MILLING of WHEAT

• Milling refers to the size reduction and separation operations used for processing of food grains into edible form.

Types of millingwater used in both methods but they differ in extent of time and temperature combination

of water treatment

Wet milling-It is a maceration process in which complete dissociation of the endosperm cell contents with the release of the starch granules from the protein network.it is done by steeping wheat for 10 days

• Dry milling- It is a fractionating process in this endosperm merely fragmented into cells.it is done by soaking wheat in water for 8-12 hrs.

Milling separates germ, because it contains lipids that could cause the flour to go rancid. and bran, because it is unappealingly dark

Cleaning the wheat

• Separation –any mixture of solid materials can be separated into different fractions according to their difference in length ,width ,thickness ,density,roughness,drag in moving air,electrical conductivity and other physical properties.

• Aspirator-This device works like a vacuum cleaner. The aspirator sucks up foreign matter which is lighter than the wheat and removes it.

• Disc separator-it 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.

• Scourer-it scrape off dirt and hair by vigorous rubbing action of beaters.

• Magnetic separator-with the help of magnets it removes small pieces of metals.

• Washer stoner-high speed rotors spin the wheat in the water bath.excess water is thrown out by centrifugal force.stones drop to the bottom and are removed. Lighter material float off leaving only the clean wheat.

Preparing the wheat for grinding

• Tempering-moisture is added to aid the separation of bran from the endosperm and to provide controlled amount of moisture and temperature throughout the milling.

Grinding the wheat

• Entoleter-a device with rapidly spinning disks which hurl(Throw an object with great force ) the grains of wheat against small metal pins. Those grains which crack are considered to be unsuitable for grinding and are removed.

• Breaker rollers-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.

• Sifter and Purifier-The product of the breaker rolls passes through metal sieves and air current to separate it into three categories.

• The finest material resembles a coarse flour and is known as middlings or farina. The middlings move to the middlings purifier and the other materials move to another pair of breaker rolls. About four or five pairs of breaker rolls are needed to produce the necessary amount of middlings.

• Larger pieces of the interior are known as semolina. • The third category consists of pieces of the interior which

are still attached to the bran.

• Reducing rollers-Middlings are ground into flour by pairs of large, smooth metal rollers.

• Each time the flour is ground it passes through sieves to separate it into flours of different fineness.

• These sieves are made of metal wire when the flour is coarse, but are made of nylon or silk when the flour is fine.

• By sifting, separating, and regrinding the flour, several different grades of flour are produced at the same time. These are combined as needed to produce the desired final products.

• Yield-maximum 72% wheat is converted into flour.

Processing the flour

• Bleaching agents(in small amounts)are added to flour to make it appear whiter (freshly milled flour is yellowish) and

• Oxidizing agents(oxidizing agents are added to flour to help with gluten development.) are usually added to the flour after milling.

• Reducing agents help to weaken the flour by breaking the protein network. This will help with various aspects of handling a strong dough.

• Aging The flour is matured for one or two months.