Research progress of wheat peeling and flour making technology
The core of the peeling and milling process is peeling, and the key to this process is the peeling machine. The adoption of a new layered peeling flour making process can enable small and medium-sized mills to achieve the high flour yield, low bran star and low ash effect achieved in the traditional flour making process of large and medium-sized mills with less investment and little change in the process.
The wheat peeling machine developed in China, using the combination of mechanical force and aerodynamic principle, the gradual pressure on the wheat skin gradually increase the method of rubbing force, so that the wheat skin and matrix displacement to achieve the purpose of the whole piece is torn and rubbed off. At the same time, the wheat grains are rotated in three dimensions by high speed airflow to achieve uniform peeling, i.e. the theory of "multi-pressure rotary peeling" is adopted for peeling and flour making. After the wheat peeling machine has been put on the market, the production operation of dozens of flour mills for 2-3 years has fully demonstrated its unique advantages of low power consumption, low temperature peeling and high peeling efficiency. The research result of "Multi-press spin peeling" has been awarded the Chinese patent and passed the expert technical achievement appraisal organized by Shaanxi Provincial Department of Science and Technology, and was highly evaluated by the senior experts in the industry. The peeling method of "multi-pressing rotary peeling" has a very different principle and structure from all kinds of peeling machines developed at home and abroad by using the principle of rice milling, which has unique technical characteristics in terms of electricity consumption, peeling effect, peeling efficiency, peeling uniformity, temperature rise, breaking rate, fullness of peeled seeds of mixed wheat, uniformity of size and adaptability to production environment. There are unique technical characteristics.
The DHA vertical peeler was introduced by Ocrim, Italy, at the 2006 International Flour Millers Association Annual Meeting and Exhibition, and can be used to peel a variety of different grains and legumes. A distributor feeds a rotor, which consists of an angled grinding impeller plus 6 cylindrical impellers. There are 4 adjustment devices on the outside to reduce the thickness of the processed material in order to achieve uniform peeling. Since its introduction in 2006, 30 peelers are now in operation in 7 mills worldwide, including mills in North Africa and the Mediterranean Gulf region, and two new Italian hard wheat flour mills have also installed Ocrim peelers. In Japan, the Peritec peeling and milling process uses a VCW type wheat peeler, which works by controlling the grinding pressure in the peeling section to rub and scrape the wheat hulls, and the peeling rate is adjustable from 5% to 15%; then it enters the polishing section to remove the bran fragments attached to the wheat by rubbing and polishing.
The current peeling machine is still unable to remove the skin of the wheat ventral groove part, can be adjusted by adjusting the grinding roller parameters of the peel mill, mainly the parameters of the ⅠB mill so that this part does not affect the quality of flour. The test shows that for hard wheat, the grinding tooth angle is 40°/70°, the grinding roller arrangement is D-D, and the grinding roller rolling distance is 0.7 mm; for soft wheat, the grinding tooth angle is 30°/70°, the grinding roller arrangement is D-D, and the grinding roller rolling distance is 0.7 mm, and the peeling and milling process has the best effect. The position of the peeling machine in the process is also very important. Through measurement and analysis, and verification by production practice, it is found that the best process position of the wheat peeling machine is before the air suction separation, and after the second water wetting wheat.
With the increase of peeling rate, the hardness of wheat tends to decrease, and the relationship between them is non-linear; research shows that the peeling rate is less than 8%~10% can effectively avoid the phenomenon of over-milling. The optimum hulling rate of wheat is 5%. If the peeling rate is too high, the endosperm of wheat will be scraped and the wheat will not be milled.
If the peeling rate is too high, the endosperm of wheat will be stripped and the flour yield will be reduced; if the peeling rate is too low, it will have a negative impact on the flour quality and the tensile area is small.