Corn Oil

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Corn Refiners Association1701 Pennsylvania Avenue, N.W.

Washington, D.C. 20006-5805202-331-1634 Fax: 202-331-2054

www.corn.org

CONTENTS

CONTENTS

5th EditionCopyright 2006

Member Companies and Pland Locations .................................... 2Foreword ............................................................................................. 3Introduction ....................................................................................... 4The Corn Wet Milling Industry ....................................................... 5General Manufacturing System ....................................................... 6Corn Oil Manufacturing Process .................................................... 9Packaging, Transport and Storage ................................................ 13Physical and Chemical Properties ................................................. 14Nutritional Properties ..................................................................... 16Production and Commercial Uses ................................................ 19Analytical Examination of Corn Oil ............................................ 22

TABLES1. Proximate Analysis of Yell Dent Corn Grain .......................... 62. Comparative Composition of Crude & Refined Corn Oil ....... 123. Approximate Composition of Refined Corn Oil:

Nutrient Values ............................................................................ 144. Food Chemicals Codex Specifications for Refined Corn Oil ... 155. Typical Chemical and Physical Data for Refined Corn Oil ....... 156. Vegetable Oil Production, 2004 ................................................ 19

FIGURES1. A Kernel of Corn ......................................................................... 62. The Corn Wet Milling Process .................................................... 73. Corn Oil Refining ........................................................................ 114. Nutritional Labeling of Corn Oil ............................................. 16

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Archer Daniels Midland CompanyP.O. Box 1470Decatur, Illinois 62525

Cargill, IncorporatedP.O. Box 5662/MS62Minneapolis, Minnesota 55440-5662

Corn Products International, Inc.5 Westbrook Corporate CenterWestchester, Illinois 60154

National Starch and Chemical Company10 Finderne AvenueBridgewater, New Jersey 08807-0500

Penford Products Co.(A company of Penford Corporation)P.O. Box 428Cedar Rapids, Iowa 52406-0428

Roquette America, Inc.1417 Exchange StreetKeokuk, Iowa 52632-6647

Tate & Lyle Ingredients Americas, Inc.(A subsidiary of Tate & Lyle, PLC )P.O. Box 151Decatur, Illinois 62521

MEMBER COMPANIES

Plants:Cedar Rapids, Iowa 52404Clinton, Iowa 52732Columbus, Nebraska 68601Decatur, Illinois 62525Marshall, Minnesota 56258-2744

Plants:Blair, Nebraska 68008-2649Cedar Rapids, Iowa 52406-2638Dayton, Ohio 45413-8001Eddyville, Iowa 52553-5000Hammond, Indiana 46320-1094Memphis, Tennessee 38113-0368Wahpeton, North Dakota 58075

Plants:Bedford Park, Illinois 60501-1933Stockton, California 95206-0129Winton-Salem, North Carolina 27107

Plants:Indianapolis, Indiana 46221North Kansas City, Missouri 64116

Plant:Cedar Rapids, Iowa 52404-2175

Plant:Keokuk, Iowa 52632-6647

Plants:Decatur, Illinois 62521Lafayette, Indiana 47902Lafayette, Indiana 47905Loudon, Tennessee 37774

PLANT LOCATIONS

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Golden corn oil sitting on the pantry shelf often serves as themost visible sign of the corn refining industry to most Ameri-cans. Although corn oil represents a relatively modest amountof all food ingredients produced by corn refiners, its householduse reminds consumers of the vast array of food and industrialproducts derived from our most abundant crop.

Long the preferred food oil for discerning consumers, corn oilwas limited in supply until recent years. The growth of cornrefining over the last twenty years, has led to greater supplies ofcorn oil being available for domestic consumption while alsocontributing to the U.S. balance of trade through exports.

The modern corn refining process creates various food andindustrial starches, sweeteners, alcohols, oil, feed ingredients andbioproducts. Each offers an excellent example of the way wecan add value to raw agricultural commodities. By doing so, weexpand markets for U.S. farmers, increase employment throughprocessing and provide a wide array of useful products toAmerican industry and consumers.

We hope you will find this booklet about corn oil useful. Pleasecontact the Corn Refiners Association, if you would like moreinformation on corn refining and its products.

Audrae EricksonPresidentCorn Refiners Association

Readers are advised that the information and suggestions contained hereinare general in nature and that specific technical questions should be referredto the Association or its member companies. Questions as to the price and/or availability of products described should be directed to individual Asso-ciation members.

FOREWORD

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INTRODUCTION

As the corn refining industryexpanded its product portfo-lio and processed more corn,the quantity of corn oil avail-able increased dramatically.Corn oil has become an im-portant item in the mix ofproducts manufactured fromAmerica’s most importantcrop, and is no longer thoughtof as simply another co-prod-uct of starch manufacture.

Annual production of crudecorn oil currently exceeds 2.4billion pounds. Nearly all ofit is refined into high-qualityoil for the food industry anddirect use by consumers. Inthe 1950s, medical researchersfound that corn oil was effec-tive in reducing serum choles-terol in humans. This re-search gave rise to anincreased demand for corn oilthat continues today.

