1212 PROTEIN & CO-PRODUCTS Industrial uses of soy protein: new ideas T he early history of soybean uti- lizaticn is a study of industrial uses of soybeans. Soybean oil was first used as a fuel and as a replace- ment for linseed oil in paints and coat- ings. Soy protein found early uses as plastic polymers, wood adhesives, syn- thetic fibers. fire foams, paper coatings, and for a wide variety of minor indus- trial uses. Most of these uses ended in me 19405 with the development of less expensive petroleum-based chemicals that provided the needed functional properties. In recent years there has been a renewed interest in developing and expanding markets for industrial uses for soy protein. Expanding the industrial use of soy protein is supported by soybean fann- ers who are financing research on soy protein through the soybean checkoff program. This article will discuss industrial uses of soy protein from three general approaches: First, it will discuss the history of industrial soy protein use. There have been 70 years of soybean utilization research 10 draw upon, so there is a long history of industrial use. Many of these uses are being retnvesrlgeted because soybeans offer some solutions to today's environmental problems. Second, it will review soybean checkoff research projects designed to find "new" industrial uses for soy- beans. Several checkoff boards are aggressively seeking to expand soy- bean use in large volume markets that could increase soybean farmers' prof- its. Research is underway to optimize protein modification conditions need- ed to improve the functional proper- ties of soy protein. Third, the final discussion will out- line the criteria needed to expand soy protein usc. Finding new uses for soybean products will not be easy. The history of soybean utilization shows that soy- beans were grown originally as an industrial crop. A report in 980 A.D. told of the Chinese caulking boats with soybean oil mixed with tung oil. Soybean oil was widely used in oil lamps to illuminate Chinese homes This article was prepared by Keith Smith, Keith Smith and Associlltes, and is based on his presentation on the topic during (II ,hI! 87th AOCS Allnual Muting & Expo. Indianapolis. Indiana, May I. /996. and temples until the 1920s. when soybean oil was replaced with kerosene. In 1880, there was a reference regarding the use of soybean oil as a substitute for linseed oil in paints. In 1907, a German chemist synthesized a polymer-that eventually would become known as Bakelite-by react- ing various phenols with formalde- hyde. In 1913, a patent was issued in France and Great Britain for preparing a soybean protein plastic. In 1917, a Japanese author published a series of articles on the use of soy protein to make plastic materials. lacquers, enamels, and imitation leathers. In 1923, a patent was issued for 11 soy- bean glue used in commercial ply- wood manufacturing. In the late 1920s. industrial use of soybeans received major attention in the popular press in the United States. Henry Ford's interest in soybean plas- tics for gear shift knobs. hom buttons. window frames, distributor caps, and other auto parts received a lot of auen- lion. He was a pioneer promoter of soybeans because of their potential for industrial-use applications. By 1936, the interest in industrial uses of farm products was so great that U.S. Department of Agriculture established a U.S. Regional Soybean Industrial Products Laboratory dedi- cated to investigating potential indus- trial uses for soybeans. Developing soy plastics was one of the laborato- ry's first major research efforts. Progress was made. but researchers were unable to solve one major tech- nical problem-that plastic over time would absorb water and degrade. During this period, the Japanese were producing a soybean fiber. In 1939. they produced 0.9-1.2 million pounds of soybean fiber. The Germans also were involved in fiber production. The Ford Motor Company at one time was making five thousand pounds of fibcr per day. Ford scientists even made up a soy fiber suit for Henry Ford to wear. In 1947, the Federal Trade Commission saw enough poten- tial in soy fibers to name them "azlon" the same way cellulose fibers were given the trade name "rayon." In the late 1940s, Azlon was used in blan- kets. hosiery, rugs and carpets, uphol- stery, underwear, hats, and other tex- tile products. Another large volume early market for soybean protein was in plywood adhesives. At one time trainloads of soybean meal were shipped from the Midwest to the Northwest for use by thc plywood industry. Soy adhesives were widely used in the manufacture of interior plywood. During World War II, soy protein foams were used by the U.S. Navy in fighting fires. During the early 1940s. two patents were issued for using hydrolyzed protein and lime to make an air-foam for fire extinguishing pur- poses. There still is a small use of pro- tein foam in fire control. but the pro- tein used is obtained from imported cattle hoof and hom meal proteins. In the late 19405 and early 1950s, the feed and food industries were improving their ability to use soybean products. Soybean products began to dominate both the feed and edible oil markets. Soybean meal and oil pro- vide the needed functional and runri- INFORM. vtJI. 7. no. 11 (Ncwember 1996)
Transcript
1212
PROTEIN & CO-PRODUCTS
Industrial uses of soy protein: new ideas
The early history of soybean uti-lizaticn is a study of industrialuses of soybeans. Soybean oil
was first used as a fuel and as a replace-ment for linseed oil in paints and coat-ings. Soy protein found early uses asplastic polymers, wood adhesives, syn-thetic fibers. fire foams, paper coatings,and for a wide variety of minor indus-trial uses. Most of these uses ended inme 19405 with the development of lessexpensive petroleum-based chemicalsthat provided the needed functionalproperties. In recent years there hasbeen a renewed interest in developingand expanding markets for industrialuses for soy protein.
Expanding the industrial use of soyprotein is supported by soybean fann-ers who are financing research on soyprotein through the soybean checkoffprogram.
This article will discuss industrialuses of soy protein from three generalapproaches:
First, it will discuss the history ofindustrial soy protein use. There havebeen 70 years of soybean utilizationresearch 10 draw upon, so there is along history of industrial use. Many ofthese uses are being retnvesrlgetedbecause soybeans offer some solutionsto today's environmental problems.
