EDAMAME: THE VEGETABLE SOYBEAN
John
Konovsky, Thomas A. Lumpkin, and Dean McClary Washington State University
FROM:
J. Konovsky*, T.A. Lumpkin, and D. McClary. 1994. Edamame: the vegetable
soybean. Pages 173-81 In A.D. O'Rourke (ed), Understanding the Japanese
Food and Agrimarket: a multifaceted opportunity. Haworth Press, Binghamton.
For
more information concerning this page contact
John
Konovsky.
INTRODUCTION
Edamame is a specialty soybean (Glycine max (L.) Merr.) harvested as
a vegetable when the seeds are immature (R6 stage) and have expanded
to fill 80 to 90 percent of the pod width. Like field-dried soybeans,
the seeds of edamame varieties are rich in protein and highly nutritious.
Worldwide, it is a minor crop, but it is quite popular in East Asia.
Edamame is consumed mainly as a snack, but also as a vegetable, an addition
to soups, or processed into sweets. As a snack, the pods are lightly
cooked in salted, boiling water and then the seeds are pushed Edamame
is consumed mainly as a snack, but also as a vegetable, an addition
to soups, or process into sweets. As a snack, the pods are lightly cooked
in salted, boiling water and then the seeds are pushed directly from
the pods into the mouth with the fingers. As a vegetable, the beans
are mixed into salads, stir-fried, or combined with mixed vegetables.
In soup, (gojiru in Japanese), the beans are ground into a paste with
miso, which is used to form a thick broth. Confectionery edamame products,
such as sticky rice topped with sweetened edamame paste (zunda mochi
in Japanese), are occasionally prepared. For marketing, edamame pods
are sold fresh on the stem with leaves and roots, or stripped from the
stem and packaged fresh or frozen, as either pods or beans.
HISTORY
China. Edamame (mao
dou) use was first recorded around 200 B.C. as a medicinal (Shurtleff
& Aoyagi, unpublished) and is still very popular (Jian 1984). Major varieties
(and their production areas) include: Sanyuewang in Zhejiang Province;
Wuyuewu around Shanghai and Nanking; Wuyueba near Hangzhou; Baishuiou
in the Chengdu area; Liuyueba around Hefei, Wuxi, and Hangzhou; Baimaoliuyuewang
and Daqingdou near Nanking; and Jiangyoudou around Shanghai (Guan 1977).
Numerous land races are still cultivated, particularly around Shanghai
and Jiangsu.
Japan. Though soybeans
were introduced from China at an early date, the first recorded use of
edamame is the description of aomame in the Engishiki (927 A.D.), a guide
to trade in agricultural commodities. It describes the offering of fresh,
podded soybean stems at Buddhist temples (Igata 1977). Early interest
in the edamame crop was seasonal, and it climaxed with the viewing of
the full moon in September and October (Shurtleff and Aoyagi, unpublished).
Historically, edamame was grown on the bunds between rice paddies, but
with the current rice surplus and official pressure to convert paddy fields
to other uses, field production is more common (Gotoh 1984). Japan is
the largest commercial producer of edamame--turning out nearly 105,000
tons in 1988 (MAFF 1990)--and it is also the largest importer of the bean,
bringing in over 33,000 tons in 1989 (JTA 1989). Taiwan supplies over
99 percent of those imports as frozen edamame. Almost all Japanese production
is consumed as fresh product during the summer months (Kono 1986).
Korea. Morse noted
edamame's (poot kong) availability in 1931 (Shurtleff and Aoyagi, unpublished).
It is still cultivated throughout the country and variety development
is underway (Hong et al. 1984), with research on crop management systems
(Lee 1986a,b).
North America. Edamame
is known by many names in North America (Shurtleff and Aoyagi, unpublished).
The most common is vegetable soybean, but also beer bean, edible soybean,
fresh green soybean, garden soybean, green soybean, green-mature soybean,
green vegetable soybean, immature soybean, large-seeded soybean, vegetable-type
soybean, and the Japanese name, edamame. Reference to green color is confusing
because mature soybean seeds with a green seed coat (or cotyledon) are
also called green soybeans.