Corn refiners invested in re-search and development thathas resulted in production ofedible oils of consistently highquality. Concurrently, devel-opment of new and improvedproducts using corn oil, manyof them conceived in re-sponse to health-related re-search in foods and nutrition,has given this oil a marketidentity that is widely recog-nized and differentiates it

clearly from other edible veg-etable oils. About 95 percentof domestically producedcorn oil is from the corn wetmilling industry, and all but asmall fraction is used in oneform or another as food.

This booklet presents a briefhistory and current descrip-tion of the corn wet millingindustry and products; a de-scription of the corn oilmanufacturing process; com-position, physical and chemi-cal properties of corn oil;commercial uses and endproducts utilizing corn oil;nutritional considerations; anda listing of methods for iden-tification and analysis of cornoil. It is the fourth in a seriesof booklets describing prod-ucts from corn. Subjects ofother volumes are: cornstarch; nutritive sweetenersfrom corn; and corn wetmilled feed products.

The growth of corn oil in themarketplace is based on itsfunctionality, economy, andacceptability in relation toother fats or oils. Amongthese factors, functionality isforemost. For health reasons,corn oil has replaced a signifi-cant amount of saturated fatand is also a top choice fortrans fat reduction in numer-ous food products.

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THE CORN WETMILLING INDUSTRY

BACKGROUNDThe origins of the Americancorn wet milling industry canbe traced back to 1842, whenThomas Kingsford began thecommercial manufacture ofstarch from corn. Previously,starch was made from wheatand potatoes, starting as acottage industry in the colo-nial period. The first starchfactory had been establishedin New England in 1802 toprovide potato starch for cot-ton cloth mills. By 1860, asubstantial amount of corn-starch was being produced inmany small plants scatteredabout the country. U.S. con-sumption of cornstarchreached about 210 millionpounds in the 1880s, but therewas significant overproduc-tion and many of the smallplants closed. After 1900,there was a steady increase inconsumption and most of thesmall plants were replaced bya small number of largeplants. By this time, corn hadsucceeded wheat and potatoesas the principal source ofstarch. Thereafter the indus-try enjoyed continuing growthwhile it began to diversify intothe complex processing indus-try that corn refining is today.

Corn syrups became a well-known article of commerceand household use in the lat-ter part of the nineteenthcentury. By 1921, research ledto a pure sugar from cornsyrup — crystalline dextrose

hydrate — which became acommercial product withina few years. In the 1950s,syrups in a range of con-trolled levels of sweetnessapproaching that of puredextrose entered the mar-ket. In 1967, enzymatictransformation of glucoseto fructose was introduced,leading to production ofhigh fructose corn syrup.Since the late 1980s, sweet-eners derived from cornhave supplied the majorityof the U.S. nutritive sweet-ener market. A wide vari-ety of starches and starchderivatives are now pro-duced to fill the needs ofmany different industries.Additionally, corn refinersare branching out to pro-duce a wide variety of spe-cialty food and feed addi-tives through otherfermentation processes.Co-products from cornrefining make importantcontributions to livestockfeeds. Production of high-quality corn oil increases indirect proportion to thegrowing volume of corngoing to starch, sweetener,ethanol and bioproductproduction, and the oil hasfound a unique and specialplace among edible oils.

The current growth anddevelopment of corn refin-ing, characterized by ad-vanced technology, thelarge number and diversity

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of products and variety ofindustries served, demon-strates that the corn kernel,like crude petroleum, hasbecome an important sourceof chemical feedstocks.

GENERALMANUFACTURING

SYSTEM COMPONENTS OF THE

CORN KERNELFigure 1 is a cross sectional dia-gram of the corn kernel, show-ing the general structure and lo-cation of the major componentsof interest in the milling process.The outer layers (hull, or bran andtip-cap), which account for about6 percent of the kernel’s weight,become a component of feedproducts. The germ (embryo),in which most of the oil resides,is about 11.5 percent. The re-mainder of the kernel is en-dosperm. Floury endosperm(white portion of the drawing) ismostly soft starch, easily sepa-rated and recovered. The stippledportion of Figure 1 is horny en-dosperm, in which starch and

Characteristic Range AverageMoisture (% wet basis) 7 – 23 16.0Starch (% dry basis) 61 – 78 71.7Protein (% dry basis) 6 – 12 9.5Fat (% dry basis) 3.1 – 5.7 4.3Ash (oxide) (% dry basis) 1.1 – 3.9 1.4Pentosans (as xylose) (% dry basis) 5.8 – 6.6 6.2Fiber (neutral detergent residue) (% dry basis) 8.3 – 11.9 9.5Cellulose + Lignin 3.3 – 4.3 3.3 (acid detergent residue) (% dry basis)Sugars, Total (as glucose) (% dry basis) 1.0 – 3.0 2.6Total Carotenoids (mg/kg) 12 – 36 26.0

Reprinted with permission form White, P.J., and Johnson, L.A., eds., 2003, CornChemistry and Technology, American Association of Cereal Chemists, St. Paul, MN.