Second, it will review soybeancheckoff research projects designed tofind "new" industrial uses for soy-beans. Several checkoff boards areaggressively seeking to expand soy-bean use in large volume markets thatcould increase soybean farmers' prof-its. Research is underway to optimizeprotein modification conditions need-ed to improve the functional proper-ties of soy protein.
Third, the final discussion will out-line the criteria needed to expand soyprotein usc.
Finding new uses for soybeanproducts will not be easy. The historyof soybean utilization shows that soy-beans were grown originally as anindustrial crop. A report in 980 A.D.told of the Chinese caulking boatswith soybean oil mixed with tung oil.Soybean oil was widely used in oillamps to illuminate Chinese homes
This article was prepared by Keith Smith, Keith Smithand Associlltes, and is based on his presentation onthe topic during (II ,hI! 87th AOCS Allnual Muting& Expo. Indianapolis. Indiana, May I. /996.
and temples until the 1920s. whensoybean oil was replaced withkerosene.
In 1880, there was a referenceregarding the use of soybean oil as asubstitute for linseed oil in paints. In1907, a German chemist synthesized apolymer-that eventually wouldbecome known as Bakelite-by react-ing various phenols with formalde-hyde. In 1913, a patent was issued inFrance and Great Britain for preparinga soybean protein plastic. In 1917, aJapanese author published a series ofarticles on the use of soy protein tomake plastic materials. lacquers,enamels, and imitation leathers. In1923, a patent was issued for 11 soy-bean glue used in commercial ply-wood manufacturing.
In the late 1920s. industrial use ofsoybeans received major attention inthe popular press in the United States.Henry Ford's interest in soybean plas-tics for gear shift knobs. hom buttons.window frames, distributor caps, andother auto parts received a lot of auen-lion. He was a pioneer promoter ofsoybeans because of their potential forindustrial-use applications.
By 1936, the interest in industrialuses of farm products was so greatthat U.S. Department of Agricultureestablished a U.S. Regional SoybeanIndustrial Products Laboratory dedi-cated to investigating potential indus-trial uses for soybeans. Developingsoy plastics was one of the laborato-ry's first major research efforts.Progress was made. but researcherswere unable to solve one major tech-nical problem-that plastic over timewould absorb water and degrade.
During this period, the Japanesewere producing a soybean fiber. In1939. they produced 0.9-1.2 millionpounds of soybean fiber. The Germansalso were involved in fiber production.The Ford Motor Company at one timewas making five thousand pounds offibcr per day. Ford scientists evenmade up a soy fiber suit for HenryFord to wear. In 1947, the FederalTrade Commission saw enough poten-tial in soy fibers to name them "azlon"the same way cellulose fibers weregiven the trade name "rayon." In thelate 1940s, Azlon was used in blan-kets. hosiery, rugs and carpets, uphol-stery, underwear, hats, and other tex-tile products.
Another large volume early marketfor soybean protein was in plywoodadhesives. At one time trainloads ofsoybean meal were shipped from theMidwest to the Northwest for use bythc plywood industry. Soy adhesiveswere widely used in the manufactureof interior plywood.
During World War II, soy proteinfoams were used by the U.S. Navy infighting fires. During the early 1940s.two patents were issued for usinghydrolyzed protein and lime to makean air-foam for fire extinguishing pur-poses. There still is a small use of pro-tein foam in fire control. but the pro-tein used is obtained from importedcattle hoof and hom meal proteins.
In the late 19405 and early 1950s,the feed and food industries wereimproving their ability to use soybeanproducts. Soybean products began todominate both the feed and edible oilmarkets. Soybean meal and oil pro-vide the needed functional and runri-
INFORM. vtJI. 7. no. 11 (Ncwember 1996)
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tional properties at costs competitivewith competing products. Soy's per-formance, price. and availability havebeen important in establishing presentuses and will be critical in anyexpanded use opportunity.
Food and feed use account for vir-tually all soybean use. Industrial usesof soybeans account for less than 3%of total soybean use. With the domina-tion of the traditional uses of soybeanproducts. it is easy to see why farmersget excited about new and exotic usesfor soybeans.
Several checkoff boards have agoal to expand industrial uses of soy-beans. The effort is aided by soybeansbeing a renewable resource that doesnot face social or political resistance.
The checkoff research program canbe subdivided into end-use areas: (a)research to increase soy protein use inadhesive formulations: (b) research toexpand soy protein use in polymers;and (c) studies to modify soy proteinto better provide the functional prop-erues needed for the various end uses.Some of the research efforts are fund-ed in part by soybean checkoff pro-grams are described in the rest of thisarticle.
Soy protein use in adhesives"Expanded research and developmentof soybean-based wood adhesive forpurpose of commercialization" is ajoint research project involving IowaState University, U.S. Forest ProductsLaboratory, Natural ResourcesResearch Institute, University ofNebraska. University of Arkansas,Texas A&M University, and Universi-ty of Illinois.
Limited research on soy-basedadhesives indicates that water solubili-ty will limit its use in many woodapplications. Researchers believe themost logical way to improve the com-petitiveness of soy-based adhesives isto modify the properties of the proteinby changes in the adhesive formula-tion. or to use the protein as a co-binder in other adhesive systems.
This research project will identifyproperties of adhesives required byvarious wood product markets andassess the ability of soy-based adhe-sives to meet the market need. Theproperties being studied are bond
strength, water resistance, cost. pro-cessing variables. and environmentaladvantages.