Other Countries. Other
countries that have produced commercial quantities of edamame include
Argentina, Australia, Israel, Mongolia, New Zealand, and Thailand. Home
gardeners are known to produce it in Bhutan, Brazil, Britain, Chile, France,
Germany, Indonesia, Malaysia, Nepal, Philippines, Singapore, and Sri Lanka
(Wang et al. 1979). USA Edamame Research. Research has been conducted
for over 50 years. Dorsett and Morse collected extensive germplasm during
1929- 31, and Morse used it to develop 49 varieties of edamame (Hymowitz
1984). Research flourished during the 1930's and 1940's because of a protein
shortage (Smith & Van Duyne 1951). The University of Illinois tested palatability
(Woodruff & Klaas 1938) and regional adaptation (Lloyd 1940) of many soybean
varieties, some of which were true edamame, and many companies experimented
with canning fresh beans (Shurtleff & Aoyagi, unpublished).
A second surge of
interest began with the rise of organic agriculture in the 1970's. The
Rodale Research Center focused on adaptability and quality (Haas et al.
1982). Basic agronomic research was begun at Cornell (Kline 1980) and
seed companies developed new varieties (e.g. butterbean). Today, some
home gardeners grow edamame, but there is little commercial production.
Asian-Americans seeking edamame are usually limited to frozen imports
in specialty supermarkets.
QUALITY
At harvest, edamame
has lower trypsin-inhibitor levels, fewer indigestible oligosaccharides,
and more vitamins than field-dried soybeans (Rackis 1978). True edamame
varieties are not easy to distinguish from immature, grain soybeans, except
for a few unique characteristics (Rackis 1981). The larger seeds of edamame
are considered superior to soybeans in flavor, texture, and ease of cooking,
but significant differences in chemical composition have not been identified.
Phytic acid levels are higher (Gupta et al. 1976) and may help explain
why edamame is more tender and cooks faster. Large-seeded soybeans have
nutritionally superior protein (Hymowitz et al. 1971), e.g., the gain-per-feed
ratio was higher for edamame fed to rats than for soybeans (Yen et al.
1970). Edamame has a slightly sweet, mild flavor and nutty texture, with
less objectionable beany taste. It has larger, easily shattered pods,
seeds with a fragile seed coat (Smith & Van Duyne 1951), and stems that
may have several podless nodes (Shanmugasundaram et al. 1989).
Edamame protein levels
were thought to be slightly higher than soybeans (Liener 1978; Smith &
Circle 1978), but recent research indicates larger seeds have a higher
percentage of oil and less protein than smaller seeds (Reddy et al. 1989).
Since protein and total sugars are negatively associated (Hymowitz et
al. 1972), too much protein leads to a lack of sweetness, an important
component of flavor. Conversely, oil content and total sugars are positively
associated, but an excessively oily taste is unacceptable.
Edamame quality is
evaluated by distributors and consumers for appearance, aroma, flavor,
and firm texture after cooking. Morphologically, edamame pods should have
white pubescence (Watanabe 1988), preferably sparse and soft (Sunada 1986);
the hilum should be light brown or gray; the pods must have two or three
seeds; most pods should be at least 5 cm long; 500 g should contain less
than 175 pods; 100 seed weight should exceed 30 g (Shanmugasundaram et
al. 1989); the pods should be completely green, with no hint of yellowing
(IDA 1990); the mature seed coat can range from yellow or green to brown
or black (Kiuchi et al. 1987); and the pods must be unblemished.
In Iwate Prefecture
(IDA 1990), grade A edamame must have 90 percent or more pods with two
or three seeds. The pods must be perfectly shaped, completely green, and
show no injury or spotting. Grade B edamame must have 90 percent or more
pods with two or three seeds, but can be lighter green, and a few pods
can be slightly spotted, injured, malformed, short, or have small seeds.
In both grades, pods cannot be overly mature, diseased, insect-damaged,
one-seeded, malformed, yellowed, split, spotted, or unripe.
