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IdentifyingValuable CornQuality Traitsfor Starch Production
A project of theIowa Grain Quality InitiativeTraits Task Team
Lawrence A. JohnsonCenter forCrops Utilization Research
Connie L. HardyCenter forCrops Utilization Research
C. Phillip BaumelEconomics
Pamela J. WhiteFood Scienceand Human Nutrition
Funded by the Iowa Corn Promotion Board306 West Towers, 1200 35th Street, West Des Moines, Iowa 50266
November 1999
Identifying Valuable Corn Quality Traits
for Starch Production
By:Lawrence A. Johnson
Center for Crops Utilization ResearchFood Science and Human Nutrition
C. Phillip BaumelEconomics
Connie L. HardyCenter for Crops Utilization Research
Pamela J. WhiteFood Science and Human Nutrition
A project of theIowa Grain Quality Initiative
Traits Task Team
Funded by theIowa Corn Promotion Board
306 West Towers1200 35th St.
West Des Moines, IA 50266
November 1999
Center for Crops Utilization ResearchIowa Agriculture & Home Economics Experiment Station
Iowa State University, Ames, IA
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Acknowledgment
This report is intended to provoke discussion and debate that will lead to a vision among researchersin public institutions, seed companies, and the starch processing and food industries for modifyingcorn traits for starch (and other complex carbohydrates) production to enhance utilization andprofitability of growing corn. The report attempts to provide direction to farmer organizations andto the corn industry about potential targets for investing research funds. One should recognize thatsome of the modifications considered required speculation about functional properties and potentialapplications. Additional research on the relationship between the structures of starch and othercomplex carbohydrates and functionality in food and industrial applications may refute some of thatspeculation. Also, this document is a consensus report taking into account the recommendationsand reviews of the consultants and advisors identified below.
Jay-lin Jane, Ph.D., Food Science and Human Nutrition, Iowa State University, Ames, IA
Morton W. Rutenberg, Ph.D., Emmar Consultants, North Plainfield, NJ
Henry Zobel, Ph.D., ABCV Starch, Darien, IL
Robert Friedman, Ph.D., Cerestar USA, Inc., Hammond, IN
Kenneth W. Kirby, Ph.D., Cedar Rapids, IA
Chung-Wai Chiu, Ph.D., National Starch & Chemical, Bridgewater, NJ
Modified starches and other complex carbohydratesfrom genetically modified corn are intended toprovide new functionalities that, in turn, makepossible new products and markets for corn. Otherimportant benefits include more uniformfunctionalities that are not possible with today’schemical modification routes, reduced processingcosts, decreased or eliminated chemical modifica-tions of the types resisted by consumers and envi-ronmentalists, and lower costs for users. Geneticmodifications may result from traditional plant-breeding techniques or through biotechnology.
Specific goals for use of genetically modified corn toproduce new starches and other complex carbohy-drates are as follows: to improve gel properties; toimprove viscosity and temperature stability; toreduce retrogradation and increase freeze-thaw andstorage stabilities; to mimic properties of gelatin andfats; to improve flavor and flavor stability; to reduceor increase digestibility; to improve adhesion andfilm formation; and to achieve more efficient pro-
Executive Summary
cessing (e.g., milling and fermentation, reducedenergy in cooking).
Twenty potential modifications (three high priorityand 17 moderate priority, based upon potential grossadded value) were identified and evaluated. The topseven market opportunities and related potentialmodifications are listed below.
Approximately 250 million bushels of corn isprocessed into starch products. Therefore, it isdifficult to identify individual genetic modificationsthat will meet corn-producer targets for productsthat generate new demand of 100 million bushels ormore. Industry has not seen starches or othercomplex carbohydrates with some of thefunctionalities considered in this report; therefore, itwas not always possible to estimate with confidencethe market potential and the impact on corn con-sumption. Many of the modifications may enablenew “niche” markets with considerable reward tospecific starch companies and to the few farmerswho produce specialty corn for those companies.
1If all of the starch modifications could be achieved (some are mutually exclusive), the total gross added valuewould be about $1.25 billion, more than 200 million bushels of modified corn could be consumed, and theaverage added value across all modifications would be about $5.80 per bushel.
Market Gross Corn AverageOpportunity Potential Modification Added Value 1 Consumed 1 Added
(million $/yr) (million bu/yr) Value 1 ($/bu)
Increase stability Introduce aldehydes into 298 40 7.45to acid and shear starch
Improve wet mill Decrease or modify hard 280 1,140 0.25yield of starch starch (horny endosperm)
Improve gel Lengthen A and B1 208 7 29.70formation chains in amylopectin
Replace expensive Introduce high levels of 120 19 6.30chemical reaction acetylation in starch
Reduce chemical Introduce natural cross- 60 3 20.00modification linking in starch
Increase viscosity Introduce cationic 60 10 6.00and water holding groups in starch
Improve flavor andimprove paper Reduce starch lipids 50 46 1.09manufacturing
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Advances in biotechnology and improved under-standing of biosynthesis of starch and othercomplex carbohydrates greatly increase thepossibilities of developing new or modified cornproducts. Hereafter, the term “starch” will beused to denote both starch and other complexcarbohydrates that are similar to starch butwould not comply with the usually acceptedterminology of starch. This report summarizesthe authors’ assessments, with input fromindustry consultants and advisors, of possiblecorn modifications to achieve new starches.
The purposes of the study were• To identify and describe possible genetic
modifications to corn that may have com-mercial value to the corn processing indus-try and to users of starch products;
• To estimate the gross added value (totalvalue before costs or other market factors)that could be derived from each of theidentified genetic modifications; and
• To rank specific genetic modifications forpotential market impact, and thus prioritizefor investing research funds.
The primary benefits of new starch productsfrom genetically modified corn are
• New or improved functionalities (perfor-mance properties, such as greatly reducedcooking energy requirements) that makepossible new products and markets for corn;
• More uniform functionalities that are notpossible with today’s chemical modificationroutes;
• Decreased processing costs for the starchindustry;
• Decreased or eliminated chemical modifica-tions that are resisted by consumers or thatare subject to environmental constraints;and
• Lower costs for starch users.
Because management costs and production risksare higher for products from specialty or identity-
Introduction
preserved grains, the rewards must be sufficientto compensate all participating parties for theirinvestments and risks.
Achieving new commercially viable starches bygenetic modification of corn presumes knowl-edge about starch biosynthesis in the kernel,starch granule structure, the relationship ofstarch structure to functional properties, andplant viability and growth requirements. Al-though these subjects are not fully understood,starch modification research is still proceeding.Continued research in these areas is key toachieving long-term goals.
In considering genetic modifications of corn toproduce new starches we included
• Modifications that are achievable throughtraditional and mutation breeding to altergene expression;
• Modifications that can be achieved throughtransgenic means by which genes for newenzymes are introduced into corn fromother plants, animals, and microorganisms;and
• Modifications that can be imagined from astarch structural viewpoint, but for which noknown natural mechanism may exist todayto achieve the modification (future findingsmay make these modifications possible).
Currently, our ability to envision the use ofgenetics and resultant enzymes to modify starchstructure and functionality is limited by ourunderstanding of enzymes. Of the more than25,000 enzymes estimated to exist, only about10% are sufficiently understood to be recognizedby the International Union of Biochemistry (1).Scientists are making rapid progress in under-standing the function and location of enzymesthat affect starch biosynthesis and the genes thatencode them. Undoubtedly, enzymes not recog-nized today will be useful in the future to alterstarch and to facilitate processing of corn intovalue-added products (2,3).
