| Food & Ingredients | | | Educ. Serv. | | | Glossary | | | References | | | Images | FAQ |
|---|
Beverages
Bread
Carbohydrates
Cereals
Creampuffs
Crystallization
Egg
Energy
Fats & Oils
Flour Mixtures
Food Systems
Fruits & Vegetables
Leavening
Meat, Fish, Poultry
Milk
Muffins
Pastry
pH
Popover
Protein
Quickbreads
Safety
Sensory
Shortened Cake
Sponge Cakes
Starchs
Sugars
Vegetable Gums
Water
|
to Top |
| OBJECTIVES | to Top |
| CONTENT | to Top |
 |
Over the last 2 million years when humans have existed as hunters and gathers. Likely, grains and seeds played a role in their diets. This is substantiated in the archaeology sites that have been dug and grains have been found. During the last 10,000 years these grains have been domesticated, and bioengineered into grains of differing characteristics. Additionally, alternate seeds and legumes have been developed into roles in the diets.
The basic commodity of most diets of the world are the grains or seeds which are made into cereals, flours and "value added" products. In the ready-to-serve category of such products we see wheat is used in over 30% of the products. It is important to remember that the source of these foods is beyond the classic expected "wheat, the only grain used." For example we see rice at 11% and oats at 22% in the ready-to-eat cereals.
 |
There are many types of grains and seeds used throughout the world. There has been use of soybean flour, rice flour, and corn flour, as well as seed flours. Additionally, increasingly variety cereals and baked products are adding old and new grains, seeds, and legumes. Cereal markets have expanded the range of uses of these sources both due to their consumer appeal and due to manufacturers responding through improved efficiencies and productivity and through advertising, market leaders, lowering prices, and cutting costs. Today, one can purchase bean flour, peanut flour, sunflower flour, buckwheat flour, soy flour and many others. However, the focus of this module is on the grain - wheat, with some discussion of the characteristics of other minor grains, such as corn, rice and rye.
A discussion of use of one of these flours or the seed/grain/root, must include both an understanding and awareness of the composition of the commodity and an understanding and awareness of its role and function in the product for which it is going to be used. Generally, the critical factor in the grain or seed is the amount and characteristic of the protein, starch, and, particularly in the legumes, the fat. However, the composition and its characteristics may be ameliorated somewhat by the degree of processing, type of processing, as well as, the initial product dependent upon production. The growing conditions and particular cultivar may bring about a variable. Otherwise, the soil, temperature, rainfall, maturity at harvest, harvesting, milling and storage processes of the products will impact that which one presents for use. This module will emphasize how these characteristics impact wheat and its resulting products. Other grains, seeds, and legume information will be added. The flour mixture portion emphasizes the manner in which these products function in different baked products.
One must be recognizant that the various types of cereals and grains are sold as whole grain, milled grain (flour), or a composite breakfast cereal. The consumer in the United States tends to think that flour refers to all-purpose white flour or, possibly, whole wheat or cake flour. Baked recipes are generally assumed to use all-purpose flour. Increasingly, other sources are being used for their cost, nutritive value, specialized functional properties, unique sensory characteristics or simply due to marketability. The many different sources may be grains, oilseeds, and legumes. The oilseeds [soybean, flax, safflower, peanut, rapeseed, coconut, cottonseed, sesame, and others] and legume flours [navy bean, lupine, lima bean, chickpea, cowpea, fababean, pigeon pea, lentil] are increasingly being used as substitutes or supplements for wheat flour in baked products.
Each of these alternate sources have their advantage and disadvantage. For example, the phenolics are a particular problem, especially for the sorghum, legumes, rapeseed and mustard. They bind up iron and so those consumers who eat high phenolic cereals may have anemia. The phenolics are intermediate in concentration in soybean, flax, peanut, and safflower flour and low in coconut, cottonseed and sesame flour. Other problems constantly are being identified and minimized, such as the gossypol in cottonseed.