Pod color is the most
visible quality of edamame. In addition to varietal influences, several
management factors affect color. In general, exposure to sunlight has
the greatest positive influence, followed by moisture level and supplemental
fertilizer. When leaves were removed at two-thirds of mature height, the
pods darkened considerably over the control by harvest due to increased
exposure to sunlight (Chiba et al. 1989); however, researchers at the
Asian Vegetable Research and Development Center (AVRDC) have suggested
lower leaf area increases sunburn (Shin 1988). The pods seem to darken
with the increased chlorophyll content caused by lower moisture levels
(AVRDC 1988). Post-anthesis application of phosphorus darkened pods slightly,
but the effects of nitrogen were mixed (Kobayashi et al. 1989). Ascorbic
acid content deteriorates with pod color (Akimoto & Kuroda 1981) and can
be used as an index of pod color and freshness.
Edamame releases a
sweet aroma when cooked. At the peak of ripeness, aromatic concentrates
have much higher levels of (Z)-3-hexenyl acetate, linalool, acetophenone,
and cis-jasmone (Sugawara et al. 1988). Several components of beany odor
were also identified: hexanal, 1- hexanol, (E)-2-hexenal, 1-octen-3-ol,
and 2-pentylfuran. Cis-jasmone is found in edamame only at the peak of
ripeness and may be the key component of aroma.
For edamame, the two
most important components of flavor are sweet and savory. Its sweet taste
is determined by sucrose content and its savory taste probably by amino
acids like glutamic acid (Masuda et al. 1988). Beany flavor increases
with maturity and can be divided into two components--beany and bitter
(Rackis et al. 1972). The beany taste may come from linolenic acid oxidized
by lipoxygenase and the bitter taste my be the lipoxygenase itself.
Many management choices
influence flavor, such as: variety selection, fertilizer application,
planting density, harvest procedures, and processing conditions (Masuda
1989). In Japan, basal fertilizer rates are generally around 50-80 kg
nitrogen/ha, 70-100 kg phosphorus, and 100- 140 kg potassium. Excessive
basal nitrogen will reduce pod set and increase the number of empty or
one-seeded pods. Supplemental nitrogen after anthesis can increase amino
acid levels but has an inconsistent effect on sugars. Kobayashi et al.
(1989) found total sugars decreased from 3.18 percent to 2.63-2.94 percent
depending on the rate and timing of nitrogen application. Abe et al. (1985)
cites contrary data, but adds that pods given supplementary fertilizer
may be damaged more easily during processing. Lower plant densities not
only darken pods but produce consistently higher amino acid levels and
sucrose during the maturation period (Chiba et al. 1989).
The date, timing,
and method of harvesting are of crucial importance. Unfortunately, sugar
and amino acid contents peak several days before beans have adequately
filled the pods. When pod color and seed size appear the best, flavor
has already begun to deteriorate. In addition, there is a daily cycle
for amino acids. A peak occurs near sunset, and the more sunlight during
the day, the higher the peak. For glutamic acid, a peak of 255 mg/g fresh
weight was reported at sunset, with a decline to 160 mg by the next morning
at sunrise (Masuda 1989). After harvest, sugar and amino acid deterioration
can affect flavor within 3-10 hours unless the beans are cooled (Chiba
& Yaegashi 1988), or unless whole plants are harvested. If whole plants
are packaged and sealed in low density, polyethylene bags, they remain
acceptable for one week at 20 oC (Iwata et al. 1982).
If the pods are adequately
green, post-harvest handling is the major influence on quality and flavor.
The need for rapid cooling cannot be overemphasized. Fresh product often
sits at room temperature for 24 hours or more before sale and use. Masuda
et al. (1988) found that frozen edamame from Taiwan often had more sucrose
(e.g., 1.7 percent vs. 1.1 percent) and amino acids (e.g., alanine at
30 mg/100 g fresh weight vs. 16 mg) than fresh edamame in Japan. Both
were significantly lower than harvest peaks (2.9 percent sucrose and 297
mg alanine). For frozen edamame, blanching is important to stop the oxidation
of fatty acids into undesirable tastes.
