Flour is a finely ground powder prepared from grain or other starchy plant foods and used in baking. The vast majority is made from wheat. Flour has been made since prehistoric times. The earliest methods used for producing flour all involved grinding grain between stones. Many varieties of wheat exist for use in making flour. In general, wheat is either hard (containing 11-18% protein) or soft (containing 8-11% protein). All-purpose flour is made from a blend of soft and hard wheat. Durum wheat is a special variety of hard wheat, which is used to make a kind of flour called Semolina. Semolina is most often used to make pasta. Flour usually contains a small amount of additives.
- Wheat is received at the flour mill and inspected. Samples of wheat are taken for physical and chemical analysis. Then wheat’s are stored in silos.
- Before wheat can be ground into flour it must be free of foreign matter. For this we do cleaning at different steps. At each step, purification the wheat is inspected.
- The first device used to purify wheat is known as a separator. This machine passes wheat and other small particles through the screen while large objects such as sticks and rocks are removed.
- The wheat next passes through an aspirator. The aspirator sucks up foreign matter which is lighter than the wheat and removes it.
- Other foreign objects are removed by disk separator, moves the wheat over a series of disks with indentations that collect objects the size of a grain of wheat. Smaller or larger objects pass over the disks and are removed.
- Another device, known as a spiral seed separator, the oval wheat grains tend to move toward the center of the cylinder while the round seeds tend to move to the sides of the cylinder, where they are removed.
- Other methods used to purify wheat include magnets to remove small pieces metal, scourers to scrape off dirt and hair.
- The purified wheat is washed in warm water and placed in a centrifuge to be spun dry. During this process any remaining foreign matter is washed away.
- The moisture content of the wheat must now be controlled to allow the outer layer of bran to be removed efficiently during grinding. This process is known as conditioning or tempering.
- Cold conditioning involves soaking the wheat in cold water for one to three days. Warm conditioning involves soaking the wheat in water at a temperature of 46°C for 60-90 minutes and letting it rest for one day.
- Wheat of different grades and moistures is blended together to obtain a batch of wheat. At this point, the wheat may be processed in an Entoleter. Those grains which crack are considered to be unsuitable for grinding and are removed.
- Then wheat moves between two large metal rollers known as breaker rolls. These rollers are of two different sizes and move at 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.
- Then air is blown up through the screen to remove the lighter pieces of bran which are mixed with the middlings. The middlings pass through the screen to be more finely ground.
- Middlings are ground into flour, Maida & Semolina by pairs of metal rollers. Each time wheat is ground it passes through sieves to separate it into flour, Maida and Semolina.
15. Then Flour, Maida, Semolina are packed into cloth bags which hold about 0.9, 2.3, 4.5, 11.3, 22.7 or 45.4 kg. For large-scale consumers, it may be packed in metal tote bins which hold 1361 kg, truck bins which hold 20,412 kg or railroad bins which hold 45,360 kg.
A kernel of wheat consists of three parts, two of which can be considered byproducts of the milling process. The bran is the outer covering of the kernel and is high in fiber. The germ is the innermost portion of the kernel and is high in fat.
Bran removed during milling is often added to breakfast cereals and baked goods as a source of fiber. It is also widely used in animal feeds. Wheat germ removed during milling is often used as a food supplement or as a source of edible vegetable oil. Like bran, it is also used in animal feeds.
Syed Mudabbar Hussain Shah
The Author is final year student of B.Sc (Hons.) in Food Engineering, Department of Food Engineering
University of Agriculture, Faisalabad