Breakfast cereals still remain a popular cereal food product. Most breakfast cereals have been processed a number of ways. The most frequent step involves milling and grinding in some manner. Specifically, cereals, are the grains or seeds of wheat, corn, rice, amaranth, barley, farina, oats, and quinoa. The dominant three grains, wheat, corn, and rice are historically used for both cereal as we define it and as a flour for baked products.
| Corn, rice, and wheat grains all have the basic structure made up of
a germ, endosperm, and bran. Each portion contributes specific components
and characteristics to the seed. It is useful to continue to remember that
in these three grains, this is the reproductive mechanism for the plant.
The bran is the outer covering. This is primarily cellulose and would contribute
fiber to the processed product. If cellulose fibrils are present they will
be abrasive in the product. Additionally, with some of these grains, the
bran also is high in phenolics.
A second primary portion of the grain is the germ. The germ is of importance to us in discussing food quality as it has a high "oil" content. The fatty acid content of the germ oil is generally very susceptible to oxidative rancidity, particularly once the germ has been "cracked" with milling. The shorter shelf life of whole wheat flour, as opposed to all-purpose flour, is attributed to this portion of the grain. The storage portion, or endosperm, of protein and starch in most typical grain is the primary part of most grains, particularly in the United States where wheat is the dominant grain. The endosperm composition, characteristics and quality are critical to all baked products. |
 Permission
to use from Wheat Foods Council
for educational purposes. The diagram above is a classic and relative
representational images of a wheat kernel. Other grains
have a similar structure. As seen above,
it is not just three major uniform portions: the bran, germ and endosperm.
There are layers and differentiations within each of these major portions.
The separation of these three parts of the grain impacts the quality of
all products for its use. Different cereal, baked products, and nutripharmaceuticals
takes advantage of the respective characteristics of the endosperms, bran
and/or germ. |
Breakfast cereals are classified the ready-to-cook, instant- and ready-to-eat cereals. Certainly, it is obvious that the type of cereal selected will impact the taste of a cereal. However, once a cereal is selected, few are eaten whole as harvested from the field.
Milling will extract the part of the grain needed for the cereal. Once milled the cereal may be left uncooked, partially cooked, or completely cooked. Other ingredients may be added. One only needs to look at the label of breakfast cereals to see these additions.
Ready-to-cook cereals are generally cracked or crushed or maybe rolled or flaked grains. The finer the particle processed the shorter the cooking period required. If fine enough it may be a quick cooking cereal.
The ready-to-eat cereals are much more variable than the changes due to type and degree of milling. The particles may be cooked, and dried or toasted under a range of conditions.
Of course, milling itself is the step for preparing the various flours that we have available. Interestingly, milling itself has not changed substantially over the last two centuries. In fact, one of the unique specialty millers here in Oregon still use the stone grinding of cereals and grains. Irregardless of the method of grinding, the flour must still meet the standards of identity by the USDA.
Classifications of Flour Streams
Permission
to use from Wheat Foods Council
for educational
purposes.
The classifications of wheat flours is obtained from the different "streams" off the mill. The above diagram is the classic example used when discussing how milling produces different types of wheat. Over the last several years the market for the different streams has changed considerably. It used to be that bran and red dog would go into cattle and pet feed. With the advent of the research indicating the advantages of bran in the diet, this product has made its way back into the "human market". For 100 grams of flour you could purchase flour varying considerable in quality depending upon the degree of extraction or the portion of extraction. For example, we could have whole wheat flour or all-purpose flour, patent flour or cake flour from the same wheat with the same kernel composition. A good example of how the selection of the "stream" in milling can influence a product is with chocolate cake mixes. I feel that Duncan Hines gives you a much better chocolate cake than the Pillsbury brand does. It may surprise you to know that the two entirely different companies with their associated brands both use Pillsbury flour. Duncan Hines pays the extra money for a better grade of cake flour and a resulting better cake mix. The grades of flour is based on the USDA standards and include bushel weight, heat damage, foreign matter, broken kernels, and presence of wheat from other classes. |
The
mixing process in cereal and cereal products is important from a variety of viewpoints.
