According to the national standards, rice in China is divided into three categories according to the classification method of rice: indica rice: including early indica rice and late indica rice; Japonica rice: including early japonica rice and late japonica rice; Glutinous rice: including indica rice and japonica rice.
All kinds of rice in China are mainly classified according to the processing accuracy. Processing accuracy refers to the peeling degree of brown rice when it is processed into polished rice. Different grades of rice have different degrees of peeling during processing. The national standard GB 1354-86 divides all kinds of rice into four grades. As far as processing accuracy is concerned, top-grade rice: there is skin on the back ditch, and the grain rice skin is basically removed, accounting for more than 85%; Standard first-class rice: there is skin on the back ditch and no more than 1/5 on the grain surface, accounting for more than 80%; Standard second-class rice: there is skin on the back ditch, and the skin on the grain surface does not exceed 1/3, accounting for more than 75%; Standard third-class rice: there is skin on the back ditch and no more than 1/2 on the grain surface, accounting for more than 70%.
The classification of all kinds of rice should also refer to the following indicators:. ① Imperfect grains: including immature grains, moth-eaten grains, diseased grains, moldy grains and intact brown rice grains without peeling at all; (2) Impurities: including bran powder, minerals (sandstone, cinder, bricks and other minerals), barnyard grass grains with shells, rice grains and other impurities (rice grains, foreign particles and other substances with no edible value). The total allowable impurity content of each grade of late japonica rice is lower than that of other types of rice.
The national standard also determines (1) yellow rice (grains with yellow endosperm and obviously different color from normal grains) contained in various kinds of rice; ② Broken rice: including big broken rice and small broken rice; ③ moisture; (4) Color, aroma and taste are required (referring to the inherent comprehensive color, aroma and taste of rice), but for the same variety and different grades of rice, the above four indicators are equivalent.
For rice that can't meet the grade quality requirements, it should be degraded. At present, the rice sold in China's grain market is mainly standard first-class rice and super-class rice.