The Comprehensive Milling Process of Nutrient-Rich Oats

The unique milling process for oats not only ensures superior quality but also preserves their nutritional benefits. At harvest time, oats are sourced from a select panel of registered local growers. They are carefully dried and stored safely until needed. The milling process involves five distinct stages:

1. Cleaning, drying, and grading: Initial cleaning removes impurities, while drying and grading ensure the oats meet quality standards.
2. Dehulling and cleaning: The hulls are removed, and the oats are cleaned again to eliminate any remaining impurities.
3. Groats to pinhead: The cleaned oats are cut into smaller pieces, known as pinheads, facilitating further processing.
4. Pinhead to oatlets: Pinheads are further processed into smaller, more uniform oatlets, which are easier to cook and use in various products.
5. Packaging and distribution: Finally, the oatlets are packaged in moisture-resistant containers and distributed to ensure they reach consumers in optimal condition.

This meticulous process guarantees high-quality oats, which are rich in dietary fiber, essential vitamins, and minerals. These nutrients contribute to heart health, improved digestion, and sustained energy levels, making oats a valuable addition to a balanced diet.
The Comprehensive Milling Process of Nutrient-Rich Oats

Rice husking

Rice botanically belongs to Oryza sativa L. of Gramineae family. Paddy is a self-pollinated crop. A complete seed of rice is called paddy and contains one rice kernel. Outer layer of rice shell is called husk. The next layer is called rice bran and the innermost part is called rice kernel.

Rice husks are the hard protective coverings of rice grains which are separated from the grains during milling process. Rice husk is an abundantly available waste material in all rice producing countries, and it contains about 30%–50% of organic carbon.

The conventional way to husk rice is to pass it between two rubber rollers that are rotating with a surface speed differential. The resulting normal pressure and shear stress causes the husk to be peeled away from the kernel.

Rice husking operation is one of the most important stages during milling process, which effectively determines the quantitative and qualitative losses of rice. A common rice milling system is a multi-stage process where the paddy is first subjected to husking by using a husker and then to the removal of brownish outer layer, known as whitening.

Husks contain a combination of cellulose, hemicellulose, and lignin, along with appreciable amounts of silica and other minor components.

Cellulose and hemicellulose are both polysaccharides; cellulose is a long straight-chain polymer containing exclusively β-glucose monomers, whereas hemicellulose is a shorter cross linked polymer that contains other sugars, such as xylose, galactose, mannose, rhamnose, and arabinose.
Rice husking

Rice polishing

The objective of a rice milling system is to remove the husk and the bran layers from paddy rice to produce whole white rice kernels that are sufficiently milled, free of impurities and contain a minimum number of broken kernels. Rice milling basically involve two processes. First is the removal of husk to produce brown rice which is called as dehulling.

Second process is removal of bran layer which also remove germ and partial portion of the endosperm. White rice is produced from brown rice by removing the bran layer and the germ. The bran layer is removed from the kernel by applying friction to the grain surface either by rubbing the grains against an abrasive surface or against each other.

Polishing of rice kernel is very vital step in rice processing to remove bran. Although the extracted bran becomes a valuable by-product as a good source of edible oil, the nutritive value of polished rice kernels gets reduced considerably including significant loss of natural fiber.

The process used to whiten brown rice can be classified as either abrasive or friction. In abrasion method, this process the grain is whitened by the abrasive action of the rice kernel passing between a moving abrasive surface and stationary screen. The hard-rough surface is usually stone or a carborundum type material. The abrasive process applies less pressure on the grain and is better suited for long grain varieties.

In the friction whitener the grain kernels are forced against each other and a metal screen by a steel-ribbed cylinder rotating inside a metal-plated cylinder.

Prior to the advent of modern polishers, several traditional methods have been used to polish rice. These methods include: pounding in mortar with pestle; beating with clubs on the floor; rubbing on the floor; beating gently with clubs in jute bags and threading under the feet of man or hooves of animals.
Rice polishing

Pearling process of cereal

Milling represents the principal procedure in the cereal industry and is classified in two categories: dry and wet, while each has its own characteristics. Dry milling separates the outer fibrous materials and germ, which are considered by-products of the grain endosperm.