The question may deal with the preparation of a quality breakfast cereal. Just
the mixing of a breakfast cereal can severally impact the product. For example,
over stirring of cooked cereals may fragment swollen starch granules and cause
it to be gummy, sticky and/or slimy. An excellent example of a cereal is cooked
oatmeal. Unfortunately, my Mother tended to overcook oatmeal when I was growing
up. I never realized that it could actually have a chewy texture. Basically, it
was somewhat similar to a gruel fed the children prisoners. Now that I know more
about food science and cereal products, I realize the difficulty in preparing
a large quantity of oatmeal. If inadequately stirred, the cereal may lump, if
overstirred the swollen starch granules will break apart and the sticky, gummy
amylose and amylopectin will spill out. Although it occurs easiest with oatmeal
due to the grain structure, wheat, rice and other cereals undergo this same change.
Mixing (see flour mixture products)of flour mixture products is dependent upon the role of mixing in developing the optimization of ingredients. Otherwise, mixing in flour mixtures is due to the addition of water to gliadin and glutenin (wheat protein) to form gluten. Essentially, with the average hard wheat flour and the appropriate amount of water, the more mixing the greater the amount of gluten development.
Cooking of cereals and pasta products is interesting and unique for each one. However, in each instance, the gelatinization of starch is an important phenomena which is taking place. That is cereals and their processed pasta products are made up of grains. The endosperm of the grain is composed primarily of starch with varying amounts and quality of protein. Heating of the cereal product in the presence of water will cause gelatinization to occur. Additionally, the heat will also cause denaturation of protein. If a whole grain is used, heat and water may soften the bran.
The change in the starch, the gelatinization, certainly takes away some of
the raw starch flavor; however, there are other changes. The gelatinization
of the starch causes the starch granule to actually swell. This swelling is
evidenced by such generalizations as we have with rice. It is more or less understood
that rice doubles in size when properly cooked. Proper cooking means adequate
space in the saucepan and, as important, adequate liquid to take this into account.
If rice doubles in size it is important to, minimally, for each cup of rice
to cook to have 2 cups of water. Myself, wanting to avoid sticking and evaporation,
I often will add an extra cup. It generally evaporates off.
Cereal scientists and producers and cooks continue to investigate the protein structure and interactions of the carbohydrates and lipids. Overall, the composition of selected grains are summarized as follows:
| Food Product | Moisture[%] |
Protein[%] |
Lipid[%] |
Carbohydrates[%] |
| |
||||
Rice, brown |
12.0 | 7.5 | 1.0 | 77.4 |
Rice, brown |
70.3 | 2.5 | 0.6 | 25.5 |
Wheat flour |
12 | 13.3 | 2 | 71.1 |
| |
||||
| |
||||
| |
||||
| |
||||
| |
||||
| |
PROTEINS
As you can see, rice, rye, corn and wheat have protein content ranging form to percent. However, in regard to functional properties, the type of proteins are critical. in viewing this simple table we see the content of major classes of proteins listed. Since most of our baked products require and take advantage of the protein characteristics in wheat this is a primary focus of this presentation. The study of wheat proteins has been done for over 200 years; however, the first comprehensive study was undertaken by Osborne over 90 years (1907) ago. Osborne divided the proteins of the wheat kernel as follows:| albumins | soluble in water |
| globulins | soluble in salt solutionsbut
insoluble in water solutions |
| gliadins | soluble in 70-90% alcohol |
| glutenins | insoluble in neutral aqueous
solutions,saline
solutions oralcohol
|
Protein research has developed a variety of methodologies that may characterize their amino acid composition, sequence, and structure. Although the method of classifying proteins, on the basis of solubility, was developed in 1907 it is still of importance. However, a considerable portion of research over the last several years has focused on delineating the complexity of the solubility fractions and , most importantly, how the sub-fractions relate to functional properties in doughs and baked products. This is done by the use of both solubility and electrophoretic techniques. Both techniques are useful in that they are dependent upon the amino acid composition of the proteins being analyzed. A number [Lookhart, 1997] of other methods are in addition to solubility, are high-performance liquid chromatography, high-performance capillary electrophoresis, acid and SDS-Page, molecular biology, antibodies, and so forth.