Both blanching time
and temperature must be controlled to reach a balance between the destruction
of trypsin inhibitors and the maintenance of good texture. The length
and temperature of storage is also significant. Ascorbic acid levels decrease
20 percent after six months at -20 oC, and 40 percent after one year.
For post-harvest management, rapid cooling (or blanching and freezing)
is essential to slow enzymatic activity and minimize deterioration.
Yield is influenced
by planting density.. Higher densities intercept more light, which increases
biomass (AVRDC 1988). Acceptable grade A and B pods/plant decrease with
higher densities, while the total yield/area of the pods increases (Shin
1988). Inter-row spacing influences yield more than intra-row spacing
(Kline 1980).
VARIETY SELECTION
Japanese classify
soybeans as summer or fall types (Kono 1986). Most edamame varieties are
temperature-sensitive, summer types; only a few are day-length sensitive,
fall types. Summer types are planted in the spring and harvested immature
after 75-100 days, while fall types are planted in early summer and take
105 days or more.
About 170 edamame
varieties are listed by the Nihon Shubyo Kyokai (JSTA 1987), and several
hundred others are available. Most are determinate (Gotoh 1984) and can
be segregated into approximately ten families with representative types
(IDA 1989; Kono 1986). Among summer types, Okuhara and Sapporo-midori
are in Maturity Group (MG) 0, Osodefuri and Shiroge are in MG I; and Fukura,
Mikawashima, and Yukimusume are in MG II. Among fall types, Kinshu, Tsurunoko,
and Yuzuru are in MG III. All have white pubescence except Okuhara, Osodefuri,
and Shiroge. Special qualities include Fukura's sweetness, Kinshu's dark
pods, Mikawashima's numerous three-seeded pods, Osodefuri's good flavor,
Shiroge's prolific branching, Tsurunoko's large seeds, and Yukimusume's
good pod color after processing. Negative features include Fukura's fragile
pods, Mikawashima's viney growth, Okuhara's short harvest period, Sapporo-midori's
lack of vigor at low temperatures, and Tsurunoko's tall growth.
Among Chinese varieties
(Guan 1977), Sanyuewang Wuyuewu, and Wuyueba are in MG's I-II, and Baishuiou,
Liuyueba, and Baimaoliuyuewang are in MG's III-IV; Jiangyoudou and Daqingdou
are fall-type soybeans in MG's V-VI. Sanyuewang, Liuyueba, and Baimaoliuyuewang
are short plants. Baishuiou, Baimaoliuyuewang, Jiangyoudou, and Daqingdou
are superior in quality, while Liuyueba, Jiangyoudou, and Daqingdou have
high yields.
PRODUCTION
Edamame can be transplanted
(teishoku) or direct-seeded (futsu roji). In Japan, transplants are used
in forced (sokusei) and early (sojuku) production systems (Kono 1986).
Planting under forced conditions in carbon dioxide-enriched, heated greenhouses
starts in November and harvest ends by July. Early spring production starts
with the planting of seedling nurseries in February; these seedlings are
then transplanted to small plastic tunnels 25-30 days later, with harvest
ending by July. Temperature management is achieved by placing dark covers
over the tunnels during cold periods to increase temperature and by using
ventilation during hot periods (Watanabe 1988). Field production begins
in early March and ends by October. Occasionally, plant tops in seeded
fields are cut after the primary leaf stage to increase plant branching
and pod set (Gotoh 1984). Early summer demand pressures farmers to harvest
as early as possible to obtain higher prices, so the onset of harvest
is being continually advanced through crop management and variety development.
Most edamame is harvested by hand. When edamame is sold on the stem, plants
are hand-cut or pulled out with the roots intact; unacceptable pods and
lower leaves are culled, and branches tied together in small, aesthetically
pleasing bundles. For sale of harvested pods, plants are cut and pods
stripped off, sorted, and packaged. In Japan, electrical-powered, stationary
pod strippers are available, and in Taiwan, AVRDC has developed a manual
pod stripper (AVRDC 1989). Initial studies on mechanical harvesting have
been conducted in Tennessee (Collins & McCarty 1969) and at INTSOY (1987).
