The Process of Wheat Flour Milling
1. Wheat Cleaning:
After the wheat harvest, get off wheat granule by mechanical, and then bagging storaged into the plants. The wheat granule from anywhere are stored in granaries by elevators and mechanical conveying. The specialized persons select and classify wheat granule to remove impurities which will damage the flour milling machines and affect the quality of flour. The detailed process includes the following:
1. use wheat sieve to remove straw, broken husk, stone, hemp rope and other debris,
2. use wheat selector to get rid of barley, oats, rye,
3. use air separator to remove dust, shell, bran and other light impurities according to different specific gravity,
4. use magnetic seperator to select the metal material out,
6. use dry type machine to remove the dust by friction,
7. use wheat washer to clean the tuft and the attached impurities, especially the material in the abdominal ditch of wheat granule. If there is smut in wheat, need add lime to clean the wheat grain.
In order to make the followed flour milling work more smoothly and improve the extraction rate, we need water and suit temperature well for flour grinding according to different types of wheat grain. Thisprocess is known as conditioning. As to soak the purified wheat granule in water for 18 to 72 hours, the wheat grain will become flexile which bran and grain can be separated easily. Wheat granule are easy to be grinded. The malt become flat, screened out easily. The way to water is that spray out water at several times. For the same purpose, we need to condition the wheat grain into suitable temperature. First heated wheat grain to 42 ~ 45 ℃, and then cool them to the temperature same as room. At last, clean wheat grain, get granule separated from the husk and sent to milling.
3. Flour Grinding Operations:
After fine pick, water and temperature condition, the wheat grain can be made bran, endosperm and malt separated to grinding operation. Becasue the endosperm and bran combined very close, the separation of them should be careful to scrape clean and minimize the damage in avoid of waste. The whole flour milling process is divided into coarse grinding, purification and reduction. Coarse grinding is by using two serrated steel roller shafts rotating running in opposite direction at different speeds, with upper roller faster than downside roller 2.5 times. Split the scarfskin of wheat gently and get out of coarse granule and bran in flat and big flaky shape. Through purification and keep the pure endosperm granule by fine separator accroding to different proportions. The light bran will float with injected wind power, the remaining heavier endosperm powder go to the reduction stage. After crush the endosperm by smooth roller flour mill, ground into powder. The crushed flat malt get out after germ separator (The process is what stone grinder can not work). Fine powder can be classified into different grade of flour by multi-storey rotary plansifter. The coarse granule sent to grind again (or use as bran). The fine particles can be cheap flour. The coarse debris sent to further processing to remove malt and fine debris, the fine debris can be fine ground into top quality flour.