 |
This image gives some indication of the complexity of the proteins due to the bonding contributions of the amino acids. These proteins that are generally said to contribute to the elastic gluten structure are the gliadins and glutenins. These two categories have high concentrations of proline, glutamine, glutamic acid and other hydrophobic amino acids. The high levels of phenylalanine and proline also result in hydrophobic (water hating) regions this permitting possible association with lipids such as digalactosyl diglyceride. The low lysine content is of interest since this nutritionally, is a limiting amino acid. Dr. Paul hypothesizes that the lysine content has been breed out of wheat by a natural selection of wheat which has a stronger less-soluble gluten. Lysine enhances the hydrophilic (water loving) nature of the protein. |
Why do grains and seeds differ in their characteristics they bring to foods? What is this substance called gluten?
Unfortunately, the chemistry and practice of gluten and gluten development is extremely complex and not fully understood. This protein was first described by the Italian scientist Becarri as early as 1728. The first experimental evidence for the heterogeneity of gluten was given by Einhof in 1810 who did the fractionation studies with alcohols. The first systematic studies of the wheat grain proteins was published by Osborne in 1907. As early as 1925, Dill published a number of gluten studies. He observed that crude gluten contains 75-80% total protein. Since that time there have been a number of extensive studies. The work by Osborne in 1907 and his classifications and fractionation scheme is still pertinent today. His studies, based on their solubility in different solvents, distinguished four major classes of proteins, namely, the water-soluble albumins, the salt-soluble globulins, the alcohol-soluble gliadin and the glutenin which are soluble (or at lest dispersible) in dilute acid or alkali solutions. The characteristics of the two main categories of gluten proteins are shown as a gross macro approach below.
GLIADINS |
GLUTENINS |
In a discussion of the gluten in flours, many students get the idea that there are these proteins called gluten in a wheat flour, which, when water is added, their elastic characteristic emerges. Gluten is the elastic, cohesive mass formed from water, gliadin, and glutenin with mixing.
The elastic nature and cohesiveness depends upon the interrelationship of the albumins and globulins, the degree of oxidation and a rather of other factors. Interestingly, if one ran an amino acid composition analysis of the classic durum flour (used for alimentary pasta (noodles, spaghetti, etc.) and good hard wheat flour they would be similar; however, their characteristics vary. This is because their arrangement on the peptide chain will vary.
If it is difficult to define and delineate the individual protein, lipid and carbohydrates and the complexity of their interactions to form a viscous elastic mass containing gluten. It is understood that gluten itself does not exist in milled wheat flour. The development of gluten appears to be simple. One adds water to a wheat flour and, with the proper mixing, an elastic, cohesive mass occurs. The mixing causes three changes in the mixture: it produces a macroscopically homogeneous system; development of a three-dimensional protein network with gas retention capacity; incorporation of air cells into the dough. The mixing allows the gluten strands to float out into the water and hydrate. With mixing, the flour protein particles are continuously rubbed and new surfaces are exposed for hydration. Essentially this process is taking dry gliadin and glutenin, "glassy polymers", and hydrates and physically changes them to yield an amorphous mass in which component protein are better able to interact and produce a dough. It appears simple and the structure likely is a relative elastic protein complex with starch. It turns out this is not the case. Certainly, anytime one is dealing with proteins, it is tremendously complex.
It is generally accepted that in baked products using wheat, the critical proteins and, to a lesser extent, the lipid and starch interact to produce the viscoelastic, cohesive mass described as gluten. a number of researchers have used diagrams to explain how the flour components develop gluten.
