key point. Chen and Pan (1977 Ref??) observed that phytic acid decreased 22% and phytase enzyme activity increased 227% during 5 days of soy sprout germination. The phytase degraded the phytic acid/phytate (which binds minerals), thus making trace minerals such as calcium, zinc, and iron present in the soy sprouts more available for human nutrition than they were in the original seed. Moreover the flatulence-producing oligosaccharides in soybeans are completely hydrolyzed (and thus eliminated) during the sprouting process, which makes sprouts virtually "gas free." Any traces of flatulence factors are removed during parboiling (Hofsten 1979; Rackis 1981).
It has long been known that many food plants (including cabbage, hops, wheat and rice germ and bran, etc.) contain estrogens (called phytoestrogens), which include specific estrogens such as isoflavones and coumestans. Estrogen is a female sexual hormone, which is also used in birth control pills and DES (a growth hormone used with livestock). Knuckles et al. (1976) and Lookhart et al. (1979) found coumesterol to increase dramatically (8- to 197-fold) during soy sprout production. Isoflavones in soybeans may also increase several fold. The reasons for the wide range and the significance for human health are not clear. Eating large amounts of soy sprouts regularly could be a problem for some women. Yet soy sprouts have less estrogenic activity than alfalfa sprouts, and one typical birth control pill has 5,000 times as much estrogen as 20 grams (dry weight basis) of soy sprouts. Thus it seems highly unlikely that serving soy sprouts once or twice a week, as they have been in East Asia for centuries, would cause any health problems. A counterbalancing plus in soy sprouts may be their sterols, which increase during germination and have been shown to lower blood cholesterol levels (Rackis 1980). Finally, sprouts require much less cooking than the whole soybeans from which they are derived (10 minutes vs. 30 minutes to 6 hours).
A different type of soy sprout research started in 1978 at the Rodale test kitchens and Organic Gardening and Farming Research Center in Emmaus, Pennsylvania. The researchers identified a number of small-seeded soybeans (less than 10 gm/100 beans as compared to 18 gm for typical soybeans) which had good agronomic properties and yielded good quality sprouts. They developed new sprouting methods (including sprouting in soil, which requires less maintenance and gives more nutritious sprouts; Weinsteiger 1980 Ref??), measured sprout growth rates and sprout taste (the fastest growers were the worst tasting since the original sugars changed to starch), and developed recipes. Small-seeded?? soybeans were found to have the best appearance, taste, and texture (Edwards and Hirsch 1980).
Shurtleff and Aoyagi (1975) did the first original research with commercial Chinese soy sprout producers since Clive McCay in the early 1940s. Based on this they developed a simple and virtually foolproof method for growing soy sprouts at home. The key steps are: Punch holes in the bottom of a deep sprouting container (such as a 2-quart plastic container); fill the container 1/7 full of whole soybeans, immerse in a pot of water and soak for 3-4 hours, no more; drain without inverting container and leave in a cool, dark place for 4-5 days; rinse four times a day, but do not mix or invert beans. The ideal sprouting temperature for both the room and the water is cool, roughly 15-19*C (60-66*F). They also published a number of popular Oriental soy sprout recipes. A few other soy cookbooks published during the 1970s (such as Woods 1974) also contained soy sprout recipes.
By 1982 there were at least nine commercial soy sprout producers in the US and at least one in Canada. Yet with all the interest in sprouts and in soyfoods production it is surprising to note that not one of these companies is run by a non-Oriental producer. Two suppliers of commercial soy sprout processing equipment were Okita Enterprises in Los Angeles and Commercial Manufacturing Co. in Fresno, California. In 1980 Shurtleff gave the first known description of the method for producing soy sprouts in a commercial plant. Chinese sprout makers all say that soy sprouts are the easiest of all types to produce. In 1980 in San Francisco, soy sprouts retailed for $0.35 a pound, the same as mung bean sprouts, but the former contained much more protein (6.2% vs. 3.8% for mung bean sprouts and 5.1% for alfalfa sprouts).
We feel sure that soy sprouts will grow in popularity in the US in the years to come, together with the growing interest in meatless diets, soyfoods, Oriental cuisine, food self-sufficiency, and low-cost protein sources. The large potential Caucasian market is still largely untapped.
HISTORY OF SOY SPROUTS IN THE THIRD WORLD
There has been virtually no interest in soy sprouts in non-Asian Third World countries, apparently because the warm climate and shortage of sanitary water makes them relatively difficult to make and store, and because other types of sprouts are not a traditional part of the diet in most of these areas. Yet there are a few exceptions. In 1936 Kale described how to make soy sprouts in India and gave many international recipes. Stahel (1946b) reported that in the market at Paramaribo, Surinam (a country with strong Indonesian influence), soy sprouts were sold daily.