Table 1.Proximate Analysis ofYellow Dent CornGrain

Figure 2 is a flow chart of thecorn wet milling process, show-ing the paths of the corn kernelthrough equipment, processes,and intermediate products tothe four main categories ofoutput products: starch, sweet-ener, animal feed and oil. Nutri-tive sweeteners are further re-fined to produce fermentationproducts and other chemicals

Figure 1.A Kernel of Corn.

protein (gluten) are intermixedand require more drastic treat-ment for separation. Table 1shows the chemical compositionconsidered representative ofAmerican yellow hybrid dentcorn.

Endo

sper

m

Starch

GermStarch

andGluten

HullFiber

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Shelled Corn

RefinedCorn

Oil

NutritiveSweeteners

StarchProductsFeed

Products

Corn Cleaners

Steep Tanks

Steepwater

GermSeparators

Germ

Grinding Mills Screens CentrifugalSeparators

Fiber Gluten

Germ Washingand Drying

Clean, DryGerm

Oil Expellersand Extractors

Crude Oil

Oil Refining(See Fig. 3)

Corn GermMeal

HydrocloneStarch Washing

Refinery

Figure 2The Corn Wet Milling Process

THE CORN WET MILLING

PROCESS

Shelled corn enters the systemthrough cleaning machines,which remove foreign material.Cleaned corn then goes to asteep tank holding up to25,000 bushels, where it soaksin circulating water, maintainedat 125°F and slightly acidifiedwith 0.1 to 0.2 percent of sul-fur dioxide. Steeping the cornfor 24 to 48 hours softens thekernel, loosens the hull andgerm and swells the en-dosperm. Steeping takes place

in a series of tanks, which areoperated in a continuous-batchprocess. The water circulatescounter currently through thetanks, so when it is finally with-drawn from the newest batch, ithas a relatively high concentra-tion of solubles. The steepingprocess facilitates separation ofthe components of the kerneland loosens the gluten bonds torelease the starch. Dischargedsteepwater, rich in protein at 35to 45 percent of total solids, isconcentrated in vacuum evapo-rators to a solids content of 35to 55 percent. Steepwater con-centrate is utilized in feed prod-ucts or in industrial fermentationmedia.

such as amino acids, organicacids and polyols.

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Fermentation andOther Chemicals

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Softened corn from the steeptanks is coarsely ground withwater in an attrition mill tofree the hull, the germ and alarge portion of the flouryendosperm starch and gluten.The slurry of coarsely groundcorn is forced under pressureinto hydroclones, which cen-trifugally separate the lightercorn germ, which is then car-ried off to washing screens.Washed germ is conveyed to adryer and from there to oilrecovery facilities. Washingsfrom the germ are piped tothe starch centrifuges. Heavyfractions from the coarsegrinding mills and germ sepa-rators are passed through finegrinding mills and washingscreens for fiber separation.Finally, the slurry is sent tocentrifuges for separation ofgluten (light phase) fromstarch (heavy phase).

The gluten fraction passes to acentrifugal concentrator and isfiltered and dried. The starchstream goes to washing cy-clones fed with fresh water;overflow, containing residualgluten from the “mill starch,”is recycled to the starch centri-fuge; underflow from thewashing cyclones, a suspen-sion of starch containing onlyabout 0.3 percent protein, ispassed through a concentratorand dryer, from which thefinished starch productemerges.

PRODUCTSEnd products of the wet mill-ing process are purified starch,a collection of feed products,and crude corn oil. Commer-cial starch products are thenmanufactured in great variety,including unmodified corn-starch, acid-modified and oxi-dized starches, dextrins, andstarch derivatives. Detailedinformation on starch process-ing and products is presentedin the booklet, “Corn Starch,”from the Corn Refiners Asso-ciation.

A large fraction of total corn-starch production is utilized inthe manufacture of nutritivesweeteners. These starch con-version products includemaltodextrins; high fructose,high maltose, and other typesof corn syrups; corn syrupsolids; and dextrose. Compre-hensive information aboutthese products is presented in“Nutritive Sweeteners fromCorn” available from the CornRefiners Association. Anothermajor use of cornstarch is as afeedstock for production ofethanol and other fermentationproducts for food and feedapplications.

The corn wet milling process isvery efficient resulting in theutilization of virtually all ofthe corn kernel. Steepwater,bran and gluten from starchproduction and germ mealfrom the oil extraction process

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are all utilized in high-qualitylivestock feeds. Manufacture,composition and uses of thesefeed products are the subjectof another Corn Refiners As-sociation booklet, “Corn WetMilled Feed Products.”

CORN OILMANUFACTURING

PROCESSCorn germ contains about 85percent of the total oil of thekernel. The rest is dispersedin endosperm and hull frac-tions and is generally utilizedin feed products. The clean,dried germ from wet millinghas an oil content of 45 to 50percent. Oil is usually ex-tracted from the germ by acombination of expelling incontinuous screw presses andsolvent extraction of the presscake. The initial expeller canrecover a little more than halfof the oil and subsequentsolvent extraction (with hex-ane or iso-hexane) will bringthe total yield to about 95percent. The solvent is re-moved by evaporation, recov-ered and re-used. The ex-pelled and solvent-extractedfractions are combined astotal crude corn oil. The oil-depleted germ is freed ofsolvent, toasted, ground andscreened. The resulting corngerm meal is combined withfiber and concentratedsteepwater to produce corngluten feed.

