From Wheat to Flour من القمح الى الدقيق

الاستقبال والنظافة و الترطيب Intake , Cleaning , whDampening , Conditioning Section ، أساسيات و تقنيات و فنيات عملية الطحن - Milling Techniques and Technology ، نظم النخل و المناخل و فنياته - Sifting System - Sifters - Plansifters ، تنقية السيمولينا (السميد) وفنياته - Semolina Purification System .
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Osama Badr
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From Wheat to Flour من القمح الى الدقيق

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From Wheat to Flour
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From Wheat to Flour

Wheat is not just wheat. Six classes and more than 30,000 varieties of wheat make possible the hundreds of favorite wheat foods enjoyed worldwide.

The miller analyzes the wheat, then blends it to meet the requirements of the end use. This science of analysis, blending, grinding, sifting and blending again – milling science – results in consistent, high-quality, healthful products.

For example, hard wheat flours provide for a variety of bread products; durum semolina and flour are used in pasta.

A blend of soft and hard wheats produces Asian noodles. Soft wheats produce an array of crackers, cookies, cereals, cakes, pancakes, breading and pastries. Pets, fish, shrimp and livestock are equally lucky to be guaranteed quality feeds. Beyond human and animal nutrition, millers provide the “glue” that keeps our walls papered and other building products affordable and available.

One edible grain has become meshed with cultures and foods all over the world. This is the story of from wheat to flour.

The Seed

More than 17,000 years ago, humans gathered the seeds of plants and ate them. After rubbing off the “glumes,” or husks, early people simply chewed the kernels raw, parched or simmered. Wheat originated in the “cradle of civilization” in the Tigris and Euphrates river valley, near what is now Iraq. More than 8,000 years ago, Swiss lake dwellers ground and mixed early wheat with water, then baked it to make unleavened cakes or bread. The Egyptians reveal both wheat and the discovery of leavened bread in ancient tombs almost 5,000 years old. The Chinese record growing wheat in 2,700 B.C.

The Roman goddess, Ceres, who was deemed protector of the grain, gave grains their common name today – “cereal.” Seven cereal grains largely sustain and nourish humankind. Six of these are part of primitive history. Oldest to youngest, they are millet, oats, barley and wheat, with rye and maize, or corn, following. Rice has a history all its own. Wheat is now the principal sustaining grain for people all over the world. Credit for its first discovery and cultivation cannot be given to any certain person or place. However, archaeologists can come close.

Wheat's earliest ancestors are wild einkorn, or “one-seed” and emmer. Archeologists have found kernels of both wild and cultivated einkorn and emmer in excavated villages in Egypt and southwestern Asia's Fertile Crescent, the area between the upper reaches of the Tigris and Euphrates rivers.

Archeological discoveries such as the one at Abu Hureyra – in what is now northern Syria – provide insight into how early Neolithic people, beginning from about 10,000 to 9,500 years ago, moved from being gatherers to farmers. They began by cultivating the grains of einkorn, emmer, oats, and barley, as well as the edible seeds, or pulses, of chickpeas and lentils.

The ability to cultivate grain marked the beginning of civilization. Once people settled in one place, crafts, arts and communication – both verbal and written – flourished. Religious practices, economic and political power, and even wars resulted, making the availability and control of wheat a vital part of human history.

The Plant

A sure way to identify plants is by their chromosomes. The earliest wheat ancestors contained 14 chromosomes, which means they were “diploid.” Early wheat plants looked like grass and had fragile stems with hulls that clung to the grain. This made them hard to thresh but perfect for reseeding themselves.

Primitive women first gathered einkorn, or Triticum monococcum (trit'-i-cum mahn-uh-kah'-cum), selecting it for its larger seeds and ease of threshing and harvesting. Their success led early humans away from hunting societies as the new agrarian communities thrived on cultivated crops.

A natural outcross between einkorn and the 14-chromosome Triticum spletoides (trit'-i-cum spel-toy'-dees) produced a wild wheat called Triticum turgidum (trit'-i-cum tur'-ji-duhm), which had 28 chromosomes, making it a tetraploid. This new wild species led to emmer, which was soon cultivated throughout the Middle East. The durum wheat now grown in the United States to make pasta and couscous was originally selected from the wild emmer wheat with large easy-to-thresh grains.

Modern bread wheat varieties have 42 chromosomes. These wheats evolved from a natural outcross between emmer wheat and another diploid wheat, Triticum tauschii (trit'-i-cum tow'-she-eye). This wheat was the source of the unique glutenin genes that give bread dough the ability to form gluten. Gluten provides bread dough the elasticity it needs to trap gas produced by fermenting yeast and therefore to “rise” or expand.

The wheat plant grows to a height of between 24 inches for dwarf varieties to 36 inches and even seven feet in some very old varieties. The principal parts of the plant area the roots (between three to eight feet in depth), the culms (stems), leaves, and spikes (head).

