This standard specifies the terms and definitions, principles, instruments, sample preparation, determination steps, result calculation and expression for the determination of wheat hardness by the hardness index method. This standard is applicable to the determination of wheat hardness. GB/T 21304-2007 Determination of wheat hardness by the hardness index method GB/T21304-2007 Standard download decompression password: www.bzxz.net
This standard specifies the terms and definitions, principles, instruments, sample preparation, determination steps, result calculation and expression for the determination of wheat hardness by the hardness index method. This standard is applicable to the determination of wheat hardness.
This standard is proposed by the State Administration of Grain
. This standard is under the jurisdiction of the National Technical Committee for Grain and Oil Standardization. This standard
was drafted by: Henan University of Technology, Wuxi Grain Machinery Factory. The
main drafters of this standard are: Zhao Renyong, Tang Daowu, Yang Hongwei, Cheng Shunchang, Zhao Xiaofeng, Bi Yanlan, Yu Hong, Fan Lu, Sun Hui, Jiang Rengen, Li Yuzhou.

The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties that reach an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard.
GB5491 Sampling and subsampling method for grain and oilseed inspection
GB/T5497 Determination of moisture content in grain and oilseed inspection
LS/T3704 Technical conditions and test methods for wheat hardness index tester

ICS67.060
National Standard of the People's Republic of China
GB/T21304—2007
Determination of wheat hardness
Hardness index method
Determination of wheat hardness--Hardness index method2007-11-23 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
2008-02-01 Implementation
This standard is proposed by the State Administration of Grain.
This standard is under the jurisdiction of the National Technical Committee for Grain and Oil Standardization. The drafting units of this standard are Henan University of Technology and Wuxi Grain Machinery Factory. GB/T21304—2007
The main drafters of this standard are: Zhao Renyong, Tang Daowu, Yang Hongwei, Cheng Shunchang, Zhao Xiaofeng, Bi Yanlan, Yu Hong, Fan Lu, Sun Hui, Jiang Rengen and Li Yuzhou.
1 Scope
Determination of wheat hardness
Hardness index method
GB/T21304—2007
This standard specifies the terms and definitions, principles, instruments, sample preparation, determination procedures, result calculation and expression for the determination of wheat hardness by the hardness index method.
This standard applies to the determination of wheat hardness. 2 Normative references
The clauses in the following documents become clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version shall apply to this standard. GB5491 Grain and oilseed inspection sampling and subsampling method GB/T5497 Grain and oilseed inspection moisture determination method LS/T3704 Technical conditions and test methods for wheat hardness index tester 3 Terms and definitions
The following terms and definitions apply to this standard. 3.1
Wheat hardness
The ability of wheat grains to resist deformation and breakage under external forces. 3.2
wheat hardness index
Wheat hardness index
The mass fraction of the sample remaining on the sieve when the wheat sample is crushed under specified conditions is expressed as HI. The larger the hardness index, the higher the wheat hardness, and vice versa. 4 Principle
Wheat with different hardness has different resistance to mechanical crushing. When crushing, wheat with harder grains is not easy to be crushed into powder, while wheat with softer grains is easy to be crushed into powder. When the sample is crushed under the specified conditions, the more sample remains on the sieve, the higher the hardness of the wheat, and vice versa, the lower the hardness of the wheat.
5 Instruments
5.1 Wheat hardness index tester: should meet the requirements of LS/T3704. 5.2 Balance: sensitivity 0.01g.
6 Sample preparation
6.1 Sampling and sub-sampling: in accordance with GB5491. 6.2 Sample pretreatment: Place the sample in the same working environment as the hardness index tester, so that its temperature is basically consistent with the ambient temperature, and the ambient temperature is controlled within the range of 5℃～45℃. The moisture content of the sample should be controlled within the range of 9%15%. If it does not meet the requirements, the sample should be placed in a low or high humidity environment for an appropriate time according to its moisture content to adjust its moisture content to the specified range. Then, remove impurities and broken grains from the sample.