REFININGCrude corn oil, because of thenatural antioxidants it con-tains, undergoes little deterio-ration when stored for longperiods, provided the tem-perature is kept well below40°C (102°F) and moistureplus volatile matter level isbelow 0.4 percent. Since vir-tually all refined corn oil isutilized in foods, the need toattain a quality suited to suchuse guides the refining pro-cess. Steps include degum-ming to remove phosphatides,alkali treatment to neutralizefree fatty acids, bleaching forcolor and trace element re-moval, winterization (the re-moval of high-melting waxes)and deodorization (steamstripping under vacuum). Fig-ure 3 is a flow chart of therefining operations. Crude oilenters the process via prelimi-nary filtration. Degummingremoves phosphatides andother materials that may beprecipitated or dissolved fromthe crude oil by hot water.This step is usually omitted inrefineries that process onlycorn oil, but is used in refiner-ies that are set up to refinesoybean oil as well as corn oil.Degumming is accomplishedby introducing hot water at alevel of 1 to 3 percent of oilvolume, or by injecting anequivalent amount of steamto hydrate the phosphatides.The phosphatides, together

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with certain other materials,absorb water and precipitatefrom the oil as a heavierphase, which is removed bycentrifugation.

When degumming is omitted,the refiner depends on an alkalirefining step, which usesroughly the same temperatureas a degumming operation, totake out the phosphatidesalong with the free fatty acids(in the form of soapstock) andto reduce color. Phospholip-ids, “corn lecithin,” can berecovered from both degum-ming and alkali refining resi-dues.

In the alkali refining step, freefatty acids are neutralized bytreatment at 82 – 100°C (160 –180°F) with a small amount ofconcentrated sodium hydrox-ide solution. Alkali refiningreduces color and also removesother non-triglyceride sub-stances, which are separatedalong with the neutralized freefatty acids and hydrated phos-phatides, by centrifugation.The alkali treated oil is usuallywashed with a small quantityof hot water to remove re-sidual soap formed by thealkali treatment. The separatedresidues from alkali treatmentare sold as soapstock or acidu-lated soapstock, which con-tains about 95 percent freefatty acids.

The oil is then decolorized bytreatment with acid-activated

clays that bleach by adsorbingcolor bodies, residual soapsand metal complexes from theoil. In plants producing par-tially hydrogenated oil alongwith regular corn oil, bleachedoil coming from the filter ispiped to the hydrogenationvessel. When that process iscompleted, the partially hydro-genated oil is passed througha filter to remove catalystparticles and other extraneousmaterial. Further bleaching,deodorization and filtrationyield a clear, pale yellow oil.

Refining of the unmodifiedoil continues with winteriza-tion. Waxes, present in the oilin small amounts characteristi-cally have high melting pointsand are readily crystallized bychilling in refrigerated vessels.They are then removed byfiltration. This produces ahaze-free finished oil whenrefrigerated.

Finally, deodorization is ac-complished by a continuoussteam distillation under highvacuum at high temperature232 – 260°C (450 – 500°F).Oil is fed into the top of thedistillation tower, while a jetof steam entering at the basecarries the volatile odorantswith it as it passes upwardsand exits near the top. Con-densed exhaust steam con-tains odor, color, flavor com-ponents and the remainingtraces of free fatty acids. Thedeodorized oil is drawn off at

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Lecithin, etc.

FinishedHydrogenated

Oil

FinishedOil

Centrifuge Degumming

Re-Wash

Filter

Alkali Refining

Deodorize

Polish Filter

Centrifuge

Bleaching

Filter

Winterize

Filter

Figure 3.Corn Oil Refining

Deodorize

Polish Filter

Hydro-genation

Filter

Post Bleach

Filter

SoapstockFree Fatty Acids

PholpholipidsColor

ResidueSpent Catalysts,

etc.

Spent ClaySoap

PhospholipidsColor

Waxes

SteamCondensate

OdorColor

FlavorFree Fatty Acids

CrudeCorn Oil

Oil

Oil

Oil

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Typical Value, %Crude Refined

Triglycerides 95.6 98.8Free fatty acids 2.5 0.05Phospholipids 1.5 0.0Unsaponifiables

Cholesterol 0.0 0.0Phytosterols 1.2 1.1Tocopherols 0.12 0.08

Waxes 0.01 0.0Color variable: very pale yellow

dark to yellowOdor and flavor strong slight corn

corn/feed slight nutty/ buttery

Cold test at 0°C (32°F) — clear for 24 hours**

*Adapted and updated from Blanchard, Paul Harwood, “Technology ofCorn Wet Milling and Associated Processes,” 1992. Table 14.1, p. 360

**Time may vary depending on producer

the bottom of the tower, thendried and passed through apolish filter to become thefinal product, refined corn oil.

Corn oil may be shipped fromrefinery to a food manufac-turer after bleaching and win-terization, leaving deodoriza-tion to be done in the foodplant. Essential aspects ofcorn oil manufacture are com-mon throughout the industry,but the refining process mayvary considerably or havesome steps eliminated, de-pending on quality and com-position of the crude oil, sta-tus of plant equipment andthe planned end use. Withcurrent technology, manufac-turing is essentially a continu-ous process.

