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Cereal Grains, Legumes and Oilseeds

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Steven C Seideman, PhDSteven C Seideman, PhD

Extension Food Processing SpecialistExtension Food Processing Specialist

Cooperative Extension ServiceCooperative Extension Service

University of ArkansasUniversity of Arkansas

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Cereal Grains, Legumes and Oilseeds

This module covers some of the basic cereal This module covers some of the basic cereal grains, legumes and oilseeds- their production, grains, legumes and oilseeds- their production, composition, processing and ultimate use.composition, processing and ultimate use.

It is a brief summary of Chapter 17 “Cereal It is a brief summary of Chapter 17 “Cereal Grains, Legumes and Oilseeds” from the book Grains, Legumes and Oilseeds” from the book FOOD SCIENCE by Norman N. Potter and FOOD SCIENCE by Norman N. Potter and Joseph H. Hotchkiss. Published by Kluwer Joseph H. Hotchkiss. Published by Kluwer Academic/Plenum Publishers, New York.Academic/Plenum Publishers, New York.

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Cereal Grains

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Cereals

Cereals are plants that yield edible grains. Cereals are plants that yield edible grains. They are consumed worldwide and make up a They are consumed worldwide and make up a

majority of the worlds calories and 50% of protein majority of the worlds calories and 50% of protein consumption.consumption.

Rice is the world’s most important food with Rice is the world’s most important food with wheat not far behind. Over 90% of rice is grown wheat not far behind. Over 90% of rice is grown in Asia where it is consumed.in Asia where it is consumed.

In the U.S., corn is the leading grain but most is In the U.S., corn is the leading grain but most is used for animal production while wheat is used used for animal production while wheat is used directly for human consumption.directly for human consumption.

5Photo courtesy of USDA

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Cereal Grains

Wheat, rice and corn production worldwide Wheat, rice and corn production worldwide is on the order of 525 million tons annually.is on the order of 525 million tons annually.

The principle cereal grains grown in the The principle cereal grains grown in the U.S. include corn, wheat, oats, sorghum, U.S. include corn, wheat, oats, sorghum, barley, rye, rice and buckwheat.barley, rye, rice and buckwheat.

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Composition of Some Cereals Grains (%)

GrainGrain

CornCorn

WheatWheat

Oats Oats RiceRice

Moisture Carbohydrates Protein FatMoisture Carbohydrates Protein Fat

11 72 10 411 72 10 4

11 69 13 211 69 13 2

13 58 10 513 58 10 5

11 65 8 211 65 8 2

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Physical Characteristics of Grain

Starchy endospermStarchy endosperm- main part of the grain - main part of the grain or kernel.or kernel.

Protective outer layersProtective outer layers- bran or hull- bran or hull Embryo or germEmbryo or germ- typically located at the - typically located at the

bottom of the kernel.bottom of the kernel.

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Milling of Cereal Grains In most milling operations, the hulls are removed In most milling operations, the hulls are removed

which are largely indigestible by humans. The dark-which are largely indigestible by humans. The dark-colored bran is also removed.colored bran is also removed.

The germ, which is high in oil, is enzymatically The germ, which is high in oil, is enzymatically active and under certain conditions would be likely active and under certain conditions would be likely to produce a rancid condition in the grain.to produce a rancid condition in the grain.

Thus, the main component of interest is the starchy, Thus, the main component of interest is the starchy, proteinaceous endosperm.proteinaceous endosperm.

Since the bran is rich in B vitamins and minerals, it Since the bran is rich in B vitamins and minerals, it is a common practice to add these back to processed is a common practice to add these back to processed grains from which they came. This is known as grains from which they came. This is known as “enrichment”.“enrichment”.

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Cereal Grains

Typically cereal grains contain a moisture of 10-Typically cereal grains contain a moisture of 10-14% if properly dried. When the moisture content 14% if properly dried. When the moisture content is higher than this, they must be dried or they may is higher than this, they must be dried or they may mold or rot in storage before they can be used.mold or rot in storage before they can be used.

Cereal grains contain about two-thirds Cereal grains contain about two-thirds carbohydrate, most is in the form of digestible carbohydrate, most is in the form of digestible starches and sugars.starches and sugars.

