This standard specifies the instruments, reagents, analytical procedures and result expression used in the determination of sedimentation value of wheat and wheat flour. This standard is applicable to the determination of sedimentation value of whole wheat flour and wheat flour. GB/T 15685-1995 Determination of sedimentation value of wheat flour GB/T15685-1995 Standard download decompression password: www.bzxz.net
This standard specifies the instruments, reagents, analytical procedures and result expression used in the determination of sedimentation value of wheat and wheat flour. This standard is applicable to the determination of sedimentation value of whole wheat flour and wheat flour.

National Standard of the People's Republic of China
Method for determination of
sedimentation value in wheat flour1 Subject content and scope of application
GB/T15685—1995
This standard specifies the instruments, reagents, analytical procedures and result expression used in the determination of sedimentation value of wheat and wheat flour. This standard is applicable to the determination of sedimentation value of whole wheat flour and wheat flour. 2 Referenced standards
GB5491
Sampling and sub-sampling method for inspection of grains and oilseeds
GB5497 Determination of moisture content in inspection of grains and oilseeds3 Principle of the method
Wheat is made into sodium dodecyl sulfate (SDS) suspension under specified crushing and screening conditions. After shaking and standing for a fixed time, the flour gluten in the suspension combines with the surfactant SDS and swells under the action of acid to form a sediment. The volume of the sediment is then determined, which is the sedimentation value.
4 Reagents
4.1 Lactic acid stock solution: 85% lactic acid (analytical grade): water = 1:8, shake thoroughly and mix for later use. 4.2 SDS (sodium dodecyl sulfate): 99% crystal research grade (serva). 4.3 SDS-lactic acid mixture: take 20g SDS, dissolve it in water, transfer it to a 1000mL volumetric flask, add 20mL lactic acid stock solution and dilute it to 1000mL with water, mix thoroughly and set aside. 4.4 Bromophenol blue aqueous solution: 10mg bromophenol blue is dissolved in 1000mL water. 5 Instruments
5.1 Pulverizer: any pulverizer that can grind the sample to a fineness of more than 95% passing through the CQ24 sieve. 5.2 Small experimental powder making machine. Www.bzxZ.net
5.3 Shaker: 60° stroke per vibration cycle, 30° up and down the horizontal plane 5.4 Stoppered volumetric cylinder: 100mL, 180~185mm between 0~100mL, total height of volumetric cylinder not less than 250mm. 5.550mL volumetric cylinder.
5.6 Stopwatch.
5.7 Balance: 0.01g sensitivity.
6 Analysis steps
6.1 Sample preparation:
Approved by the State Administration of Technical Supervision on August 17, 1995 and implemented on January 1, 1996
6.1.1 Sampling in accordance with GB5491.
6.1.2 Preparation of whole wheat flour sample:
GB/T 15685—1995
Take 200g of wheat sample, add water or air-dry according to the actual moisture content of the wheat sample, adjust the moisture content of the wheat sample to about 14%, and keep it sealed for 2-3 hours, then crush it with a grinder, mix it evenly, and put it in a sealed container for later use. 6.1.3 Preparation of wheat flour sample:
Take 500g of wheat sample, according to the requirements of wheat flour milling, the moisture content of soft wheat sample is adjusted to about 14%; the moisture content of hard wheat sample is adjusted to 15%-16%, and flour is made with a small laboratory experimental flour mill. 6.2 Determination of moisture content: Determine the moisture content of the sample according to GB5497. 6.3 Sampling: When the moisture content of the sample is 14%, the weight of whole wheat flour is 6.00±0.01g, and the weight of wheat flour is 5.00±0.01g. If the moisture content of the sample is higher or lower than 14%, the weight of the sample must be converted into the weight of the sample equivalent to the weight of the sample when the moisture content is 14%, and the weight of the sample must be calculated according to formula (1) and (2).
Weight of whole wheat flour (g)
6.00×0.86×100
(100 m)
Weight of wheat flour (g) -
Where: m-
—the mass of water in 100g of the sample, g. Weigh the sample in a dry stoppered measuring cylinder. 5.00 × 0.86
(100 一m)
（1）
（2）
6.4 Place the weighed sample and the prepared reagent at room temperature of 22±1℃ until the temperature of the sample and the reagent is balanced with the room temperature to obtain accurate results.
6.5 Add 50mL of bromophenol blue aqueous solution to the weighed sample volume, plug the stopper, start timing, and immediately shake up and down quickly for 15s, stand upright and let stand. At 2min, shake up and down quickly for 15s and let stand. At 4min, quickly add 50mL of SDS lactic acid mixture, and immediately turn it upside down four times and let stand. After that, turn it upside down four times every 2min, that is, at 6, 8 and 10min, respectively, and let stand (if a volume shaker is used, after adding the bromophenol blue solution, plug the stopper and place it on the shaker, and shake it automatically according to the procedures specified in the above manual operation). 6.6 After the last inversion and shaking, the whole wheat flour sample is allowed to stand for 20 minutes and the number of milliliters of sediment in the measuring cylinder is read. After the wheat flour sample is allowed to stand for 40 minutes, the number of milliliters of sediment in the measuring cylinder is read. 6.7 If the number of samples to be measured is large, four measuring cylinders can be used as a group to carry out two sample double tests at the same time, and the experimental operation should be arranged according to the following shaking schedule.
Shaking schedule
(1) Mix with bromophenol blue
Size number
Shake for 15 s
Number of measurements
(3) Add 50 mL of SDS
(2) Mix with bromophenol blue
Shake for 15 s
The same sample should be measured at least twice.
Mixed upside down 4 times
5'30″
(4)Up and down
Upside down 4 times
(5)Up and down
Upside down 4 times
8'30″
(6)Up and down
Upside down 4 times
10'00\
10'30″
11'00*
11'30\
(7)Reading
Whole wheat flour
30'00\
30'30\
31'00\
31'30″
50°00\
50'30\
51'00\
8 Expression of results
8.1 Expression method
GB/T15685--1995
The volume of sediment read out (mL) is the sedimentation value of the sample. If the two determination results meet the requirements of repeatability (8.2), the arithmetic mean of the two determination results shall be taken as the determination result. If they do not meet the repeatability requirements, repeat the determination twice. The results are expressed to one decimal place.
8.2 Repeatability
The difference between the two determination results of the same sample carried out simultaneously or successively by the same analyst using the same instrument should not exceed 2mL. 8.3 Reproducibility
The allowable difference of the results of the same sample measured in two different laboratories is as follows: For sedimentation values ​​below 20mL, the absolute difference should not exceed 2mL3For sedimentation values ​​greater than 20mL, the relative difference should not exceed 10%. Additional remarks:
This standard was proposed by the Science and Technology Quality Bureau of the Ministry of Domestic Trade. This standard is under the jurisdiction of the State Grain Reserve Bureau. This standard was drafted by the Chengdu Grain Storage Science Research Institute of the Ministry of Domestic Trade. The main drafters of this standard are Li Yuanxin, Tang Zilun and Qi Xianmei. 485
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