The History of Wheat and Flour Milling
Archeologists date the first tools of ancient man as early as 250,000 years ago. Hand axes, stone knives and bludgeons were used in hunting food and for protection. But it was only 10 or 15 thousand years ago that man began to turn his tool-making skill to the production of agricultural implements. His transition from hunting food to raising food marked the beginnings of civilization. Within a few thousand years, larger urban centers of culture known as cities came into existence.
The collection of food, wheat and other grains offered man a number of advantages. Grains could be stored without spoiling. They could be stocked or carried from place to place and prepared in any number of ways. Grain could be traded for other essentials or comforts, eventually leading to the development of commerce and a means of supplying food for city populations from distant fields.
The first step in planting grain is breaking up the soil so that the seed may be covered. The most primitive instrument for this probably was a sharp digging stick or a sharp stone lashed to a handle. Egyptian drawings show the use of a triangular tool made by hinging two sticks at one end. The longer stick served as a handle and the shorter as a blade, swung with a chopping or hoeing action. A hoe of this type dating from 1,000 B.C. has been found intact. Other Egyptian drawings from 2,500 B.C. show such a hoe-like instrument or plow equipped with a pair of handles, drawn by oxen. A similar, one- handled-plow with a single point, dating from 300 B.C. was found in Denmark. In many parts of the world today, farmers use implements almost as crude and primitive.
Great changes in the agricultural revolution came with the development of iron and steel and are today scarcely 160 years old. In 1819, a New York State farmer, Jethro Wood, patented a cast iron plow. Iron was soon replaced by steel, and a series of plowshares were attached to a single frame in an implement called a gang plow. With his tractor, today’s farmer pulls a series of steel points fitted to a single frame to help pulverize the soil after plowing. This implement is called a spike harrow and is used to reduce the soil to smaller fragments. Soil kept pulverized and free from weeds retains moisture needed by the seeds and wheat plant.
To sow seeds into soil ancient Egyptians cast seed wheat directly into the mud left by the retreat of annual floodwaters along the Nile. Cattle were driven over the area to trample the seed into the ground. For thousands of years, a more common method of sowing seed has been the broadcasting of wheat – scattering it evenly by hand- a procedure still used today in many parts of the world. Working in this fashion, with a sack of grain slung over his shoulder, it would take a skilled man about 90 minutes to sow just one acre of wheat.
The modern farmer seeds his field with a machine called a drill. Seed for planting is contained in a hopper at the top, from which the seed is funneled evenly down into the earth and covered lightly with soil.
As in planting, instruments used to harvest wheat evolved during ancient times from the first sharp stones fitted into a wood or bone handle into skillfully crafted cutting instruments. The adaptation of iron and steel helped man develop the sickle, a balanced tool that was easy to swing. Even after 4,000 years sickles are still widely used. They are light enough for work by women and children. They permit the cutting of wheat at any height, so that the straw can be left standing or cut separately. The importance of the sickle in the history of man reaches a point of symbolism – perpetuated in the Russian hammer and sickle device, and in many works of art.
An improvement over the sickle was the scythe- a longer blade with only a slight curve, fastened at right angles to a long wooden handle. Wheat could be cut faster with a scythe, and the worker could stand upright. But the straw had to be cut close to the ground, leaving it attached to the wheat head. A scythe is also a heavier instrument that requires a strong man for prolonged use.
As the wooden plow was displaced by iron and steel, better and more efficient methods of cutting were developed. In 1831 Cyrus McCormick invented a mechanical reaper. The two wheeled, horse-drawn invention pushed a series of moving, scissor-like blades against the grain to clip if close to the ground. A rotating paddle wheel swept the stalks against the cutting bales so they fell on a platform as the machine moved forward.
The modern farmer usually takes a sample of wheat to a local elevator for testing to check moisture content, which determines whether or not it is ready to harvest and can be stored. Wheat is relatively hard and dry when ripe. At this time, the crop is also an easy target for destructive fire, wind, rain or hail during a critical week to 10-day period when the grain must be cut.
A number of methods can be used to thresh out the cut grain and remove the wheat from its glumes. For thousands of years, wheat heads were spread on a plot of bare, hard ground or threshing floor. Cattle or horses were driven around and around until hooves accomplished the removal of the wheat from the chaff. Separation was completed by winnowing-or tossing the mixture into the air so that the wind blew away the lighter chaff and the heavier wheat dropped back.
The mechanical ingenuity that led to the development of a reaper also led to the development of the threshing machine. Industrialization- the use of new sources of power in steam and internal combustion engines, the improvement of transportation, and the growth of cities with greater need for food- served to revolutionize agriculture. During the 19th and early 20th centuries, the time required for cultivation and complete harvest of one acre of wheat declined from an estimated 83 hours to little more than two man-hours. The invention of several machines made this saving possible.
One of the inventions, the threshing machine, used power fans to separate the chaff from the grain. The machines were expensive and often purchased by companies of farmers or independent businessmen. Local groups called “threshing rings” were formed of ten to twenty-five growers, and the farmers would cut and shock the grain in the fields belonging to members. The shocked grain was hauled in from the field and fed into the threshing machine. Chaff and straw were blown out into the pile on one side. Clean grain poured into a wagon or bags on the other side. The “threshing rings” also hired itinerant workers from the cities. This annual migration of thousands of harvest hands came to an end after the end of the First World War with the development of the combine, first as a unit to be drawn by horse or tractor and finally self propelled.