The changes in compositionaccomplished by refining areindicated in Table 2. Refiningincreases purity from 95 – 96percent to about 99 percenttriglycerides. The substancesremoved in attaining this levelof purity are ones that detractfrom the value as a high-qual-ity edible oil for varied uses.Free fatty acids lower thesmoke point of oils in fryingoperations. Phospholipids atthe levels ordinarily found incrude oils must be removedbecause they produce darkcolors upon heating the oiland form a precipitate, orsludge, in the presence ofsmall amounts of moisture infrying vats. They also signifi-cantly affect flavor if not re-moved. Color, odor, and

Table 2.Comparative Composition ofCrude & Refined Corn Oil*

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flavor must be removed be-cause of consumer prefer-ence. In addition, these refin-ing steps solve importantsafety concerns with smokingoils and will remove potentialcontaminants, which may bepresent in any agricultural rawmaterial. Processing is con-trolled to retain the toco-pherols in the refined oil.This is an advantage becauseof their antioxidant activity,which helps retard develop-ment of rancidity, and for theVitamin E activity of certaintocopherols.

Crude corn oil in bulk — mov-ing between plants, from starchplant to a distant refinery or toan export terminal — is shippedin rail tank cars or, sometimes,in highway tankers. Food grade,fully refined corn oil in bulk isoften shipped from refinery tofood manufacturer in highwaytankers, depending on the quan-tity and distance. Smaller quan-tities of corn oil are shippedfrom refinery or repacker to theuser in drums or cans. Largerquantities, which are shippedfor export, are carried by ocean-going parcel tankers.

Although corn oil in packagedproducts is well protectedagainst rancidity by the naturalantioxidants it contains, furtherprotection by displacingheadspace air with nitrogen issometimes practiced. To ensure

PACKAGING,TRANSPORT,

AND STORAGE

adequate shelf life, consumerpackages of corn oil are oftenfilled under nitrogen into eitherglass or plastic bottles. Like-wise, snack foods fried in cornoil can be given added protec-tion against rancidity by pack-aging in laminated foil and plas-tic bags that, in filling andsealing, have air in the packagedisplaced by an inert gas suchas nitrogen. Storage at ambi-ent room temperature or loweris also necessary to prevent de-terioration in packaged pre-pared foods containing polyun-saturated oils.

Corn oil has little or no sensi-tivity to indoor, incandescentlight, but prolonged exposure tofluorescent lighting may resultin development of measurablerancidity. The consumer pack-ages of clear glass or plasticnow used permit color and clar-ity of the product to be easilyseen for the relatively brief pe-riod it usually remains on anopen shelf. Contact with cop-per promotes the rapid devel-opment of rancidity in polyun-saturated oils. For this reason,metal drums, plant storagetanks, rail and highway trans-port tanks, valves, piping andprocess equipment must bescrupulously free of copper atall places where there could beany contact with the oil. Pro-longed contact with iron mayalso cause problems, but iron isof much less concern in this re-gard than copper.

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Physical and chemical data onvegetable oils serve a number ofpractical uses: assessment ofnutritional values; specificationwriting for sale and purchase ofoils, in consideration of intendeduse; quality control and monitor-ing of refining and food manu-facturing processes; backgroundinformation for chemical, bio-logical and medical research in-volving fats; and regulation offood quality and safety by pub-lic agencies charged with that re-sponsibility.

Corn oil may be supplied to theuser in the crude state for fur-ther refining, in intermediate re-

PHYSICAL ANDCHEMICAL

PROPERTIES

fined stages or in the finished(fully refined) form. Tables 3through 5 present data concern-ing the physical and chemicalproperties of finished (fully re-fined) corn oil.

Table 3 represents the infor-mation on refined corn oilthat is of primary concern tonutritionists and dieticians.Table 4 lists the primary speci-fications for corn oil that havebeen adopted by the Commit-tee on Food Chemicals Codexof the National Academy ofSciences/National ResearchCouncil. Purchase specifica-tions for crude and refined

(Amount in 100 Grams of Oil)

Weight (grams) 100.0Moisture (grams) NoneProtein (N x 6.25) (grams) NoneFat, Total (grams) 100.0 Triglycerides (grams) 98.8

Polyunsaturates, Total (grams) 59.7 Cis, Cis Only (grams)* 58.7Monounsaturates (grams) 26.0Saturates, Total (grams)* 13.1

Unsaponifiable Matter (grams) 1.2Cholesterol (milligrams) NonePhytosterols (milligrams) 1000 Tocopherols, Total (milligrams) 88Alpha-tocopherol (milligrams) 19Gamma-tocopherol (milligrams) 67Delta-tocopherol (milligrams) 3

Carbohydrate, Available (grams) None

Ash (grams) NoneSodium (milligrams) NoneEnergy (calories) 885

*Polyunsaturated and saturated fats as defined for nutrition informationlabeling, 21 CFR 101.9 (1994).

Table 3.Approximate Composi-tion of Refined Corn Oil:Nutrient Values

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corn oil may be obtained fromindividual oil producers. Ad-ditional chemical and physicalmeasurements that are used to

characterize edible oils, pre-senting ranges that typify re-fined corn oil, are shown inTable 5.