The operations of milling generally remove much The operations of milling generally remove much of the indigestible fiber and fat from these grains of the indigestible fiber and fat from these grains when they are to be consumed for human food.when they are to be consumed for human food.

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Wheat

Wheat is classified into one of two types –Wheat is classified into one of two types –Hard wheatHard wheat is higher in protein than soft is higher in protein than soft and produces a stronger dough used for and produces a stronger dough used for bread-making. bread-making. Soft wheatSoft wheat is better for is better for batters and cake baking.batters and cake baking.

Wheat milling is basically a succession of Wheat milling is basically a succession of pulverizing steps to break down the pulverizing steps to break down the endosperm. endosperm.

14Photo courtesy of USDA

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Photo courtesy of USDA

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Photo courtesy of USDA

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Conventional Wheat Milling

Milling is a progressive series of disintegrations Milling is a progressive series of disintegrations followed by sieving. The disintegrations are made followed by sieving. The disintegrations are made by rollers set progressively closer and closer by rollers set progressively closer and closer together. The first rollers break open the bran and together. The first rollers break open the bran and free the germ from the endosperm. The second free the germ from the endosperm. The second and third rollers further pulverize the brittle and third rollers further pulverize the brittle endosperm and flatten out the semiplastic germ. endosperm and flatten out the semiplastic germ. The flakes of bran and flattened germ are removed The flakes of bran and flattened germ are removed by the sieves under the first few sets of rollers. by the sieves under the first few sets of rollers.

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Conventional Wheat Milling

The pulverized endosperm is run through The pulverized endosperm is run through successive rollers set still closer together to grind successive rollers set still closer together to grind it into finer and finer flour, which is sifted under it into finer and finer flour, which is sifted under each set of rollers to remove the last traces of each set of rollers to remove the last traces of bran.bran.

As flour is progressively milled, it becomes whiter As flour is progressively milled, it becomes whiter in color, better in bread-making quality but lower in color, better in bread-making quality but lower in vitamin and mineral content.in vitamin and mineral content.

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Uses of Wheat Flour

The uses of wheat flour in the baking The uses of wheat flour in the baking industry include the making of breads, industry include the making of breads, sweet doughs, cakes, biscuits, doughnuts, sweet doughs, cakes, biscuits, doughnuts, crackers and the like. crackers and the like.

Another use of wheat flour and courser Another use of wheat flour and courser milled fractions of wheat are alimentary milled fractions of wheat are alimentary pastes such as macaroni, spaghetti and other pastes such as macaroni, spaghetti and other forms of noodles and pasta.forms of noodles and pasta.

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Uses of Wheat Flour Alimentary pastes are mostly milled wheat flour Alimentary pastes are mostly milled wheat flour

and water. The wheat is usually hard durum and is and water. The wheat is usually hard durum and is milled to yield course particles called “semolina”. milled to yield course particles called “semolina”.

Alimentary pastes may also contain eggs, salt and Alimentary pastes may also contain eggs, salt and other minor ingredients.other minor ingredients.

They differ from bakery doughs in that alimentary They differ from bakery doughs in that alimentary pastes are not leavened.pastes are not leavened.

Alimentary pastes are usually made with 100 parts Alimentary pastes are usually made with 100 parts wheat flour/ 30 parts water, mixed, and extruded wheat flour/ 30 parts water, mixed, and extruded into thin sheets, cut into noodles or other shapes into thin sheets, cut into noodles or other shapes and then dried.and then dried.

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Rice

Rice is unusual compared to other grains in that it Rice is unusual compared to other grains in that it is not ground into flours before consumption. is not ground into flours before consumption. Worldwide, rice is primarily consumed as an Worldwide, rice is primarily consumed as an intact grain.intact grain.

The milling process is designed to remove only The milling process is designed to remove only the outer bran layer and hull without breaking the the outer bran layer and hull without breaking the kernel. kernel.

It is often used in the U.S. as a carbohydrate It is often used in the U.S. as a carbohydrate source for making beer because its bland flavor.source for making beer because its bland flavor.