The modern combine, in one operation, performs the five basic jobs in harvesting once done by hand labor:
- Cutting – replaces the sickle, scythe or cradle
- Feeding – eliminates hauling the cut or bunched stalks of wheat
- Threshing – formerly accomplished by flail or some other method of extracting the whole grain from its hull
- Separating – tedious discarding of stalks
- Cleaning – separating the wheat berry from all other particles
The combine reduced the man hours of work of harvesting one acre of wheat from 46 hours to 30 minutes or less and freed thousands of men for productive work outside the farm.
Wheat is transported from the field to a storage facility and eventually to a mill. Since prehistoric times, the goal of milling has been the separation of outer bran and germ from the inner, more digestible, endosperm of the wheat berry. While primitive man probably simply chewed wheat as food, and later learned to parch it for easier eating, archeological excavations of even the earliest known villages indicate forms of grinding.
The teeth of people from excavated villages dating back to 6,700 BC show no signs of wear that would indicate they chewed wheat. Apparently those early people already knew the use of stones for milling wheat. Pairs of stones, one for pounding or rubbing against another, are found at sites of ancient settlements in almost all parts of the world. Although crude, the pounding or rubbing of whole grain effectively reduces the kernel into flour or meal.
The pounding of two stones together would create wear at the point of impact. A depression was created. If two stones of the right shape are rubbed together the same wearing action evolved into simple mills in which wheat was poured in from the top and flour emerged from the grinding surfaces. The ancient Egyptians used saddlestones and mixed their crudely sifted four with a liquid containing natural yeast to create loaves of leavened bread in many different shapes and varieties. The process is illustrated in crude murals found in Tombs along the Nile River.
The addition of levers to millstones gave millers more power to grind greater quantities of wheat. The extension of the top stone made a hopper for the grain, a Grecian invention, called an “hourglass mill”. For thousands of years, flour for man’s bread was produced by mills of exactly the same principle, modified to harness the power of men, horses, or oxen, or water, or wind power geared to turn the stones one against another. Fabric or mesh was used to sift the flour even as today, and the stones were dressed or scored with furrows to direct the flour out from the center to the outer edge of the grinding surface. A combination of sifting and grinding produced white flour.
The application of wind or waterpower to the task of turning the grinding stones made possible larger mills with increased output of flour to sell in bigger markets. The Romans are believed to have been the first to use waterpower for milling flour, about 100 B.C.
19th Century Milling
In the 19th century, the industrial development that made possible the invention of reapers and threshing machines was also reflected in mill design and construction. Power carried by shafts, belts and gears was used to turn one or a series of stones. Water began to displace wind as a more dependable source of power and larger milling plants were built near sources of waterpower.
An American millwright, Oliver Evans, introduced screw conveyors to move flour and wheat horizontally and bucket elevators to lift grain and its milled products called grist. He assembled these machines, together with sifters or bolters, in the first continuous system in which wheat was milled into flour as a single uninterrupted operation. Machines were also added to clean the wheat to produce purer flour.
The gradual adaptation of industrial techniques and the dependence on water as a source of power, together with improved transportation by barge or rail and the expansion of the wheat lands westward, forced the shifting of milling centers in the same direction. From New York, Philadelphia, and Baltimore, the center of milling represented by the largest output of flour moved progressively to Rochester, St. Louis, Minneapolis and Buffalo-wherever the ever changing equation of transportation advantages and lower power costs combined to make wheat readily available and the shipment of finished flour more economical..
The use of harder wheat, initially imported from Canada in the middle of the 19th century, as well as the mechanization of milling, encouraged the widespread adaptation of a method called “New Process.” First used in Hungary, the miller using the “New Process” set his mill stones farther apart to crack rather than crush the wheat. He slowed the turning speed of the millstones at the same time to reduce the heat of friction and to grind and separate the wheat gradually into bran and white flour.
The stone grinding of wheat soon reached a high degree of proficiency, milling at extration rates that produced about 72 percent flour and 28 percent millfeed. Only a few workers were needed to tend the machines and handle the grain and flour. In 1870, the average mill employed fewer than three persons. Flour milling is perhaps not only one of the oldest industries, but also the first fully automated manufacturing process in the history of man.
The “New Process” mills in the United States used repeated grinding and bolting to eventually produce excellent white flour, equal to the best of Europe. Stone-ground whole wheat flour is occasionally featured as premium flour even today.
In the United States of 100 years ago, almost every settlement where there was a source of waterpower included a small community mill. Although the trend was toward larger plants of merchant mills that produced flour for sale commercially in larger market areas, the smaller grist mill, grinding either wheat or corn and sometimes alternating as a sawmill, continued to operate. In 1870, more than 22,000 mills served the total population of about 30 million people. Most of the small grist mills were driven by waterpower.
