According to the structural characteristics of wheat grains, wheat peeling and flour milling are to peel off the cortex, which accounts for 70% of the total amount of wheat outside before grinding, leaving a relatively pure "refined wheat", and then grinding and processing it into flour. Because most of the wheat husks have been stripped, and then the wheat skin and endocarp in the wheat grain are separated from the endosperm, which greatly reduces the task of stripping and scraping, reduces the possibility of wheat husks mixed into wheat flour, and provides conditions for maximizing the quality of wheat flour.
2. Cleaning technology and equipment for wheat peeling and flour milling.
The cleaning process of wheat peeling and milling is as follows: raw wheat, sifting, gravity grading destoner, selection, moisture, sifting, spraying, moisture bin, magnetic separator, peeling, air selection, vibrating dampener, magnetic separation, net wheat bin, and IB mill.
|flow sheet of wheat cleaning and flour processing|
|Wheat and the husk|
3. Advantages and disadvantages of wheat peeling and flour making.
Compared with traditional flour milling technology, wheat peeling and flour milling technology has obvious advantages. With the help of machinery, it strips and scrapes wheat, removes several layers of wheat skin with low toughness and strength, and then grinds and extracts wheat flour after stripping and scraping, so as to achieve the purpose of rational and economic utilization of wheat resources. The use of wheat peeling technology and improved flour milling technology can improve the flour-making efficiency. The yield of low ash wheat flour and crude flour in the centrifugal grinding system can be increased by 2%. At the same time, the sand impurities mixed in the outer skin can be removed, and the service life of the tooth roll of the mill can be greatly improved. Since 70% of the wheat husk has been removed in the cleaning stage, the back road flow can be enlarged appropriately and the production capacity can be increased by about 10%.
Because the bran source mixed with wheat flour can be reduced by 60%~70% by stripping wheat husk ahead of time, the ash content of wheat flour can be reduced, and the color of wheat flour can be improved, which lays a foundation for improving the quality of wheat flour. By peeling, wheat not only removes a lot of dust, but also removes bacteria and fungi, and reduces the pollution of wheat flour such as pesticide residues. Using peeler instead of wheat washing, wheat beating, wheat scrubbing and surface treatment simplifies the cleaning process, saves about 80% of water and over 20% of equipment investment. In the process of flour milling, because the wheat cortex has been grinded off before entering the mill, the grinded materials can be classified and sifted to put forward more pure residue and wheat core. Therefore, the slag grinding system can be simplified, and the cleaning facilities with large volume, complex structure and large exhaust volume can be omitted.
After peeling, wheat cracks due to endosperm structure, loosening and holding waste heat, which is conducive to accelerating the penetration rate of water in the endosperm. After adding water for 2 to 4 hours, the purpose of moistening wheat can be achieved. It can effectively adopt the advanced technology of multi-export single-wheel dynamic moistening. The storage capacity of the dynamic wheat is only about 25% of the traditional process, and the wheat spray water process before grinding can be omitted. Peeling off the cortex and retaining the paste layer to the maximum extent is the unique feature of peeling and flour making process. The aleurone layer contains albumin and globulin. When the dough is fermented, they have the properties of enzyme coagulation. Therefore, wheat flour produced by peeling and flouring process is not only nutritious, but also has a larger volume of bread. According to the determination of alpha-amylase by experts concerned, the ratio of damaged starch content of the same raw material after peeling and traditional flour milling is 4:9, which shows that the starch damage caused by peeling is far less than that of traditional flour milling, thus greatly increasing the dough stability time and improving the baking performance of wheat flour.
Because of the special structure of wheat grains, it is impossible to completely peel and process the flour, and the drawbacks of wheat peeling and flour making technology are more prominent. Firstly, there is no obvious separation layer between cortex and endosperm, on the contrary, there is a close combination between them, which obviously can not peel off the cortex like the rice hulling method. At the same time, because the wheat grain has a groin which contains 1/4-1/3 of the whole epidermal tissue and irregularity of its shape, it is difficult to peel off the cortex including the groin without breaking the endosperm. Secondly, because of the uneven peeling, the wheat bark still retains seed coat, especially about 30% of the bran in the wheat groin needs to be removed in the flour road.
Because the exocarp with high fibre content is peeled off, the bran entering the flour is thin and fragile, the Endosperm on the bran is difficult to scrape, and the seed coat with pigments is not peeled off. It is more difficult to separate from wheat flour than the traditional method. Mixing into wheat flour affects the color and ash. Thirdly, peeling and moistening part of the endosperm starch exposed, high viscosity, in case of power failure, public rest, wheat arching and caking which will result in difficulties in inter-flour processing. Because of the short road and strong grinding, the processing accuracy is low. When the Powder yield is less than 4% than that of foreign advanced traditional technology, the total ash content is higher than 0.1%. Because of the distinct structure of wheat and brown rice, it is easy to strip the outer skin of wheat grain, excluding wheat furrows. It is difficult to strip the outer skin completely without harming the endosperm. The control of watering and moistening before peeling still needs to be improved. Some peeling machines will inevitably block the screen, reduce the rate of leaking wheat or peeling, and arching of storage barn. All of these need to be improved by automatic control technology. The change of wheat grain properties after peeling and the subsequent research on the technical characteristics and technological settings of grinding rollers need to be further improved.
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