The Roller Mill was created by Hungarian bakers in the late s[1] and its popularity spread worldwide throughout the s. Roller mills now produce almost all non-whole grain flour. Enriched flour is flour that meets an FDA standard in the United States. Roller milled white enriched flour makes up over 90% of the flour that comes out of the United States.
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The significance of the roller mill that produces white flour
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In , well over 90% of the United States commercial flour production was not whole grain.[2] Virtually all of this non-whole grain flour was produced on flour roller mills. These unique mills were first developed in Europe in the s,[1] soon after were patented and introduced into the United States[3] and quickly came to dominate the world's flour milling industry as they continue to do today.
Flour roller mills were specifically designed to efficiently separate the bran and germ elements of the wheat kernel. What remains is the endosperm, generally referred to as white flour. White flour is often artificially enriched to restore some of the nutrition lost by separating out the bran and the germ elements. In the U.S., white flour is nearly always artificially enriched to restore some of the nutrition lost by removing the bran and germ elements. Enrichment rules vary among countries.[4]
Overview of the wheat kernel
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Wheat and other grains grow on a stalk and have an outer covering known as the husk, or the hull, which is not nutritional to humans. When the hull is removed, it is often referred to as chaff. The edible part of the wheat kernel is a wheat berry composed of the bran (about 14% of the kernel volume), the germ (about 3% of the kernel volume), and the endosperm (about 83% of the kernel volume).
The wheat berries' outer protective shell is the bran. The bran is rich in dietary fiber and fatty acids, and contains significant quantities of starch, protein, vitamins, and minerals. The germ is a source of several nutrients,[5] including vitamin E, folate, phosphorus, thiamin, zinc, and magnesium, as well as fatty acids and fatty alcohols. The germ is also a source of fiber. The endosperm's natural purpose (like all fruits) is to give nutrition to the germ in the form of starch when the seed is planted in the soil and sprouts into a plant. It also contains some oils and protein.
Background of the invention
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In early America, flour mills used mill stones that were set close together and turned at high speed, crushing all the components of the wheat kernel into an indiscriminate flour.[citation needed] This was generally referred to as low milling.[6] At the time, without refrigeration or sealed storage, the heightened water absorption properties of the crushed bran fiber and the oil-rich germ shortened the shelf life of this flour. It was also more attractive to insects and vermin. Sifting or bolting could separate some of the elements because the thicker bran seed coat of the soft winter wheat varieties would crack into relatively large fragments.[citation needed] In this era, the limited amount of endosperm that could be sifted into a whiter flour was understandably preferred by consumers.[citation needed]
Stone milled soft white wheat, which is lower in protein, dominated United States production before the introduction of Red Fife hard red spring wheat in the s and Turkey hard red winter wheat in the s.[citation needed] The higher gluten and protein properties of these hard wheats offered better bread-making qualities than the soft wheat varieties.[7] U.S.commercial millers initially significantly discounted the hard wheats because the white endosperm that customers preferred could be more easily sifted from the soft wheats.[8]
However, millers worldwide began to experiment with high grinding,[9] or placing the mill stones further apart and turning them at slower speeds.[10] The process was to first crack the wheat kernel and then to extract the flour by a succession of grindings and siftings. The white endosperm flour yield was enhanced by the addition of device known as the middlings purifier, which sent a blast of air into the mixture of partially-ground kernels as they were being sifted, lifting the bran particles upward into a separate holding area. A patent was granted to George Christian for this device,[11] and the consistent output of high quality flour thus became known as patent flour.[8] However, the use of mill stones in this high grinding process soon proved not to be optimum.