The invention of the steam engine by James Watt in 1769, the introduction of the more efficient roller mill system, and the application of the middlings purifier, combined to make possible model milling. The steam engine could be geared directly to the turning of millstones or employed to raise water into reservoirs, freeing the miller from his dependence on sources of natural power. Watt designed an English mill powered by steam in 1780. Less than 30 years later, Oliver Evans used steam to drive a Pittsburgh flour mill. By 1870, steam was used in 5, 383 of the 22, 573 flour mills in America.
The first mention of rollers to replace grindstones first occurred in 1558 with the publication of an engineering handbook by an Italian, Agostino Ramelli. His drawings illustrated a number of devices later adapted to modern milling. In 1662, another mechanical genius, G.A. Bockler, developed a mill using two corrugated rollers together with an agitating device for sifting the grind. Eventually the use of rollers for milling was widely adopted in western and central Europe. A concentration of roller mills in and around Budapest gave the name, “Hungarian,” to the process.
Word of the new roller process came to America. In the beginning rollers were used in combination with grindstones. An all-roller mill was constructed and operated briefly in Philadelphia in 1876. The first installation of commercial importance was made in Minneapolis in 1878.
Roller mills offered several advantages. They eliminated the cost of dressing millstones. They permitted longer, more gradual extraction, or the making of a larger amount of better grade flour from a given amount of wheat. The product itself was more uniform, cleaner and more attractive. Rollers were superior for milling harder bread wheats, reducing the kernel slowly into flour fragments to separate the bran. Roller milling also made possible the construction of larger, more efficient mills, hastening the abandonment of community mills and stone grinding.
The third factor in the milling revolution, with new sources and application of power and the roller system, was the use of the middlings purifier. Edmund La Croix in Minnesota first constructed this machine in the United States in 1865. It first filled an urgent need in the making of flour by the “New Process” method and was later adapted to roller milling. Flour made from endosperm particles free of bran is usually the highest grade, and the “New Process” yield of this type of flour was small. The middlings purifier improved the yield.
Rather than working the entire wheat berry into a powder in one grinding, a miller using the gradual reduction process strives to break up the endosperm into bran free granular “middlings” or farina. Regrinding this material makes the best grades of flour. In the LaCroix machine, the coarse middlings passed over a vibrating screen. An upward current of air lifted off most of the branny particles, or “purified” the middlings.
Air currents produced by fans had long been used in milling to clean wheat. Bolting cloth to sift the flour and obtain finer granulation had been employed for hundreds of years. La Croix put the two together for a more versatile and efficient system of flour separation. An earlier process to separate bran from middlings had been patented in 1865, and flour produced with it was know as “patent,” a name still applied to more refined grades of flour. The invention and use of the middlings purifier made possible the continuous improvement of the flour stream as progressed through a mill to the final product.
The second half of the 19th century was a period of immense development and change in flour milling. Hundreds of patents were issued for mechanical purifiers, sifters, cleaners, dust collectors, grain washers and other milling equipment. Together, these improvements and refinement of the basic process- separating the outer bran and germ from floury, inner endosperm- made possible the modern mill.
20th Century Milling
Wheat arrives at modern mills and elevators by ship, barge, rail or truck. Chemists in product control, who inspect and classify grain, take samples of each shipment. A small quantity is milled into flour. The character of the wheat itself, it’s milling and baking qualities, determine how it is handled. Different wheats are usually blended before milling to achieve the desired end product. Similarly, different types of flour are blended to customer specifications and to provide desired baking characteristics.
The average bushel of wheat weighs about 60 pounds. At the standard extraction rate, providing about 72 percent flour and 28 percent mill feed, approximately 2.3 bushels of wheat are required to produce 100 pounds of flour.
A simplified schematic flow chart of 20th century milling is available by selecting the How Flour is Milled link. The flow chart displays the elementary steps in processing wheat into flour and explains the use and value of each separate machine. It is quite probable, however, that no two flour mills will ever be quite alike in terms of an exact sequence, placement or identity of machinery. The men who build the machinery, millwrights, constantly modify and improve the equipment according to the suggestions of technicians or the millers themselves. Equipment size, shape, housing, source of power and daily capacity all serve to individualize each flour mill.
The chart below shows the average composition of wheat, white flour, and bran
Average Composition of Wheat, White Flour and Bran*
|Water or moisture||12.00||13.50||13.00|
|Mineral mater or ash||1.80||.40||5.80|
|Protein or nitrogenous matter||12.00||11.00||15.40|
|Cellulose or crude fiber||2.20||.25||3.60|
|Fat or ether extract||2.10||1.25||3.60|
*Swanson, C.O., Wheat and Flour Quality, p. 21
All flour consists chiefly of carbohydrates, protein, fats, vitamins and minerals, and traces of cellulose or fibrous materials.
As with the wheat itself, the composition of individual flours varies, depending on both the wheat and milling process. As the protein content of the flour increases, carbohydrate decreases. The mineral content varies with the grade, with lower grades generally showing higher mineral or ash values. Whole wheat or graham flour, as the name implies, contains everything in the wheat berry including bran and germ. Whole wheat flour is higher in protein than white flour milled from the same wheat.