The research will develop and opti-mize adhesive formulations containingsoy protein products to meet the needsof the identified wood products mar-ket. These studies will involve proteinmodification, formula optimization. ormodifying wood products processingprocedures.
"Development of soybean-derivedmaterials as major adhesives compo-nents for structural (exterior) endjointing of lumber" is a project direct-ed by Roland Kreibich ConsultingService.
Kreibich has evaluated various soyprotein products that could be used indeveloping an endjoint resin. He hasoptimized processing conditions (pro-tein concentration, catalyst type, andtime-temperature-pressure relations)needed for commercial use. Strengthand wood failure of joints bondedwith resin formulas containing soyprotein hydrolyzates has been evaluat-ed in the laboratory. Kreibich hasshown that the hydrolyzed soy pro-teins have a role in glues that are usedin joining lumber.
The research project will optimizeand laboratory test the formulation ofthese adhesives for three importanttimber species. Mill trial tests will beconducted to demonstrate the value ofthese formulations to the wood indus-try. These studies are underway. andthe research will be communicated tothe forest products industry throughthe publication of results in technicalpublications and the trade press.
"Use of soy protein in foamed ply-wood glues" is a project undertakenby the USDA Agricultural ResearchService at the University of Illinois.Lars Dunn will investigate the poten-tial use of soy protein products inwood adhesives that could be appliedin a foamed state. The research willseek to optimize fonnulation and pro-cessing conditions. The researchshould help determine the proteinproperties important to the perfor-mance of foamed plywood glues.Dunn is working with industry tomake sure the results will have com-mercial application to the wood prod-ucts industry.
"Modified soy flour as an adjunctto wood product adhesives" is underway at the Natural ResourcesResearch Institute, University of Min-nesota. It is a project to manufacturewood composites (oriented strandboard. particle board, medium densityfiber board) with adhesives that usesoy protein as a major component.The research group will replace com-ponents of existing wood adhesiveswith soy flour. A secondary objectiveof the study will be to understand themechanism of wood-bonding for soyflour modified with acid and basechemicals. The Natural ResourcesResearch Institute works closely withthe wood products industry, They havea wood products pilot plant that canbe used to test soy products.
"Soy protein hydrolyzates toimprove the properties ofurea-formaldehyde additives used bythe wood industry" is a project atRoland Kreibich Consulting Service.The research team will conduct stud-ies to determine if high-protein frac-tions from soybeans can enhance theproperties of urea-formaldehydeadhesives used in the manufacture ofwood composite panels. The studieswill (a) optimize the reaction condi-tions between hydrolyzed soy proteinand urea resins; (b) determine whetheradhesive cure kinetics are influencedby the addition of soy proteinhydrolyzates to urea resin adhesives;(c) determine strength and durabilityof particle boards produced fromhydrolyzed soy protein-urea resinadhesives; and (d) determine whetherthe addition of hydrolyzed soy proteinto urea resins will lower formaldehydeemissions from particle boards. Thesestudies will have an important impacton soy protein use in urea-fonnalde-hyde adhesives.
Soy protein polymers"An integrated soy plastic research,development. and commercializationprogram" is a joint project involvingIowa State University. University ofConnecticut. and the U.S. Anny Nat-ick Research. Development and Engi-neering Center. Larry Johnson andJay-Lin Jean at Iowa State Universityhave developed plastic-like materialsfrom soy protein and soy protein/com
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PROTEIN & CO-PRODUCTS
at the University of Southern Missis-sippi where Shelby Thames has beenfunded to develop a novel soy pro-tein-lignin composite for use by theconstruction industry. The researchteam will design, synthesize, and for-mulate a soy-derived composite. Theywill characterize the physical andchemical properties of the soy-derivedcomposite. A market study will beconducted to determine use potentialsfor the soy-derived composite. If theproject is successful, the technologywill be transferred to a pilot-plantoperation to produce sufficient materi-al for a commercial evaluation.
"Development of an environmen-tally favorable macromolecular emul-sifier derived from soy protein" isanother project at the University ofSouthern Mississippi. RobertLochhead has received funds to con-duct a feasibility study to determine ifsoy protein is a viable candidate as asource of protein in the developmentof a biodegradable, protein emulsifier.
Soy protein modification"Novel and value-added productsfrom structurally modified soy pro-teins" is a joint project involving theUniversity of Arkansas and TexasA&M University.
The team of Heniarachchy andRhee are modifying soy protein. usingvarious chemical and enzymatic meth-ods, to produce protein products withgreater value for industrial applica-tions. They are developing simple andsensitive methods to understand andmonitor structural changes duringmodification. They will establishassay methods for measuring selectedfunctional properties of modified pro-
starch blends that have valuable prop-erties in products and markets target-ing environmental issues. Because oftheir environmental friendliness, soyproteins are attractive packaging alter-natives to conventional plastics usedby the fast-food industry and the mili-tary.
The goal of this research is to inte-grate research, development, and com-mercialization efforts to make soy-based plastics an important material inmeeting the need for more "environ-mentally friendly" plastics. The pro-ject's specific objectives includeexpanding processing studies to pro-duce soy plastics for selected enduses, cataloging properties of soyplastics deemed commercially usefuland practical, and evaluating thebiodegradability of the soy. Throughprocessing and formulation, they planto improve and tailor physical proper-ties of selected soy plastics for specif-ic end uses.