Graphic – Parts of the wheat grain head

Today, the grain head, not the straw or dried stem, is the goal for production, so the shorter varieties are much more popular with farmers. Shorter stems stand better and don't bend as easily, making them less vulnerable to wind or rain damage and easier to harvest.

A Class Act

Six classes bring order to the thousands of varieties of wheat. The classes are hard red winter, hard red spring, soft red winter, durum, hard white, and soft white. They all have origins in seeds that were hand-picked and carried to the United States by European farm immigrants.

Wheat Varieties

For centuries, wheat plants were improved by carefully selecting the best grain from certain well-adapted plants during harvest. Selection was based on reliability of growth and harvest, productivity, disease-resistance, and suitability for their food use. This select grain was used for seed the next year. Because wheats are self-pollinating, they held their characteristics in succeeding generations.

At the turn of the century, plant scientists began to produce new varieties through hybridization and wheat breeding. Parent plants were selected for their desirable traits – greater disease and insect resistance, ease in harvesting, shorter growing seasons, better milling and baking qualities, and higher yields. Parent wheats possessing the desired traits were crossed by covering or exposing select plants during pollination.

Today, wheat breeders select within these new populations of wheat the characteristics they seek to improve. The ones chosen are grown in fields (field-tested) and evaluated for their strengths in production, milling and baking quality. Only the seed selections that pass all the tests are made available to farmers to grow.

Modern wheat breeders are geneticists who scientifically develop wheat varieties to meet the needs of farmers, millers and bakers. It is not an overnight process, it takes 10 to 12 years of lab and field tests at a cost of around $500,000 per new variety before a seed wheat can be released for production.

Advances in wheat breeding focus on certain genes in the chromosome arrangement of reproductive cells that control specific desirable characteristics of the plant.

The wheat breeder has a wheat gene bank offering selections from about 30 different wheat species. Included are the earliest wheat species and grasses that originally crossed to produce wheat.

By mapping the location of important traits or attributes on the wheat chromosomes, wheat researchers produce a genetic roadmap for wheat. Being able to better examine qualities in the lab before doing field testing saves valuable time and resources for the wheat breeder and wheat industry. Testing time may be reduced by as much as two years yet produce better results.

Where Wheat is Grown

Wheat is an extremely versatile crop. The six classes and their thousands of varieties make it possible to plant wheat fields at sea level or on rolling, high-altitude slopes. Wheat is grown from Florida to the Canadian border, in the arid Arizona and on coastal plains. In fact, somewhere in the world, wheat is being harvested every month of the year.

Spring wheats are planted just prior to or in April. They do not go through a dormant stage, but mature until harvested.

Planting of winter wheats begins before September in the northern United States and continues through October in the southern regions. These “winter” wheats will sprout and grow in the fall until a winter freeze occurs. The wheat will then become dormant until spring, when it will mature until harvest. Winter wheat is harvested in May in the southern regions and goes through July in the north.

How Wheat Flour is Milled

Diagram

A closer look inside the mill shows us how flour is made and the great care and science used to make this basic ingredient for so many favorite foods. Every mill is just a little different, depending on the kind of flour needed for the end product. However, most mills follow most of the steps in roughly the same order.

Product Control

Wheat arrives at the mill by truck, ship, barge, or rail car. Before the wheat is even unloaded, samples are taken to ensure it passes inspection. X-rays may be used to detect any signs of insect infestation. Meanwhile, product control chemists begin their tests to classify the grain by milling and baking a small amount to determine end-use qualities.

The results from these tests determine how the wheat will be handled and stored. Millers may blend different wheats to achieve the desired end product. The wheat will then be stored at the mill in large bins.

Storing wheat is an exact science. The right moisture, heat and air must be maintained or the wheat may mildew, sprout, or ferment.

Cleaning the Wheat

The first milling steps involve equipment that separates wheat from seeds and other grains, eliminates foreign materials such as metal, sticks, stones and straw; and scours each kernel of wheat. It can take as many as six steps.

Magnetic Separator

The wheat first passes by a magnet that removes iron and steel particles.

Separator

Vibrating screens remove bits of wood and straw and almost anything too big and too small to be wheat.

Aspirator

Air currents act as a kind of vacuum to remove dust and lighter impurities.

De-Stoner

Using gravity, the machine separates the heavy material from the light to remove stones that may be the same size as wheat kernels.

Disc Separator

The wheat passes through a separator that identifies the size of the kernels even more closely. It rejects anything longer, shorter, more round, more angular or in any way a different shape.

Scourer

The scourer removes outer husks, crease dirt and any smaller impurities with an intense scouring action. Currents of air pull all the loosened material away.

Conditioning the Wheat

Tempering

Now the wheat is ready to be conditioned for milling. This is called tempering. Moisture is added in precise amounts to toughen the bran and mellow the inner endosperm. This makes the parts of the kernel separate more easily and cleanly.

Tempered wheat is stored in bins from eight to 24 hours, depending on the type of wheat – soft, medium or hard. Blending of wheats may be done at this time to achieve the best flour for a specific end-use.

Impact Scourer

Centrifugal force breaks apart any unsound kernels and rejects them from the mill flow.

