The classification and testing methods of grain particle size

The classification and testing methods of grain particle size are as follows:

I. National Standards and Testing Methods for Particle Size

‌Current Standard‌
According to Inspection of Grain and Oil - Determination of Particle Size for Flour (GB/T 5507-2008), circular test sieves are used to separate particles by sieving, with the percentage of residue on the sieve determining the particle size.

‌Equipment Requirements‌: Sieve diameter 300mm, rotation radius 50mm, sieving capacity ≥200g, equipped with stainless steel sieves (e.g., CQ10-CQ16, corresponding to mesh sizes 25-107).

‌Procedure‌: After sieving, the residue is weighed, the percentage calculated, and results must meet specific processing grade requirements.

‌Historical Standard Comparison‌
GB 5507-1985 stipulated similar methods, but the 2008 standard updated equipment parameters and sieve models to better suit modern processes.

II. Practical Classification of Particle Size

‌Whole Grains (Coarse Grains)‌

‌Definition‌: Whole grains or minimally processed grains retaining bran and germ, such as whole wheat flour, brown rice, and oats.

‌Typical Indicators‌: Dietary fiber ≥9g/100g (whole wheat flour).

‌Refined Grains (Fine Grains)‌

‌Definition‌: Refined grains retaining only the endosperm, such as white rice and refined white flour.

‌Processing Characteristics‌: Removal of outer structures results in finer particles and significantly reduced fiber content.

III. Impact of Modern Technology

Post-2020 revisions to national wheat flour standards eliminated particle size grading, as light milling techniques now directly extract high-precision endosperm, making particle size an unnecessary quality indicator.
Particle size testing remains relevant for process control and quality verification, but dietary health recommendations now focus more on whole grain retention.

ST114C Round Flour Checking Sieve is researched and developed by our company according to national standard GB/T 5507-2008 "testing of grain and oil, degree of flour thickness". It's a professional instrument for testing degree of thickness of flour and grain. It has the advantages of reasonable structure, steady operation, stable performance, sturdy and durable, easy to operate. And it is the necessary testing equipment used by the Quality and Technical Supervision Bureau, grain and oil quality inspection departments, food processing industry, schools and so on departments need to test the degree of thickness of flour and grain.

In terms of structure, a worm gear with a stable center of gravity and high precision is selected for variable speed transmission, and the plane rotation movement is made through the eccentric connecting rod mechanism, and the pressing rod seat integrated with the tray makes the sieve fixed more firmly.