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We recognized that some modifications mayadversely impact the isolation of starch and wetmilling of corn. These may not be attractive totoday’s corn processing industry. Some geneticmodifications may require capital investments innew processing methods because the products ofsome modified starches may not exist as in-soluble granules. Other changes envisioned ingrain composition and endosperm structurecould result in savings due to lower energy,utility and capital costs, and reduced use ofprocessing chemicals.
Corn starch today is chemically altered for somefood and industrial applications. The U.S. Foodand Drug Administration requires the word“modified” to appear on food labels containingthese starches. If corn could be geneticallyengineered to produce these modified starchesin the kernel, foods containing these starcheswould not need to carry the “modified” designa-tion in the ingredient listing under presentlabeling laws. These changes should be wel-comed in the starch and food industries as wellas by many consumers, although we also recog-nize growing consumer resistance to “geneticallymodified organisms.” Processor savings fromreduced chemical use or eliminated chemicalprocessing are also important.
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In considering potential commercial values ofnew starches from genetically modified corn,three steps were undertaken:
1. Potential structural changes to starch wereidentified and how those changes mightaffect functionality were speculated; then
2. The applications and products in which themodified corn or starch might be usefulwere speculated; and finally
3. The functional properties and performancecharacteristics of competitive materials werecompared to estimate potential market sizesand gross added values of the corn or starchmodifications.
Additional research on the relationship betweenstarch structure and function in food and indus-trial applications may refute some of that specu-lation.
A list of potentially useful modifications wasfirst developed after several discussion sessionsamong Iowa State University scientists and staff.Ideas also resulted from a workshop meeting ofpublic-sector and industry scientists. At the endof the report is the template of the analysis formthat we used to evaluate functionality changesfor each modification. The list of modificationswas then provided to consultants and to indus-
Methodology
try scientists for comment and estimation ofgross added value and consumption of themodified corn.
In some cases, we were able to identify strategiesby which the desired modification could beachieved. However, we did not limit ourselvesto modifications that could easily be achieved.We also included descriptions of possible newmaterials (other complex carbohydrates) toreplace typical corn starch in the endosperm andmaterials that could be useful in new applica-tions.
In the real world, the actual sales volume for anew starch product from genetically modifiedcorn is determined by overall supply and de-mand, and how closely the functional propertiesmeet the application’s requirements. Whenthere is an existing commercial starch withproperties similar to those of a new geneticallymodified starch, the sales volume can be morereadily estimated. Accurate sales volumes ofspecific starch products are usually proprietary.The market values of starches with functionalproperties that are not fully defined, or forwhich no competing products with similarfunctionality are available for comparison, weredifficult to forecast and subject to more error.
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For those unfamiliar with the detail of starchand polysaccharide chemistry, a glossary ofterms commonly used in this report follows.
Alpha linkages – A specific type of linkagebetween glucose units as in normal starch
Absolute amylose – Amylose content as mea-sured by newer and more precise methods
Apparent amylose – Amylose content as mea-sured by older and less precise traditional meth-ods
Beta linkages – A specific type of linkage be-tween glucose units as in cellulose
Cross-linking – Bonds between linear starchchains that alter the physical and chemicalbehavior of starch
Degree of substitution (d.s.) – Average numberof hydroxyl groups derivatized peranhydroglucose unit in a starch molecule
Functionality – performance property contrib-uted by a specific ingredient, such as binding,water-holding capacity, film-forming, adhesion,gel stability, and viscosity
Enzyme – A protein having the ability to cata-lyze chemical reactions
Gelatinization – The melting of the crystallineregions of the starch granule
Paste – A dispersion of gelatinized starch
Pericarp – The outer layer surrounding the cornkernel
Polysaccharide – A polymer of sugars (e.g.,starch, cellulose, etc.)
Retrogradation – Recrystallization of gelatinizedstarch as in staling of bread
Starch granules – Discrete bodies of starch,which, in their native form, are comprised ofamylose and amylopectin, have large portions ofcrystallinity, and are insoluble in water
Viscosity – Fluidity of a liquid
Glossary
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Annual U.S. corn production is 9–10 billionbushels. During the 1997/1998 market year,234 million bushels of corn was processed intostarch, resulting in 7.4 billion lb of starch prod-ucts (4). Annual growth in U.S. corn starchproduction is expected to be 3.5% through theyear 2010, unless genetic modifications causemajor new processing plants to open. Corn isthe most important and economical source ofstarch in the United States. Exports of cornstarch account for less than 3% of total U.S.starch production.
Starch is the major carbohydrate storage productin corn kernels comprising 70–72% (dry basis)of the kernel. Starch exists as insoluble, par-tially crystalline granules that assume size andshape characteristics of the plant species. Theamount and extent of crystallinity alter itsphysical properties and affect its ability to bechemically modified. Insolubility as granules isimportant to the current wet-milling process;modifications that change solubility may ad-versely impact starch recovery. Starch is madeup of individual units of glucose, linked to-gether in chains by alpha 1-4, and occasionalalpha 1-6, linkages. The 1-4 linkages producelinear chains that primarily comprise moleculescalled “amylose,” whereas the alpha 1-6 linkagesserve as branching points to produce branched-chain molecules called “amylopectin.”
The proportions of the two types of polymerscomprising starch are established genetically.Normal corn starch contains about 27% “appar-ent” amylose, as determined by traditionalmeasures (about 18% absolute amylose con-tent). Amylose is a predominantly linear poly-mer (there may be minor amounts of very shortbranches) with glucose units linked by alpha 1-4bonds. Amylopectin, a highly branched poly-mer, comprises the majority of the starch gran-ule. Amylopectin has glucose units linked byalpha 1-4 and alpha 1-6 (branch points) bonds.
Current Uses of Normal Corn Starch
Plant geneticists have developed varieties ofcorn containing all amylopectin (waxy corn)and other varieties containing more than 70%amylose (high-amylose corn or amylo-maize)that are now grown commercially (a recentpatent was awarded for corn containing starchwith 85–95% amylose). Identity is preservedthroughout production, processing, and market-ing. Identity preservation and specialty grainproduction are not new concepts to many cornproducers and the starch industry.
Native starch extracted from corn is a dry, soft,usually white powder. It is insoluble in coldwater, alcohol, and most organic solvents.When the granules are heated in a water suspen-sion, they bind water, increase in size, and losetheir crystallinity, and the suspension becomesthicker until it forms a paste. This process iscalled gelatinization. The temperature at whichthe starch gelatinizes is an important functionalproperty and often serves as a means of classify-ing starches from different sources.
The granular structure of starch is important torecovery processes and the abilities of commer-cial starches to fill specific product needs. Thephysical and chemical properties of starch makeit useful in food and industrial applications asthickeners, suspension agents, emulsifiers, gels,adhesives, and films. Thickening properties areuseful in puddings, gravies, sauces, pie fillings,and in some industrial applications (e.g., paper,adhesives) where viscosity is important. Starchpastes in foods can hold fat and protein particlesin suspension to give desirable flavor, texture,and appearance; likewise, in paper coatings andin some adhesives, clay particles are suspendedin starch pastes (5). Gel formation is importantin puddings, salad dressings, and adhesives.When starch pastes are spread on smooth sur-faces, the resulting strong, stable films areparticularly useful in paper coatings and sizings,textile sizings, corrugated board, and adhesives.
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Today’s commercially important properties ofstarch often depend on the relative proportionsof amylose to amylopectin, and tend to vary fromone plant species to another. Once gelatinized,starches with high percentages of amylose formfirm gels and strong, tough films. Waxy cornstarches, which are nearly 100% amylopectin,gelatinize easily and yield nearly transparent,viscous pastes that will not gel. Behavioralproperties of starches from different plants andmodified starches usually fall between these twoextremes.
