Wheat milling: The milling of wheat consists of the separation of bran and germ from endosperm and reduction of endosperm to fine flour. There are three distinct methods of milling wheat: stone milling, roller milling, and fragmentation milling. Irrespective of the method of milling, all wheat grains will go through two main stages before being milled:
Cleaning: Cleaning of the grain is the main step before milling. The objective is to remove grains of other cereals, seeds from a variety of field weeds, straw, dust and mud from fields, stones, live and dead insects, small rodents and their excreta and small pieces of metal.
The processing stage of cleaning is usually broken down into four separate operations:
(a) Screening: The grain is passed through several sieving operations to remove items both larger and smaller than it. It is then passed along a conveyor belt, where any pieces of metal are removed magnetically and dust, rodent hairs etc. are removed by the use of current air.
(b) Sorting: At this stage, all non-wheat grains such as barley and oats are removed by passing through a range of separators which remove all foreign grains by virtue of their size.
(c) Scrubbing: The grain is passed through scanners which remove any mud or dirt and the beard and bee wing from each grain (the bee wing is the epidermis or outer layer of the bran coatings).
(d) Washing: This operation cleans the grains by removing any fine dust and hairs, and also any stones, which have not been removed previously. After washing the grain is centrifuged to remove excess surface water.