How Is Wheat Flour Manufactured in a Flour Mill? – History, Process & Technology

by Mar 6, 2019blog

Wheat flour made from grinding wheat grains in a flour mill makes up key ingredients in many Indian daily diets. Indians cannot imagine a day where they don’t eat one or the other food product made from wheat grains. Although wheat flour forms such an important part of our daily diet, we really don’t know how the wheat is processed? How the grains travel from the field to the flour mill and onto our plate.

Although flour can be prepared from various plants and grains, wheat is generally preferred by a vast majority of people. Dough made from wheat flour is well suited for baking bread, chapatis and many other delicious recipes.

Wheat flour has been made from prehistoric times. Of Course, there were no flour mills earlier, the earliest method used for producing wheat flour involved grinding rain between two stones. These methods included the mortar and pestle (a stone club striking grain held in a stone bowl), the saddle stone (a cylindrical stone rolling against grain held in a stone bowl), and the quern (a horizontal, disk-shaped stone spinning on top of grain held on another horizontal stone). These devices were all operated by hand.

This blog will guide you through every procedure wheat grain undergoes before it turns into wheat flour. This guide includes:

● The Anatomy of a wheat grain
● History of wheat flour milling machines
● Manufacturing process
● Benefits of wheat flour

After reading this guide you will get a thorough understanding of how the wheat grains are processed in a flour mill to wheat flour manufactures , we consume almost every day.

So, let’s get started…

The Anatomy of a Wheat Grain:

Image Source – Fab Flour

It is pretty straight forward, each tiny grain is typically divided into 3 small parts, each having its own importance.

  • Bran –  Bran is the most outermost layer of the wheat grain. It makes nearly 14.5% of the total grain weight. Bran contains a tiny amount of proteins, 3 major types of B-vitamins, trace minerals and dietary fibres, making it valuable to improve digestive health. Depending upon the class of wheat, the bran may be white or red in colour.
  • Endosperm – The largest part of the wheat kernel, it constitutes about 83% of grain weight. The end sperm contains the highest amount of proteins, carbohydrates, iron & major B-vitamins. When only endosperm is used to make flour, the flour is enriched with folic acid to compensate for the loss occurred due to eliminating other parts. 
  • Germ – Germ forms about 2.5% of kernel weight and is the embryo of the wheat plant. It contains high-quality proteins, complex b-vitamins and trace minerals. Due to high-fat content, the germ is usually separated to increase the product shelf life and is usually separated in a flour mill.

History of Wheat Flour Milling

Let’s understand how the flour milling process evolved over the years.

Early Flour Milling Process:

Archaeological excavations from the earliest known village indicated different forms of grinding using stones. Stones were paired for pounding or rubbing against each other. Although rough, rubbing stones against each other would effectively reduce grains into flour or meal.

This principle was used to create the first simple flour mills, two stones of right shape were rubbed together in which wheat was poured from the top and flour emerged from the grinding surfaces. Then the addition of leavers to grinding stone gave them the ability to mill a large quantity of wheat flour. For thousands of years, civilization used the same principle as a flour mill only modified to harness the energy of horses, oxes, wind or water.

19th Century Flour Milling Process:

The industrial revolution made possible the invention of reapers and threshing machines which also led to the revolution of flour mill design. 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 water power.

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 Flour Milling Process:

Wheat arrives at modern flour 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 kinds of wheat 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 Process of Manufacturing Wheat Flour

The raw materials:

Although wheat flour is made from wheat there are some amounts of additives added when wheat undergoes commercial flour milling. Flour intended to use for different applications are treated differently. Flour used in baking bread is made from hard wheat. The high percentage of protein in hard flour makes the dough rise than the soft wheat. Flour used in cakes and pastries is made from soft wheat. All-purpose flour is the combination of both hard wheat and soft wheat. Durum wheat is a special kind of wheat used to make semolina, which in turn is used to make pasta products.

Wheat flour processed in commercial flour mills contains a small number of additives. Bleaching agents such as benzoyl peroxide are added to make the flour look whitish. Oxidizing agents such as potassium bromate, chlorine oxide is used to enhance the baking quality of the wheat flour. The additives are added a few parts per million.

The manufacturing process:

Grading the raw material: Once the wheat grains are receiving to the flour mill. It is tested for various physical and chemical qualities and graded on several factors, but mostly on their protein content. The wheat is stored in silos until the next process.

