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CROP INSIGHTS •••• VOL. 12 •••• NO. 10 •••• PAGE

®Registered trademark of Pioneer Hi-Bred International, Inc. ©2002, PHII

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CROP INSIGHTS Corn Processing

by Steve Butzen and Troy Hobbs

Summary

• Food corn dry milling and wet milling are traditionalprocessing industries that separate the corn kernel into itsvarious component parts.

• Food corn alkaline cooking is a method of processingwhole corn for tortilla and snack food production.

• The dry-grind method of ethanol production is a rapidlygrowing corn processing technique to generate ethanol forfuel.

• This Crop Insights will discuss these four methods of

processing corn grain for food and industrial uses.

• Future Crop Insights articles will provide more detailedinformation on each of these processing segments.

Introduction

Each year, U.S. farmers plant an average of 78 million acresof corn and produce over 9 billion bushels of grain – about40% of the entire world supply. Planted and harvested cornacreage has been relatively stable in the U.S. in recent years(Table 1). Corn yields have increased due to breedingadvances, including the insertion of the Bt gene for corn

borer resistance.

Table 1. U.S. Corn Production, 2000 - 2002.

2000 2001 2002*

M i l l i o n A c r e s

Planted Area 79.6 75.8 78.9

Harvested Area 72.4 68.8 71.0

% Harvested 91% 91% 90%

Yield / harvested acre 136.9 138.2 125.2

M i l l i o n B u s h e l s

Total Production 9,915 9,507 8,886

* Projected. Source: USDA WASDE report. August, 2002

Use of corn in food and industrial processing has increaseddramatically in the last decade, but the bulk of the U.S. corncrop is still utilized for livestock feed or export (Figure 1).

Figure 1. 2002/03 U.S. Corn Crop Utilization (Source:USDA and Pioneer Hi-Bred Marketing Dept.).

Seed - 0.2%

BeverageAlcohol - 1.4%

Feed - 58.7%

Wet Milling 14.3%

Food 1.9%Dry-grind

Ethanol 3.9%

Exports - 19.7%

Recent increases in total corn processing are largely due toincreases in high fructose corn syrup and ethanol production.Corn bushels processed for food and industrial uses nowexceed 2 billion bushels annually. Food and industrial usesof the U.S. corn crop are shown in Figure 2.

Figure 2. 2002/03 U.S. Corn Food and Industrial Uses(Source: USDA, ERS, Feed Outlook, August 2002).

High FructoseCorn Syrup

25%

Cereals &

Other Products9%

Alcohol -

Beverageand Mfg.

6%

AlcoholFuel 39%

Glucose &Dextrose

10%Starch - 11%

Corn Kernel Composition

Understanding the composition of the corn kernel is key tounderstanding corn processing goals and methods. The cornkernel is composed of four main parts – the endosperm,pericarp, germ (embryo) and tip cap. Each of these has adistinctly different function and composition:





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The Endosperm is about 82% of the kernel's dryweight and is the source of energy (starch) and protein forthe germinating seed. There are two types of endosperm, softand hard. In the hard endosperm, starch is packed tightlytogether; in the soft endosperm, the starch is loose. Whencorn dries in the field before harvest, the moisture losscauses the soft endosperm to collapse and form a dent in the

top of the kernel. End-products of the corn endosperminclude starch, corn syrup, dextrose and ethanol. Remainingprotein (gluten) is used for animal feed.

The Pericarp, also called the hull, is the outer coveringof the kernel that protects it from deterioration. It is water-and water vapor-resistant and is undesirable to insects andmicro-organisms. The pericarp, comprising about 5% of totaldry weight of the kernel, is processed into animal feed.

The Germ, the only living part of the corn kernel, isabout 12% of the kernel’s dry weight. It contains theessential genetic information, enzymes, vitamins andminerals for the kernel to grow into a corn plant. About 25%

of the germ is corn oil, which is the most valuablecomponent of the corn kernel. After oil is removed, theremaining germ components are used in feed.