The amount and quality of protein in a flour will influence the amount of
water that it will hold. Ultimately, water makes up about 45% of a bread dough
and about 35% of the bread itself. During mixing, it is known that considerable
amount of water becomes bound.
Many different ingredients will impact gluten development. Common ones are as follows: flour, sugar, fat, liquid.
The type of flour will affect the strength of gluten. The influence of the type of flour is dependent upon the flour composition and the role of flour in the baked product. For example, soy flour does not impact the elasticity of the structure as it does not contain gluten.
Sugars generally will serve to decrease the strength of gluten development due to its competition for water. Additionally, it will actually decrease gluten strength once formed. It apparently does this latter for some as yet not defined reason.
Sugar likely affects gluten strength due to its competition for water. Because the sugar is an effective competitor, it inhibits the gliadin-glutenin-water complex and thus gluten is weakened. There has been some indication that gluten may weaken it for some as yet undetermined subtle reason.
Fat and shortening will decrease the strength of gluten as it inhibits its development. Essentially, it prevents the gliadin and gluten from coming in contact with the water and forming the complex gluten.
 |
The affect of fat upon gluten development is much more complex. In the past, it has been "understood" that fat decreases gluten strength. It may serve as a "water-proofer" so that the water, gliadin and glutenin do not interact. For this course, we will continue to emphasize that fat decreases gluten strength. Otherwise, fat will tenderize the structure of a product as it decreases gluten development.
The type of liquid will impact gluten development and the ultimate gluten strength. There needs to be enough liquid that the
 
The processing of pasta varies considerably, depending upon which of the pasta varieties is being made. A discussion with pasta makers and a review of the labels of the many different types that one can purchase would indicate that the flour used will make a difference as well as the added ingredients and actual pasta making. |
| Since the best pasta is made from durum wheat and semolina
flour, quality pasta depends upon the milling of the flour. The durum
wheat (Triticum durum) is first cleaned, tempered and than milled
into the streams indicated at the right. This allows for selection of
the product that one wishes.
|
| Noodles are generally rolled out; however, the majority of the pastas are extruded products. With the dies on the extrusion auger there can be gotten the many types of products indicated. The diagram indicates the essential equipment, the extrusion press, the shaker or spread, a predryer, finish dryer, and storage unit. Noodles themselves indicate that the wheat cultivar, noodle drying process, quality of cooking water, cooking time and elapsed time after cooking will influence the firmness, resilience, and surface characteristics of the noodles. |  |
What are alimentary pastes primarily made from?
What type of flour is used for products as noodles, macaroni, or spaghetti?
What is an ingredient which noodles have that macaroni does not have?
Why are commercial egg noodles more popular with consumers than homemade noodles?
What is the difference between egg noodles and other forms of pasta?
Why would you expect macaroni and spaghetti to stick together when cooked?
Extra cooking/over cooking changes the noodles in what way?
| GLOSSARY | to Top |
albumins
aleurone
layer alimentary
paste all-purpose
flour amylase
amylose
barley
bleached
flour bleaching
of flour
blend
bound
water bran
break
and shred
brew
brewer
brown
and serve
buckwheat
carotenoid
pigments
coagulation
converted
rice dark
rye flour
disulfide
bond endosperm
enriched
flours flavonoid
pigments
germ
gliadin
globulins
gluten
glutenin
graham
flour grain
mills green
flour hard
wheat hot
cross bun
hydration
capacity
instantized
wheat flour
instant
cereals knead
light
rye flour
lipase
lipoprotein
maillard
reaction
maltase
maltodextrins
maltose
maturing
of flour
metabolic
mill
millet
milling
oxidation
phenolic
compound
phenols
polished rice
potassium
bromate precursor
protease
pumpernickel
flour ready-to-cook
cereals reducing
substance
rye
flour semolina
shred
soft
wheat spelt
sponge
straight
grade white flour
steep
stoma
teff
flour tempering
unbleached
flour white
rye whole
wheat
| REVIEW | to Top |
Review your last meal you ate? What possible cereal products did you eat there? What are some possibilities?If you go to a grocery or health food store and look for products which emphasize the different portions of a grain, what might you find? Would I find similar products for all grains?