Dry milling can also refer to pearling. Pearling is the process, prior to milling that with the application of abrasion and friction removes effectively only the bran layers from the cereal grains (rice, oat and barley), allowing nutritious parts, such as the aleurone layer to remain in the intact kernels. This pre-treatment potentially could also improve milling yields of superior flour quality.

The industry also uses this technology in wheat flour milling because it lowers the capital investment costs, giving the benefit of better-quality products. Removal of the outer kernel layers to a desired level prior to milling means less bran to be removed during the subsequent milling process, fewer stages, and better flour and semolina yield.

The by-products of the pearling process, ≈30–40% of the total kernel weight, are mainly used in animal feed. These by-products contain interesting amounts of bioactive compounds such as β glucans, tocopherols, and tocotrienols.
Pearling process of cereal

Milling in ancient Egypt

Neolithic Egyptians developed bread from emmer, barky, and even a type of millet. The grain was stored in beehive-shape silos until needed and they ground the grain on flat stones called querns and then baked in and oven or in heated clay bread molds.

Both men and women assisted in making bread, with men performing many of the tasks. Women generally were the millers. Figures of women milling grain have been found in the tombs of the later Old Kingdom (c.2575-2510 BC) to early Middle Kingdom (c.2030-1640 BC).

Milling itself was a tedious process and the cause of many injuries. Several handfuls were place on a stone quern with a gently curve surface for milling. The upper surface is not perfectly smooth, but is kept somewhat roughed. A stone shaped like rolling pin with a curve to match the curvature of the grinding surface was rolled back and forth, grinding the grain into flour, which was caught in a container at one end of the quern.

The miller kneeled over on the ground, grinding on the wide saddle quern; then in the Middle Kingdom, the milling process was performed on workbenches. The rotary quern was not invented until about the fifth to third centuries BC, somewhere in the western Mediterranean.
Milling in ancient Egypt

Gradual reduction system in wheat milling process

Milling is the most common processing technique for wheat grains for human consumption. Roller mill is the primary technology used for milling wheat into flour.

The technology is a gradual reduction system so that damage to the components of wheat is minimized during four milling.

The gradual reduction system of flour milling is the process of taking the whole wheat berry and via a series of grinding and sieving stages, producing white flour of the desired quality and yield. This gradual reduction is done to control the level of starch damage.

The gradual reduction system has enabled the production of flours of low ash content and high yield. Specialist, high quality flours are produced by extracting high purity sub-products from within the process.

Many variations in the detail of the process flow sheet emerged in the years after the perfection of the gradual reduction system. This was due to the varying requirements of customers and even political directives.
Gradual reduction system in wheat milling process

What is breakfast cereal?

Breakfast cereals have been define as “processed grains for human consumption”.

Indeed, one or more of the cereal grains or milled fractions thereof indeed major constituents of all breakfast cereals, approaching 100% in the case of cereals for cooking.

The portions drops well below this in many ready to eat cereals, and less than 50% in presweetened products having nutritive sweeteners )sucrose, or fructose, dextrose, and other corn-based products) as substantial constituents.

In broad terms , then, breakfast cereal ingredients may be classified as:
1) grains or grain products,
2) sweeteners, caloric or otherwise
3) other flavoring or texturizing macro ingredients
4) microingredients for flavor or color, micro ingredients for nutritional fortification and shelf life preservation.
What is breakfast cereal?

White flour milling

The aim of milling is two fold
*to grind cleaned and tempered wheat
*to separate the outer husk from the internal endosperm into a variety of suitable forms for customer.

Wheat is passed through a series of machines that apply the principles of particle size and density separation.

Foreign materials such as metal, sticks, stones, straw, seeds and other grain are removed in steps by a magnetic separator, vibrating screens, a destoner, a disc separator and a scourer.

These are six different principles or separation normally used in wheat cleaning. These differentiations are by width, length, specific gravity, air resistance, natural peculiarity and scouring or rubbing.

After cleaning, the wheat is tempered prior to be milled. In this stage, the moisture content of the grain is increased by adding water and by allowing the grain to sit for a period of time.

White flour is the ultimate product of flour milling. The aim of white flour milling is to extract a maximum amount of endosperm from wheat berry in as pure a form as possible.

In general, 100 pounds of wheat will produce 72 pounds of flour. The wheat is passed through a series of machines to break open the wheat kernels and reducing of the endosperm by grinding to obtain the final product – plain flour. Most white flour is milled in high-speed steel roller mills.