"Soybean composites" is a project
The research will target developinglarge molecular emulsifiers from soyprotein that have the needed activityand are environmentally superior tooil-based products. The research willcharacterize and evaluate the function-ality of large molecular emulsifiersthat contain soy protein.
USB to fund 20 projects on industrial soy use'The New Uses Committee of the United Soybean Board(USB) earlier this year approved $4.3 million in fundingfor 20 new product development and commercializationprojects.
'The funds come from a grower-approved program inwhich growers contribute part of the sale of their soy-beans into a fund for research and market developmentprograms.
Tbe new projects approved recently were:Adhesives-fundamental research on hydrolysis prod.
UCIfrom soy protein isolates, to be done at Battelle Memo-rial Institute, Columbus. Ohio: evaluation of soy isolatesfor use as binders, extenders and modifiers in woodadhesvies, to be done at Mississippi State University,Greenville. Mississippi: production test of modified soyflour adhesive for use in sttandboard manufactwing. to bedone at the University of Minnesota, Duluth. Minnesota.
Coatings--evaluation of composite soy dispersion aspaint binders. to be done at ICI Paints, Strongville. Ohio;reactive diluent demonstration project in California, to bedone by researchers at Eastern Michigan University.Ypsilanti, Michigan.
Lubricants--develop chemically modified soybean oilfor use as lubricant oil basestock, to be done at Caterpil-lar Inc., Peoria, Illinois: identify functional telomers from
soybean oil and to evaluate soy-based lubricants for spe-cific purposes. to be done at International Lubricants Inc .•Seattle, Washington.
Solvents=evaluate methyl ester cleaners for screenprinting inks. develop packaging for products containingsoy methyl esters, to be done al Frammar Chemical Inc.,Normal, Illinois.
Inks-define chemical, physical. and economicrequirements of soy-based resin polymers use for inkmanufacturing, to be done at OmniTech InternationalLrd., Midland, Michigan.
Composites-evaluate soy protein and hulls as addi-tives in adhesives for wood-based building panels. to bedone at The Robertson Corporation, Brownstown, Indiana.
Plastics--explore development of polyurethanes usingsoy ingredients, to be done at the University of Missouri,Columbia, Missouri.
Swfactants--develop soybean-derived monomers andsurfactants for emulsions, polymerization and detergents.to be done at University of Southern Mississippi. Harries-burg, Mississippi.
General--conduct market analysis studies regardingadhesives, coatings, plastics, lubricants and solvents,work to be done at OmniTech International LId., Mid-land, Michigan.
INFORM. Vol. 7. no. " (November 1996)
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teins important in novel nonfood, non-feed industrial applications. The prod-ucts that they are producing are beingevaluated in the joint adhesive project.
"Efficient. environmentally benigncross-linking of soy protein and studyof hydrolytic stability of the resultingnetwork polymers" is being pursuedby Iowa State University's Dr. Kostic,who will apply new methods of bioor-ganic chemistry to soy proteins usedin plastics, coatings. and composites.The research team will develop newchemical modifications that optimizeconditions for spontaneous cross-link-ing soy protein isolates. The researchwill characterize the properties ofchemically-modified and cross-linkedprotein structures. A secondary objec-tive is to determine how metal com-pounds modify protein hydrolysis.
"Protein functionality" is anotherproject of an Iowa State Universityteam to determine the functionalityproperties. or desired traits, needed insoy protein with potential industrialuse applications. The group is seekingto initiate research that can discover.or modify, soy protein products thatcould have industrial use applications.The research team also will character-ize the chemical and physical proper-
~NX.SPRESS
ties of the soy protein products. Theresults obtained during the first yearwill be used to develop proposals forcommercialization of one or moremodified soy protein products thathave industrial use applications.
"Characterization of commercialsoy protein products for new applica-tion" at the Food Protein Research andDevelopment Center, Texas A&MUniversity, involves K.C. Rhee andco-workers who are seeking to devel-op a data bank of physical, chemical,and functional propenies of commer-cially available soy protein productsthat have industrial applications. Theywill determine physicochemical prop-erties of selected protein productsusing advanced analytical technolo-gies. The functional properties (solu-bility, water binding, viscosity. emul-sion activity, foam formation, and gelformation) for each of the proteinproducts will be reported and madeavailable to potential industrial usersof soy protein.
As one can see, several researchgroups are working hard to expand theinformation initially begun over 50years ago. These projects are takingadvantage of past failures and usingresearch to modify soy protein charac-
terisrics 10 meet industrial use needs.Several of the projects discussed
are receiving funds from both the stalecheckoff and the United SoybeanBoard. Soybean farmers are hopefulthat the funds they are providing willresult in new uses for soybeans andreclaim some of the uses that were10Sl in the 1940s and 1950s to lessexpensive petroleum-based chemicals.
Any successful new soybean pro-tein use must meet four criteria. Todevelop into a significant new use, anew soy-based product must: (a) beneeded-without a need, there is nopurpose in trying to develop a new soyprotein use; (b) have performanceadvantages over the product that itintends to replace; (c) have a priceadvantage over the product to bereplaced; and (d) be available com-mercially in amounts to satisfy thepotential demand.
In summary. with a little luck anda lot of hard work, we anticipateresearchers will be able to producesoybean products that will have theperformance and price structureneeded to replace existing products.The future is extremely optimisticfor expanded industrial use of soyprotein.