GB/T21304—2007
6.3 Moisture determination: According to the provisions of GB/T5497, determine the moisture content of the sample and enter the measured value into the instrument weighing and calculation system. 7 Determination steps
7.1 Instrument inspection
Before each measurement, the screen of the hardness index tester should be checked. If the mesh of the screen is damaged, replace it in time. After the new screen is used several times, the two ends are slightly concave, which is a normal phenomenon.
When the instrument is not used for a long time or used continuously for more than 120 times, use the "wheat hardness index standard sample" to check the instrument according to the provisions of the instrument manual. Instruments that do not meet the specified requirements shall not be used for sample measurement. 7.2 Weighing of the receiving hopper and screen system
Before each measurement, the mass of the receiving hopper and screen system (including the screen and screen seat) should be weighed and entered into the instrument weighing and calculation system. If the instrument does not have a weighing and calculation system, it should be deducted when calculating the results. 7.3 Instrument Preheat the instrument
Use about 25g of wheat and operate according to 7.4.2 to 7.4.4. Test the machine 5 times 7 times to preheat the instrument. Clean the instrument's crushing system, receiving hopper, screen system, etc. and set aside. 7.4 Determination
7.4.1 Accurately weigh the prepared sample (25.00±0.01)g. 7.4.2 Open the end cover of the hardness tester, align one cavity (the concave part between the two knives) of the crushing system rotor upwards with the feed port, and close and lock the end cover. || tt||7.4.3 Open the cover of the feed hopper, pour all the weighed samples into the feed hopper, and close the cover of the feed hopper. 7.4.4 Turn on the tester, and the sample will be crushed for 50 seconds before it stops automatically. 7.4.5 After the instrument stops, open the end cover, carefully take out the receiving hopper and the screen system, and clean the residue on the screen according to the provisions of the instrument manual. During the cleaning, prevent the screen system from separating from the receiving hopper to prevent the residue on the screen from falling into the receiving hopper and (or) the material in the receiving hopper from being withdrawn. .
7.4.6 Weigh the undersize material together with the receiving hopper and the screen system, and obtain the mass of the undersize material m1 after deducting the mass of the receiving hopper and the screen system, accurate to 0.01g.
7.4.7 Clean the instrument's crushing system, receiving hopper, screen system, etc. for the next measurement. 8 Result calculation and presentation
For instruments equipped with a weighing and calculation system, the results are automatically calculated and printed out after weighing. For instruments not equipped with a weighing and calculation system, calculate according to formula (1): HI = 100-m×25
<10 k ×(12 -w) kz ×(25-t)
Wherein:
HI—hardness index of the sample when it is corrected to 12% moisture and the ambient temperature is 25°C; ml—mass of the sample passing through the sieve after crushing, in grams (g); W—moisture content of the sample, %;
t——ambient temperature, in degrees Celsius (°C); (1)
kl—moisture correction coefficient, 1/%, when m<10, kl=0.8; when 10≤m<12.5, kl =1.0; when m≥12.5, =1.6;
k2——temperature correction coefficient, 1/℃, when m<7, kz=0.03; when 7≤m<10, kz=0.07; when m≥10, kz=0.12. The calculation result shall be retained to one decimal place.
1) The standard sample of wheat hardness index can be made by the expert committee organized by the relevant standardization technical committee or by the manufacturer of the instrument that meets the requirements of LS/T3704-2007 standard. Www.bzxZ.net
GB/T21304-2007
When the difference between the two test results is not greater than 1.5, the arithmetic mean of the double test results shall be taken as the hardness index of the sample; if the difference between the two test results is greater than 1.5, the test shall be repeated. The test result shall be retained to an integer. GB/T21304-2007
People's Republic of China
National Standard
Wheat hardness determination-Hardness index method
GB/T21304—2007
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