Indicate the parts of the diagram of a "typical" kernel of wheat.
)
Where in the typical kernel of grain, are the following found?
){kind=link}
){kind=link}
){kind=link}
How were the oats made instant?
For enrichment of a cereal grain, what nutrients must be added?
How would one store ground or cracked whole grain cereals to keep best?
Why does the amount of water an uncooked cereal will absorb in the cooking process vary?
What is the form of cereal which requires the largest proportion of water in cooking?
Which type of cereal, whole, granulated, flaked, ground, has the biggest increase in volume? Why?
How can lumping in cooked cereals can be prevented?
How much should a cereal, such as rice, be stirred? Why?
Why might one have a sticky, gummy cooked cereal?
Why does brown rice requires a much longer cooking time than white rice?
How does the texture of minute rice differ from the texture of polished rice?
What is the appearance of instant rice so much different from that of long-grain or short - grain rice?
Why is wild rice so expensive?
How much should a cereal, as rice, be stirred? Why?
How much does rice usually increase in volume in cooking?
When cooking 1/3 cup of regular white rice, how much should you expect to get?
What is the primarily composition of the endosperm of the grain?
What part of the typical wheat kernel is the most likely source of all-purpose
flour? What part of the wheat kernel has gliadin and glutenin?
What part of the wheat kernel is most susceptible to lipid oxidation (i.e.
rancidity)? What part of the wheat kernel has the most starch? Draw a chart
listing, identifying, and describing the properties of the proteins in wheat
flour. How do the glutenin and gliadin differ and how are they similar?(list)
| GLUTENIN | GLIADIN | ALBUMINS |
What are the distinguishing characteristics between
Flour is sometimes termed as "hard flour", what is a definition of hard
flour?...
of soft wheat flour?
Which flour that has the greatest hydrating capacity - all-purpose or cake flour or bread (hard wheat) flour?
Soft wheat flour differs from hard wheat flour in what way?
What additives may manufactures add during milling of flour?
What changes occur when flour either ages naturally or chemical treatment is used for the maturing process
If Hillary had a "green wheat flour" (unaged) but, due to a fire, a "small portion" of oxidizing chemical was released and permeated throughout her 1000 lbs of flour and improved it.
What is gluten? Discuss the mechanism of gluten formation (indicate specifically the reactants, method of production).
| Graph the relationship of amount of protein versus moisture (water) required for optimum gluten development versus gluten content in a common wheat (i.e. all-purpose Gold Medal flour). |  |
It is likely apparent that more than the percent protein is important for a flour to have a "good" gluten strength. There is considerable variation in protein content among grains and oilseeds. What brief statement or generalization(s) can be made about the range of proteins in grains versus oilseeds.
TRUE OR FALSE. A "hard" flour will make the best quality baked product.
Some flours have poor gluten development. How could the lack of gluten development be used as an advantage?
The grain having gluten potential is corn or buckwheat or rice or wheat?
Which is the best, optimum method for evaluating the gluten quality?
How does gluten impact the gluten developed? How does unscalded milk or raw milk affect gluten strength?
The glutenball is made by mixing a wheat flour with water and developing the gluten. This well-developed gluten dough is than washed with cold water. On the basis of area of gluten balls,
| CODE | GLUTEN BALL, mm3 |
| A | 64 |
| B | 16 |
| C | 100 |
| D | 144 |
| E | 49 |
Even assuming the optimum available gluten from the flour, it may not
attain maximum strength due to other ingredients and/or preparation techniques.
In this regard, summarize influential factors in the following table and
indicate the reason for the affect.
| FACTORS WHICH WERE VARIED FROM THE OPTIMUM
(vs living) |
Affect Upon Gluten Strength
increased gluten strength |
Reason for Effect Upon Gluten
|
| to Top |
OSU Disclaimer.