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Wheat Milling Process

Shelby Purvis

Principles of Artisan Bread Baking

10/29/2015

            In 6700 B.C., when the grinding of wheat berries first happened, they used stone bowls and long stones to grind the wheat berries into flour. Later on came power mills that began with the use of wind and water. Over the years, “the U.S. grain processing industry has evolved to efficiently  co-mingle  and move vast quantities of grain from rural America to population centers  so consumers  can have safe,  healthful products with consistent quality,” (North American Milers’ Association-NAMA).  More than 900 million bushels of a two billion bushel crop is consumed each year in the U.S wheat milling industry. “In modern milling of refined flours the wheat kernels are cleaned and tempered by the addition or removal of moisture and then split open by a pair of rolls,” (Flour).

The wheat milling process first starts off with the inspection of the wheat kernels and to make sure it passes inspection. The kernels get tested in four different areas; moisture content, test weight, unsound kernels, and foreign material. “At unloading, product control chemists begin their tests to classify wheat and determine end-use qualities. The results from these tests determine how the wheat will be handled and stored,” (North American Millers’ Association-NAMA).Throughout the storage, handling, and milling, the grading and testing of the grade and quality factors of the grain continues.

Grain is then delivered to mills in trucks and railcars while being covered. How far the grain needs to get delivered depends on how far the mills are. Sometimes they need to travel hundreds of miles to get from point A to point B, but other times they just travel locally. Depending on the time of year and whether or not there needs to be more deliveries by the conveyances.

The grain then gets stored in bins after it has passed inspection. Storing grain can be very temperamental because they need the right moisture, heat and air that must be maintained or they can ferment, sprout, or even mildew. After they are stored, they must go through a process, called fumigation, to eliminate insects and pests. Wheat is then separated by protein level and quality. They are then cleaned again to remove foreign materials like metal, sticks, and stones by machines that are called the cleaning house.

The grain first goes through a magnetic separator that removes all metal so that it is not in the finished product. They are then passed through vibrating and rotating separators that remove wood, straw, and just anything else that is too big. They then get air currents that act as a vacuum which removes dust and their impurities. The grain gets passed to remove stone by the use of gravity to separate the heavy material from the light. They go through the disc separator next which determines the size of the kernel even more closely, rejecting anything that looks unfamiliar. The husks are then removed by the scourer. Some newer mills separate by color.

Next is tempering where moisture is added to toughen the bran and relax the inner endosperm to make it easier for separating more cleanly. Depending of the type of wheat and its moisture level; the time, temperature, and the wheat soaking for about 6 to 24 hours must be determined. The grinding and sifting of the wheat kernels into flour is next. “The science of analysis, blending, grinding, sifting and blending again results in consistent end products,” (North American Millers’ Association-NAMA). They then get passed through the corrugated rolls that begin to separate of bran, endosperm and sperm. They are then sifted and “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,” (North American Millers’ Association-NAMA). Towards the end of the process, the flour is now to be bleached where they are exposed to chlorine gas or benzoyl peroxide to brighten the flour and make it whiter in color. The flour then gets passed through a device that measures out and releases enrichment, as well as malt to add loaf height and flavor.

After the milling is all done, the flour goes through a series of lab tests to ensure it meets specifications. Although dry flour does not minimize microbial growth, when baking the flour, or even cooking or boiling it, can kill any pathogens to be present.

 

 

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