Table 4.Food Chemicals CodexSpecifications for RefinedCorn Oil

Arsenic Not more than 0.5 mg/kgColor (AOCS-Wesson) Not more than 5.0 redFree Fatty Acids (as oleic acid) Not more than 0.1%Iodine Value 120 - 130Lead Not more than 0.1 mg/kgLinolenic Acid Not more than 2.0%Peroxide Value Not more than 10 meq/kgUnsaponifiable Matter Not more than 1.5%Water Not more than 0.1%

Food Chemicals Codex, Fifth Edition, pp. 122-123, National AcademyPress, 2003.

Table 5.Typical Chemical andPhysical Data forRefined Corn Oil

Iodine Value (Wijs) 122 – 131Saponification Value 189 – 195Viscosity (Sayboldt-Universal, 100°F) 165 – 175 secondsRefractive Index @ 25°F 1.470 – 1.474Specific Gravity @ 60°F 0.922 – 0.928Weight per gallon @ 60°F 7.7 poundsMelting Point 12 – 17°FSmoke Point 445 – 460°FFlash Point 630 – 640°FFire Point 690 – 700°FCloud Point 7 – 12°F

Typical Fatty Acid Profile Grams/100 gm. oil

Linoleic 18:2 (polyunsaturated) 54 – 60Linolenic 18:3 (polyunsaturated) 1Palmitic 16:0 (saturated) 11 – 13Stearic 18:0 (saturated) 2 – 3Oleic 18:1 (monounsaturated) 25 – 31

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ROLE OF CORN OIL IN

THE DIETCorn oil can play a major role inthe human diet. It is a concen-trated source of energy (calo-ries), is very digestible, providesessential fatty acids and VitaminE, and is a rich source of poly-unsaturated fatty acids, whichhelp regulate blood cholesterollevels and lower elevated bloodpressure (1,2). Animal and hu-man studies show that at least97 percent of the oil is digestedand absorbed. Like all fats andoils, corn oil provides 9 kcal (38kjoules)/gram, or about 120 kcalper one tablespoon (14g) serv-ing. Corn oil is a rich source oflinoleic acid, an essential fattyacid that the body cannot make.

NUTRITIONALPROPERTIES

The National Research Counciland the Food and AgricultureOrganization/World Health Or-ganization recommend about 2-4 percent energy in the form ofessential fatty acids with an ad-ditional 3 percent of energy forwomen who are pregnant or arebreast feeding. A tablespoonserving of corn oil will satisfy thedaily essential fatty acid require-ment for a healthy child or adult.

LABELINGA typical Nutrition Facts panelfor corn oil is shown in Figure4. Corn oil may be labeled “Acholesterol and/or sodium freefood.” When this descriptor isused the following statementmust appear: “Contains 14

Nutrition FactsServing Size 1 tbsp (14 g)Servings Per Container (pint) 32

Amount Per ServingCalories 120 Calories from Fat 120

%Daily Value*Total Fat (14 g) 22% Saturated Fat (2 g) 9%Polyunsaturated Fat (8 g)Monounsaturated Fat (4 g)

Cholesterol (0 mg) 0%Sodium (0 mg) 0%Total Carbohydrate (0 g) 0%Protein (0 g)

Vitamin E 15%

Not a significant source of dietary fiber, sugars, vitamin A,vitamin C, calcium, and iron.*Percent Daily Values are based on a 2,000 calorie diet.Ingredients: Corn Oil

Figure 4.Nutritional Labeling ofCorn Oil

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grams of fat per serving. See Nu-trition Facts panel for informationon total fat, saturated fat and othernutrients.”

CHOLESTEROL AND

CORONARY HEART DISEASEThe relationship between dietaryfat, blood cholesterol and lipo-protein levels and coronaryheart disease has been exten-sively studied for fifty years. Itis now widely accepted that adiet high in saturated fat andcholesterol is one of many caus-ative factors in the developmentof atherosclerosis and coronaryheart disease. Regression equa-tions relating type of fat and itseffect on blood cholesterol,based on 248 metabolic dietcomparisons (3), show that satu-rated fats raise, polyunsaturatedfats lower and monounsaturatedfats have no effect on bloodcholesterol levels. Saturated fatsare approximately twice as pow-erful in raising cholesterol levelsas polyunsaturated fats are inlowering them. The NationalCholesterol Education Programand the American Heart Asso-ciation recommend a diet inwhich total fat is less than 30percent of calories, saturated fatis less than 10 percent of calo-ries, polyunsaturated fat is up to10 percent of calories and cho-lesterol is 300 mg or less per day.

Corn oil has been used exten-sively in research studying therelationship of dietary fat toblood cholesterol levels. This is

because corn oil was theonly highly polyunsaturatedoil readily available to inves-tigators and patients in themid-1950s. Due to its highstability, pleasant taste andmultifunctional usage, cornoil became the standardagainst which other oilswere compared to assesscholesterol-lowering abilitiesof oils. In a survey of theliterature, 30 clinical studies(39 diet comparisons) werefound where corn oil was asignificant part of the diet.A total of 1,160 subjectswere studied; the averagecholesterol lowering was 16percent. This is greaterthan the 3-14 percent cho-lesterol lowering anticipatedby the National CholesterolEducation Program. Simi-lar benefits are not likely toresult for the general popu-lation as diets are strictlycontrolled in clinical trials.However, the level of totaland saturated fat and cho-lesterol in the diet hassteadily decreased over thepast 10 to 15 years.