The Tip Cap is the only area of the kernel not covered bythe pericarp. It was the attachment point of the kernel to thecob. It is the major entry path into the kernel, and comprisesabout 1% of the kernel’s dry weight. Its end-use is in feed.

Food Corn – Dry Milling

Dry milling is the process of mechanically breaking andseparating corn into physical component parts. Rudimentarydry mills were operating hundreds of years ago. Early millsground whole corn, including the germ, into meal, flour andother staples, but these products had high fat levels thatlimited shelf life. De-germing equipment was developedaround 1900, allowing millers to supply low-fat grits, mealsand flours with greatly increased shelf life.

The dry milling industry consumes 120-140 million bushelsof grain annually, which requires about a million acres and

350,000 units of seed corn to produce. The mix is about 80-85% yellow and 15-20% white.

The dry milling industry has consolidated in the past fewdecades due to over-capacity. During this period the numberof dry mills declined from 150 mills in 1965, to 80 in 1985,to about 50 in 2002. However, the 10 largest mills accountfor over 80% of the output.

The Dry Mill Process

In the dry milling process, dry corn is cleaned, “tempered”with steam and water, and then de-germed. De-germingremoves the hull (pericarp), germ and tip cap from thekernel. Subsequent processes separate, aspirate, reduce, sift,dry and cool the various corn products.

The goal of the dry mill process is to retain the hard (horny)endosperm as large, distinct pieces and to remove the germand pericarp to yield a low-fat, low-fiber product. Conse-

quently, dry millers prefer hard-textured (HT) corn with ahigh percentage of horny endosperm, high test weight, lowlevels of broken kernels and foreign material, and lowmycotoxin levels.

Flaking Grits Corn Grits

Corn Meal Corn Flour

After de-germing, successive reduction and siftingyields the dry mill corn products shown above.

Food Uses of Dry Mill Products

• Breakfast cereals - flaking grits are used for corn flakes;corn meal and corn flour are used for puffed and shapedcereal.

• Brewing beer - brewers grits enhance beer clarity,stability and flavor. As a source of carbohydrates, theyimprove brewing economics (compete with rice and corn

syrup).

• Prepared mixes - corn meals and corn flours add flavor,texture, and color to mixes for corn breads, corn muffins,hush puppies, corn dogs, pancakes and waffles.

• Snack foods - corn meals are used in extruded snackproducts, such as corn puff balls and “Bugles”.

The Corn Kernel

Pericarp

Germ

HardEndosperm

SoftEndosperm

Tip Cap







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Refining a Bushel of Corn (Wet Mill Process)

A bushel of corn (56 pounds at 15% moisture) yields:

32 pounds of starch

or 33 pounds of sweetener

or 2.5 gallons of fuel ethanol

AND:

11.4 pounds of gluten feed

3.0 pounds of gluten meal

1.6 pounds of corn oil

After steeping, the corn slurry is passed through a series ofgrinders to separate the corn germ. The corn oil from thegerm can then be extracted on-site or sold to crushers forextraction. The fiber, gluten and starch components thatremain are further segregated using centrifugal, screen andhydroclonic separators.

The steeping liquor is concentrated in an evaporator to createa nutrient-rich solution called heavy steep water . Thisconcentrated product is co-dried with the fiber component tobe sold as corn gluten feed to the livestock industry. Heavy

steep water is also sold by itself as a feed ingredient, as afermentation feed stock, and for use in environmentallyfriendly products for melting ice from roads.

The gluten (protein) component is filtered and dried toproduce corn gluten meal, a popular feed ingredient inlivestock feeds, especially for poultry operations.

The starch can be processed in three ways: fermented intoethanol, dried and sold as dried or modified corn starch, orprocessed into corn sweeteners.