For frozen product, standard methods for processing have been described
(Liu & Shanmugasundaram 1982).
CURRENT RESEARCH
Quality aspects such
as darker green, unblemished pods, earlier maturity (in Japan), higher
pod set (for mechanical harvesting), lower temperature tolerance, longer
harvest period, and a trypsin-inhibitor-free, sweet and savory flavor
are major breeding objectives, with adequate seed size, seeds/pod, and
pubescence already well established in the breeding lines. Pod shatter
is a problem for seed production, but easily opened pods are important
for vegetable production. Yield is a secondary consideration because of
the high value of edamame, but disease resistance is important in some
areas, particularly the tropics.
Active public research
programs have been found at AVRDC for variety development (Shanmugasundaram
et al. 1989), at INTSOY for mechanical harvesting (INTSOY 1987); and at
Iwate Prefecture Agricultural and Horticultural Experiment Station for
land race collection (Kiuchi et al. 1987), variety development (Kiuchi
et al. 1989), crop management (Chiba et al. 1989; Kobayashi et al. 1989),
and post-harvest management (Chiba & Yaegashi 1988). Other research programs
include the Japanese National Food Research Institute at Tsukuba's study
on quality (Masuda 1989) and Washington State University's evaluation
of varieties and production systems. Many Japanese seed companies (Sakata
and Yukijirushi, etc.) also have variety development programs underway.
Other prefectures in Japan sponsor local research, and China, Korea, Sri
Lanka, and Thailand all have active research programs.
SUMMARY
In
the United States, edamame has potential as an easier-to-grow, better
tasting, more nutritious substitute for lima beans. Served in the pods,
it might appeal to consumers interested in natural foods, particularly
if it were grown organically. In spite of drastic changes in the Japanese
diet, demand is slowly rising and traditional foods like edamame continue
to be very popular (Cook 1988). In a hungry world, with research and
education, edamame could be a very nutritious, savory, and inexpensive
addition to local diets, especially in calorie, protein, and vitamin
deficient regions of the world.
LITERATURE CITED
Abe, I., Y. Okuda,
T. Iwata, and K. Chachin. 1985. Kikai dakkyo edamame no sendo hoji gijutsu
ni kansuru kenkyu. Engei Gakkai Happyo Yoshi, Fall S60:494-495.
Akimoto, K. and S.
Kuroda. 1981. Quality of green soybeans packaged in perforated PE/PP film.
Engei Gakkai Zasshi 50:100-07.
AVRDC. 1988. Progress
Report, Crop Improvement Program, Soybean Physiology. Asian Vegetable
Research and Development Center, Tainan.
AVRDC. 1989. Progress
Report Summaries 1988. Asian Vegetable Research and Development Center,
Tainan. Chiba, Y. and S. Yaegashi. 1988. Quality change of green soybeans
after harvest. Tohoku Nogyo Kenkyu 41:287-88.
Chiba, Y., S. Yaegashi,
and H. Sato. 1989. Cultivation method of green soybean I: effect of plant
density on quality and yield. Tohoku Nogyo Kenkyu 42:279-80.
Collins, J.L. and
I.E. McCarty 1969. Handling of vegetable soybeans mechanically. Soybean
Digest 12:20-21.
Cook, A. 1988. The
Evolution of Japanese Spending Patterns: 1963-84. Washington State University
IMPACT Center Report No. 26, Pullman.
Gotoh, K. 1984. Historical
review of soybean cultivation in Japan. Tropical Agriculture Research
Series 17:135-42. Guan, P.Z. 1977. (Vegetable bean). Pages 333-38 In S.X.
Li (ed), (Vegetable Cultivation, South China). Chinese Agricultural Publishers,
Beijing.
Gupta, A.K., M. Kapoor,
and A.D. Deodhar. 1976. Chemical composition and cooking characteristics
of vegetable and grain-type soybeans. Journal of Food Science and Technology
13:133-37.
