There are two methods of milling rice, namely, chemical and mechanical methods. Chemical method, led by the solvent extraction of rice, it began in the rice bran oil softening rice cortex, whitening and mild, milling process with rice bran oil and n-hexane mixture continuously spraying, forming "drizzle" moisture, resulting in low temperature rice lossless, the by-product of rice bran oil and edible defatted rice bran. Another means of chemical method is enzymatic, it uses fiber enzyme this "biological tool", the cortical fiber cut short, apart, without milling can make rice cortex off, complete the rice production task. However, the design idea of chemical method has not been popularized and applied because of its large investment, high cost and poor economic returns.

Rice is produced by mechanical method in our country so far. It is made of special equipment (rice mill) to peel and grind white. If the force is mainly pressure, the form of peeling is regarded as wiping away; if the peeling is realized at high speed, the form of peeling is converted into grinding. Generally speaking, the two characteristics coexist in the equipment, but only in different models. The utility model has the advantages that the iron roller mill is stronger than the grinding machine, and the grinding process of the emery roller mill is more than the wiping off.

The action of wiping off comes from the relative movement between the particles and between the particles. When the adhesion between the cortex and the endosperm is smaller than the friction force, the cortex will be pulled and erased, and the brown rice will be fair and fair. However, this friction force is not greater than the structural strength of the endosperm to ensure the integrity of the rice grains. In order to achieve the best of both worlds, it is suitable for high strength, soft brown cortex processing, for the strength of fragile easily broken rice. The grinding force mainly comes from the high speed rotation between the inner roll and the outer cylinder and the sand blade of the surface emery particle. The brown rice is used as interlayer and is constantly crushed in the chaotic movement, so that the skin layer breaks and falls off, and the brown rice is milled white. It is characterized by its low pressure, high wire speed and large centrifugal acceleration. It is suitable for the processing of rough brown rice with weak strength and hard surface

Although rice is little, beige is dark, not bright and clean, and easy to appear uneven precision.

Two kinds of grinding each have their own advantages, in practice, most of the two kinds of "white" and "use", to avoid weaknesses, in order to achieve better results. For example, the sand roller rice mill used in China is a mixture of milling machine, a meter high, high yield, little broken, beautiful beige.