The grain is ripped open rather than crushed, and the germ and bran are sifted out, leaving 70 to 73 percent of the grain – the endosperm, or starch and protein.

Roller mills consist of a sequence of paired iron roller, some grooved and some smooth, that rotate inwards. Because one roller is set to spin at a faster rate than the other the grains caught in the middle are twisted and chopped.

In this process, the bran and germ layers of the grains are stripped away, leaving only white, pulpy interior kernel or endosperm.

Additives of less than 1 weight % are added to the flour by a mixing process. White flour has been enriched for years with niacin, thiamin, riboflavin and iron and folic acid is added to reduce the incidence of neural tube birth defect in developing human embryos.

Family flour for retail sale is packed in 5, 10, or 25 pound bags. Bakery flour may be packed in 50 or 100 pound bags or shipped in bulk trucks or railcars.

White flour milling

Milling of Cereal

The objective of cereal milling is to remove the bran and germ from the seed and to free the endosperm. This left whole as in rice milling, ground into coarse pieces (wheat semolina, maize grits) or milled into flour.

Since prehistoric times up to the middle of the 19th century, cereal grains were ground in small mills, driven by hand, wind or water power.

The process of milling wheat into flour was revolutionized around 800 BC in Mesopotamia, when animal, water and wind power were harnessed for the first time to run the large stones used for grinding.

In ancient Rome the mill and the bakery were the very same enterprise. The grain were milled and worked up without delay to dough and bread.

The flour ground in such a mill was whole grain flour, because the complete cereal grains poured into the mill on top, came out out as flour at the bottom.

Probably the most ancient technique involves the grinder rocking backwards and forwards while grasping an ellipsoid stone in both hands which crushes the grain within a larger concave stone suits in front of the grinder.

Both upper and lower stone are usually made from a hard igneous rock such as granite or basalt to avoid the production of stone in the grinding process.

Around the Mediterranean and possibly also in China during the first half of the first millennium BC, there were two sophisticated versions of the handmill the hopper-rubber and the lever mill.

Moving to the milling process proper, it was in 1878 that Henry Simon took 19 British millers, to Hungary to view the all steel rollermill invention.

This machine became the heart of what is known as the gradual reduction system, commonly used.
Milling of Cereal

Milling process of wheat

The single term ‘milling’ applied in the context of cereals, covers a wide range of processes. In general they are methods of transforming whole grains into forms suitable for consumption or for conversion into consumable products.

The conventional milling process of wheat first involves washing to remove foreign substance such as dirt or rocks.

Milling is a process by which kernel components are separated physically or chemically.

Once the endosperm is separated it subsequently is ground multiple times in reduction rolls to become finer and finer for flour.

As the bran and germ are removed, the refined flour contains streams that contain less vitamins and minerals.

If flours streams of the endosperm are blended during the milling process various flours are created.

Other products of the process, e.g. vital gluten, can supplement other edible products. Millfeeds, the material remaining after all the usable flour is extracted is used by the feed industry either directly or as a feed supplement.
Wheat milling practices might cause significant differences in flour quality, which are due to flour particle size, extraction rate, and the level of starch damage.

In general, 100 pounds of wheat will produce 72 pounds of flour. The remaining 28 pounds is classified as millfeed.
Milling process of wheat

Grain Processing: Milling

Grain Processing: Milling
Threshing removes the grain from the stem. However, the grain is not usually ready for cooking until the husk (glumes) has been removed.

Wheat, sorghum and pearl millet usually thresh naked that is without the glumes. Maize is on a cob covered with a sheath: the sheath must be removed and the grain taken from the cob.

A combine harvester threshes the maize free from both sheath and cob. Barley, oats, rice and most of the small millets thresh with the glumes adhering tightly to the kernel so that even a modern threshing machine or a combine harvester cannot remove the grain from this husk.

The first step in any milling process for this latter group is to remove the glummer.

This is done by rubbing the grains one against the other in a mortar or by simple rotary machine, by splitting off the glumes in a disk huller, or by use of rubber rollers rotating at a differential speed. The objective at this stage of milling is to obtain as high an out-turn as possible of whole grains.

