How flour is produced in a mill?

We love eating tasty snacks like pasta, bread, pastries, cakes, etc. But do you know what's the main ingredient of all these dishes?
Interesting Engineering

We love eating tasty snacks like pasta, bread, pastries, cakes, etc. But do you know what's the main ingredient of all these dishes? Well, it is flour. It's a finely ground powder made from grain or starchy food plants and is mostly used in baking. Though flour can be obtained from various plants, a majority is made from wheat. Dough made from wheat flour is well-suited for making bread as it contains a high amount of gluten, a substance containing strong elastic proteins. 

Interestingly, an average person eats 130 pounds (60kg) of wheat annually in the US. And to meet the demand, the country produces 55 million tons of wheat yearly. Further, in 2021, the wheat flour per capita consumption in the US was 127.3 pounds, and during 2021-22, the production increased to 49 million metric tons, making the country the fifth largest wheat producer. Out of this, 50% is exported, 39% is for human consumption, 10% is for livestock feed, and 4% is for seedlings. 

Now the question is how we get flour. How is it produced on such a large scale?  

This video shows the journey of every single wheat grain, right from growing the farm to its processing to getting served on your plate. 

Farmers grow wheat, but to convert it into flour, it is sent to modern factories or mills. In America, the largest single-site wheat flour mill is North Dakota Mill and Elevator Association in Grand Forks, North Dakota. The complex can produce 2474 tons of finished product per day and store 5 million bushels. But China has produced more than 2.6 billion in the past twenty years and is currently the world's largest wheat producer. 

Once the wheat reaches its destination, i.e., mills, the process begins. 

The first step is to decide which flour will be made as the type, quality, and protein content of wheat determine the category of flour. For example, white flour for bread has high protein and rough texture, cake flour has low protein and soft texture, and all-purpose flour that we use for everything has medium protein content. Therefore, quality tests help select the right wheat type before its processing. 

Secondly, the wheat is cleaned, and all unwanted materials like husk are removed. Then, it is sent to the milling machines, followed by weight measurement, where it's crushed by the steel rollers and passed through a sieve. 

If the grains are too big and cannot pass through a sieve, they pass to another milling machine. However, if some grains are still unprocessed, they are vacuumed and sent back to milling machines, and the cycle repeats. 

The mills grind endosperm, the wheat kernel's soft inner part, to make flour. For this, the bran is removed from the kernel's hard skin, and the seed is churned. This process happens as soon as the wheat kernels enter the first milling machine, and the endosperm is turned into dust. 

Parallelly, an air purifier is used between each milling station to remove leftovers by lifting light bran above the crushed endosperm. The flour is then grounded, sifted, and purified until it is free from foreign matter. 

After all checks, the flour gets ready for packaging and is transported to the market to be cooked into your favorite dishes.