Most corn starch is sold in the unmodified formto be used in paper and board production,adhesives, salad dressings, beer, canned foods,dry food mixes, molding starch, and laundrystarch. A major deficiency of unmodified cornstarch in many commercial uses is its extremelyhigh viscosity (thickness of solution) whenheated and its tendency to “retrograde” or “set-back” (recrystallize) at ambient or low tempera-tures. Retrogradation is a problem in manyapplications because the resulting gel becomesfirm and tough, weeps moisture (syneresis), andmay become brittle as it loses internal moistureand partially recrystallizes. Starches from ge-netically modified corn might be used to solvethese types of practical problems facing industryand consumers.
Corn starch is plentiful and relatively inexpen-sive. Therefore, the U.S. starch industry hasfound ways to alter the properties of corn starchto fit processing and application needs ratherthan to substitute starches from other sources.Inherent properties of the corn starch granulecan be altered by mild chemical and/or heattreatment to improve starch performance. Suchmodified starches and starch derivatives provideusers with a range of products to fit individualprocesses and applications. However, modifiedand derivatized starches cost more than com-mon corn starch and are required by law to belabeled as “Food starch – modified” on foodproduct labels. The term “modified” used witha food ingredient is often perceived negativelyby consumers, especially in some export mar-kets (Asia and Europe).
Common treatments to reduce viscosity in cornstarch pastes are acid modification, oxidation,and enzyme modification. These treatmentssplit bonds between individual or groups ofglucose units in starch chains. By carefullycontrolling the process, a starch chemist canproduce starches with a wide range of viscosi-ties. Derivatization techniques also may affectviscosity, but they usually are done to enhanceor impart other functional behaviors, such as gelformation and solubility, that are different fromthose of the parent starch.
Cross-linked starches are those in which linksare created between and among glucose chains,making them more stable to processing condi-tions such as heat, pH, and shear. Thesestarches are important to the food industrybecause of great variation in cooking and storagetemperatures (e.g., microwavable foods), pro-cessing equipment, and ingredient combina-tions. Stabilized starches, another group ofstarch derivatives, are specifically stabilizedagainst gelling and may have other uniquefunctional characteristics.
Hydroxyethyl and hydroxypropyl starches arestarch derivatives used in paper and food manu-facture, respectively, because of their abilities toform clear, stable pastes. Cationic starches(those that are chemically altered to carry apositive charge) are used in paper manufactureto impart strength and color retention by addingpositively charged starch molecules to thenegatively charged cellulose in paper pulp.Starch acetates are used both as textile sizingsand as food thickeners. Starches often are firstcross-linked to improve viscosity in processing,and then acetylated (chemical groups are addedto starch chains) to prevent retrogradation of thestarch paste.
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The current market for corn starch products infood and industrial applications demands ap-proximately 250 million bushels of corn; there-fore, individual genetic modifications that willgenerate 100 million bushels or more of newdemand are unlikely except for those modifica-tions that enhance the milling process. How-ever, several modifications will likely generateadded economic impact equivalent to 100million bushels of commodity corn. Somemodifications provide starch functionalities thatare available today, but only through chemicalprocesses; other modifications may offer im-provements over current starch products, ormay provide new functionalities that industryhas not seen. Many modifications could resultin new niche markets and considerable rewardfor individual farmers who produce specialtycorn for specific starch processors.
The modifications were ranked as follows basedon estimates of commercial benefits (potentialU.S. market impact) by the authors and industryconsultants. Priority rankings were assignedbased upon the amount of potential gross addedvalue. High-priority modifications have poten-tial added values exceeding $200 million peryear, whereas those having less than $200 millionper year but more than $2 million per year werejudged to be moderate priority. Three modifica-tions were judged to have high potential grossvalues and 17 were judged to have moderatepotential gross added values. The moderate-priority modifications may have potential forspecific companies in marketing specialtyproducts, but the potential gross added value isprobably not sufficiently large to impact largenumbers of corn producers. Table 1 (pages 18-22) provides more details on estimated marketsize, potential additional value per pound ofstarch, estimated corn consumption, and poten-tial added value per bushel of corn for thosemodifications judged to be high or moderatepriority.
High priority – Relatively high gross addedvalue
• Introduce aldehyde groups into amyloseand/or amylopectin
• Decrease, eliminate, or modify horny en-dosperm proteins for improved wet millingand increased starch yield
• Lengthen A and B1 chains of
amylopectin
Moderate priority – Modest gross added value• Introduce high levels of acetylation into
amylose and/or amylopectin• Achieve natural cross-linking or enhance
potential for cross-linking• Introduce a cationic (positively charged)
group into amylose and/or amylopectin• Decrease starch lipids• Alter all linkages from alpha to beta in
amylopectin• Introduce o-methyl, o-acetyl, o-succinyl, o-
glycosyl, o-phosphatyl, or o-galactosylgroups into amylopectin and/or amylose
• Increase absolute amylose to >90%• Reduce numbers of B
2, B
3, and B
4 chains in
amylopectin• Increase molecular weight of amylose• Alter 1-4 linkages from alpha to intermittent
beta in amylose and/or amylopectin• Introduce an anionic (negatively charged)
group into amylopectin and/or amylose• Decrease absolute amylose to 5–10%• Increase phytoglycogen to >90%• Decrease molecular weight of
amylose• Replace starch with cyclodextrin• Shorten A and B
1 chains in amylopectin
• Increase phytoglycogen to 25%
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Opportunities for New Starches from Genetically Modified Corn
Other modifications judged to have little or noadded values and thus would not be recom-mended targets are the following:
Low priority – Little gross added value• Increase starch content• Reduce pericarp thickness• Introduce phosphate groups into amylopec-
tin to simulate potato starch• Introduce new alpha-(1-2) and alpha- (1-3)
linkages into amylopectin• Replace starch with polyhydroxybutyrate
and/or polyhydroxyvalerate (biodegradablepolymers produced today by fermentation)
Abandon – No gross added value• Produce germless kernels to simplify milling• Alter granule shape• Increase granule mean size• Decrease granule mean size• Narrow granule size distribution• Increase molecular weight of amylopectin
without altering chain length• Replace starch with levulan (otherwise
known as fructan, a polymer of fructose;fructose could be produced by hydrolysis offructan rather than isomerization of glu-cose)
If nearly all of the starch modifications identified(high and moderate priority) could be achieved,the total gross added value would be about$1.25 billion, over 200 million bushels of modi-fied corn could be consumed, and the averageadded value across all modifications would beabout $5.80 per bushel. However, some pro-posed modifications are mutually exclusive.
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The following is a more detailed discussion ofthe modifications judged to be important infood and industrial applications (potentialmodifications are shown in italics).
Food applications
About 100 million lb (dry weight) of stabilized,cross-linked starches is used annually by theNorth American food industry. Prices of thesestarches range from $0.50/lb to $0.90/lb depend-ing upon the specific modification and contractarrangements. These starches often are pro-duced from waxy corn. The market for cross-linked waxy corn starch is about 30 million lbwith prices ranging from $0.50/lb to $0.75/lb(compared with $0.10–0.15/lb for normal cornstarch).