Germ

Separation

Germ

Oil

Refining

Corn Oil

Fiber

Gluten Feed

Wet or Dry

Wet Gluten

Starch-Gluten

SeparationGrinding

Screening Starch

Drying Syrup

RefiningFermentation

Dex-

trose

Ethanol

ChemicalsStarches

High Fructose

Corn Syrup

Corn

Syrup

Gluten Meal

Dry, 60% Protein

Corn Steeping

Corn Wet Milling Process

Starch

Conversion

As the diagram above illustrates, the wet milling processrenders corn into its basic oil, starch, and protein (gluten)components. Oil is an end product, and starch may be aswell, or it may be further processed to ethanol, corn syrup orother derivatives. Gluten is dried and sold as corn glutenmeal (60% protein). The pericarp fiber and concentrated

steep water are combined to produce corn gluten feed (21%protein).

Several IP programs are available for growers who wish toproduce corn for wet milling. These include approved hybridlists and hybrid-specific contracting programs. Pioneerworks with the wet milling industry to develop hybrids tomeet industry specifications, and assists corn growers inselecting appropriate hybrids and participating in industryprograms.

One of the recent developments in the wet milling industry isthe understanding of hybrid differences for wet-millingstarch yield. Some hybrids naturally release a higherpercentage of starch in the extraction process. Pioneer’sexperience with wet millers has demonstrated that focusingon total extractable starch, rather than just total starchcontent, is the key to optimizing yield of starch per bushel ofcorn.

Pioneer is developing high-yielding hybrids with high levelsof total extractable starch for the wet-milling industry. These

High Extractable Starch (HES) hybrids are well adapted togrowing conditions where major processing facilities are

located, and offer high-yield potential and excellentagronomic performance that growers require. Pioneer hasalso developed a rapid assay technique to quickly evaluategrain for its level of extractable starch. This technique isuseful in rating current hybrids as well as those underdevelopment.

Desirable Corn Grain Characteristics For Wet Milling

Above average level of extractable starch

Low levels of damage and molds/diseases

Low levels of cracked and broken kernels

Low foreign material

Low temperature dried corn

Dry-grind Ethanol Production

The surging ethanol industry in the U.S. is being driven bythe need for renewable energy sources to replace traditionalfossil fuel usage in automobiles. The benefits of thisreplacement include increased energy security, reduced airpollution, and lower cost of agricultural programs due to

higher corn prices. Today’s market values ethanol as a high-quality octane enhancer, a fuel extender, and an oxygenatingcomponent to improve air quality.

Approximately 2.2 billion gallons of fuel ethanol will beproduced in the U.S. during 2002, requiring 850 millionbushels of corn. If current U.S. legislation targeting energyindependence and cleaner-burning fuels is passed, demand





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for ethanol is expected to increase to 4.5 - 5 billion gallonsby 2010.

About half of the current ethanol output is produced in dry-grind processing plants, consuming over 500 million bushelsof corn. About 4 million acres and 1.5 million bags of seedcorn are needed to meet this requirement.

Value of Ethanol as a Fuel Additive

•

The addition of 10% ethanol to gasoline increases theoctane level, reducing the inefficiencies of refininggasoline into high octane components.

• By extending fuel, ethanol reduces U.S. dependence onforeign oil.

• Ethanol increases the oxygen content of gasoline, whichimproves air quality in dense traffic areas. Ethanolreplaces fossil-based fuel oxygenates such as MTBE.

The Dry-grind Process

Converting corn to alcohol is not a new concept; however,

the methodology has been refined in recent years to increasethe efficiency of the process. The dry-grind process beginsby grinding whole corn and adding water to form a “mash”,which is then processed in a high temperature cooker.Enzymes are added to reduce starch to simple sugars(hydrolysis), and yeast is added to convert the sugars toalcohol (fermentation).

