Germ rice refers to rice that has a germ retention rate of more than 80% that meets the requirements of rice grades. Rice embryos account for 2% to 3.5% of the weight of rice grains and are the nutrient essence in rice. Foreign experts call it the source of nutrition. The protein and fat in the rice embryo are all above 2%, and it also contains a variety of vitamins and trace elements that the human body needs. The amino acid composition is relatively balanced, and is a full-price protein. 70% to 80% of fats in rice germ oil are unsaturated fatty acids, and natural vitamin E is as high as 2 to 3 mg/g. It also contains plant sterols, oryzanol and other special ingredients. Long-term consumption of germ rice can effectively prevent various diseases such as beriberi and cheilitis, which has caused widespread concern at home and abroad. Japan began researching germ rice and germ rice machines in the 1930s. Now germ rice has been eaten by most people in Japan. The REMTA-type embryo-milling machine produced by Sazuma Manufacturing Co., Ltd. keeps rice embryos at a rate of over 80%. The research on germ rice in China began in the early 1990s. The nutritional value of germ rice is unknown to most people. There is no producer of germ rice. A small number of grain processing companies imported germ rice from Japan and other countries are expensive. The single price is about 300,000 RMB, and the degree of automation is high. Once failure occurs, it is difficult to repair in time. Therefore, the introduction of equipment to engage in germ rice production is not suitable for Chinaâ€™s national conditions. .
1 Principle of processing of germ rice The embryo is located at the lower end of the belly of brown rice and the tissue is loose. Germ and radicles are connected by a very short embryonic axis and their attachment to the endosperm is weak. When the brown rice is repeatedly peeled and peeled in the whitening room of the rice machine, the shedding of the germ in the rice grain is increased several times, and the higher the processing precision is, the more the rice embryos fall off. Therefore, the processing of germ rice should follow the following principles.
(1) Quick light grind, multi-channel white;
(2) The rice mill roller adopts the combination of sand and iron, the sand roller grinds the road to open rough, and the iron roller wipes off the main whitening effect;
(3) Using blast air milled rice, negative pressure cited.
2 Defects of Germ Rice Produced by Common Rice Mills
2.1 Horizontal milling machine Rice horizontal rice milling machine is affected by the self gravity of the rice grain fluid during the whitening process. The density of the grain fluid in the cross section of the whitening chamber is not uniform, and the density of the rice fluid in the lower half of the milling chamber is high. The half density is small, therefore, the whitening pressure of the rice grains in the lower part of the whitening room is very large, and it is easy to produce broken rice. In the upper part of the grinding room, the rice grain density is small and the gap between the rice grains is large, and the roller rotates at high speed. Under the action of the roller, the rapid collision between the rice grains and the white room components also easily generates broken rice, especially the small broken rice and rice bran produced. The rice processed by this type of machine almost completely sheds the germ.
2.2 The vertical self-gravity of the rice mill in the vertical rice mill accelerates the speed of the rice through the whitening chamber. The short time of the rice passing through the whitening chamber results in a slightly weaker grinding action on the rice. In the multi-channel whitening process, the frequency of shearing and bending of rice embryos increases, which is extremely unfavorable to the preservation of embryos.
2.3 Grinding pressure adjustment Whether horizontal or vertical rice machine, the white pressure adjustment is mostly controlled by heavy pressure gate. Because the quality of heavy weight is non-continuous, adjustment of the white pressure is difficult to achieve precise and continuous adjustment.
3 Germ picking machine process selection
3.1 The use of sand first and second iron mills The vertical mill rice is transported by the conveyor into the grinding and grinding room. Under the action of the fast rotating grinding wheel, the friction between the rice grains and the rubbing layer are peeled off. The process is characterized by rapid light grinding, low rolling pressure and slight damage to the embryo. The whitening pressure of rubbed white room is relatively large, the speed is relatively low, and the pressure and friction are used to make the deformation of the barium layer finally separated from the endosperm to achieve the purpose of whitening.
3.2 rice in the white room in the direction of the flow of rice in the milling room white flow against the direction of gravity, under the action of the conveyor and the weight of rice, the rice is full of the entire grinding chamber, the friction between the rice to enhance the role of rice and sand rollers, mechanical parts The collision is relatively weak, which is conducive to the retention of the embryo. In addition, the rice grain spirals up through the diversion ring and enters the rubbing and whitening chamber in the grinding chamber. The direction of flow is the same as the direction of gravity. The rolling of rice grains is more than that of turning, and the bending and shearing forces are more Small, the reservation of the embryo is very favorable.
3.3 Uses 4 to 5 mills and air blasting to grind white and reduce the number of white pits. The large grinding pressure will increase the whitening efficiency, but the broken rice is more, and the remaining embryo rate will naturally decrease; Smaller, the distribution rate of rafts is better, but the number of multi-channels is too much, the efficiency is low, and the number of embryo damages increases. Combining the technology of similar foreign products, it is ideal to use 4 to 5 mills. The use of air-blown whitening helps to reduce the temperature and moisture of the rice and increase the cross-section hardness of the rice grains. At the same time, the rice grains can be rolled evenly to avoid over-grinding locally and to retain the embryos. The rice milling process described above meets the processing characteristics of the germ rice and achieves the optimum combination of factors for increasing the rate of embedment.
4 The structure and regulation of germ rice mill
4.1 germ rice machine structure According to ergonomic principles, this machine is designed for vertical, fully enclosed. It mainly consists of feeding system, grinding and grinding system, rubbing and whitening system and fans. Figure 1 shows an assembly drawing.
4.2 Embryo rice machine regulation
4.2.1 Flow regulation The flow rate of rice grain into the white room is measured by a flow meter. This method stabilizes the flow of rice grains at a certain value, creating favorable conditions for the adjustment of the grinding resistance and the rubbing resistance.
4.2.2 Grinding Impedance Adjustment Grinding Grinding pressure is large, whitening efficiency is high, and the rate of embedment is low. When the grinding pressure is small, the embryo rate is high. The size of the grinding resistance depends on the size of the throttle opening. The throttle ring is connected by a spring and a rotating pull rod. By rotating the pull rod, the opening amount of the throttle ring can be precisely adjusted, thereby achieving the adjustment of the grinding resistance.
4.2.3 Elimination impedance adjustment Erosion resistance is adjusted by the outlet pressure gate. The normal rice machine adjusts the pressure in the white room by increasing or decreasing the weight. The machine controls the positive and negative rotation of the stepping motor by a programmable controller. The stepper motor drives the grain guide cone to move up and down to control the outlet flow rate, so that the grinding pressure can be continuously and accurately adjusted. Flow, grinding pressure and rubbing pressure are closely related to the effect of leaving the embryo rate. Establishing a stable relationship between the three is the key to determining the rate of leaving the embryo. The adjustment of the machine can easily meet this requirement.
5 Conclusion Based on the whitening principle of germ rice, a reasonable whitening process was determined. In the actual production test of the vertical germ rice mill designed for more than 2 months, the rate of retained embryo has been stable at more than 80%, which has met the design requirements. .
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