Presentation on theme: "Cereal Grains, Legumes and Oilseeds 1211"— Presentation transcript:
1Cereal Grains, Legumes and Oilseeds 1211 Steven C Seideman, PhDExtension Food Processing SpecialistCooperative Extension ServiceUniversity of Arkansas
2Cereal Grains, Legumes and Oilseeds This module covers some of the basic cereal grains, legumes and oilseeds- their production, composition, processing and ultimate use.It is a brief summary of Chapter 17 “Cereal Grains, Legumes and Oilseeds” from the book FOOD SCIENCE by Norman N. Potter and Joseph H. Hotchkiss. Published by Kluwer Academic/Plenum Publishers, New York.
4Cereals Cereals are plants that yield edible grains. They are consumed worldwide and make up a majority of the worlds calories and 50% of protein consumption.Rice is the world’s most important food with wheat not far behind. Over 90% of rice is grown in Asia where it is consumed.In the U.S., corn is the leading grain but most is used for animal production while wheat is used directly for human consumption.
5Rice is the most widely consumed food in the world making up the majority of the calories and 50% of the protein consumed.Photo courtesy of USDA
6Cereal GrainsWheat, rice and corn production worldwide is on the order of 525 million tons annually.The principle cereal grains grown in the U.S. include corn, wheat, oats, sorghum, barley, rye, rice and buckwheat.
7Composition of Some Cereals Grains (%) CornWheatOats RiceMoisture Carbohydrates Protein FatThis table shows the composition of some cereal grains. Note that cereal grains are low in moisture and high in both carbohydrates and protein.
8Physical Characteristics of Grain Starchy endosperm- main part of the grain or kernel.Protective outer layers- bran or hullEmbryo or germ- typically located at the bottom of the kernel.
9This is the structure of wheat which would be similar to rice, oats and barley. Note the endosperm, bran and germ.
10This is a diagram of the structure of a kernel of corn This is a diagram of the structure of a kernel of corn. Notice the starch, hull and germ parts.
11Milling of Cereal Grains In most milling operations, the hulls are removed which are largely indigestible by humans. The dark-colored bran is also removed.The germ, which is high in oil, is enzymatically active and under certain conditions would be likely to produce a rancid condition in the grain.Thus, the main component of interest is the starchy, proteinaceous endosperm.Since the bran is rich in B vitamins and minerals, it is a common practice to add these back to processed grains from which they came. This is known as “enrichment”.
12Cereal GrainsTypically cereal grains contain a moisture of 10-14% if properly dried. When the moisture content is higher than this, they must be dried or they may mold or rot in storage before they can be used.Cereal grains contain about two-thirds carbohydrate, most is in the form of digestible starches and sugars.The operations of milling generally remove much of the indigestible fiber and fat from these grains when they are to be consumed for human food.
13WheatWheat is classified into one of two types –Hard wheat is higher in protein than soft and produces a stronger dough used for bread-making. Soft wheat is better for batters and cake baking.Wheat milling is basically a succession of pulverizing steps to break down the endosperm.
14Wheat is grown primarily in the great plains region of the United states including north Texas, Oklahoma, Kansas, South Dakota and North Dakota.Photo courtesy of USDA
15Wheat combining starts in Texas in May and ends in Canada in September. Photo courtesy of USDA
16Most wheat is stored in large silos in the midwest until it is needed to produce bread. Photo courtesy of USDA
17Conventional Wheat Milling Milling is a progressive series of disintegrations followed by sieving. The disintegrations are made by rollers set progressively closer and closer together. The first rollers break open the bran and free the germ from the endosperm. The second and third rollers further pulverize the brittle endosperm and flatten out the semiplastic germ. The flakes of bran and flattened germ are removed by the sieves under the first few sets of rollers.
18Conventional Wheat Milling The pulverized endosperm is run through successive rollers set still closer together to grind it into finer and finer flour, which is sifted under each set of rollers to remove the last traces of bran.As flour is progressively milled, it becomes whiter in color, better in bread-making quality but lower in vitamin and mineral content.
19Uses of Wheat FlourThe uses of wheat flour in the baking industry include the making of breads, sweet doughs, cakes, biscuits, doughnuts, crackers and the like.Another use of wheat flour and courser milled fractions of wheat are alimentary pastes such as macaroni, spaghetti and other forms of noodles and pasta.
20Uses of Wheat FlourAlimentary pastes are mostly milled wheat flour and water. The wheat is usually hard durum and is milled to yield course particles called “semolina”.Alimentary pastes may also contain eggs, salt and other minor ingredients.They differ from bakery doughs in that alimentary pastes are not leavened.Alimentary pastes are usually made with 100 parts wheat flour/ 30 parts water, mixed, and extruded into thin sheets, cut into noodles or other shapes and then dried.