Research areas considered to be useful weregenerally those that would reduce or eliminatethe need to chemically treat corn starch toachieve desirable properties. Some goals thatwould be important to the food industry are
• Achieve natural cross-linking or enhancepotential for cross-linking to improve pastestability to acid and shear (e.g., introducealdehyde or phosphate groups into amylopectinand/or amylose)
• Mimic hydroxylated and acetylated starches(shorten A and B
1 chains in amylopectin)
• Bind cations and increase viscosity andwater-holding capacity (add an anionic[negatively charged] group)
• Prevent retrogradation and reduce gelatini-zation temperature (introduce o-methyl, o-succinyl, o-glycosyl, o-acetyl, o-phosphatyl, oro-galactosyl groups into amylose or amylopectin)
• Improve wet milling and increase starchyield (decrease amount of, eliminate, ormodify horny endosperm proteins)
• Improve flavor (decrease starch lipid)
Natural cross-linking might be achieved byintroducing small amounts of diester cross-linksin the granule by introducing diphosphate,
Market Needs for New Starches
diadipate, or disuccinate ester bonds by geneticmodification. Naturally cross-linked waxy cornstarch would be very useful to the food industry,both for its functional properties and absence ofchemical modification. Naturally cross-linkedstarch or enhanced potential for cross-linkinglikely will be best accomplished on waxy cornthat already contains mostly branched starchchains of amylopectin. Introduction of groups,such as o-succinyl groups, may provide interac-tion sites for cross-linking. Various levels ofcross-linking are needed to provide productssuited to a variety of applications. Perhaps thisalteration could be accomplished by eliminatingsome cross-links from a highly cross-linkedstarch by using a simple treatment such as mildalkaline or enzymatic hydrolysis. Alternatively,enhanced potential for cross-linking might beachieved by genetic modification. Perhapsstarch could be modified to contain glucuronicacid units, which might be induced to formintermolecular ester bonds by dry heat, thusproducing cross-linking.
Shortening A and B1 chains of amylopectin is one
approach that would allow adequate sites forcross-linking but fewer long outer chains thatcould retrograde.
Addition of anionic moieties (i.e., glucuronic acid,phosphate, sulfate) also would provide electro-static interaction among long chains of amyloseand amylopectin that would reduce or preventretrogradation and could give gum-like proper-ties. Further interaction of negatively charged(anionic) groups with cations (di- and trivalentmetal ions with positive charges) might lead toinsolubilization, water-resistance, gel-formation,and chelation (binding of metallic ions) proper-ties important in wastewater treatment, metalrecovery, and wet-end paper manufacture.
Introducing o-succinyl or o-galactosyl substituentsmay provide enhanced potential for cross-linking as already discussed.
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Introducing o-methyl or o-glycosyl groups shouldachieve low-temperature sol (colloidal suspen-sion of solids in a liquid) stability. Interspersingsingle glucose units (o-glycosyl) along thechains of amylose would prevent hydrogen bondassociations and retrogradation. This type ofmodification would provide high viscosity withlow-temperature stability, lower gelatinizationtemperature, and possibly easier solubility inwater. These properties would be particularlyuseful in high-amylose corn starch. This type ofmodification might fit into the biosyntheticpathway with less disruption of plant metabolicprocesses than would other approaches. Be-cause starch composition would not change, thisnew starch would likely not require labeling as“modified food starch,” and it should have noadverse effects if used as livestock feed.
Introducing low levels of acetylation, particularlyin high-amylose corn starch, is another approachto achieve low-temperature stability, but theindustrial method for achieving this modifica-tion is already inexpensive. Corn that producesstarch acetate in granular form by genetic modi-fication may allow more uniform substitutionalong starch chains. A wide range of food andindustrial products could be developed based onstarches of various degrees of acetylation.
Gelatin currently fills the large market for clear,thermo-reversible (gel when chilled, liquidwhen warm) gels in food production. Recentconcern about “mad cow disease” could reducegelatin use, but no good substitutes are avail-able. The ability to produce similar gels withcorn starch could result in a new market forstarch, if a clear gel could be produced. Anestimated 140 million lb of gelatin is used inconfectionery applications in the United Statesand Europe. Depending upon the grade, theprice of gelatin currently is around $2.20/lb.
One possible approach for gaining the desired gelproperties that may allow corn starch to com-pete with gelatin is to lengthen A and B
1 chains in
amylopectin. Increased retrogradation and lackof clarity in the gel may result from this modifi-cation alone and would cause problems in someapplications. However, these problems could be
addressed with another chemical or geneticmodification that attaches substituent groupsalong the starch chains (e.g., phosphate groups)to reduce retrogradation and provide clarity.
In addition to the above-mentioned modifica-tions, two other modifications could improvecorn starch for food applications. Decreasedstarch lipid and decreased amount of, eliminated,or modified horny endosperm proteins couldimprove gelling properties and reduce thetypical “cardboard” flavor of corn starch. Thesemodifications would be most useful in waxycorn starch, recognizing that one drawbackwould be poorer low-temperature stability.
Decreased, eliminated, or modified horny endospermproteins should improve starch recovery duringwet milling and may increase processing efficiency(but breakage susceptibility could increase). Ifcoupled with decreased starch lipid, flavor andcolor also may improve. Impact on sales volumeis not well defined. If accomplished on waxycorn starch, the market volume is estimated at100 million lb. Flavor removal and increasedwhiteness could expand the market for cornstarch in both food and pharmaceutical areas.
Industrial applications
The demand for industrial corn starch in theUnited States is projected to rise 4.5% per yearthrough the year 2000 when 7 billion lb valuedat $1 billion is expected to be produced. Indus-trial corn starch may account for an increasingportion of total U.S. corn starch use. Traditionalapplications, primarily adhesives, paper, andboard, are expected to remain the dominant usesfor corn starch. Adhesives and paper and paper-board production provide growing markets formodified starches, accounting for 47% of currenttotal demand (4).
Approximately 1 billion lb of hydroxyethylstarches is used in paper coatings and sizings.The current price of hydroxyethyl starch in largebulk quantities is $0.14/lb versus common cornstarch at $0.09/lb. Industrial starch pricesranged from $0.05/lb to $0.18/lb over the period1986–1996.
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The demand for modified industrial corn starchesis projected to expand 6.6% per year reaching3.2 billion lb by the year 2000 (6), althoughrecent growth has been at a much lower pace.The demand for special types of starch used inthe production of degradable plastics and super-absorbent polymers could rapidly grow. Cornstarch supplied 60% of the starch used in de-gradable plastics in 1995 (175 million lb at$0.15/lb) (6). Super-absorbent polymers arematerials that can absorb several hundred timestheir own weight in water. Those super-absorb-ing polymers made from corn, used mainly inagricultural applications (e.g., seed coatings,fertilizer carriers), continue to be a small marketfor corn starch at 33 million lb (at $0.12/lb) (6).
Traditional markets—paper and paperboard,adhesives, and textiles—will continue to providethe mainstay applications, jointly accounting forabout 80% of total industrial starch sales. Growthwill be aided by the increasing tendency of usersin the paper and paperboard industry to purchaseproprietary modified corn starches rather thanto convert unmodified starches in-house (6).
New structures in the kernel that have possiblecompetitive potential in industrial products interms of functionality and economics includethe following:
• Provide sites for cross-linking and improvepaste stability to acid and shear (achievenatural cross-linking or enhance the potentialfor cross-linking such as introducing aldehydegroups into amylopectin and/or amylose)
• Decrease retrogradation rate and improvefilm formation (increase the molecular weightof amylose)
• Provide sites for attaching block co-polymersand improve paper coatings and adhesives(introduce aldehyde groups)
• Improve water resistance in adhesives(introduce high levels of acetylation (d.s. 1-3)into amylose or amylopectin)
• Bind anions, increase viscosity and water-holding capacity, improve gelling and floc-culation (introduce a cationic [positivelycharged] group into amylose)
• Reduce reformed amylose particles (RAPS)(decrease starch lipid)
• Improve film and solution properties, anddecrease retrogradation (introduce linkagesbetween glucose units other than alpha 1-4and alpha 1-6)
• Replace an expensive enzyme reaction inproducing cyclodextrin (replace starch withcyclodextrins)
The benefits of naturally cross-linked starches andenhanced potential for cross-linking were discussedearlier with food applications in terms of viscositystability under varying processing and storageconditions. These same properties also wouldbe valuable in adhesives and coatings and wouldbe in great demand in industrial applications ifthe cost was competitive. Approximately1.2␣ billion lb of starch is used in corrugating, 20%of which is in the carrier portion of the adhesive.The carrier cost is about $1.00 to $1.60 per drylb. The bulk of the adhesive is unmodified cornstarch. Requirements include a stable viscosityover fluctuating operating temperatures andduring agitating and pumping in the adhesiveapplication system. The final bond must showhigh tack to allow high machine speeds and alsoshow high cohesive strength (fiber tear) and, ina number of applications, water resistance.
