GB/T 5497-1985 Grain and oilseeds - Determination of moisture content
Some standard content:
National Standard of the People's Republic of China
Inspection of grain and oilseeds
Methods for determination of moisture content
Inspection of grain and oilseedsMethods for determination of moisture contentThis standard applies to the determination of moisture content of commercial grain and oilseeds. 1105℃ constant weight method
Instruments and appliances
1.1.1 Electric thermostatic box;
1.1.2 Analytical balance: sensitivity 0.001g;
Laboratory electric grinder or hand-cranked grinder;1.1.4 Grain selection screen;
GB/T 5497-85
1.1.5 Dryer with color-changing silica gel (color-changing silica gel cannot be used after it turns red, and should be dried at 130-140℃ until it turns blue before use). 1.1.6 Aluminum box: inner diameter 4.5cm, height 2.0cm. 1.2 Sample preparation
Take a certain amount of samples from the average sample and prepare the samples according to the method specified in the following table: Sample preparation method table
Granular raw grains and finished grains
Peanut kernels, tung kernels, etc.
1Quantity of subsamples, g|
30～50
130～50
1About 50
Peanut fruit, tea seed, tung nut"
About 100
Lantern seed, Xanthoceras sorbifolia, etc.
Cotton seed, sunflower seed, etc.
Rapeseed, sesame, etc.
Sweet potato slices
【About 100
Preparation method
Remove large impurities and minerals, and the grinding fineness shall not be less than 90% passing the 1.5mm round hole sieve||t t||Remove large impurities and minerals, and the fineness of the crushing should not be less than 90% passing through a 2.0mm round hole sieve
1 Take the clean kernel and cut it into thin slices less than 0.5mm with a hand-cranked slicer or a knife. ■ Cut and shred
Take the clean fruit (seed) and peel it, weigh them separately, and calculate the percentage of shell and kernel; grind or grind the shell; cut the kernel into thin slices. Take the clean seeds and cut or smash them with a mortar
Whole grain sample with large impurities removed
Take the clean slices and grind them to the same fineness as granular grain
Sweet potato shreds Sweet potato strips
Operation method
|About 100
" Take the clean shreds and strips and grind them to the same fineness as granular grain 1.3.1 Constant temperature: Make the mercury ball of the thermometer in the oven about 2.5cm away from the drying net, and adjust the oven temperature to 105±2℃. 1.3.2 Drying aluminum box: Take a clean empty aluminum box and place it on the drying net below the mercury ball of the thermometer in the oven. Bake for 30 minutes to 1 hour, take it out, place it in a desiccator to cool to room temperature, take it out and weigh it, and bake it for another 30 minutes until the weight difference between the two weights does not exceed 0.005g, which is constant weight.
1.3.3 Weighing the sample: Use the aluminum box (W0) that has been baked to constant weight to weigh about 3g of the sample. For oilseeds with shells, the sample can be weighed according to the ratio of kernels to shells or the kernels and shells can be weighed separately (W1, accurate to 0.001g). 1.3.4 Drying the sample: Put the lid of the aluminum box on the bottom of the box and put it on the drying net around the thermometer in the oven. Bake it at 105℃ for 3 hours (90 minutes for oilseeds), then take out the aluminum box, cover it, place it in a desiccator to cool to room temperature, take it out and weigh it, and then repeat the above method to bake it again. Take it out and cool it every 30 minutes and weigh it once until the weight difference between the two weights does not exceed 0.005g. If the latter weight is higher than the former weight, the former weight shall be used for calculation (W2). 1.4 Calculation of results
The moisture content of grain and oilseeds shall be calculated according to formula (1): W1-W2
Moisture (%)=
Where: wo—weight of aluminum box, g;
W1—weight of sample and aluminum box before baking, g;
W2—weight of sample and aluminum box after baking, g.
When the moisture content of shelled oilseeds is determined separately by kernel and shell, the moisture content of shelled oilseeds shall be calculated according to formula (2); Moisture (%)=M1×A+M2×(1-A)....(2)Where: M1——percentage of kernel moisture, %; M2——percentage of shell moisture, %;
A——percentage of total kernel output, %.
The allowable difference between the two test results shall not exceed 0.2%. The average is the test result. The test result shall be rounded to the first decimal place.
