Cereals are one of the main food sources for humans. During the production process of cereals, they are inevitably affected by various impurities. These impurities may come from fields, transportation, storage and other links. In food production, a full understanding of the different types of impurities in grains will help to take appropriate cleaning and processing measures to ensure the quality and hygienic safety of the final product.

 1. Large impurities：

Large impurities mainly include larger impurities, such as large particles of soil, stones, etc. These large impurities may cause damage to mechanical processing equipment of grains and require effective screening and removal during the cleaning process.

 2. Medium impurities：

Medium debris is between large debris and small debris, including medium-sized stones, plant residues, etc. Removal of impurities requires the use of appropriate screening and cleaning methods to ensure grain quality.

 3. Small impurities：

Small impurities refer to smaller impurities, such as small particles of soil, silt, etc. Cleaning small impurities usually requires water washing and other methods to ensure that the surface of the grain is clean.

 4. Side by side sand and gravel:

Side-by-side gravel refers to the presence of sand and stones in the grain. These impurities may affect the quality of the grain and food processing equipment and need to be removed through appropriate treatment.

 5. Light impurities:

Light impurities refer to slight impurities in grains, such as slight soil, dust, etc. The removal of light impurities usually requires separation of grains and light impurities through methods such as winnowing.

 6. Magnetic impurities:

Magnetic impurities include magnetic impurities, such as iron filings, magnetic particles, etc. These impurities can be efficiently removed by magnetic separation equipment to ensure food safety.

 7. Exotic grains:

Exotic grains refer to other grain seeds that are different from the main grain and are not expected to exist. Cleaning foreign grains usually requires screening and sorting.

 8. Surface impurities:

Surface impurities mainly adhere to the outer surface of grains, including dust, microorganisms, etc. These microscopic surface impurities can be removed through appropriate cleaning methods.