SafflowerJoseph R. Smith
Hardbound. 624 pages. 1996ISBN 0-93531 &.01.0Item .1083list Price: S 150.00 Member Price: S120.00
To order eontoet AOCS PreuP\IbIIcotloN Ordef Deportrr.ntF'I1one: 1·217·359·5401. eld. 128loI-fTH: 1-800-l36-AOCS (U.SJConodIl)
Contents. History • The Early Days of the Industry • Characteristics ofSafflower • Development of the Pacific Vegetable Oil Strategy • Alternativesto the Pacific Vegetable Oil Strategy • Developmental Research • Processingand Handling Research • Industrial Oil Research • Medical. Pharmaceutical.Cosmetic, and Edible Research • Protein and Meal Research • AnalyticalResearch • Unconventional Use Research • The Rise and Fall of PacificVegetable Oil-Pan I • The Rise and Fall of Pacific Vegetable Oil-Pan LI •Oleic Safflower. Safflower Around the World • 1980s to the Present •Safflower Today. and Where It Is Going. Appendix A: U.S. and World AcreageReports _ Appendix 8: North American Safflower Variety Descriptions.Appendix C: Recommended Cropping Practices. Appendix 0: Legal andTechnical Regulation ofTrnde
INFORM. Vol. 7. no. II (November 1996)
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PROTEIN & CO-PRODUCTS
Immaturesoybeans:direct use
for foodAlthough most soybeans are harvestedat the mature stage and further pro-cessed into a variety of products forhuman or animal uses, in certain areasof the world, such as China. Japan andsome other Far East countries orregions, considerable quantities areharvested at the immature stage fordirect human consumption.
With green to yellowish greencolor. soft texture, and large seed size,the immature beans normally are har-vested at about 80% maturity. Imme-diately after they are cut, the greensoybean plants are taken to marketswhere they are sold by the bunch. Theyellowish-green pods are picked fromthe plants and then steamed or boiledin water, normally for less than 20minutes. After being lightly salted orspiced, the cooked beans in pods can
Cooked, Immature soybean. served •• a vegetable
serve as an hers d'oeuvre, often withbeer or other alcoholic drinks. Alter-natively, the green soybeans can beshelled, then cooked for serving as agreen vegetable with a main meal. Theproduct is known as qing dou inChina, meaning green beans, and asedamame in Japan.
In the West, developing food prod-UCtS from immature soybeans nodoubt will expand food uses of soy-beans and help meet an increasingdemand for nutritious vegetables bycertain consumers. Already, frozen orcanned immature soybeans haveappeared in the Western market. Theyare alternatives to frozen or cannedpeas. green beans, and other vegeta-bles. At least one U.S. company. Sun-Rich Inc. of Hope. Minnesota, is mar-keting immature soybeans under the
This article 11-'(lS' prepared/or INFORM by KiShunLiu, pmject leader for the Soyfood Laboratory atHart: Seed, a lUIit o/Monsanlo Co., P.O. Box 946.Stuttgart, AR 7Zt6{).
brand name of "Sweet Beans."In this article, an attempt is made
to discuss immature soybeans in termsof their nutritional quality, organolep-tical characteristics, food utilization.quality attributes, and current con-straints in developing value-addedproducts from them. Limited informa-tion on the subject is available (I).
Compositional changes during mat-urationDuring seed development and matura-tion, young soybeans undergo manycompositional changes before reach-ing maturity. Understanding thesechanges helps compare the nutritionalquality of immature soybeans and thatof mature ones.
Weight and color change as soy-beans mature. During soybean matu-ration, dry matter in the Hawkeye vari-ety increases from 16 to about 90%(Table I) (2). However, the averagefresh weight, expressed as mg/seed,increases from 30 to a peak at 568 andthen decreases to about 209 at thematurity. Soybean pod color changesfrom the immature green to yellowand then to brown at the mature stage.The color of the soybeans in the podswill change from green to light green,yellow-green. yellow, and then tobuff-brown. The best time to pick
INFORM. Vol. 7. no. 11 (November 1996)
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triglycerides, while the latter arereserved in another organelle knownas protein bodies. The compositionof the dry soybean seed is about 30%protein (Table 2) and 5% oil (Table3) at approximately 25 days afterflowering, according to Rubel et al.(3). These levels represent about 2%of the total protein and about I% ofthe total oil that will be found inmature soybeans. From 24-40 daysafter flowering, the oil percentageincreases rapidly to 20%, which rep-resents about 30% of the total oil ina mature soybean. At the same lime,the protein percentage increases to34%, also representing about 30% ofthe total protein in a mature soybean.During the remainder of the develop-ment (about 25 days), dry percentagevalues of most components remainessentially constant, but 70% of totalprotein and oil are synthesized. Sinceimmature soybeans are normally har-vested between 50-60 days afterflowering. they contain 11-16% pro-tein and 8- I I % oil on fresh basis.The actual amounts depend on har-vest time.
Fatty acid composition. Rubel etat. (3) found that from 24-40 daysafter flowering the percentage ofpalmitic, stearic, and linolenic acids inthe oil decreases (Table 4), while thepercentage of oleic and linoleic acidsincreases. Although the percentagevalues of the individual fatly acidschange markedly, the total amount ofall fatly acids increases. During theremaining stage of soybean develop-ment, relative percentages of fatlyacids remain essentially constant.However, Sangwan et at. (4) reporteda decrease in oleic acid and anincrease in linolenic acid during laterstage of development (from 45 daysafter flowering). The discrepancyamong reports might be due to differ-ent varieties or assay methods used.