Introduction of aldehyde groups might achieve thedesired levels of cross-linking by introducingsubstituent groups into linear amylose chains andlinear sections of amylopectin. If these modifi-cations could be made genetically, the placementof these additional side chains might be moreuniform and better controlled than is possiblewith chemical modifications done today. Galac-tose oxidase, an enzyme, will catalyze the oxida-tion of the C-6 hydroxyl of galactose to analdehyde. If a galactosyl starch can be made inthe granule by genetic modification and genes tointroduce and activate galactose oxidase action,aldehyde-containing starch could result.
Aldehyde groups also might be useful in furthermodifying starch by creating block copolymers(linkages with other polymers such as proteinsand lipids), which are valuable in paper coatingand sizing, textile sizing, and in paper wet-endmanufacture. In this case, the aldehyde groups
14
would need to be attached to the nonreducingends of the starch molecule.
Introducing high levels of acetylation (d.s. 1-3)could provide polymers with water resistanceand insolubility, which would improve adhesiveproperties of starch for corrugating applications.An unusual application of a naturally acetylatedstarch could be as a biodegradable hot-meltadhesive in repulping processes. Current meth-ods for producing high levels of acetylation instarch are expensive and not in line with manypotential applications.
Introduction of cationic groups (e.g., amine groupsfrom glucosamine that give a positive charge topart of the molecule) is an important part ofamphoteric (molecules with negative and posi-tively charged portions) starches for papermanufacture and in wastewater treatment. Theestimated market in the U.S. paper industry isabout 300 million lb in a price range of $0.15/lbto $0.30/lb.
Decreased starch lipid was mentioned above interms of flavor and color removal for food andpharmaceutical applications. Naturally defattedstarch also would solve a common problem inpaper manufacture known as reformed amyloseparticles (RAPS), which are blamed on lipidsassociated with the amylose portion of starch.In fermentation processes, a naturally defattedstarch would reduce the amount of sludge andrelated filtration problems.
Introduction of linkages other than alpha 1-4 andalpha 1-6 into starch might provide new anddifferent properties for markets in which starchis not currently a player. Starch behavior isdetermined by the configuration of the molecule,so changes in position and type of glycosidicbonding are likely to change starch functionalproperties.
Creation of polymers with alternating spans ofalpha 1-4 and beta 1-4 linkages might allow newabilities for the molecule to complex and associ-ate with similar sections or with other moleculesof natural and synthetic polymers. Such abilitiesmay lead to more effective warp sizing of tex-
tiles, paper coating binders, paper sizing, andadhesives. A related modification, insertion ofbeta 1-4 linkages intermittently in starch chains,also would change molecular configuration,potentially improving film formation in coatingsand adhesives.
Altering all alpha 1-4 and 1-6 linkages to betalinkages would yield polymers similar to cellu-lose. This modification would drastically de-crease digestibility of the corn by humans andmonogastric animals. Introducing new alphalinkages (i.e., 1-2, 1-3) into starch could pro-duce a material that mimics dextrans (polysac-charides from yeasts and bacteria, which formhighly viscous, slimy solutions) having possibleapplications in food and medical products.
A small market might be achieved by replacingstarch with cyclodextrin. Cyclodextrins, likestarch, are comprised of linkages betweenglucose molecules, but in a closed ring structurerather than in a linear chain. The hydrophobic(water-resisting) center of the ring is an effectiveencapsulation space for other small molecules,such as flavors, spices, and drugs. Cyclodex-trins are currently used as flavor protectors inthe food industry and are produced by a seriesof enzyme treatments to starch. Conceivably,cyclodextrins could be produced in the cornkernel if these enzymes were present and activethere. The world market for cyclodextrins wasestimated at 2–5 million lb in 1993. The poten-tial is considerably greater with more regulatoryapprovals and new uses (7). Current and poten-tial markets are in foods and pharmaceuticals,but the current enzymatic production method isexpensive. Transgenically moving cyclodextrin-ase into corn is attractive provided cyclodextrincan be recovered in meaningful quantities fromcorn through processing.
Biopolymers are organic substances consisting ofrepetitive linkages of similar molecules. Starchand cellulose are examples of biopolymers inwhich the repetitive unit is glucose; proteins arebiopolymers of amino acids linked by peptidebonds. Synthetic structural materials, such asplastics, are polymers of petroleum-derivedhydrocarbons. These polymers form rigid
15
materials with many uses, but are often notbiodegradable.
Manufacture of biodegradable films may benefitby increasing the molecular weight of amylose.This modification is likely to provide better filmformation if better plasticizer systems are devel-oped. Although retrogradation rate would bereduced, which would benefit most applications,the reduction would probably be insufficient tobenefit food applications requiring low-tempera-ture stability. This trait would be most useful inhigh-amylose corn starch.
16
This study identified a number of genetic modi-fications to corn for starch production that havevalue-added potential in specialty markets.Although no single corn or starch modificationwas identified that could increase corn con-sumption by 100 million bushels, several had highgross added values even if few additional poundsof starch were used. Modifications providingenhanced potential for cross-linking and modifi-cations greatly improving freeze-thaw andstorage stabilities and reducing retrogradationcould have major market impact.
The properties of modified corn or starch sug-gested to have value potential are as follows(modifications to deliver the desired propertyare in italics):
• Provide sites for cross-linking, and improvepaste stability to acid and shear (introducealdehyde groups into amylopectin and/oramylose);
• Improve wet milling and increase yield ofstarch (decrease, eliminate, or modify hornyendosperm proteins);
• Improve gel formation and mimic gelatin ifa clear gel can be formed (lengthen A and B
1
chains in amylopectin [further chemicaltreatment, such as phosphorylation, may berequired]);
• Improve water resistance in adhesives andenable hot-melt adhesives (introduce high levelsof acetyl into amylose and/or amylopectin);
• Achieve natural cross-linking or enhancepotential for cross-linking (introduce aldehydegroups into either amylose or amylopectin);
• Bind anions and increase viscosity andwater-holding capacity (introduce a cationicgroup into amylopectin and/or amylose);
• Improve flavor and eliminate RAPS (decreasestarch lipid);
• Decrease digestibility, water solubility, andretrogradation (alter all linkages from alphato beta in amylopectin);
• Prevent retrogradation and reduce gelatini-zation temperature (introduce o-methyl, o-acetyl, o-succinyl, o-glycosyl, or o-galactosylgroups into amylopectin and/or amylose);
Conclusions
• Increase retrogradation and reduce digest-ibility (increase absolute amylose to >90%);
• Provide for easier cooking and improvefreeze-thaw stability (reduce number of B
2, B
3,
and B4 chains in amylopectin);
• Decrease retrogradation rate and improvefilm formation (increase molecular weight ofamylose);
• Decrease digestibility (alter 1-4 linkages fromalpha to intermittent beta in amylopectin);
• Bind cations, provide sites for cross-linking(introduce an anionic group into amylopectinand/or amylose);
• Provide properties intermediate to normal andwaxy starches (decrease amylose to 5–10%);
• Decrease paste viscosity, gel formation andretrogradation, and increase water-holdingcapacity (increase phytoglycogen to >90%);
• Increase retrogradation rate (decrease mo-lecular weight of amylose);
• Replace the expensive reaction required tomake cyclodextrin (replace starch withcyclodextrin);
• Mimic hydroxypropylated and acetylated starch(shorten A and B
1 chains in amylopectin); and
• Achieve a modest decrease in paste viscosity,gel formation, and retrogradation, andincrease water-holding capacity (increasephytoglycogen to >25%).