When other methods are used to determine the moisture content, the results shall not exceed 0.5% compared with this method. 2 Constant temperature and time drying method
2.1 Apparatus and utensils: Same as 1.1.
2.2 Sample preparation: Same as 1.2
2.3 Sample quantity calculation: This method uses a quantitative sample. First calculate the bottom area of the aluminum box, and then calculate the sample quantity (bottom area × 0.126) based on 0.126g per square centimeter. If an aluminum box with a diameter of 4.5cm is used, the sample quantity is 2g; if an aluminum box with a diameter of 5.5cm is used, the sample quantity is 3g.
2.4 Operation method
Use an aluminum box that has been dried to constant weight to weigh a quantitative sample (accurate to 0.001g). When the oven temperature rises to 135-145℃, place the aluminum box containing the sample on the drying net around the thermometer in the oven. Within 5 minutes, adjust the oven temperature to 130±2℃, start timing, and take out after drying for 40 minutes, cool in a dryer, and weigh. 2.5 Result calculationwwW.bzxz.Net
The calculation of moisture content by the constant temperature and timing method is the same as 1.4. 3 Tunnel oven method
The tunnel oven method uses 160±2℃ for determining the moisture content of cereals and grains, and 130±2℃ for determining the moisture content of oilseeds and beans, and 30 minutes for drying.
3.1 Instruments and utensils
3.1.1 Tunnel oven;
3.1.2 Stopwatch.
3.2 Sample preparation: Same as 1.2.
3.3 Operation method
3.3.1 Temperature setting: Lay the instrument flat, insert the thermometer into the drying room, make the mercury ball about 1cm away from the drying box opening, and turn on the power to set the temperature.
3.3.2 Weighing the drying box: Push three clean drying boxes into the drying room, and push another one after 10 minutes. At this time, one of the first drying boxes will be pushed out of the tunnel. Put this drying box on the weighing pan on the drying oven, add a 10g weight, and adjust the screw on the quadrant scale so that the pointer points to the zero point of the scale. Remove the weight and put the prepared sample into the drying box, increase or decrease the sample until the pointer stops at zero. Then evenly distribute the weighed sample in the drying box, push it into the drying room, close the left door, and count at the same time. 3.3.3 Drying samples: When using the 160℃ drying method for 20 minutes, push a baking box with a sample into the drying room every 6 minutes and 40 seconds; when using the 130℃ drying method for 30 minutes, push a baking box with a sample every 10 minutes. When the fourth sample box is pushed in, the drying time of the first sample box has expired, and it is pushed out onto the weighing pan. Pull down the fixed support rod of the balance pointer and observe the value indicated by the pointer, which is the measured moisture percentage. The allowable difference between the two test results is not more than 0.5%. 4
Two-time drying method
When the moisture content of grain is above 18%, the moisture content of soybean and sweet potato slices is above 14%, and the moisture content of oil is above 13%, the two-time drying method is adopted.
4.1 First drying: Weigh 20g of whole grain sample (W1 accurate to 0.001g), put it into a drying box with a diameter of 10 or 15cm and a height of 2cm and spread it flat. Grains are dried at 105℃, and soybeans and oilseeds are dried at 70℃ for 30-40min, then taken out and naturally cooled to constant weight (the difference between the two weighings should not exceed 0.005g). This is the weight of the sample after the first drying (W1). 4.2 Second drying: Sample preparation and operation methods are the same as 1.2 and 1.3. 4.3 Result calculation
When the moisture content is determined by the double drying method, it is calculated according to formula (3): WX W2-W1X W3
Moisture (%)=
W——sample weight before the first drying, g; W1—sample weight after the first drying, g:
W2——sample weight before the second drying, g; W3——sample weight after the second drying, g. X100.3)
The allowable difference between the two test results shall not exceed 0.2%. The average shall be the test result. The test result shall be rounded to the first decimal place.
Additional Notes:
This standard was proposed by the Ministry of Commerce of the People's Republic of China. This standard was drafted by the Grain Storage and Transportation Bureau of the Ministry of Commerce. The main drafters of this standard are Gao Xiuwu, Yang Haoran, Wu Yanxia and Lv Guifen. Issued by the National Bureau of Standards on November 2, 1985
Implementation on July 1, 1986
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