Amino acid composition. Of the 17amino acids detected, quantities ofarginine, serine, glutamic, glycine,and leucine increase linearly with soy-bean development whereas histidineand alanine linearly decrease.although there is some variationamong the fWO cultivers studied (5). Inaddition, there is an overall decreasein total free amino acids (6), which
PROTEIN & CO-PRODUCTS
Table 1Fresh weight, dry matter, and color characteristics of maturing soybeansof Hawkeye varIety (adapted from Ref. 2)
immature soybeans for direct con-sumption is when the seed colorchanges from green 10 light green. Atthis stage, seeds are at about 80%maturity.
Protein and oil accumulations,During maturauon. soybeans under-go mass syntheses of storage lipidsand proteins. The former are storedin oil bodies, mainly in the form of
INFORM. Vol. 7. no. 11 (Novembef 1996)
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may partially explain that immaturesoybeans taste better than matureones.
Carbohydrates. Sugars that havebeen detected in soybean seedsinclude glucose. fructose. galactose,sucrose, raffinose. and stachyose.Sucrose appears early in the seeddevelopment, followed by raffinoseand stachyose, which are not detecteduntil 40-50 days after flowering (Fig-ure I) (5). Dimethyl sulfoxide(DMSO) soluble starch reaches amaximum value at 30-40 days afterflowering and then declines sharply toalmost nonexisting at the maturestage. The total water-soluble polysac-charides amount increases whenexpressed on wet basis but decreaseswhen expressed on dry mailer basis.Thus, immature soybeans containhigher amounts of simple sugars andmuch lower amounts of oligosaccha-rides than do mature soybeans (5,7).This is consistent with a commonimpression that flatulence is infre-quent after ingestion of immature soy-beans.
Vitamins. During maturation, bothascorbic acid and p-carotene decreaseand reach their lowest values at themature stage (Figure 2) (8). Ascorbicacid in immature beans could be ashigh as 40 mg/IOO g fresh weight. Itdecreases to 2 mg/l 00 g soakedweight at the mature stage. Similarly,immature soybeans contain Bcaroteneas high as 0.46 mg/IOO g fresh weight;this figure decreases to 0.12 mg / I00 gsoaked weight when beans are mature.The concentration of 8-tocopherol insoybean seeds was found to be thehighest at the early phase of poddevelopment in the field conditions,then decreased during the later stage(9). At the same time a and r toco-pherols increased.
Antinutritionat [actors. Collinsand Sanders (10) reported that, on amoisture-free basis, trypsin inhibitor(TI) levels increased with soybeanmaturation in all four cultivars stud-ied although there was a differencein the rate of increase. However, Yaoet at. (11) observed no changes in TIactivities in two soybean culrivarsstudied. Thus, the specific cultivarwill have a great influence on bothvalues and change patterns of TI
Table 4Changes In fatty acid composition of 011In maturing soybeansof Harosoy 63 variety (adapted from Ref. 3)
Days after Fatty acid composition (%)flowering C16:0 C18:0 C18:1 C18:2 C18:3
Table 5Effects of maturation and processing on trypsIn inhibItory activity(trypsin units inhibited/mg dry sample) in sOYbefns of two cultivars(adapted from Ref. 7)
I·' - "'- ,5 , , , , , , , , sr• '"1 c-e _ m to w so ~ ro ., '" o rc ro '" ~ se ., 30 0u Days after flowering "!,~
" " 8u " ~
""'''' .....ro ro
•• •• •2 ,~~77:,~~~, 2
001020300103060700(020)(1010306070 0
Days after floweringFIgure 1. Changes In carbohydrate content In maturing soybeans (Harosoy 63 variety).DMSO starch., dimethyl sulfoxide soluble starch (Raf. 5)
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PROTEIN & CO-PRODUCTS
80 water) or steaming immature soy-beans for 20 minutes completelyeliminates TI activity. However, formature soybeans, 100% destructioncould only be achieved by soakingplus boiling.
Immature soybeans also containless phyric acid, which is widelybelieved to interfere with mineralabsorption in the body. According 10Liu (12). phytate content increasedfrom 0.84% to 1.36% on a dry matterbasis in one variety and from 0.86% to1.39% in another during soybean mal-urmion.
tsoflavones. During soybean mat-uration. there are changes in the totalconreru of isoflavones as well as oftheir isomer compositions (13), Ingeneral. the maionylgenistin andgenistin content increased during thelate stage of soybean development.whereas malonyldaidzin and daidzinaccumulated throughout the wholeperiod (Figure 3). Minor isoflavoneglycosides. such as malonylglycitinnnd glycitin. also were detected.lsoftavones have been shown to exertmany health benefits, including can-cer prevention and treatments (14).However. their presence is partiallyresponsible for objectionable taste ofsoy products (13). Lower contents ofisoflavones are consistent with the fact
Organoleptic features of immaturesoybeansImmature soybeans have severalorganoleptic features that are superi-or to mature ones. These includetheir green color, larger size, softertexture. sweeter and better taste, andreduced beany flavors. Larger beansize results from two factors: highmoisture content and genotypicselection for large-seeded varieties.The young age of the seed tissue andgenotypic selection account for softtexture of immature beans. Thesweeter and somehow delicious tasteof immature soybeans is attributed totheir higher content of simple sugarsand free amino acids, and lower lev-els of isoflavones.
Rackis et al. (2) compared flavorprofile in soybeans harvested at differ-ent maturing stages, in terms of bothbeany and biller flavors. The tastepanel involved found the flavor inten-sity values of beany characteristics didnor show any significant trends withmaturation, but there was a significantincrease in the intensity value for bit-ter flavor. The authors auributed thelower bitter flavor in immature soy-beans in part to lower lipoxygenaseactivity found in such beans. Therewas an overall increase in lipoxyge-nase activity in maturing soybeans,although the value fluctuated.