21RiceRice is unusual compared to other grains in that it is not ground into flours before consumption. Worldwide, rice is primarily consumed as an intact grain.The milling process is designed to remove only the outer bran layer and hull without breaking the kernel.It is often used in the U.S. as a carbohydrate source for making beer because its bland flavor.
22Rice production in the United States is primarily in eastern Arkansas, the coastal regions of Texas and in californiaPhoto courtesy of USDA
23Rice MillingRice milling begins with whole grains of rice being fed by machine between abrasive disks or moving rubber belts. These machines, known as shellers or hullers, do not crush the grains but instead rub the outer layer of hull from the underlying kernels.The hulls are separated from the kernels by jets of air and the kernels, known as brown rice, move to another abrasive device called a rice-milling machine.
24Rice MillingHere the inner layers of bran and germ are dislodged by the rubbing action of a ribbed rotor. The endosperms with bran and germ removed can now be further polished to a white, high glossy finish.As in the case of wheat, the higher the degree of milling or polishing, the lower are the remaining vitamin and mineral contents. This is particularly serious in the case of rice because entire populations depend on rice as the principle item of diet.
25Enrichment Rice can be enriched in one of two ways; 1)Coat the polished rice with the enrichment mixture (thiamin, niacin and iron) and then coat the grains with a waterproof film material.2)Parboiling whole rice including the hulls, bran and germ in water for 10 hr at 70C. This causes the B vitamins and minerals from the hulls, bran and germ to leach into the endosperm. The rice is then dried, milled and polished. This is often referred to as “converted rice”.
26CornCorn is consumed as both whole kernels ( a vegetable) or as a flour.Popcorn pops because the moisture expands upon heating and explodes because it cannot escape.Corn can be dry-milled like wheat or wet-milled. Wet milling is popular and is used to make corn syrups and high fructose corn syrup
27CornCorn is milled to remove hulls and germ, both of which can be fed to livestock. The germ is an important source of corn oil.Corn can be dry milled similar to wheat where the end product is corn meal or if further refined, corn flour. In this process, the hulls and germ are also removed and the endosperm reduced in size.
31Corn is often used to make snack foods like tortilla chips.
32Wet Milling of CornIn wet milling, corn kernels are placed in large tanks of warm water with generally an acid and sulfur dioxide as a preservative.The softened kernels are then run through an attrition mill to break up the kernels. The pasty mass is then pumped to settling troughs. Here is where the oil rich germ floats to the top, is skimmed off to be pressed for oil.The watery slurry is then filtered to remove the hulls.
33Wet Milling of CornThe watery slurry now containing the starch and protein fractions is passed through high speed centrifuges to separate the heavier starch from the lighter protein fraction.The starch is dried to yield “corn starch”.The protein fraction is dried and referred to as corn gluten or zein which is commonly used for animal feed.
34Corn SyrupCorn syrup is made from the corn starch fraction that has been exposed to acid or starch-splitting enzymes.This hydrolyzed starch contains varying proportions of dextrins, maltose and glucose and is used as a sweetner.
35Barley, Oats and RyeBarley, oats and rye are primarily used for animal feed.Barley and rye also provide sources of fermentable carbohydrate in the production of fermentable beverages.The flour from rye can be used to make flour for breads but cannot be used by itself because the protein content is too low.Most oats used for human consumption are in the form of rolled oats, an ingredient in breakfast cereals.
36Barley, Oats and RyeBarley is also used to produce barley malt. In this process, the barley seed is allowed to germinate to a sprout. The dried barley sprout is now called barley malt and is used in the brewing industry to help digest starchy material into sugars for rapid yeast fermentation. The malt also adds a distinctive flavor to beer. Malt further adds flavor to breakfast cereals and malted-milk concentrates.
37Breakfast CerealsMost breakfast cereals are made from the endosperm of wheat, corn, rice and oats.In “ready to eat” breakfast cereals, the endosperm is broken down or ground into a mash and then converted into flakes by squeezing the broken grits or mash between rollers. The mash can be extruded into a number of different shapes or the endosperm can be kept intact as kernels to be puffed as in the case of puffed rice.
38Breakfast CerealsIn all cases, the flaked, formed or puffed cereals must be oven-cooked and dried to develop the toasted flavor and to obtain the crisp, brittle textures desired.This crispness requires that many ready-to-eat cereals be dried to 3-5% moisture content.
42Baking ScienceBaking, by definition, refers to the application of heat in an oven. This is a very strict definition for baking. It can also include all the reactions and processes that occur before the item is placed in an oven.