Once free from glumes, all grains may be treated in the same way. Cereals have an outer layer and a gem, known collectively as bran, which is rich in lipids that rapidly oxidize to give off-flavors.

The bran also tends to be less easily digested than the endosperm.

The objective of the second stage of milling is, therefore, to remove the bran. In the case of rice, the grain is required whole, so great care is taken not to break the grain.

Most other cereals are eaten as flour or meal (a coarse flour). The more of the bran that is removed, the better the flour will keep.
Grain Processing: Milling

Wheat Grain Processing

Wheat Grain Processing
Wheat is harvested by combines that cut the stalk remove and collect the seed, and either return the straw to the soil, to be plowed under with the stubble and thus provide hummus or compress and bale it for future use as litter, ensilage and so on.

Wheat may be bagged in jute sack and stored in warehouses or it may be stored in bulk in elevators. The latter method provides the best protection against rodent and insect infestation.

The moisture content of bulk stored wheat should not be higher than 14.5% and that of sack stored wheat not higher than 16%. Otherwise, microorganism may grow and cause heating and spoilage. When it is necessary to lower the moisture content of wheat it may be dried in bins by blowing hot air (not higher in temperature than 175 degree F) across the bins.

In preparing wheat for milling, it is blown into hopper scales that record the quantity of uncleaned wheat. Some of the coarser impurities are removed by this process. The grain then passes over a series of coarse and fine sleeves that further remove contaminating materials, including chaff and straw. Still in dry states stones may be removed by passing wheat over short openings that allow the heavier stones to fall out of mass and be trapped.

The wheat is next passed over discs or cylinders containing indented surface that remove seeds short or longer than wheat following a pass through a magnetic separator to remove any metals present. The next cleaning process is dry scouring to remove adhering dirt.

The wheat is then washed in water, a process that both removes dirt and adds 2 – 3% water to the grain. The added water is necessary to provide desirable conditions for milling. A stone trap is including in the washer. Excess water is removed by centrifugation. A second wet cleaning with a light brushing action is ordinarily used, followed by aspiration (blowing air through the grain), which is the final cleaning operation.

The grain is then carried into a bin from which it is fed to the milling operation. This bin is located on the top floor of the flour mill, the grain having been elevate do this position during the various cleaning operation.

In milling, grain is fed automatically though scale hoppers that regulate the flow of the seeds at rates corresponding to those of the following operations:

Milling may be carried out by passing the grain through a series of corrugated rolls rotating toward each other, which remove chunks of the endosperm from the bran. After each passage through the break rolls, the material is sifted through cloth, or wire sieve and separated according to particle size.

The various streams of different sized flour particles are finally blended to provide the different grades of flour. The more finely ground flour is nearer to white but less nutritious than the coarser ground flour.

This results from the more effective removal of bran and germ from finely ground flour. Impact milling is now used in some operations. With this method, the seed is broken open by impact in a machine. Flour particles of different sizes are separated by air classification or by centrifugation.
Wheat Grain Processing

Oats Processing: Test upon Receiving

Oats Processing: Test upon Receiving
Oats arrive at the mill by way of bulk railroad car or truck. The first step is sampling to ensure that the oats are of suitable quality for milling.

Several samples are taken with a grain probe in an attempt to obtain a representative sample of the oats in the transport vehicle. Among the characteristics typically examined are test weight (Ib/bu), sound count, kernel width, and evidence of infestation.

The test weight of the oats is very important because it is a measure of the amount of groat or berry present. Milling oats should weigh at least 36Ib/bu and preferably more.

Since then groat is the portion processed for human food, a high groat to hull ration is desired. This ratio can vary greatly. Separation of groats and hulls in four samples of oats showed groat percentages ranging from 67.4 to 74.2%.

The sound count is defined by government: as including “kernel and pieces of oats kernels (except wild oats) which are not badly ground damaged, badly weather damaged, diseased, frost damaged, heat damaged, insect bored, mold damaged, sprout damaged, or otherwise materially damaged.”

The width of the oats is important because thin oats have a lower groat content. The width is measured with screens with slotted openings. If the evidence if insect infestation is found, treatment utilizing approved fumigants must be initiated.

Acceptable oats are then passed over a receiving separator to remove field trash, such as corncobs or other coarse materials, and to remove some of very fine material, such as chaff dust.
Oats Processing: Test upon Receiving