Food uses and market potentialUse as a green vegetable constitutesby far the largest use of immature soy-beans in the Orient and elsewhere.The product is marketed mainly inthree different forms: fresh. frozenand canned, although fresh consump-tion is most popular. As described ear-lier, fresh green soybeans are simplysimmered with or without pods, andlightly salted before serving as a snackor a dish with a main meal. Althoughbest served fresh and in season, imma-ture soybeans can also be frozen orcanned just like other vegetables.Such products are more popular in theWest than in the Orient. They can beused in side dishes, salads, tacos, ricedishes, casseroles. mixed vegetables,soups or stews. stir frying dishes. andmeat dishes. They can be cooked overa stovetop. in a microwave. or in asteamer. In addition. in Japan. cooked
1221
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1.5.000
i~~ 10.000
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Days aflel" flowering
Figure 3. l.otlavone accumulation during maturation of Maple Arrow .oybean seedl (Rei.13). Peak Iraa ahoWI the chang-e In rel,tive ,moun~ ollsoHavone glycosJ.deslOl'" a c.rtalndry weight.
" 60
as30
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Fiber
Sweel beans • Peaso Sweet corn • Green beans
110....... !.OOO <aIorie die1 (m <1>1' """"1)
FIgura 4. Fiber, Iron, calcium, and protaln eont.ntsln Immatura soybeans (Sweet Beans),peas, sweet corn, Ind green belns
that immature soybeans taste less bit-ter and less astringent than matureones.
In vivo assay for nutritional quali-ty. The low content of aminutritionalfactors and the soft texture of imma-ture soybeans should improve proteindigestibility. Indeed, in one rat-feed-ing study (15). immature soybeanswere shown to have a higher proteinefficiency ratio (PER) than maturesoybeans (Table 6). This pattern holdstrue whether or not the soybeans areautoclaved. In another study. the netprotein utilization and PER of imma-ture soybeans were found 10 be com-
parable 10 thai of casein and lean beef(16).
Comparison with other frozen veg-etables. Immature soybeans have fourtimes more fiber than corn, greenpeas, and green beans; they also havea much higher content of iron. calci-um and protein (Figure 4), accordingto SunRich Inc .. which markets imma-ture soybeans. More importantly.immature soybeans contain iso-flavones while corn. green peas. andgreen beans do not. Therefore, theyare better alternatives to frozen orcanned peas and green beans in termsof nutrition and health benefits.
INFORM. Vol. 7, no. 11 (November 1996)
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PROTEIN & CO-PRODUCTS
Table 6In vivo studies on the nutritive value of soybean proteins (Ref. 16)
80dy weight (g) Nitrogen ProteinSoybeans Initial Final absorbed (%) efficiency ratio
green soybeans are also available inthe market Known as hitashi mallie,the product is packaged, with a littleof the cooking liquid, in a sausage-shaped plastic container.
Immature soybeans also can beroasted to dryness, and then salted orspiced 10 serve as roasted products.Already available in the Japanese mar-ket, the product, known as irori lIlame.has a crunchy texture, greenish-beigecolor, and delicious taste. Other fooduses of immature soybeans are expect-ed after further exploration. Somehave suggested making a slurry andspray-dry product after grinding. Oth-ers have just begun to realize the mar-ket potential for immature soybeans.According to Peter Golbitz ofSoyatech Inc. (personal communica-tion), if fresh green soybeans were toreplace 3% of frozen and canned peasand green beans businesses in theUnited States, the total bushels of soy-beans needed to supply the marketwould be 1.45 million bushels.
Quality attributes or immature soy-beansDesirable quality attributes for soy-beans intended for consumption asgreen vegetables include large seedsize, soft texture, good flavor, and ahigh content of protein, free aminoacids, and total sugars. Factors affect-ing these attributes include cultivar,growing seasons, harvest time, andstorage conditions.
Genotypic variation. Over theyears, in the Far East region, soybeancultivars thai have the previously men-tioned desirable traits for fresh con-sumption have been obtained throughnatural selection and plant breeding.These varieties, once referred to as
"garden-type of soybeans" by someWesterners, are now known asedamame type. They do not differ fun-damentally from field varieties, exceptthat they are generally larger in size,more tender in texture, lower in beanyflavor, higher in protein, lower in oiland yield, and have a clear hilum.They also have a tendency to shatterfrom the pod. resulting in substantialloss if harvest is delayed until themature stage.
Growing seasons. Akazawa andFukushima (17) reported both geno-typic and year-to-year variations infree amino acids, total sugars. pro-teins, and starch contents of immaturesoybeans. The free amino acids gener-ally were higher in soybeans ofedamame cultivar than they were inordinary soybean cultivars, while theyear-to-year variation depended onsolar radiation from flowering to har-vest.
Harvest time. Harvest time affectsimmature soybean quality mainlybecause of the compositional changesthat occur during maturation, as dis-cussed previously. In one report withthree edamome cultivars (6), therewere decreases in ascorbic acid, sug-ars, and free amino acids with soy-bean maturation.
Storage conditions. Due to theirhigher moisture content and tender tis-sue, immature soybeans deterioraterapidly upon storage. Minamide andHata (6) reported that ascorbic acidand free amino acids in immaturebeans decreased rapidly after harvest,but total sugar content remainedalmost unchanged during storage forseven days at 20°C. Increases in pro-tein and starch contents with storagealso have been reported (17).