43Classifications Baked items can be placed in one of four categories. 1)Yeast-raised goods –breads, etc leavened by CO2 from yeast fermentation2)Chemically leavened goods-layered cakes, doughnuts, biscuits etc that are raised by CO2 from baking powders and chemical agents.3)Air-Leavened goods- angel cakes and sponge cakes made without baking powder4)Partially leavened goods- pie crusts, certain crackers, where intentional leavening agents are used yet a slight leavening occurs from expanding steam and other gases during the oven-baking operation.
44Baking Ingredients and their Function The following goes through the major baking ingredients and how they function
45Breads and buns make up the majority of baked goods
47Gluten and Starch of Wheat Flour The principle protein in wheat flour is called “gluten”.Gluten has the property of when moistened and worked by mechanical action, it forms an elastic dough. This is accomplished by forming linkages between protein molecules. The more the dough is worked, the more linkages are formed. This is the reason that doughs are “kneaded” when a strong dough is required. However, the gluten can weaken and breakdown under excessive mechanical agitation such as over-mixing.
48Gluten and Starch of Wheat Flour Wheat starch does not form elastic films like gluten but rather gelatinizes when moistened, forming a paste material.The character of the dough or batter depends on the type of flour used. Real rigid doughs are made from flours with a high gluten content (hard wheat) and make good bread.Flours with a lower gluten content (soft wheat) make better batters that are less chewy and more tender.
49Leavening AgentsYeast and baking powders are not the only leavening agents. Water in dough or batters turns to steam in the oven and the expanding steam contributes to leavening.Air in the dough or batter also expands when heated and contributes to leavening.
50YeastsThere are two forms of yeast used in baking- moist pressed cakes and dehydrated granules.Both contain billions of living cells (Saccharomyces cerevisiae) .When rehydrated, both forms begin metabolism and fermentation.In fermentation, simple sugars are converted to carbon dioxide gas and alcoholThe heat of the oven kills the yeast and inactivates its enzymes thus stopping fermentation.
51Baking PowdersBaking powders contain particles of sodium bicarbonate and some acid (like monocalcium phosphate) and generate CO2 by the following reaction;3CaH4(PO4)2+ 8NaHCO3Monosodium Phosphate + SodiumbicarbonateEqualsCa3(PO4)2+4Na2HPO+8CO2+8H2OTricalcium phosphate+ Disodium phosphate+Carbondioxide+ water
52EggsEggs can function as a principle structure builder in cakes and also contribute to nutrition, flavor and color of the finished product.Like gluten, egg whites are a mixture of proteins that forms films and entraps air when whipped and on heating, it coagulates to produce rigidity.The yolks of eggs contain similar proteins.Eggs are important to use when working with low-protein flours as in the case of angel cakes and sponge cakes.
53ShorteningUnlike flour and eggs, which are structure builders and tougheners, shortening is a tenderizer. The beating of shortening in some recipes is called for to entrap air prior to the incorporation of other ingredients to finish the batter. When the batter is baked in the oven, the shortening melts and releases the air bubbles which contribute to the leavening action of baking powders and expanding steam. The melted shortening then deposits around the cell walls of the coagulating structure to contribute a tenderizing effect and lubricate the texture.
54SugarsSugar, like shortening, is a tenderizer in baked goods. It also adds sweetness and in the form of sucrose, provides additional fermentable substrate in yeast raised goods.
56Legumes and OilseedsLegumes are flowering plants having pods which contain beans or peas.Legumes include various peas and beans, most of which are low in fat but soybeans are the exception.The term “oilseed” is applied to those seeds, including soybeans, which are processed for their oil.Oilseeds include peanuts seed, cottonseed, sunflower seed, rapeseed, flaxseed, linseed and sesame seeds.Both legumes and oilseeds contain considerably more protein than cereal grains.
57Legumes and OilseedsLegumes (beans and peas) and oilseeds are much higher in protein than grains and oilseeds are much higher in fat than grains.Soybeans are legumes that have oilseed characteristics.
58SoybeansSoybeans are very versatile food products used for both animal and human foods.Soybeans can have up to 23% fat.Soy protein is quite extensively used for animal feed as a protein source.
59Soybeans are grown extensively in the midwest primarily as a protein source in animal feeds. Photo courtesy of USDA
60PeanutsPeanuts contain 25% protein and 50% oil. They are used mainly to produce peanut butter (50% of the crop).They can also be used to make flour and used for oil.
61Peanuts are a legume that grows underground,. Photo courtesy of USDA
62Conclusions From this series, you should have learned; 1)The types, composition, structure and processing of cereal grains2)How breakfast cereals are made3)The science of baking4)The category of legumes and oilseeds.