Haas, P.W., L.C. Gilbert,
and A.D. Edwards. 1982. Fresh Green Soybeans: analysis of field performance
and sensory qualities. Rodale Press, Emmaus.
Hong, E.H., S.D. Kim,
and Y.H. Hwang. 1984. Production and use of and research on soybeans in
Korea. Tropical Agriculture Research Series 17:81-93.
Hymowitz, T. 1984.
Dorsett-Morse soybean collection trip to East Asia: a 50 year perspective.
Economic Botany 38:378-88.
Hymowitz, T., D.W.
Mies, and C.J. Klebek. 1971. Frequency of trypsin- inhibitor variants
in seed protein of four soybean populations. East African Agricultural
and Forestry Journal 37:73-77. Hymowitz, T., F.I. Collins, J. Panczner,
and W.M. Walker. 1972. Relationship between the content of oil, protein,
and sugar in the soybean seed. Agronomy Journal 64:613-16.
Igata, S. 1977. Nihon
Kodai Kokumotsushi. Yoshikawa Kokubun, Tokyo.
INTSOY. 1987. INTSOY
research focuses on green soybeans as commercial frozen vegetable. International
Soybean Program Newsletter 37:1-2.
Iwata, T., H. Sugiura,
and K. Shirahata. 1982. Keeping quality of green soybeans by whole plant
packaging. Engei Gakkai Zasshi 51:224- 230. IDA. 1989. Yasai, Kaki Saibai
Gijutsu Shishin. Iwate-ken Department of Agriculture, Morioka.
IDA. 1990. Iwate-ken
Seikabutsu To Shukka Kikaku Shido Hikkei. Iwate-ken Department of Agriculture,
Morioka.
JSTA. 1987. Yasai
Hinshu Meikan. Japanese Seed Trade Association, Tokyo.
Jian, Y. 1984. Situation
of soybean production and research in China. Tropical Agriculture Research
Series 17:67-72
Kiuchi, Y., H. Ishikawa,
N. Nitta, and T. Sasaki. 1987. Collection of crop genetic resources and
their characteristics in Iwate Prefecture I: characteristics of local
soybean varieties. Tohoku Nogyo Kenkyu 40:139-40.
Kiuchi, Y., H. Ishikawa,
N. Nitta, T. Sasaki, and T. Sato. 1989. New vegetable-type soybean varieties:
Iwamamekei 1, Iwamamekei 2, Iwamamekei 3, Iwamamekei 4, and C9. Iwate
Kenritsu Nogyo Shikenjo Kenkyu Hokoku 28:27-39.
Kline, W.L. 1980.
The Effect of Intra and Interrow Spacing on Yield Components of Vegetable
Soybeans. Master's Thesis, Cornell University.
Kobayashi, T., M.
Orisaka, K. Miyashita, and Y. Chiba. 1989. Cultivation method of green
soybean II: effects of fertilization and soil management on quality and
yield. Tohoku Nogyo Kenkyu 42:281- 82.
Kono, S. 1986. Edamame.
Pages 195-243 In, Sakukei o Ikasu Mamerui no Tsukurikata. Nosangyoson
Bunka Kyokai, Tokyo.
Lee, D.K. 1986a. Studies
on the utilization of green soybeans 1: effect of sowing dates on growth
and yield in green soybeans. Research Reports of the Rural Development
Administration--Crops (Korea) 28:136-41.
Lee, D.K. 1986b. Studies
on the utilization of green soybeans 2: effect of vinyl mulching and tunnels
for early cultivation on yield of green soybeans. Research Reports of
the Rural Development Administration--Crops (Korea) 28:142-46.
Liener, I.E. 1978.
Nutritional value of food protein products. Pages 203- 77 In A.K. Smith
and S.J. Circle (eds), Soybeans: chemistry and technology. AVI, Westport.
Liu, C. and S. Shanmugasundaram.