Constraints and challengesAlthough immature soybeans haveseveral nutritional and organolepticadvantages over mature soybeans, atpresent the market is very limited,mainly because of difficulty in har-vesting. Tender immature soybeansare very susceptible 10 damage orbruising during harvesting. When theyare bruised or damaged, oxidativereactions occur rapidly, leading to off-flavor formation and surface brown-ing. Other constraints include a shortshelf life, some degree of hard-to-eliminate beany flavor, overall lowfield yield compared with maturebeans, and lack of marketing efforts.In addition, their green color limitstheir use solely to consumption as agreen vegetable.
SummaryAs a green vegetable, immature soy-beans are highly nutritious, as indi-cated by their high content of pro-tein, oil, ascorbic acid, J3-carotene,fiber, iron, and calcium, low levels oftrypsin inhibitors, oligosaccharides,and phytnte , and ultimately highPER values. They have tender tex-ture, sweet and delicious taste, andversatility for processing. They alsocontain certain amounts ofisoflavones. Therefore, the outlookfor the market of immature soybeansappears promising. However, marketsuccess will depend largely onefforts to solve certain constraintsassociated with production, harvest-ing, processing, and marketing ofimmature soybeans. Apparently. tosolve these problems requires collab-orative work among people with dif-ferent disciplines, including food sci-entists, geneticists, plant breeders,engineers. and marketing specialists.Current research revealing the healthbenefits of soyfoods will no doubtserve as a driving force for us totackle these challenges.
AcknowledgementsThanks are expressed to Neal Bringeof Monsanto for his valuable com-ments as well as information regard-ing SunRich Sweet Beans, and toAllen Routh, president of SunRichInc., for his comments and permissionto use Figure 5.
INFORM.Vol. 7, no. 11 (November 1996)
ReferencesI.Rackis. J.J .. Comparison of the
Food Value of Immature, Mature.and Germinated Soybean, inQuality 0/ Selected Fruits andVegetables 0/ Nonh America, edit-ed by R. Teranish and H. Berrero-Benitz. American Chemical Soci-ety symposium series. No. 170.pp. 183-212. 1981.
2. Rackis. 1.1 .. D.H. Honig, 0.1.Sessa and H.A. Moser. Lipoxyge-nase and Peroxidase Activities ofSoybeans as Related to the FlavorProfile During Maturation, CerealChern. 49:587-597 (1972).
3. Rubel. A .. R.W. Rinne and D.T.Canvin. Protein. Oil, and FattyAcid in Developing SoybeanSeeds, Crop Sci. 12:739-741(1972).
4. Sangwan. N.K .. K. Gupta and K.S.Dhindsa, Fatty Acid Compositionof Developing Soybeans, 1. Agnc.Food Cnem. 34:415-417 (1986).
7. Liu, K., and P. Markakis, Effectof Maturity and Processing on theTrypsin Inhibitor and Oligosac-chari des of Soybeans, 1. FOOlISci.52m222-223. 225 (1987).
8. Bates. R.P., and R.F. Matthews.Ascorbic Acid and ~-Carotene inSoybeans as Influenced by Maturi-ty, Sprouting, Processing and Stor-age, Proc. Fl. Slate Hort, Soc.88:266-271 (1975).
9. Lee, LB., and K.W. Chang.Changes in Concentration ofTocopherols and Fatty Acids Dur-ing Germination and Maturationof Soybean (Glycine max),Han 'guk: Nonghwa Hakhoechi36(2),'27-'33 (1993).
10. Collins, J.L., and G.G. Sanders.Changes in Trypsin InhibitoryActivity in Some Soybeanvarieties During Maturation andGermination. 1. Food Sci.41"68-172 (1976).
II. Yao, J.J., L.S. Wei and M.P. Stein-berg, Effect of Maturity on Chem-ical Composition and Storage Sta-bility of Soybeans, 1. Am. OilChem. Soc. 60: 1245-1249 (1983).
12. Liu, K., Effects of Processing andMaturity on Certain Antinutrition-al Factors in Soybeans, M.S. the-
sis, Michigan State University.East Lansing, Michigan, 1986.
13. Kudou, S., Y. Fleury, D. Welti, D.Magnolato, T Uchida, K. Kita-mura and K. Okubo, MalonylIsoflavone Glycosides in SoybeanSeeds (Glycine max Merrill).Agric. BioI. Chem. 55:2227-2233(1991).
14. Aldercreutz, H., Y. Moosavi. J,Clark, K. Hbckerstedr, E.Hamalainen. K. Mahala, T.Makela and T Hase, Dietary Phy-toestrogens and Cancer: In Vitroand In Vivo Studies, 1. SteroidBiochem. Mol. 8iol. 41:331-337(1992).
15. Everson, G.J., H. Steenbock, D.C.Cederquist and H.T. Parsons. TheEffect of Germination. the Stageof Maturity. and the venery uponthe Nutritive Value of SoybeanProducts, 1. Nutr. 27:225-229(1944).
16. Standal, R.B., Nutritional Value ofProteins of Oriental SoybeanFoods, Ibid. 81:279-285 (1963).
17. Akazawa, T., and T. Fukushima.Relationship of Varietal Traitsand Cultivating Conditions to theContent of Several Ingredients inGreen Soybeans (£damame).Yamagala Iraig oku Kiyo,Moga.ku (Japanese),11(2),415-421 (1991). •
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