Traditional Procedure for milling
Traditional procedure for milling is done stone grinder, that is chakki stone. This method results in a 90-95% extraction rate of flour, which retains almost all nutrients of the grain and also it eliminating indigestible parts like cellulose and phytic acid.and carries away minerals.
MODERN MILLING
It is the separation of endosperm from germ to bran and pulverizing the endosperm in to fine powder is called modern milling.
Examples : Aatta flour, maida
Milled wheat consist of 70% wheat flour and 30% byproducts (12%=Bran, 15%=Broken, 3%=Germ)
Modern milling consist of 5 steps
- Receiving and storing
- Cleaning and washing
- Conditioning or tempering
- Breaking and reduction
- Packaging and storage.
1. Receiving and storage
Grains are harvested in optimum condition like optimum moisture, temperature, light and humidity & stored in dry pool place.
2. Cleaning and washing
Wheat first subject to cleaning to remove various type of impurities, together with damage, shrunken and broken kernels which are collectively called screening. Impurities that are adhere to grain are removed by washing or dry scouring which loosen the impurities. Which are then blown away by an air current.
Other impurities in the form of particle unattached to grain are separated by making use of characteristics in which the impurities differ from wheat. This include difference in size, shape, terminal velocity, specific gravity, magnetic and electrostatic property, color and surface roughness.
Various steps involved in screening are :
1. Vibrating screen
This remove bits of straw and other materials. The second screen removes forign material like seeds.
2. Aspirator
It lifts the lighten impurities in the wheat. The stream of grain is directed across screens while it sucks the dust.
3. Disc separator
After the aspirator it moves in to disc separator consisting of disc in a horizontal axis. the surface of disc indented to catch individual grains of wheat. But reject larger or small material.
4. Scourer
The wheat, then moves in to scourer. Scourer is a machine in which beaters attached to central shaft through the wheat violently against the surrounding drums, Buffing each kernel and breaking of the kernel hairs.
5. Magnetic separator
The stream of wheat next passes over a magnetic separator that pulse out iron and steal particles contaminated during harvesting.
6. Washer stone
A high speed rotator spin, the wheat in the water bath. Excess water is thrown out by centrifugal force. Stones dropped to the bottom are removed. Lighter materials float off, leaving only cleaned materials.
3. Conditioning and tempering
Wheat is tempered before the start of grinding. Tempering is the process of adding moisture to dry grain to roughen the bran. It aids the separating bran from endosperm and helps to provide constant controlled moisture and temperature through out the milling. The percentage of moisture, length of socking and time & temperature are 3 important factors in tempering with a different requirement in soft, medium and hard wheat. Dampened wheat is held in bin for 8-24 hours. The outer layer of wheat tends to be brittle and tempering toughen the bran coat to permit more complete separation of endosperm.
With in the kernel tempering , condition of the endosperm, so that floury particles break more freely in milling. 3 reasons for the conditioning of wheat include :
- To toughen the bran, so longer extraction and reduce ash content.
- Moisture migration from bran to endosperm.
- To ensure ease of milling.
There are 3 ways to condition a wheat, they are
- Warm conditioning
- Hot conditioning
- Steam conditioning
Warm conditioning
60-90 minutes at 46C and allow to stand for 24 hours.
Hot conditioning
Similar to warm conditioning, Temperature increases 60C or higher.
Steam conditioning
Add 5% additional water and 30-60 minutes stands. It is efficient, time saving and faster than hot conditioning.
4. Breaking and reduction
The cleaned and conditioned wheat is subjected to milling to separate germ or bran. Here reduce endosperm in to finest flour to extract white flour from wheat. After this process white flour, germ, bran and residual endosperm are obtained. This byproducts are used for animal feeding. Flour milling is achieved by grinding in roller mills. Grinding is carried out by 4 to 5 steps. In each grinding stage endosperm is separated from bran coat. In India different roller mills are worked through out the country.
5. Packaging and storage
The wheat germ in the whole wheat contains high nutritional value like vitamins, minerals, proteins, fat, vitamins. Most of these fats are unsaturated fatty acids, which are easy to oxidize and detrained. Thus effecting the quality of flour. There for whole wheat flour is always stored in dry, cool places with general shelf life of 30 days and it is shorten in summer and slightly longer in other seasons.
FLOUR TREATMENTS
1. Bleaching
Flour contain yellow pigment (xanthophyll) which is not desired for the making of white bread. When the flour is exposed to air, the color of the flour is is bleached by oxidation. When the flour is is stored in bulk, this change is slow, so it is treated with chemicals. Chemicals used for bleaching are chlorine, chlorine dioxide, benzyl peroxide and acetone peroxide.
2. Maturing
The bread making quality of freshly milled flour is increased with storage for 1 to 2 months. This change occur rapidly if the flour is exposed to the action of air. During such aerated storage, enzymatic changes occur. Fats are first hydrolyzed by lipase to fatty acid.
Guys, Thank you for visiting my blog. I hopes you should understand about milling of wheat. If you have any doubts regarding this blog, you can feel free to comment below. If you like my blog, you can check my previous blogs as well. Thank you again. Have a nice day.
0 Comments