The quality of rice in China is determined according to the processing precision. The processing precision refers to the degree of rice back groove and grain skin. According to the provisions of the national standard Rice GB1354-86, rice is divided into four grades according to its processing accuracy, namely, special grade, standard grade I, standard grade II and marked grade III.

The classification of rice is closely related to the classification of rice. The domestic and international markets are generally divided into three categories of indica rice, japonica rice and glutinous rice according to grain shape and quality. It is described as follows:

(1) Indica rice
Indica rice refers to the rice made from non glutinous rice of indica type. The shape of rice grains is slender or oblong, and the length of the elder is more than 7 mm. After cooking, the rice yield is high, the viscosity is small, the rice quality is relatively fragile, and it is easy to break during processing. The cross section is oblate, and the color is white and transparent, but there are also translucent and opaque. According to the rice harvest season, it can be divided into early indica rice and late indica rice. Early indica rice grains are wide, thick and short, pink white, with large white belly, more flour, fragile texture, less viscosity than late indica rice, and poor quality. The grain of late indica rice is long and thin, slightly flat, with fine tissue, generally transparent or translucent, small belly white, many hard grains, high oil content, and good quality.
In the international market, there are long grain rice and medium grain rice according to the length of indica rice grains. Long grain rice is thin and long, the ratio of length to width is generally greater than 3, and it is generally waxy white transparent or translucent. It is crispy and oily. It is soft, tough, strong but not sticky after cooking. It tastes delicate and delicious. Qimei, Simiao and Blue Crown produced in Guangdong Province of China are all long grain rice.
Medium grain rice is round and slightly fatter than long grain rice. The ratio of length to width is between 2 and 3. It is generally translucent, with white belly and more powder. It is loose after cooking and tastes rough. The quality is not as good as long grain rice. Most of the rice produced in Hubei, Guangxi, Jiangxi, Sichuan and other provinces in China belongs to medium grain rice. Zines in the United States is also medium grain rice.
According to the length of rice, Thai rice standards can be divided into four types: super long (more than 7 mm), long (6.6~7 mm), medium (6.2~6.6 mm) and short (less than 6.2 mm).

(2) Japonica rice
Japonica rice is milled with japonica non glutinous rice. Rice grains are generally oval or round. The rice grains are plump and plump, the cross section is nearly round, the ratio of length to width is less than 2, the color is waxy white, transparent or translucent, the texture is hard and tough, the viscosity after cooking is large, soft and delicious, but the rice rate is low.
Japonica rice is divided into early japonica rice and late japonica rice according to the harvest season. Early japonica rice is translucent, with large white belly, few hard grains and poor rice quality. Late japonica rice is white or waxy white, with small white belly, many hard grains and excellent quality.
Japonica rice is mainly produced in North China, Northeast China and South Jiangsu. Xiaozhan rice and Shanghai white japonica rice are excellent japonica rice. The yield of japonica rice is much lower than that of indica rice.

(3) Glutinous rice
Glutinous rice, also known as glutinous rice, is milky white, opaque, transparent after cooking, sticky, and small in swelling. It is generally not used as a staple food, but is mainly used for making cakes, dumplings, Yuanxiao, etc., and as a raw material for wine making.
Glutinous rice can also be divided into indica rice and japonica rice. The grain shape of indica and japonica rice is generally long oval or slender, milky white and opaque, and some are translucent and sticky, while japonica glutinous rice is generally oval, milky white and opaque, and some are translucent and sticky, and the rice quality is better than that of indica and japonica rice.

Indica rice and japonica rice are particularly important among the above three kinds of rice, especially the trade volume of indica rice. Southeast Asia, Africa and Latin America mainly consume indica rice, especially long grain rice. People in Japan, Korea, Italy and other countries like to eat japonica rice. In Europe, both indica and japonica rice are consumed.



In the international market, according to the degree and method of rice processing, rice is classified as follows:

(1) Brown rice
After being processed, the husk of rice is only ground to brown rice, which is a complete fruit. Brown rice can be eaten only after further processing. The trade volume of brown rice is small.

(2) White rice
After the brown rice is further processed, the cortex and embryo (i.e. fine bran) are removed, and basically only the endosperm is left, that is, white rice or rice we usually eat. There are four grades of rice in China: special grade, first grade, second grade and third grade.
Thai white rice refers to non waxy brown rice that has been processed and milled. There are 11 levels, including 100% Grade A, 100% Grade B, 100% Grade C, 5%, 10%, 15%, 20%, 25% (above), 25%, 35% and 45%.

(3) Steamed millet
Steamed rice is rice made by soaking rice in hot water, heating it with steam and drying it, and then milling it. Steamed rice has higher rigidity and yield than ordinary rice; The nutrients of the husk infiltrate into the rice after being soaked in water to improve the nutritional value of the rice; It is easy to cook, but the rice is not generally accepted by consumers because it turns yellow and has a smell of oil after being processed.

(4) Broken rice
The part of rice that is crushed during processing is called broken rice. Thai broken rice is divided into white broken rice and small white broken rice.