Purifying the wheat:

● Before the wheat grains are transferred into a flour mill, the grains need to free from any unwanted foreign particles. This requires grains to undergo various cleaning processes. After each cleaning process, the grains are checked and if necessary, the process is repeated again.

● The first device used in the cleaning process is called a separator. This machine passes the wheat from a different metal screen of various sizes. The wheat and other similar sized objects pass through the screen mesh leaving behind big rocks and stones.

● Next, the wheat passes through an aspirator, which works like a vacuum cleaner sucking out all the particles lighter than wheat grain.

● Next, the grains pass through disk separator, which moves the wheat over a series of disks. Grains and similar weight objects are collected in one place. Smaller or lighter weighing objects are automatically separated.

● Another device called spiral seed separator works on the principle of centrifugal force. The wheat grains are oval in shape while most of the other plant seeds are round in shape. When grains are processed in the seed separator, the oval wheat grains come in the centre, while the round plant seeds are thrown at the edge of the container, where they are separated.

● Other methods used to purify wheat include magnets to remove small pieces of metal, scourers to scrape off dirt and hair, and electronic colour sorting machines to remove material which is not the same colour as wheat.

Preparing the wheat grains for grinding:

● The purified wheat grains are washed in warm water and dried in a centrifugal pump. The remaining impurities are washed away in this process.

● Now the moisture content of the wheat grains must be controlled in order to peel away the bran effectively during grinding. The process is known as conditioning.

● There are various methods used for conditioning. Cold conditioning involves soaking the wheat grains in cold water for 1 to 3 days. Warm conditioning involves soaking the wheat at 40 degrees Celcius for 60 to 90 minutes. Hot conditioning involves soaking wheat at 60-degree Celsius for a very short period.

● Even after conditioning if the moisture content is too much, the additional moisture is removed using warm vacuum dryers.

Grinding the Wheat in Flour Mills:

● Wheat of different grades and moisture is blended together to make the kind of flour they are manufacturing. The wheat grains are spun against metal pins in a device called entoleter. The grains which cracks are considered unsuitable for flour manufacturing and are separated.

● The wheat grains passed through metal rollers. The rollers are of two different sizes moving at two different speeds. They also contain spiral grooves which crack open the grains of wheat and begin to separate the interior of the wheat from the outer layer of bran. The product of the breaker rolls passes through metal sieves to separate it into three categories. The finest material resembles a coarse flour and is known as middlings. Larger pieces are semolina. The third part contains parts attached to the bran. The middlings are collected in a separate beaker. The other two products are again passed through a different pair of metal rolls. Nearly five to six pair of metal rolls are necessary to manufacture the desired amount of middlings.

● Next, the middling purifier moves the middlings through a vibrator and air is blown from the top to separate the bran particles from the middlings. The middlings passing through various screens are finely grounded.

● Middlings are then made to pass through metal rollers and the flour manufactured is made to pass through sieves of different size. The flour passing through sieves is separated by their fineness. By sifting and regrinding, different grades of wheat flour are produced. Later these different grades are combined to manufacture the desired product.

Processing the wheat flour in Flour Mills:

● Few amounts of additives are added since the nutrients are lost during commercial flour milling. Bleaching and oxidizing agents are added so wheat could give good baking properties. Vitamins and minerals are added to make the flour more enriched.

How is Quality Maintained in Flour Manufactured at Commercial Flour Mills?

● Quality maintenance starts as soon as the grains come in the flour mill. The wheat grain is tested for various physical and chemical properties. It is only after grains passing certain standard tests are selected for milling. The wheat content is primarily checked as people are interested in wheat as a good source of protein.

● During purifying, each sample was taken out and tested to check its purity. If the wheat is not as per standard requirements, the process is repeated again.

● The equipment used in flour milling is thoroughly cleaned using hot steam and ultraviolet light. The equipment is also treated with antibacterial agents and antifungal agents to kill any microscopic organisms which might contaminate it. Hot water is used to remove any remaining traces of these agents.

● The final product is tested in a test kitchen to ensure that it has complied with government standards for nutritional content.

Benefits of Wheat Flour

There is a reason why we Indians use whole wheat flour as a staple food product. Some of the benefits of wheat flour include:

● They are high in nutrition and fibre
● It lowers your risk of heart diseases
● Reduce your risk of obesity
● Lower the risk of type 2 diabetes
● They support healthy digestion

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aligned to Samrat India’s policies”.