In research where corn oilwas compared to other oils,nine human feeding studiesinvolving 391 men andwomen showed that cornoil had the greatest choles-terol-lowering abilities. Infact, three studies showcorn oil to be superior tosunflower oil in overall cho-lesterol lowering. The total

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composition of an oil, whichincludes the fatty acid compo-sition, triglyceride structureand non-triglyceride compo-nents, contributes to that oil’sability to lower serum choles-terol. Among liquid vegetableoils, no oil is better than cornoil to lower blood cholesterollevels.

BLOOD PRESSURENumerous human studiesshow that diets enriched inpolyunsaturated fatty acidscan significantly lower el-evated blood pressure. Cornoil was used in many of thesestudies (4). Corn oil dietshave shown blood pressurelowering of about 12 percentin men and 5 percent inwomen who had elevatedblood pressure (mild hyper-tension). No significant effectof polyunsaturates has beennoted in persons with normalblood pressure.

TRANS FATTY ACIDSThe Food and Drug Admin-istration adopted regulationsthat require the labeling ofretail foods for trans fattyacids in January 2006. Theprimary reason for this re-quirement is the fact thatnumerous studies have shownthat, like saturated fatty acids,trans fatty acids elevate bloodcholesterol levels. (5)

The requirement mandates aseparate line item for trans fat

directly below the saturated fatline on the Nutrition Factspanel. Items containing lessthan 0.5 grams of trans fat perserving can be declared as 0grams. If the food containsless than 0.5 grams of total fat,a footnote can replace the transline that says, “Contains aninsignificant amount of transfat.” Items that have levels ofless than 0.5 grams per servingof both saturates and trans fatcan bear the statement, “Satu-rated fat free.” Items that offera 25 percent reduction in satu-rates per serving can bear thestatement, “Reduced satu-rates.”

The average trans fatty acidintake is estimated at 2-4 per-cent of the total energy con-sumed. The average saturatedfat intake estimate is 12-14percent. Current dietary ad-vice is to reduce consumptionof both saturated and transfatty acids.

Where do trans fatty acidscome from? Trans fatty acidsoccur naturally in ruminantanimals, such as cows. Tallowand milk fat can contain be-tween four and 11 percent transfatty acids. In vegetable oilprocessing, most trans fattyacid formation occurs duringpartial hydrogenation. Partialhydrogenation of liquid veg-etable oils to produce moresolid and stable forms for usein products such as marga-rines and shortenings has

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been carried out for over 90years. During hydrogenation,some of the naturally occur-ring cis double bonds in theunsaturated fatty acids arechanged into trans doublebonds, which makes the fattyacid molecule appear and actsimilarly to that of a saturatedfatty acid. Small amounts oftrans fatty acids, typically 0.5 –3 percent, are also formedduring deodorization of non-hydrogenated salad oils. Thisis the final step in oil process-ing where the oil is exposed tohigh temperature.

1. B.F. Hauman, Corn Oil. J.Am. Oil Chem. Soc. 62:1524-31, 1985

2. J. Dupont, P.J. White, M.P.Carpenter, E.J. Schaefer, S.N.Meydani, C.E. Elson, M.Woods and S.L. Gorbach,Food uses and health effectsof corn oil. J. Am. Col. Nutr.9:438-470, 1990

3. D.M. Hegsted, L.M. Ausman,J.A. Johnson and G.E. Dallal,Dietary fat and serum lipids;an evaluation of the experi-mental data. Am. J. Clin.Nutr. 57:875-883, 1993

4. J.M. Iacono and R.M.Dougherty, Effects of poly-unsaturated fats on bloodpressure. Ann. Rev. Nutr.13:243-260, 1993

5. J.T. Judd, D.J. Baer, B.A.Clevidence, P. Kris-Etherton,R.A. Muesing and M. Iwane.Lipids 37, no2: 123-131, 2002

CORN OIL PRODUCTIONThe amount of corn oil pro-duced, which is controlled bythe total volume of corn pro-cessed, has increased steadilysince 1973. Between 1956 and1974, average annual growthin production of crude cornoil was 3.2 percent. From1974 through 2002, the rateof increase climbed to 5.75percent annually.

Corn oil is now the secondleading vegetable oil producedin the United States, second inimportance only to soybeanoil. Domestic corn oil pro-duction was 2.5 billion poundsin 2004 and soybean oil,which has dominated the U.S.vegetable oil market was 18.7billion pounds. Relative pro-duction of major vegetableoils is shown in Table 6.

Vegetable oil statistics are avail-able online from the U. S. De-partment of Agriculture Eco-nomic Research Service athttp://usda.mannlib.cornell.edu/data-sets/crops/89002/.