If all of the starch modifications could be achievedthe total gross value would be about $1.25 billion,more than 200 million bushels of corn could beconsumed, and the average added value acrossall modifications would be about $5.80 perbushel. However, some of the modificationsoverlap or are mutually exclusive, so this totalgross value would not be realized; but severalmodifications could potentially be stacked toprovide a combination of benefits in one hybrid.
All of the above-mentioned modifications couldreduce corn yields and/or adversely affect pro-cessing characteristics. These risks, as well asincreased costs involved in preserving identitywill reduce the total added values that werecalculated in this report (net added values willbe considerably less than the gross added values).
17
TAB
LE 1
. M
arket
Opport
unit
ies,
Est
imat
ed C
onsu
mpti
on a
nd G
ross
Added
Val
ues
for
Var
ious
Gen
etic
Modif
icat
ions
to C
orn
for
Sta
rch P
roduct
ion
1
Po
ssib
le C
orn
Gro
ssP
roje
cted
Est
imat
edP
roje
cted
Est
imat
edo
r S
tarc
hA
dd
edM
ark
et S
ize
Ad
dit
ion
alC
on
sum
pti
on
Ad
ded
Mar
ket
Op
po
rtu
nit
yM
od
ific
atio
n t
oV
alu
e(m
illi
on
lb
Val
ue
of
Mo
dif
ied
Val
ue
Del
iver
Des
ired
(mil
lio
no
f st
arch
/yr)
($/lb
of
Co
rn (
mil
lio
n($
/bu
)P
rop
erty
$/y
r)st
arch
)b
u/y
r)
Hig
h P
rio
rity
Pro
vide
site
s fo
r cr
oss-
linki
ng to
impr
ove
stab
ility
toIn
trod
uce
alde
hyde
282
1,20
00.
07–0
.40
382.
21–1
2.60
acid
and
she
ar; p
rovi
de “
natu
ral”
repl
acem
ent f
or a
grou
ps in
to e
ither
com
mon
che
mic
al r
eact
ion;
rep
lace
form
alde
hyde
inam
ylos
e or
am
ylo-
resi
ns in
cor
ruga
ting
and
adhe
sive
s; p
rovi
de s
ites
for
pect
inat
tach
blo
ck c
opol
ymer
s.
Impa
rt te
mpo
rary
wet
str
engt
h to
pap
er a
nd p
repa
re16
400.
30–0
.50
1.5
9.45
–15.
75w
ater
-res
ista
nt p
aper
coa
tings
and
wat
er-r
esis
tant
adhe
sive
s.
Dec
reas
e ca
pita
l and
ope
ratin
g co
sts
for
wet
mill
ing
Dec
reas
e,28
036
,000
0.00
5–0.
011,
140
0.16
–0.3
3an
d st
arch
rec
over
y (in
crea
sed
star
ch y
ield
); r
educ
eel
imin
ate,
or
(pot
entia
lly a
llst
eepi
ng ti
me;
elim
inat
e S
O2
and
asso
ciat
ed h
andl
ing
mod
ify h
orny
star
ch a
nddi
fficu
lties
; low
er p
rote
in c
onte
nt o
f sta
rch
to r
educ
een
dosp
erm
pro
tein
ssu
gar,
and
off-
flavo
rs a
nd c
olor
s.so
me
etha
nol)
Impr
ove
gel f
orm
atio
n; p
rovi
de m
ore
stab
le v
isco
sity
;Le
ngth
en A
and
B1
207
150
0.90
–1.9
07
28.3
5–59
.85
enab
le m
anip
ulat
ion
of s
truc
ture
s to
giv
e a
varie
ty o
fch
ains
in a
myl
o-pr
oper
ties;
may
pro
vide
a th
erm
o-re
vers
ible
cle
ar g
elpe
ctin
(re
alis
ticth
at c
ould
sub
stitu
te fo
r ge
latin
; may
ret
rogr
ade
fast
erm
odifi
catio
n,un
less
an
addi
tiona
l che
mic
al tr
eatm
ent (
e.g.
,pr
ogre
ss a
lread
yph
osph
oryl
atio
n) o
r ge
netic
mod
ifica
tion
also
is u
sed.
mad
e bu
t opt
imum
0.8
0.8
0.90
–1.1
00.
0328
.35–
34.6
5no
t yet
ach
ieve
d
Use
ful i
n ph
otog
raph
ic fi
lm. V
ery
clea
r fil
m is
nee
ded,
whi
ch w
ill r
equi
re a
n ad
ditio
nal c
hem
ical
trea
tmen
t(e
.g.,
poss
ibly
pho
sphy
oryl
atio
n or
add
ition
of o
ther
hydr
ophi
lic g
roup
s) o
r ge
netic
mod
ifica
tion.
18
Po
ssib
le C
orn
Gro
ssP
roje
cted
Est
imat
edP
roje
cted
Est
imat
edo
r S
tarc
hA
dd
edM
ark
et S
ize
Ad
dit
ion
alC
on
sum
pti
on
Ad
ded
Mar
ket
Op
po
rtu
nit
yM
od
ific
atio
n t
oV
alu
e(m
illi
on
lb
Val
ue
of
Mo
dif
ied
Val
ue
Del
iver
Des
ired
(mil
lio
no
f st
arch
/yr)
($/lb
of
Co
rn (
mil
lio
n($
/bu
)P
rop
erty
$/y
r)st
arch
)b
u/y
r)
Mo
der
ate
Pri
ori
ty
Rep
lace
a r
elat
ivel
y ex
pens
ive
chem
ical
rea
ctio
n;In
trod
uce
high
120
600
0.15
–0.2
519
4.73
–7.8
8pr
ovid
e “b
iode
grad
able
hot
-mel
t” a
dhes
ives
with
leve
ls (
d.s.
1–3
) of
impr
oved
wat
er r
esis
tanc
e.ac
etyl
atio
n
Pro
vide
nat
ural
sub
stitu
te fo
r ch
emic
al c
ross
-link
ing
toA
chie
ve n
atur
al60
100
0.40
–0.8
03.
212
.60–
25.2
0in
hibi
t gra
nule
sw
ellin
g, r
esis
t bre
akdo
wn,
elim
inat
ecr
oss-
linki
ng o
rst
icki
ness
, im
prov
e ac
id a
nd s
hear
sta
bilit
y; e
limin
ate
enha
nce
pote
ntia
lne
ed fo
r a
chem
ical
rea
ctio
n.fo
r cr
oss-
linki
ng(e
.g.,
intr
oduc
eo-
succ
inyl
gro
ups)
Incr
ease
vis
cosi
ty a
nd w
ater
-hol
ding
cap
acity
; bin
dIn
trod
uce
catio
nic
6030
00.
15–0
.30
104.
73–9
.45
elec
trol
ytes
; im
prov
e ge
lling
and
floc
cula
tion;
pro
vide
grou
ps (
e.g.
,si
tes
for
cros
s-lin
king
; may
be
usef
ul in
pap
er s
izin
g,gl
ucos
amin
e) in
tow
aste
wat
er tr
eatm
ent,
and
prot
ein
inte
ract
ions
in fo
ods
eith
er a
myl
ose
oran
d ph
arm
aceu
tical
s.am
ylop
ectin
)
Elim
inat
e so
urce
of “
card
boar
d” fl
avor
and
odo
rD
ecre
ase
star
ch8
500.
