GB/T 5494-2026Inspection of grain and oils - Determination of impurities and defective kernels in grain and oilseeds (English PDF)

4.1.1 Balance. Sensitivity

0.01 g,

0.1 g.

4.1.2 Grain Sieve. Meets the requirements of GB/T 36091.

4.1.3 Electric Sieving machine. Rotate clockwise and counterclockwise for 1 min each, with the speed of 110 r/min ~ 120 r/min.

4.1.4 Sample divider. Meets the requirements of LS/T 3545.

4.1.5 Dehulling equipment. Does not damage dehulled kernels or rice (such as peanut kernels, brown rice).

4.1.6 Sub-sampling plate

4.1.7 Analytical disc.

4.2 Lighting requirements The operation shall be carried out under diffused sunlight or a standard light source conforming to GB/T 22505. As per the method in 4.4.1.1.1, assemble the sieve layers; pour in the specimen; and cover it with the sieve cover. Then place the sieve on a glass plate or smooth tabletop; and sieve with both hands at a speed of 110 r/min to 120 r/min, rotating clockwise and counterclockwise for 1 min each. The sieve rotation range shall be controlled to increase the sieve diameter by 8 cm to 10 cm. The post-sieve operation is the same as in 4.4.1.1.1.

4.4.1.2 Inspection of impurity content from large samples According to the provisions of 4.3, take the sample to the large sample mass (m) specified in Table 1, accurate to

0.1 g. Perform screening twice according to the screening method specified in 4.4.1.1.1 or 4.4.1.1.2 (four screenings for extra-large grain and oilseeds). Then pick out the large impurities on the sieve layer and combine them with the undersize material from the lower sieve; weigh it (m1), accurate to

0.01 g; and calculate according to Formula (1). If large impurities are attached to grains, the grains shall be returned to the large sample. For example, corn cobs shall be hulled and the kernels removed, classifying them as impurities. For paddy rice samples, a 1.5mm-diameter round-hole sieve shall be placed under a 2.0mm- diameter round-hole sieve. Samples shall be taken according to the provisions of

4.3 to the large sample mass (m) specified in Table 1, accurate to

0.1 g. The samples should be screened twice according to the screening method specified in 4.4.1.1.1 or 4.4.1.1.2.Large impurities on the 2.0mm-diameter round-hole sieve shall then be removed. Whole grain rice and whole grain brown rice remaining on the 1.5mm-diameter round-hole sieve shall be removed and added to the rice sample on the 2.0mm-diameter round-hole sieve. The undersize material from the 1.5mm-diameter round-hole sieve and other materials remaining on the 1.5mm-diameter round- hole sieve, along with the large impurities on the 2.0mm diameter round-hole sieve, shall be weighed together (m1), accurate to

0.01 g, and calculated according to Formula (1).

4.4.1.3 Inspection of impurity content from small samples From the specimens tested for impurity from large samples, take a sample according to the provisions of

4.3 to the small sample mass (m2) specified in Table 1, accurate to

0.01 g. Pour it into the analytical dish; pick out the impurities according to the product standard; weigh it (m3), accurate to

0.01 g; and calculate according to Formula (2).

4.4.1.4 Inspection of inorganic impurity content Pick out the inorganic impurities from the picked-out small sample impurities; weigh it (m4), accurate to

0.01 g; and calculate according to Formula (4). NOTE

4.4.2 Inspection of impurity and defective kernel content from rice

4.4.2.1 Inspection of undersize material (bread crumbs) Take approximately 200 g (m') of sample, accurate to

0.1 g; and place it twice into a

1.0 mm diameter round-hole sieve. Sieve according to the sieving method specified in 4.4.1.1.1 or 4.4.1.1.2.After sieving, gently tap the sieve to allow the undersize material (bread crumbs) to fall to the bottom. After all specimens have been sieved, brush off the undersize material (bread crumbs) remaining on the bottom of the sieve; combine and weigh (m1'), accurate to

0.01 g. Pour the oversize sample into an analytical disc.

4.4.2.2 Inspection of inorganic impurity content From the inspected undersized material (bread crumbs) specimen, separate and weigh the inorganic impurities (m2'), accurate to

0.01 g. Separate and weigh the organic impurities (m3'), accurate to

0.01 g. NOTE. The inspection of mineral content refers to the same procedure as the inspection of inorganic impurity content.

4.4.2.3 Inspection of other impurity content Separate and weigh the other impurities (m4') according to the product standard, accurate to

0.01 g. Calculate the content using Formula (11). NOTE

1.Foxtail millet grains are removed from millet; proso millet grains from proso millet rice; Japanese millet grains from Japanese millet rice; sorghum husks from sorghum kernel; quinoa grains from quinoa rice, etc. NOTE

2.This test is performed when specified in the product standard.