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Photo courtesy of USDA

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Rice Milling

Rice milling begins with whole grains of rice Rice milling begins with whole grains of rice being fed by machine between abrasive disks or being fed by machine between abrasive disks or moving rubber belts. These machines, known as moving rubber belts. These machines, known as shellers or hullers, do not crush the grains but shellers or hullers, do not crush the grains but instead rub the outer layer of hull from the instead rub the outer layer of hull from the underlying kernels.underlying kernels.

The hulls are separated from the kernels by jets of The hulls are separated from the kernels by jets of air and the kernels, known as brown rice, move to air and the kernels, known as brown rice, move to another abrasive device called a rice-milling another abrasive device called a rice-milling machine.machine.

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Rice Milling Here the inner layers of bran and germ are Here the inner layers of bran and germ are

dislodged by the rubbing action of a ribbed rotor. dislodged by the rubbing action of a ribbed rotor. The endosperms with bran and germ removed can The endosperms with bran and germ removed can now be further polished to a white, high glossy now be further polished to a white, high glossy finish.finish.

As in the case of wheat, the higher the degree of As in the case of wheat, the higher the degree of milling or polishing, the lower are the remaining milling or polishing, the lower are the remaining vitamin and mineral contents. This is particularly vitamin and mineral contents. This is particularly serious in the case of rice because entire serious in the case of rice because entire populations depend on rice as the principle item of populations depend on rice as the principle item of diet.diet.

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Enrichment

Rice can be enriched in one of two ways;Rice can be enriched in one of two ways; 1)Coat the polished rice with the enrichment 1)Coat the polished rice with the enrichment

mixture (thiamin, niacin and iron) and then coat mixture (thiamin, niacin and iron) and then coat the grains with a waterproof film material.the grains with a waterproof film material.

2)Parboiling whole rice including the hulls, bran and 2)Parboiling whole rice including the hulls, bran and germ in water for 10 hr at 70C. This causes the B germ in water for 10 hr at 70C. This causes the B vitamins and minerals from the hulls, bran and vitamins and minerals from the hulls, bran and germ to leach into the endosperm. The rice is then germ to leach into the endosperm. The rice is then dried, milled and polished. This is often referred to dried, milled and polished. This is often referred to as “converted rice”.as “converted rice”.

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Corn

Corn is consumed as both whole kernels ( a Corn is consumed as both whole kernels ( a vegetable) or as a flour. vegetable) or as a flour.

Popcorn pops because the moisture expands upon Popcorn pops because the moisture expands upon heating and explodes because it cannot escape.heating and explodes because it cannot escape.

Corn can be dry-milled like wheat or wet-milled. Corn can be dry-milled like wheat or wet-milled. Wet milling is popular and is used to make corn Wet milling is popular and is used to make corn syrups and high fructose corn syrupsyrups and high fructose corn syrup

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Corn

Corn is milled to remove hulls and germ, Corn is milled to remove hulls and germ, both of which can be fed to livestock. The both of which can be fed to livestock. The germ is an important source of corn oil.germ is an important source of corn oil.

Corn can be dry milled similar to wheat Corn can be dry milled similar to wheat where the end product is corn meal or if where the end product is corn meal or if further refined, corn flour. In this process, further refined, corn flour. In this process, the hulls and germ are also removed and the the hulls and germ are also removed and the endosperm reduced in size.endosperm reduced in size.

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Photo courtesy of the USDA

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Photo courtesy of USDA

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Photo courtesy of USDA

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Wet Milling of Corn

In wet milling, corn kernels are placed in large In wet milling, corn kernels are placed in large tanks of warm water with generally an acid and tanks of warm water with generally an acid and sulfur dioxide as a preservative.sulfur dioxide as a preservative.

The softened kernels are then run through an The softened kernels are then run through an attrition mill to break up the kernels. The pasty attrition mill to break up the kernels. The pasty mass is then pumped to settling troughs. Here is mass is then pumped to settling troughs. Here is where the oil rich germ floats to the top, is where the oil rich germ floats to the top, is skimmed off to be pressed for oil.skimmed off to be pressed for oil.

The watery slurry is then filtered to remove the The watery slurry is then filtered to remove the hulls.hulls.