10–0
.20
1.6
3.15
–7.2
0(e
spec
ially
in p
aper
coa
tings
and
food
s w
ith h
igh
star
chlip
id (
espe
cial
ly in
cont
ent)
.hi
gh-a
myl
ose
star
ch)
Elim
inat
e “r
efor
med
am
ylos
e pa
rtic
les”
in p
aper
421,
400
0.01
–0.0
544
0.32
–1.5
8m
anuf
actu
re th
at p
rese
ntly
thre
aten
s st
arch
in th
ism
arke
t.
Dec
reas
e sl
udge
in fe
rmen
tatio
n.0
18,0
000.
0057
00.
00
19
Po
ssib
le C
orn
Gro
ssP
roje
cted
Est
imat
edP
roje
cted
Est
imat
edo
r S
tarc
hA
dd
edM
ark
et S
ize
Ad
dit
ion
alC
on
sum
pti
on
Ad
ded
Mar
ket
Op
po
rtu
nit
yM
od
ific
atio
n t
oV
alu
e(m
illi
on
lb
Val
ue
of
Mo
dif
ied
Val
ue
Del
iver
Des
ired
(mil
lio
no
f st
arch
/yr)
($/lb
of
Co
rn (
mil
lio
n($
/bu
)P
rop
erty
$/y
r)st
arch
)b
u/y
r)
Pro
vide
ver
y di
ffere
nt fi
lm a
nd s
olut
ion
prop
ertie
s;A
lter
all l
inka
ges
4010
00.
15–0
.75
3.2
4.73
–23.
63de
crea
se d
iges
tibili
ty (
wei
ght c
ontr
ol);
dec
reas
e(1
-4 a
nd 1
-6)
from
retr
ogra
datio
n; e
limin
ate
wat
er s
olub
ility
.al
pha
to b
eta
inam
ylop
ectin
Pos
sess
cel
lulo
se-li
ke p
rope
rtie
s. H
igh
prio
rity
cellu
lose
Und
eter
-U
ndet
erm
ined
0.50
–1.0
0U
ndet
erm
ined
15.0
1–31
.50
is e
xpen
sive
and
val
uabl
e to
the
chem
ical
indu
stry
.m
ined
Pot
entia
llyla
rge
Pre
vent
H-b
ond
asso
ciat
ions
to im
prov
e co
ld-w
ater
Intr
oduc
e o-
met
hyl,
3510
00.
40–0
.80
3.2
12.6
0–25
.20
solu
bilit
y; p
reve
nt r
etro
grad
atio
n; p
rovi
de h
igh-
o-ac
etyl
, o-s
ucci
nyl,
(mos
tly w
axy)
visc
osity
, low
-tem
pera
ture
sta
bilit
y, lo
w g
elat
iniz
atio
no-
glyc
osyl
, o-g
alac
tosy
llin
king
, and
may
allo
w “
natu
ral”
labe
ling.
subs
titue
nts
into
eith
er a
myl
ose
oram
ylop
ectin
Pro
vide
mor
e co
mpl
ete
retr
ogra
datio
n an
d m
ore
Incr
ease
abs
olut
e33
500.
15–1
.15
1.6
4.73
–36.
23“r
esis
tant
” st
arch
(to
hum
an d
iges
tion)
, whi
ch m
ay b
eam
ylos
e to
>90
%im
port
ant i
n fa
t mim
etic
s; im
prov
e gr
anua
le in
tegr
ity;
(pat
ent r
ecen
tlyim
prov
e fil
m fo
rmat
ion.
awar
ded)
Eas
ier
cook
ing,
mor
e op
aque
pas
te, a
nd d
ecre
ased
gel
Red
uce
num
ber
of26
750.
20–0
.50
2.4
6.30
–15.
75st
reng
th; i
mpr
ove
free
ze-t
haw
sta
bilit
y an
d sl
ower
B2,
B3,
and
B4
retr
ogra
datio
n.ch
ains
inam
ylop
ectin
Dec
reas
e re
trog
rada
tion
rate
in fo
od a
pplic
atio
ns o
fIn
crea
se m
olec
ular
810
00.
05–0
.10
3.2
1.57
–3.1
5hi
gh-a
myl
ose
star
ch.
wei
ght o
f am
ylos
e(r
ealis
tic m
odifi
catio
n,Im
prov
e fil
m fo
rmat
ion
in b
iode
grad
able
pla
stic
s,al
read
y in
pro
gres
s)18
175
0.08
–0.1
25.
62.
52–3
.78
corr
ugat
ion,
and
adh
esiv
es.
Dec
reas
e di
gest
ibili
ty; i
ncre
ase
diet
ary
fiber
; red
uce
Alte
r 1-
4 lin
kage
s20
500.
30–0
.50
1.6
9.45
–15.
75w
ater
sol
ubili
ty; c
ould
incr
ease
affi
nity
with
oth
erfr
om a
lpha
tosu
bstr
ates
.in
term
itten
t bet
ain
am
ylop
ectin
20
Po
ssib
le C
orn
Gro
ssP
roje
cted
Est
imat
edP
roje
cted
Est
imat
edo
r S
tarc
hA
dd
edM
ark
et S
ize
Ad
dit
ion
alC
on
sum
pti
on
Ad
ded
Mar
ket
Op
po
rtu
nit
yM
od
ific
atio
n t
oV
alu
e(m
illi
on
lb
Val
ue
of
Mo
dif
ied
Val
ue
Del
iver
Des
ired
(mil
lio
no
f st
arch
/yr)
($/lb
of
Co
rn (
mil
lio
n($
/bu
)P
rop
erty
$/y
r)st
arch
)b
u/y
r)
Incr
ease
vis
cosi
ty a
nd w
ater
-hol
ding
cap
abili
ties;
Intr
oduc
e an
ioni
c7
100
0.05
–0.0
83.
21.
58–2
.52
prov
ide
site
s fo
r cr
oss-
linki
ng to
pro
duce
sta
biliz
edgr
oups
(e.
g.,
(mos
tly w
axy)
star
ches
res
ista
nt to
aci
d an
d sh
ear
for
adhe
sive
s an
dgl
ucur
onic
aci
d,co
atin
gs; m
ay b
e us
eful
in p
rote
in in
tera
ctio
ns in
food
sph
osph
ate)
into
and
phar
mac
eutic
als.
amyl
ose
oram
ylop
ectin
Bin
d el
ectr
olyt
es, a
s in
was
tew
ater
trea
tmen
t and
met
al7
500.
12–0
.15
1.6
3.78
–4.7
3re
cove
ry; p
rovi
de s
ites
for
atta
chm
ent o
f oth
er p
olym
ers;
elim
inat
e on
e st
ep in
pro
duci
ng a
mph
oter
ic s
tarc
h.
Com
pete
with
pot
ato
star
ch.
610
00.
04–0
.08
3.2
1.26
–2.5
2
Pro
vide
an
inte
rmed
iate
am
ylos
e le
vel b
etw
een
norm
alD
ecre
ase
abso
lute
1650
0.15
–0.5
01.
64.
73–1
5.75
star
ch a
nd w
axy,
giv
ing
prop
ertie
s in
term
edia
te to
amyl
ose
to 5
–10%
norm
al a
nd w
axy
star
ch; u
niqu
e ge
latio
n pr
oper
ties.
Dec
reas
e ge
l for
mat
ion
and
retr
ogra
datio
n; d
ecre
ase
Incr
ease
phy
to-
1650
0.25
–0.4
01.
67.