After fermentation, the liquid is transferred to distillationcolumns where the ethanol is separated from the remaining“stillage”. This 190-proof ethanol is then dehydrated toapproximately 200 proof in a molecular sieve system. Adenaturant (usually gasoline) is added at about 5%

concentration to render it undrinkable and not subject tobeverage alcohol tax. The product is then shipped to gasolineterminals or retailers.

In addition to ethanol, some dry-grind plants collect and sellcarbon dioxide, which is produced as a by-product offermentation. Other outputs from the dry-grind ethanolprocess include distillers grains and distillers solubles.Distillers grains includes the fiber, oil, and proteincomponents, as well as the non-fermentable starch. Distillerssolubles includes protein, oil and other water-solublenutrients. These two products are typically combined andsold as wet distillers grains with solubles (WDGS) or drieddistillers grains with solubles (DDGS).

Dry-Grind Ethanol Plants Increasing

Although dry-grind plants currently supply less than one-halfof the total ethanol production, this industry is growing at arate of over 10% per year. This growth is attributed to theeconomics of constructing dry-grind plants, which are lesscomplex and less capital-intensive than wet-mill plants. As aresult, the increased demand for ethanol is expected to be

met primarily by construction of new dry-grind plants.Currently, there are about 44 dry-grind plants in operation,and an additional 10 are under construction (as of August,2002.) This includes four in Iowa, two in South Dakota andtwo in Nebraska.

The grain traits desirable for ethanol production include

High Total Fermentables (HTF), low stress cracks, and lowoccurrence of molds/diseases. Pioneer research has shownthat the HTF trait is a more accurate indicator of grain valuefor dry- grind ethanol production than is total starch. Pioneerhas developed a rapid assay technique to help profile Pioneerbrand hybrids and determine which products offer thehighest total fermentables to maximize ethanol yields.

Conclusion

The volume of corn processed for food and industrial uses isincreasing each year, and pending ethanol legislation willlikely accelerate this trend. As corn becomes less a

commodity and more targeted to specific end uses, it haspotentially higher value in the marketplace.

Pioneer research has clearly shown that corn hybrids havedifferent values based on their individual grain traits andintended end use. To help growers and end users realize thisextra value opportunity, Pioneer is characterizing existinghybrids and developing new hybrids targeted for specificend-use market segments such as those discussed in thisarticle. Pioneer is also expanding its capabilities in the end-use market area by adding end-use account managers andother technical resources to service these markets.

Table 3 summarizes the four corn processing market seg-

ments, including important end-use traits, estimated marketpotential and expected market growth. Future Crop Insightsarticles will further explore each of these market segments.

Distillers

Grains

Liquify

Saccharify

Cook

Grind Fermentation

Distillation

Centrifugation

Distillers

Solubles

Enzymes

Corn

CO2

Ethanol

Evaporator

Distillers

Grains

w/ Solubles

Thin

Stillage

Dry-Grind Ethanol Process





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Table 3. Summary of U.S. Food and Industrial Corn Market Segments.

U.S. Food and Industrial Corn Market Segment Summary*

Market Segment End-use Trait Estimated

Grain Premiums

Estimated 2002

Market Potential

Annual

Growth Rate

($/Bushel) Million Bushels Million Acres

Dry Milling Hard Texture (HT)** $0.03 - $0.20 120 - 140 0.9 - 1.0 0% - 1%

Alkaline Cooking Alkaline Cooking (AC)** $0.10 - $0.30 40 - 60 0.3 - 0.4 3% - 5%

Wet Milling High Extractable Starch (HES) $0.03 - $0.10 1,400 - 1,600 10.0 - 11.5 1% - 3%

Dry-grind Ethanol High Total Fermentables (HTF) $0.00 - $0.05 400 - 500 2.9 - 3.6 10% - 12%

Total - Food and Industrial Corn Market Segments 1,960 - 2,300 14.1 - 16.5

* Does not include exports.

** Yellow Food Corn (YFC) and White Food Corn (WFC) Source: Pioneer Hi-Bred Marketing Dept.

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