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Wet Milling of Corn

The watery slurry now containing the starch The watery slurry now containing the starch and protein fractions is passed through high and protein fractions is passed through high speed centrifuges to separate the heavier speed centrifuges to separate the heavier starch from the lighter protein fraction.starch from the lighter protein fraction.

The starch is dried to yield “corn starch”.The starch is dried to yield “corn starch”. The protein fraction is dried and referred to The protein fraction is dried and referred to

as corn gluten or zein which is commonly as corn gluten or zein which is commonly used for animal feed.used for animal feed.

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Corn Syrup

Corn syrup is made from the corn starch Corn syrup is made from the corn starch fraction that has been exposed to acid or fraction that has been exposed to acid or starch-splitting enzymes.starch-splitting enzymes.

This hydrolyzed starch contains varying This hydrolyzed starch contains varying proportions of dextrins, maltose and proportions of dextrins, maltose and glucose and is used as a sweetner.glucose and is used as a sweetner.

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Barley, Oats and Rye

Barley, oats and rye are primarily used for animal Barley, oats and rye are primarily used for animal feed.feed.

Barley and rye also provide sources of fermentable Barley and rye also provide sources of fermentable carbohydrate in the production of fermentable carbohydrate in the production of fermentable beverages.beverages.

The flour from rye can be used to make flour for The flour from rye can be used to make flour for breads but cannot be used by itself because the breads but cannot be used by itself because the protein content is too low.protein content is too low.

Most oats used for human consumption are in the Most oats used for human consumption are in the form of rolled oats, an ingredient in breakfast cereals.form of rolled oats, an ingredient in breakfast cereals.

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Barley, Oats and Rye

Barley is also used to produce barley malt. In this Barley is also used to produce barley malt. In this process, the barley seed is allowed to germinate to process, the barley seed is allowed to germinate to a sprout. The dried barley sprout is now called a sprout. The dried barley sprout is now called barley malt and is used in the brewing industry to barley malt and is used in the brewing industry to help digest starchy material into sugars for rapid help digest starchy material into sugars for rapid yeast fermentation. The malt also adds a yeast fermentation. The malt also adds a distinctive flavor to beer. Malt further adds flavor distinctive flavor to beer. Malt further adds flavor to breakfast cereals and malted-milk concentrates.to breakfast cereals and malted-milk concentrates.

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Breakfast Cereals

Most breakfast cereals are made from the Most breakfast cereals are made from the endosperm of wheat, corn, rice and oats. endosperm of wheat, corn, rice and oats.

In “ready to eat” breakfast cereals, the endosperm In “ready to eat” breakfast cereals, the endosperm is broken down or ground into a mash and then is broken down or ground into a mash and then converted into flakes by squeezing the broken converted into flakes by squeezing the broken grits or mash between rollers. The mash can be grits or mash between rollers. The mash can be extruded into a number of different shapes or the extruded into a number of different shapes or the endosperm can be kept intact as kernels to be endosperm can be kept intact as kernels to be puffed as in the case of puffed rice.puffed as in the case of puffed rice.

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Breakfast Cereals

In all cases, the flaked, formed or puffed In all cases, the flaked, formed or puffed cereals must be oven-cooked and dried to cereals must be oven-cooked and dried to develop the toasted flavor and to obtain the develop the toasted flavor and to obtain the crisp, brittle textures desired.crisp, brittle textures desired.

This crispness requires that many ready-to-This crispness requires that many ready-to-eat cereals be dried to 3-5% moisture eat cereals be dried to 3-5% moisture content.content.

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Baking Science

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Baking Science

Baking, by definition, refers to the Baking, by definition, refers to the application of heat in an oven. This is a application of heat in an oven. This is a very strict definition for baking. It can also very strict definition for baking. It can also include all the reactions and processes that include all the reactions and processes that occur before the item is placed in an oven.occur before the item is placed in an oven.

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Classifications Baked items can be placed in one of four categories.Baked items can be placed in one of four categories. 1)1)Yeast-raised goodsYeast-raised goods –breads, etc leavened by CO –breads, etc leavened by CO22

from yeast fermentationfrom yeast fermentation 2)2)Chemically leavened goodsChemically leavened goods-layered cakes, -layered cakes,

doughnuts, biscuits etc that are raised by COdoughnuts, biscuits etc that are raised by CO22 from from baking powders and chemical agents.baking powders and chemical agents.

