First-class rice: the back furrow has no skin, or it has skin and no grain, and more than 90% of rice embryo and grain surface cortex have been removed. Because the first-class rice basically removes the cortex and aleurone layer of brown rice, and the crude fiber and ash content are very low, the rice has high swelling property, high rice yield and good edible quality.
Second-class rice: The percentage of husk, rice embryo and surface control cortex removed from the back ditch is lower than that of second-class rice, and the rice yield and digestion and absorption rate are slightly lower than that of first-class rice.
Third-grade rice: there is skin on the dorsal groove, and less than one-fifth of the grain surface cortex remains over 80%. The ash and crude fiber in rice are high, and the rice yield and digestibility of "information source: adjacent grain m110" are lower than those of first-class rice and second-class rice.
Four-grade rice: more than 75% of the rice furrows have skin, and the residual cortex on the surface of rice grains does not exceed one third. Because a large number of cortex and aleurone layer remain in rice, the content of coarse grains and ash in rice increases.
Extended data:
The National Standards Committee issued 23 new and revised national standards for rice, which changed the grade of rice products from four-level modulation to three-level, reduced the maximum limit of impurities and other indicators, and changed the processing accuracy of the original national standards from "first-level" and "second-level" to "fine grinding" and "third-level" to "suitable grinding".
References:
People's Daily Online-National Standards Committee released 23 new national standards? Horizontal modulation of rice products