PRODUCTIONAND

COMMERCIALUSES

Soybean Oil 18,710Corn Oil 2,470Cottonseed Oil 915Sunflower Oil 305Canola Oil 626

Source: Bureau of the Census andAgricultural Marketing Service

Table 6.Vegetable Oil Production, 2004(Million Pounds)

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FOOD USE OF

VEGETABLE OILSOverall the major vegetableoils such as soybean, corn,cottonseed, and canola com-prised more than 95 percentof the vegetable oil consumedin the United States in 2004.The vast majority of this useis in three categories: (1) salador cooking oil which takesaround 47 percent of domes-tic consumption; (2) shorten-ing (fluid, semi-solid, or solidbaking and frying fats) whichaccounts for about 43 percentof domestic vegetable oilconsumption; and (3) marga-rine which accounts for about10 percent of domestic veg-etable oil consumption.

FOOD USES OF CORN OILThe principal food uses ofcorn oil (as either consumeror institutional products) in-clude:

Salad and cooking oil - 100percent corn oil or inblends with other liquidvegetable oils.Margarine – both 100 per-cent corn oil in the oilphase or in blends withother vegetable oils.Blends of butter (40 per-cent) and corn oil marga-rine (60 percent).Mayonnaise and emulsion-type salad dressings.

As an oil ingredient in a vari-

ety of packaged and restau-rant foods, including:

Spaghetti sauce;Potato chips and snackfoods;French fries and breadedfried foods;Baking mixes;Frostings and whippedtoppings;Crumb coatings for meatand poultry; andBaked goods.

Only a minor amount of totalcorn oil production is blendedwith other vegetable oils withthe exception of corn oil inconsumer packages such asthose listed above in whichingredient statements showcorn oil as part of a blend orone of several optional oilsthat may be used. There are afew such products that indi-cate only corn oil is used. Usein packaged foods representsa small fraction of total cornoil consumption.

The output of cooking oil isdivided between consumerand institutional packagedproducts and industrial fryingoils furnished to snack foodproducers and restaurant fry-ing operations. Corn oil maybe blended with other oils inpackages for home use inorder to provide desirableflavor to other oils. Institu-tional frying use of corn oil

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has expanded dramatically inthe last decade as fast foodcompanies have switchedpotato frying from an animalfat to a vegetable oil base.Historically, both non-hydro-genated and partially hydroge-nated corn oil have been usedfor frying applications. Re-cently, the use of non-hydro-genated corn oil has increased,primarily to address trans fattyacid concerns.

Margarine began to displacebutter as a household spreadbeginning in the 1930s. How-ever, before 1950, use of cornoil in margarine manufacturewas minimal. The discoveryin the 1950s that corn oil hada favorable impact on serumcholesterol dramatically ex-panded its use in margarine.Corn oil margarines areamong the highest inpolyunsaturates of all theleading margarines. Use ofcorn oil in margarine was onlyabout one million pounds inthe 1930s, but increased toaround 15 million pounds inthe 1950s, 50 million poundsin the 1960s and up to 250million pounds in the early1980s. Corn oil use for marga-rine production has decreasedsince the early 1980s as sup-

plies have been diverted toinstitutional frying uses.

INDUSTRIAL USE OF

CORN OILConsumption of corn oil innonfood uses represents anegligible percentage of totalconsumption. Small amountsare used in the manufactureof resins, plastics, lubricantsand similar oils. A smallquantity of highly refined oilis used by the pharmaceuticalindustry in certain dosageforms and for other purposes.

The residues and byproductsfrom corn oil refining amountto 8 to 10 percent of thecrude oil entering the process.The bulk of these residues arein the form of soapstock,which contains the neutralizedfree fatty acids and phosphati-des. Most materials recoveredfrom soapstock have indus-trial end uses, but oil can be asource of edible forms of freefatty acids and lecithin. It ispossible to recover smallquantities of phytosterols andother substances fromsoapstock and the minor resi-dues. Recovered waxes fromthe winterizing step are uti-lized industrially or in animalfeeds.

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Published literature providesnumerous sources and de-scriptions of methods ofanalysis for various chemicaland physical properties ofcorn and other food oils. TheCorn Refiners Association hasdeveloped various analyticalmethods for numerous prod-ucts of the corn wet millingindustry, including corn oil.

These “Standard AnalyticalMethods” are published bythe Association and may beobtained for a reasonablecost. Methods developedspecifically for use with cornoil are:

H-10: Cold TestH-12: Color (Spectropho-tometric)H-22: Free Fatty AcidsH-32: Iodine Number(Wijs Method)

In addition, a number ofother professional societiespublish methods that may beof use to the producer anduser of corn and other veg-etable oils. In particular, thereader is referred to the meth-ods published by the AOACInternational (2200 WilsonBlvd., Suite 400, Arlington,Virginia 22201, www.aoac.org)and the American Oil Chem-ists’ Society (P.O. Box 3489,1608 Broadmoor Drive,Champaign, Illinois 61826,www.aocs.org).

ANALYTICALEXAMINATIONOF CORN OIL

Corn Refiners Association1701 Pennsylvania Avenue, N.W. • Washington, D.C. 20006-5805

202-331-1634 Fax: 202-331-2054 • www.corn.org