1982. Frozen vegetable soybean industry in Taiwan. Pages 199-212 In M.C.
Ali and L.E. Siong (eds), Vegetables and Ornamentals in the Tropics. University
Pertanian Malaysia, Serdang.
Lloyd, J.W. 1940.
Range and adaptation of certain varieties of vegetable soybeans. Illinois
Agricultural Experiment Station Bulletin 471:77- 100.
Masuda, R. 1989. Yasai
no reito--edamame. Refrigeration 64:359-76.
Masuda, R., K. Hashizume,
and K. Kaneko. 1989. Effect of holding time before freezing on the constituents
and the flavor of frozen green soybeans. Nihon Shokuhin Kogyo Gakkaishi
35:763-70.
MAFF. 1990. Statistical
Handbook. Ministry of Agriculture, Forestry, and Fisheries, Tokyo.
Rackis, J.J. 1978.
Biochemical changes in soybeans: maturation, post- harvest storage and
processing, and germination. Pages 34-76 In H.O. Hultin and M. Milner
(eds), Post-harvest Biology and Technology. Food and Nutrition, Westport.
Rackis, J.J. 1981.
Comparison of food value of immature, mature, and germinated soybeans.
Pages 183-212 In R. Teranishi and H. Berrero-Benitz (eds), Quality of
Fruits and Vegetables in North America. American Chemical Society, Washington.
Rackis, J.J., D.H.
Hoing, D.S. Sessa, and H.A. Moser. 1972. Lipoxygenase and peroxidase activities
of soybeans as related to flavor profile during maturation. Cereal Chemistry
49:586-597.
Reddy, P.N., K.N.
Reddy, S.K. Rao, and S.P. Singh. 1989. Effect of seed size on qualitative
and quantitative traits in soybean (Glycine max (L.) Merr.). Seed Science
and Technology 17:289-95.
Shanmugasundaram,
S., T.C.S. Tsou, and S.H. Cheng. 1989. Vegetable soybeans in the East.
Pages 1978-87 In A.J. Pascale (ed), World Soybean Research Congress IV:
actas proceedings.
Shin, H.R. 1988. Effect
of Drought Stress and Plant Density on Yield and Quality of Vegetable
Soybeans. AVRDC Research Report, Tainan.
Shurtleff, W. and
A. Aoyagi. Unpublished. History of fresh green soybeans and vegetable-type
soybeans. Chapter 22 In W. Shurtleff and A. Aoyagi (eds), History of Soybeans
and Soyfoods.
Soyfoods Center, Lafayette.
Smith, A.K. and S.J. Circle. 1978. Chemical composition of the seed. Pages
61-92 In A.K. Smith and S.J. Circle (eds), Soybeans: chemistry and technology,
volume 1, proteins. AVI, Westport.
Smith, J.M. and F.O.
Van Duyne. 1951. Other soybean products. Pages 1055-1078 In K.S. Markley
(ed), Soybeans and Soybean Products, volume 2. Interscience, New York.
Sugawara, E., T. Ito,
S. Odagiri, K. Kubota, and A. Kobayashi. 1988. Changes in aroma components
of green soybeans with maturity. Nihon Nogei Kagaku Kaishi 62:148-55.
Sunada, K. 1986. Hokkaido
No Mame Saku Gijutsu. Nogyo Gijutsu Fukyu Kyokai, Sapporo.
Wang, H.L., G.C. Mustakas,
W.J. Wolf, L.C. Wang, C.W. Hesseltine, and E.B. Bagley. 1979. Soybeans
as human food--unprocessed and simply processed. USDA Utilization Report
5.
Watanabe, M. 1988.
Tunneru saibai--Sapporo-midori. Nogyo Gijutsu Taikei (yasai) 13:1-8.
Woodruff, S. and H.
Klaas. 1938. A study of soybean varieties in reference to their use as
food. Illinois Agricultural Experiment Station Bulletin 443.
Yen, J.T., T. Hymowitz,
L. Spilsbury, J.D. Brooks, and A.H. Jensen. 1970. Utilization by rats
of protein from trypsin-inhibitor variant soybeans. Journal of Animal
Science 31:21