3)3)Air-Leavened goodsAir-Leavened goods- angel cakes and sponge cakes - angel cakes and sponge cakes made without baking powdermade without baking powder

4)4)Partially leavened goodsPartially leavened goods- pie crusts, certain - pie crusts, certain crackers, where intentional leavening agents are used crackers, where intentional leavening agents are used yet a slight leavening occurs from expanding steam yet a slight leavening occurs from expanding steam and other gases during the oven-baking operation.and other gases during the oven-baking operation.

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Baking Ingredients and their Function

The following goes through the major The following goes through the major baking ingredients and how they baking ingredients and how they

functionfunction

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Gluten and Starch of Wheat Flour The principle protein in wheat flour is called The principle protein in wheat flour is called

“gluten”.“gluten”. Gluten has the property of when moistened and Gluten has the property of when moistened and

worked by mechanical action, it forms an elastic worked by mechanical action, it forms an elastic dough. This is accomplished by forming linkages dough. This is accomplished by forming linkages between protein molecules. The more the dough is between protein molecules. The more the dough is worked, the more linkages are formed. This is the worked, the more linkages are formed. This is the reason that doughs are “kneaded” when a strong reason that doughs are “kneaded” when a strong dough is required. However, the gluten can weaken dough is required. However, the gluten can weaken and breakdown under excessive mechanical and breakdown under excessive mechanical agitation such as over-mixing.agitation such as over-mixing.

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Gluten and Starch of Wheat Flour Wheat starch does not form elastic films like Wheat starch does not form elastic films like

gluten but rather gelatinizes when moistened, gluten but rather gelatinizes when moistened, forming a paste material.forming a paste material.

The character of the dough or batter depends on The character of the dough or batter depends on the type of flour used. Real rigid doughs are made the type of flour used. Real rigid doughs are made from flours with a high gluten content (hard from flours with a high gluten content (hard wheat) and make good bread. wheat) and make good bread.

Flours with a lower gluten content (soft wheat) Flours with a lower gluten content (soft wheat) make better batters that are less chewy and more make better batters that are less chewy and more tender.tender.

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Leavening Agents

Yeast and baking powders are not the only Yeast and baking powders are not the only leavening agents. Water in dough or batters leavening agents. Water in dough or batters turns to steam in the oven and the turns to steam in the oven and the expanding steam contributes to leavening.expanding steam contributes to leavening.

Air in the dough or batter also expands Air in the dough or batter also expands when heated and contributes to leavening.when heated and contributes to leavening.

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Yeasts

There are two forms of yeast used in baking- There are two forms of yeast used in baking- moist pressed cakes and dehydrated granules.moist pressed cakes and dehydrated granules.

Both contain billions of living cells Both contain billions of living cells (Saccharomyces cerevisiae) .(Saccharomyces cerevisiae) .

When rehydrated, both forms begin metabolism When rehydrated, both forms begin metabolism and fermentation.and fermentation.

In fermentation, simple sugars are converted to In fermentation, simple sugars are converted to carbon dioxide gas and alcoholcarbon dioxide gas and alcohol

The heat of the oven kills the yeast and inactivates The heat of the oven kills the yeast and inactivates its enzymes thus stopping fermentation.its enzymes thus stopping fermentation.

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Baking Powders

Baking powders contain particles of sodium Baking powders contain particles of sodium bicarbonate and some acid (like monocalcium bicarbonate and some acid (like monocalcium phosphate) and generate COphosphate) and generate CO22 by the following reaction; by the following reaction;

3CaH3CaH44(PO4)(PO4)22+ 8NaHCO+ 8NaHCO33

Monosodium Phosphate + Sodium Monosodium Phosphate + Sodium bicarbonatebicarbonate EqualsEqualsCaCa33(PO(PO44))22+4Na+4Na22HPO+8COHPO+8CO22+8H+8H22OOTricalcium phosphate+ Disodium phosphate+Carbon Tricalcium phosphate+ Disodium phosphate+Carbon dioxide+ waterdioxide+ water

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Eggs

Eggs can function as a principle structure builder Eggs can function as a principle structure builder in cakes and also contribute to nutrition, flavor in cakes and also contribute to nutrition, flavor and color of the finished product.and color of the finished product.