88–1
2.60
visc
osity
; inc
reas
e w
ater
-hol
ding
cap
acity
.gl
ycog
en to
>90
%(li
kely
to b
eIn
crea
se d
iges
tibili
ty, w
hich
may
be
impo
rtan
t in
all
diffi
cult
to m
ill)
Not
fed
asN
ot fe
d as
8,00
00.
05–0
.20
lives
tock
feed
s.st
arch
star
ch
Incr
ease
ret
rogr
adat
ion
rate
and
rap
id g
ellin
g in
Dec
reas
e14
500.
15–0
.40
1.6
4.73
–12.
60co
nfec
tione
ry p
rodu
cts;
may
be
usef
ul a
s “r
esis
tant
”m
olec
ular
wei
ght
star
ches
for
redu
ced
calo
rie fo
ods;
may
be
usef
ul in
of a
myl
ose
corr
ugat
ing
carr
iers
.
Rep
lace
an
expe
nsiv
e en
zym
e re
actio
n in
pro
duci
ngR
epla
ce s
tarc
h6
50.
50–2
.00
0.16
15.7
5–63
.00
cycl
odex
trin
. Cyc
lode
xtrin
pro
vide
s st
abili
ty to
flav
ors
with
cyc
lode
xtrin
and
arom
as, a
nd p
rovi
des
a w
ay to
enc
apsu
late
(may
be
diffi
cult
ingr
edie
nts
and
bind
hyd
roph
obic
sub
stan
ces.
to m
ill)
21
Po
ssib
le C
orn
Gro
ssP
roje
cted
Est
imat
edP
roje
cted
Est
imat
edo
r S
tarc
hA
dd
edM
ark
et S
ize
Ad
dit
ion
alC
on
sum
pti
on
Ad
ded
Mar
ket
Op
po
rtu
nit
yM
od
ific
atio
n t
oV
alu
e(m
illi
on
lb
Val
ue
of
Mo
dif
ied
Val
ue
Del
iver
Des
ired
(mil
lio
no
f st
arch
/yr)
($/lb
of
Co
rn (
mil
lio
n($
/bu
)P
rop
erty
$/y
r)st
arch
)b
u/y
r)
Min
imiz
e lo
w-t
empe
ratu
re r
etro
grad
ing
(esp
ecia
llyS
hort
en A
and
B1
510
00.
04–0
.06
321.
26–1
.89
usef
ul in
froz
en a
nd r
efrig
erat
ed fo
ods)
; pro
vide
chai
ns o
f am
ylo-
(mos
tly w
axy)
func
tiona
lity
of h
ydro
xypr
opyl
ated
and
ace
tyla
ted
pect
in (
real
istic
star
ch; a
llow
“na
tura
l lab
elin
g.”
mod
ifica
tion,
wor
kal
read
y in
pro
gres
s)
Dec
reas
e ge
l for
mat
ion
and
less
ret
rogr
adat
ion;
Incr
ease
phy
to-
250
0.03
–0.0
51.
60.
95–1
.58
decr
ease
vis
cosi
ty a
nd in
crea
se w
ater
-hol
ding
glyc
ogen
to >
25%
capa
city
.(m
ay b
e di
fficu
ltto
mill
bec
ause
of
Incr
ease
dig
estib
ility
, whi
ch m
ay b
e im
port
ant i
nin
crea
sed
wat
erN
ot fe
d as
Not
fed
as8,
000
0.05
–0.2
0al
l liv
esto
ck fe
eds.
solu
bilit
y)st
arch
star
ch
1 The
met
hodo
logy
use
d to
dev
elop
this
tabl
e in
clud
ed th
e fo
llow
ing
step
s: 1
. Ide
ntify
ing
pote
ntia
l str
uctu
ral c
hang
es to
cor
n or
sta
rch
(col
umn
2) a
nd s
pecu
latin
g ho
w th
ose
chan
ges
mig
ht a
ffect
thei
r pr
oper
ties
(col
umn
1); 2
. Spe
cula
ting
abou
t app
licat
ions
and
pro
duct
s in
whi
ch th
e m
odifi
ed c
orn
or s
tarc
h m
ight
be
usef
ul; a
nd 3
. Com
parin
g w
ith th
efu
nctio
nal p
rope
rtie
s, p
erfo
rman
ce c
hara
cter
istic
s, m
arke
t siz
es, a
nd c
osts
ver
sus
thos
e of
com
petit
ive
mat
eria
ls in
spe
cific
app
licat
ions
to a
rriv
e at
a v
alue
for
the
star
ch(c
olum
n 5)
and
an
estim
ated
mar
ket s
ize
(col
umn
4) fo
r th
e m
odifi
ed c
orn
or s
tarc
h.
22
References
1. Neidleman, S., Enzymology and Food Processing, in Biotechnology in Food Processing, editedby S.K. Harlander and T.P. Labuza, Noyes Publications: Park Ridge, NJ, pp. 37–56 (1986).
2. Wasserman, B.P., C. Harn, C. Mu-Forster, and R. Huang, Progress toward genetically modifiedstarches, Cereal Foods World 40:810–817 (1995).
3. Mu-Forster, C., R. Huang, J.R. Powers, R.W. Harriman, M. Knight, G.W. Singletary, P.L. Keeling,and B.P. Wasserman, Physical association of starch biosynthetic enzymes with starch granules ofmaize endosperm, Plant Physiol. 111:821–829 (1996).
4. U.S. Department of Agriculture, Economic Research Service, Feed Outlook, March (1999).
5. Corn Refiners Association, Corn Starch, Corn Refiners Assn.: Washington, DC (1986).
6. The Freedonia Group, Industrial Corn Starch, in Industrial Starch and Other Corn Chemicals to2000, Report 843, Freedonia Group: Cleveland, OH (1996).
7. Duxbury, D.D., Cyclodextrins: Opening up worldwide markets, Food Processing, pp. 88-90 (April1993).
23
Template Used to Evaluate Genetic Modifications
Category Title
Compositional/structural change or genetic modification:
Anticipated benefits/applications:
Potential problems:
Relative feasibility:
Estimated commercial significance:
Anticipated changes in starch functionality:• Granule properties:
Dusting characteristics -Coating properties -Flow properties of dry starch -Cold-water solubility -Granule integrity -Digestibility -
• Gelatinization properties:Gelatinization temperature -Gelatinization range -Gelatinization enthalpy (energy, difficult to cook) -
• Paste characteristics:Pasting temperature -Hot-paste viscosity -Cold viscosity -Resistance to shear thinning -Paste clarity -Amount of lipid binding -
• Gel properties:Gel strength -Gel clarity -Freeze-thaw stability -Water-holding capacity -Susceptibility to starch-degrading enzymes -Retrogradation rate -
• Films, plastics, and binders:Film formation -Water resistance -Tensile strength -Adhesion -
• Other:Color -Flavor -
24
IowaGrain Quality
Initiative Center for Crops Utilization ResearchCCUR Iowa State University, Ames, IA 50011
EDC 194 November 1999
File: Agronomy 2
Issued in furtherance of Cooperative Extension work, Acts of May8 and June 30, 1914, in cooperation with the U.S. Department ofAgriculture. Stanley R. Johnson, director, Cooperative ExtensionService, Iowa State University of Science and Technology, Ames,Iowa.
. . . and justice for allThe U.S. Department of Agriculture (USDA) prohibits discriminationin all its programs and activities on the basis of race, color, nationalorigin, gender, religion, age, disability, political beliefs, sexualorientation, and marital or family status. (Not all prohibited basesapply to all programs.) Many materials can be made available inalternative formats for ADA clients. To file a complaint ofdiscrimination, write USDA, Office of Civil Rights, Room 326-W,Whitten Building, 14th and Independence Avenue, SW, Washing-ton, DC 20250-9410 or call 202-720-5964.
