There are two ways to mill rice, namely: chemical and mechanical methods. In the chemical method, the first is solvent extraction and rice milling. It starts with rice bran oil to soften the brown rice skin layer, and then it is lightly whitened. During the rolling process, it is sprayed with rice bran oil and n-hexane mixture continuously to form “fine rain”. Moisturizing, ultimately low-temperature white rice, by-product rice bran oil and edible defatted rice bran. Another method of chemical method is enzymatic hydrolysis, which uses the "biocutter" of fibrin, which cuts the cortical fiber into short and loose shelves, and can remove the brown rice cortex without grinding, and complete the task of rice making. However, the design ideas of chemical methods are expensive, costly, and economically inefficient, and have not been promoted and applied.
In China, the mechanical method has been widely used to produce rice, which is peeled and whitened by the mechanical force generated by the special Rice mill machinery (rice mills machines). If the force is mainly pressure, the form of peeling is regarded as rubbing off; if peeling is achieved at high speed, the form of peeling is converted into grinding. In general, the two characteristics co-exist in the device, but it seems to be weak in different models. The rubbing of the iron mill is stronger than the grinding, and the grinding of the rice mill machinery exceeds the rubbing.
The effect of rubbing comes from the relative movement between the walls and between the grains. When the binding force between the cortex and the endosperm is less than the frictional force, the cortex will be pulled off and erased, and the brown rice will be white. However, when the friction is not greater than the structural strength of the endosperm, the rice is intact. In order to achieve the best of both worlds, it is suitable for the processing of brown rice with high strength and soft skin. For brown rice with weak strength, it is easy to cause broken rice. The force of milling mainly comes from the high-speed rotation between the inner roller and the outer cylinder and the sand blade of the surface diamond grains. The brown rice is continuously crushed as a sandwich in the chaotic travel, causing the cortex to rupture and fall off, and the brown rice is whitened. The characteristics of this whitening are: low pressure, high linear velocity; large centrifugal acceleration, which is suitable for the processing of brown rice with weak strength and hard surface. Although the broken rice is small, the beige color is dark, the light is not smooth, and the accuracy is not easy. Evenly.
The two kinds of whitening have their own advantages. In practice, most of them are used in two kinds of whitening, and they are used to avoid shortness to achieve better results. For example, the horizontal mill machinery used in China is a mixed whitening machine with high rice yield, less broken rice, large output and beautiful beige color.
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