From the entoleter, the wheat flows to grinding bins, large hoppers that will measure or feed wheat to the actual milling process.

Graphic - Kernel of Wheat

Graphic - Cross Section View of Wheat

Grinding the Wheat

The wheat kernels, or berries, are now in far better condition than when they arrived at the mill and are ready to be milled into flour. Wheat kernels are measured or fed from the bins to the “rolls,” or corrugated rollers made from chilled cast iron.

This modern milling process is a gradual reduction of the wheat kernels. The goal is to produce middlings, or coarse particles of endosperm. The middlings are then graded and separated from the bran by sieves and purifiers. Each size returns to corresponding rollers and the same process is repeated until the desired flour is obtained.

The rolls are paired and rotate inward against each other, moving at different speeds. Just one pass through the corrugated “first break” rolls begins the separation of bran, endosperm and germ.

The Miller's Skill

The miller's skill is demonstrated by the ability to adjust all of the rolls to the proper settings that will produce the maximum amount of high-quality flour. Grinding too hard or close results in bran powder in the flour. Grinding too open allows good endosperm to be lost in the mill's feed system.

The miller must select the exact milling surface, or corrugation, on the break rolls, as well as the relation and the speed of the rollers to each other to match the type of wheat and its condition. Each break roll must be set to get as much pure endosperm as possible to the middlings rolls. The middlings rolls are set to produce as much flour as possible.

From the rolls, the grist is sent way upstairs to drop through sifters. The grist is moved via pneumatic systems that mix air with the particles so they flow, almost like water, through tubes. This is a great advance in health and safety from earlier methods of moving the grist with buckets.

Sifters

The broken particles of wheat are introduced into huge, rotating, box-like sifters where they are shaken through a series of bolting cloths or screens to separate the larger from the smaller particles.

Inside the sifter, there may be as many as 27 frames, each covered with either a nylon or stainless steel screen, with square openings that get smaller and smaller the farther down they go.

Up to six different sizes of particles may come from a single sifter, including some flour with each sifting. Larger particles are shaken off from the top, or “scalped,” leaving the finer flour to sift to the bottom.

The “scaled” fractions are sent to other roll passages and particles of endosperm are graded by size and carried to separate purifiers.

Purifiers

In a purifier, a controlled flow of air lifts off bran particles while at the same time a bolting cloth separates and grades coarser fractions by size and quality.

Four or five additional “break” rolls, each with successively finer corrugations and each followed by a sifter, are usually used to rework the coarse stocks from the sifters and reduce the wheat particles to granular “middlings” that are as free from bran as possible. Germ particles will be flattened by later passage through the smooth reduction rolls and can be easily separated. The reduction rolls reduce the purified, granular middlings, or farina, to flour.

The process is repeated over and over again, sifters to purifiers to reducing rolls, until the maximum amount of flour is separated, consisting of close to 75 percent of the wheat.

There are various grades of flour produced in the milling process. The remaining percentage of the wheat kernel or berry is classified as millfeed – shorts, bran and germ.

Bakers buy a wide variety of flour types, based on the products they produce. The flour the consumer buys at the grocery store, called “family flour” by the milling industry, is usually a long-patent all-purpose or bread flour. Occasionally short patent flour is available in retail stores.

“Reconstituting,” or blending back together, all the parts of the wheat in the proper proportions yields whole wheat flour. This process produces a higher quality whole wheat flour than is achieved by grinding the whole wheat berry. Reconstitution assures that the wheat germ oil is not spread throughout the flour so it does not go rancid so readily.

Bleaching the Flour

Toward the end of the line in the millstream, if the flour is to be “bleached,” the finished flour flows through a device, which releases a bleaching-maturing agent in measured amounts.

It has been known for centuries that freshly milled flour makes a lesser quality baked product. In the old days, flour was stored for a few months to mature, or naturally oxidize. This whitened the flour and improved its baking characteristics. The modern bleaching process simply duplicates this natural oxidation process, but does so more quickly.

In the bleaching process, flour is exposed to chlorine gas or benzoyl peroxide to whiten and brighten flour color. Chlorine also affects baking quality by “maturing” or oxidizing the flour, which is beneficial for cake and cookie baking. The bleaching agents react and do not leave harmful residues or destroy nutrients.

Enrichment

The flour stream passes through a device that measures out specified quantities of enrichment. The enrichment of flour with four B vitamins (thiamin, niacin and riboflavin) and iron, began in the 1930s. In 1998 folate, or folic acid, was added to the mix of B vitamin. If the flour is self-rising, a leavening agent, salt and calcium are also added in exact amounts.

Before the flour leaves the mill, additional lab tests are run to ensure that the customers get what they ordered.

Finally, the flour millstream flows through pneumatic tubes to the packing room or into hoppers for bulk storage.

Family flour for retail sale may be packed in 5-, 10-, 25-pound bags. Bakery flour may be packed in 50- to 100-pound bags or sent directly to bulk trucks or rail cars.
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