Grains processing systems
Flour milling
Wheat, rye and barley, and sometimes rice, are milled to produce flour.
In flour milling the grain is cracked open to allow separation of the various
components of the grain. The endosperm is retained along with varying amounts
of the bran, aleurone and germ components producing flour of different extraction
rates.
Polishing
In rice milling, the husk is removed to produce brown rice. Pearling or
abrasive milling involves removal of the bran and germ layers to produce white
or polished rice.
Malting
Barley is mainly germinated and dried to produce malt for brewing beer,
making vinegar and whisky and for flavouring breakfast cereals. Barley grains
are milled in the same manner as rice to produce pearled barley grains (mainly
used for soups). Barley can also be milled to produce flour and flakes. Barley
flakes are produced by flattening the grain between rollers. They are used in
the manufacture of breakfast cereals.
Flaking
Oats are usually eaten as a whole grain as it is difficult to separate
the bran from the endosperm. Oats are dried or steamed to inactivate enzymes
which break down the relatively high fat content of oats, and in so doing, prevent
the development of rancidity during processing.
The groats (endosperm) and bran layer are then separated from the hull to produce old-fashioned oat flakes. The groats can be cut, heated with steam and then rolled to make oat flakes. Oat flour is made by grinding steam-heated groats. Oatmeal can be added to white flour for bread-making.
Kibbling or cracking
Cracked or kibbled grains, usually rye and wheat, are cracked and broken
open by passing the grains through a steel-bladed mill. They are sometimes soaked
and then added to bread dough to add texture and flavour.
Maize Milling
Maize is either dry milled or wet milled or the immature maize can be eaten
fresh as a vegetable (sweet corn).
In dry milling, the germ of the corn kernel is removed and the endosperm milled to produce grits, flour, meal and hominy feed. Maize meal is used to make tortillas.
In wet milling, the protein and starch are separated. The starch is used in packaged foods. It is also hydrolysed to produce dextrose, corn syrup solids or glucose for use in food production. Fibre and protein by-products of wet milling are used as animal feed.
The germ is used as raw material for maize oil production by mechanical pressing or by extraction methods.
More than 95% of maize produced in the USA is used to produce a wide range of food ingredients, industrial products, animal feeds and alcoholic beverages.
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