Like gluten, egg whites are a mixture of proteins Like gluten, egg whites are a mixture of proteins that forms films and entraps air when whipped and that forms films and entraps air when whipped and on heating, it coagulates to produce rigidity.on heating, it coagulates to produce rigidity.

The yolks of eggs contain similar proteins.The yolks of eggs contain similar proteins. Eggs are important to use when working with low-Eggs are important to use when working with low-

protein flours as in the case of angel cakes and protein flours as in the case of angel cakes and sponge cakes.sponge cakes.

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Shortening

Unlike flour and eggs, which are structure builders Unlike flour and eggs, which are structure builders and tougheners, shortening is a tenderizer. The and tougheners, shortening is a tenderizer. The beating of shortening in some recipes is called for to beating of shortening in some recipes is called for to entrap air prior to the incorporation of other entrap air prior to the incorporation of other ingredients to finish the batter. When the batter is ingredients to finish the batter. When the batter is baked in the oven, the shortening melts and releases baked in the oven, the shortening melts and releases the air bubbles which contribute to the leavening the air bubbles which contribute to the leavening action of baking powders and expanding steam. The action of baking powders and expanding steam. The melted shortening then deposits around the cell walls melted shortening then deposits around the cell walls of the coagulating structure to contribute a of the coagulating structure to contribute a tenderizing effect and lubricate the texture.tenderizing effect and lubricate the texture.

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Sugars

Sugar, like shortening, is a tenderizer in Sugar, like shortening, is a tenderizer in baked goods. It also adds sweetness and in baked goods. It also adds sweetness and in the form of sucrose, provides additional the form of sucrose, provides additional fermentable substrate in yeast raised goods.fermentable substrate in yeast raised goods.

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Legumes and Oilseeds

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Legumes and Oilseeds Legumes are flowering plants having pods which Legumes are flowering plants having pods which

contain beans or peas.contain beans or peas. Legumes include various peas and beans, most of Legumes include various peas and beans, most of

which are low in fat but soybeans are the exception.which are low in fat but soybeans are the exception. The term “oilseed” is applied to those seeds, The term “oilseed” is applied to those seeds,

including soybeans, which are processed for their including soybeans, which are processed for their oil.oil.

Oilseeds include peanuts seed, cottonseed, sunflower Oilseeds include peanuts seed, cottonseed, sunflower seed, rapeseed, flaxseed, linseed and sesame seeds.seed, rapeseed, flaxseed, linseed and sesame seeds.

Both legumes and oilseeds contain considerably Both legumes and oilseeds contain considerably more protein than cereal grains.more protein than cereal grains.

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Legumes and Oilseeds

Legumes (beans and peas) and oilseeds are Legumes (beans and peas) and oilseeds are much higher in protein than grains and much higher in protein than grains and oilseeds are much higher in fat than grains. oilseeds are much higher in fat than grains.

Soybeans are legumes that have oilseed Soybeans are legumes that have oilseed characteristics.characteristics.

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Soybeans

Soybeans are very versatile food products Soybeans are very versatile food products used for both animal and human foods.used for both animal and human foods.

Soybeans can have up to 23% fat.Soybeans can have up to 23% fat. Soy protein is quite extensively used for Soy protein is quite extensively used for

animal feed as a protein source.animal feed as a protein source.

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Photo courtesy of USDA

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Peanuts

Peanuts contain 25% protein and 50% oil. Peanuts contain 25% protein and 50% oil. They are used mainly to produce peanut They are used mainly to produce peanut butter (50% of the crop). butter (50% of the crop).

They can also be used to make flour and They can also be used to make flour and used for oil.used for oil.

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Photo courtesy of USDA

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Conclusions

From this series, you should have learned;From this series, you should have learned;

1)The types, composition, structure and 1)The types, composition, structure and processing of cereal grainsprocessing of cereal grains

2)How breakfast cereals are made2)How breakfast cereals are made

3)The science of baking3)The science of baking

4)The category of legumes and oilseeds.4)The category of legumes and oilseeds.

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