The invention of the roller mill
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The improved functionality of baked products made with a finer flour mixture first got international attention at the Paris International Exposition.[1] The Hungarian baking exhibitors clearly out performed their French counterparts. They credited the finer flour that Hungarian millers were able to produce by using more uniform steel rollers instead of mill stones for their higher quality baked goods. The notoriety of their flour was the motivation for staging the Vienna International Exhibition held to promote the merits of this new technology. A patent employing the use of grooved steel rollers geared to mill at different speeds was later granted in the U.S.in .[citation needed] The obvious efficiency of the roller mill prompted adoption over the next decade and came to dominate the commercial flour industry. No all-millstone mills of any significance were built in the U.S. after that with the commercial flour grindstone virtually disappearing from the flour milling scene in all developed countries by the early s.[citation needed]
To enhance output, millers experimented with flour tempering,[12] or hydrating the outer shell of the wheat berry, which facilitates the elimination of the bran and the germ. This is now a key step in the roller milling production of white endosperm flour. In contrast, whole grain milling systems that process the entire wheat kernel in one pass keep the grain as dry as possible. In , these "single stream" systems actually produced a modest amount of the whole grain flour that was commercially milled. Most of the commercial whole grain flour produced is reconstituted or recombined after first being separated by roller mills.[13]
Flour enrichment
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In the s and s, specific deficiency disease syndromes were first identified and documented in the United States.[14] In order to improve the nutritional status of the population, in the FDA established a standard of identity for any flour labeled as enriched. These standards have been amended over the years, but they continue as the basis for the addition of thiamin, niacin, riboflavin, folic acid, and iron, with the addition of calcium as optional. Under this regulation, fortification of flour and bread products is not mandatory, but if a product is labeled as enriched, it must meet the standards of identity described in the FDA regulations. The National Labeling Education Act of provided for federal preemption of standards of identity, nullifying any state laws that made enrichment of flour and bread products mandatory.[4]
References
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For rolling mills that roll metal into various shapes, see rolling (metalworking)
An early 20th-century oil-seed roller-mill from the Olsztyn district, Poland A late 19th century double roller mill displayed at Cook's Mill in Greenville, West Virginia in Closeup of Barnard's Roller Mill, New Hope Mills Complex, New York Cutaway drawing of a centrifugal roller mill for mining applications,Roller mills are mills that use cylindrical rollers, either in opposing pairs or against flat plates, to crush or grind various materials, such as grain, ore, gravel, plastic, and others. Roller grain mills are an alternative to traditional millstone arrangements in gristmills. Roller mills for rock complement other types of mills, such as ball mills and hammermills, in such industries as the mining and processing of ore and construction aggregate; cement milling; and recycling.
Types
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Two-roller mills
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Two-roller mills are the simplest variety, in which the material is crushed between two rollers before it continues on to its final destination. The spacing between the rollers can be adjusted by the operator. Thinner spacing usually leads to that material being crushed into smaller pieces.
Four-roller mills
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Four-roller mills have two sets of rollers. in a four-roller mill, the grain first goes through rollers with a rather wide gap, which separates the seed from the husk without much damage to the husk, but leaves large grits. Flour is sieved out of the cracked grain, and then the coarse grist and husks are sent through the second set of rollers, which further crush the grist without damaging the crusts. Similarly, there are three-roller mills, in which one of the rollers is used twice.
Five- and six-roller mills
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Six-roller mills have three sets of rollers. In this type of mill, the first set of rollers crush the whole kernel, and its output is divided three ways: Flour immediately is sent out the mill, grits without a husk proceed to the last roller, and husk, possibly still containing parts of the seed, go to the second set of rollers. From the second roller flour is directly output, as are husks and any possible seed still in them, and the husk-free grits are channeled into the last roller. Five-roller mills are six-roller mills in which one of the rollers performs double duty.
Gristmill conversion
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In the 19th century roller mills were adapted to grist mills before replacing them. The mill used either steel or porcelain rollers.[1] Between the years and , the Hungarian milling industry upgraded and expanded the use of stone mills combined with roller mills in a process known as Hungarian high milling. Hungarian hard wheat so milled was claimed as integral to the "First in the world" success of the Vienna Bakery of the Paris Exposition.[2]
Other applications
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Working principle
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A motor or other prime mover drives the hanger of the grinding roller to rotate through a V pulley and center bearing. The roller, which is hung by a bearing and pendulum shaft, will roll along the inner circle of the roll ring while the hanger is rotating. A dust removal blower will generate negative pressure at the inlet and outlet of the grinder to prevent dust and radiating the heat in the machine.
History
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Modern era roller mills were re-invented by the Hungarian engineer András Mechwart in , then quickly spread to other parts of Europe and Americas.
See also
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References
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