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National Standard of the People's Republic of China
Inspection of grain and oilseedsMethods of determination of crude fat
Inspection of grain and oilseedsMethods of determination of crude fatThis standard applies to the determination of crude fat content in commercial grains and oilseeds. 1 Soxhlet extraction method
1.1 Apparatus and tools
1.1.1 Analytical balance: sensitivity 0.0001g
1.1.2 Electric thermostatic box;
1.1.3 Electric constant temperature water bath:
1.1.4 Crusher, mortar;
1.1.5 Dryer with color-changing silica gel:
1.1.6 Filter paper tube;
GB/T5512-85
1.1.7 A set of Soxhlet extractor (all parts must be cleaned and dried at 105℃, and the extraction bottle must be dried to constant weight); 1.1.8 Wide-mouth bottle, degreasing thread, degreasing cotton, degreasing fine sand. 1.2 Reagents
Anhydrous ether (AR)
1.3 Sample preparation
1.3.1 Take 30-50g of the net sample of cereals and beans (except peanuts) after removing impurities, grind it through a 1.0mm diameter round hole sieve and put it into a wide-mouth bottle for later use.
1.3.2 Take 20g of the net sample of small oilseeds such as sesame, rapeseed, flaxseed, etc. after removing impurities, put it into a wide-mouth bottle for later use.
1.3.3 Take 30-50g of the sample of large oilseeds such as peanuts, hemp seeds, sunflower seeds, tea seeds, etc., remove impurities, shell each grain, weigh the kernel and shell separately, calculate the percentage of the total kernel, and then cut or slice the kernel and put it into a wide-mouth bottle for later use. 1.4 Operation method
1.4.1 Sample wrapping: From the spare samples, weigh 2-5g of sample in a drying box, dry at 105℃ for 30min, pour into the mortar while hot, add about 2g of defatted fine sand and grind together. After the sample and fine sand are ground into oily state, transfer them cleanly into the filter paper tube (plug a layer of absorbent cotton at the bottom of the tube and dry at 105℃ for 30min), use absorbent cotton to dip a small amount of ether to clean the sample and fat on the mortar, put it into the filter paper tube, and finally plug the absorbent cotton into the upper part to press the sample. 1.4.2 Extraction and drying: Install the extractor properly, then place the filter paper tube containing the sample into the extraction tube, and inject ether to above the height of the siphon tube at the same time. After the ether flows out, add ether to two-thirds of the height of the siphon tube. Use a small piece of absorbent cotton to gently plug the upper opening of the condenser tube, open the water inlet of the condenser tube, and start heating extraction. The heating temperature is such that the ether refluxes at 120 to 150 drops per minute, and refluxes more than seven times per hour. The extraction time depends on the oil content of the sample, which is generally more than 8 hours. The extraction is carried out until the ether in the extraction tube is checked with a glass piece (drip test) and there is no trace of oil. After the fat is extracted, use long-handled tweezers to remove the filter paper cylinder, heat it to make the ether reflux twice, then recover the acetaldehyde, remove the condenser and the extraction cylinder, heat to remove the residual acetaldehyde in the extraction bottle, dip acetaldehyde with absorbent cotton to clean the outside of the extraction bottle, and then bake the extraction bottle at 105°C for 90 minutes, then 20 minutes, until it is constant weight (the difference between the two weights before and after is within 0.0002g, which is considered constant weight). The weight added to the extraction bottle is the weight of the crude fat. 1.5 Calculation of results
The wet basis content, dry basis content and standard water and impurity content of crude fat are calculated according to formulas (1), (2) and (3) respectively: W1
Crude fat (wet basis %)=
Crude fat (dry basis %)=
X10000
W(100-M)
W1(100-M standard)
Crude fat (standard water and impurity content, %)
W(100-M)
W1 Where: W1-
crude fat weight, g;
sample weight, g;
sample moisture percentage, %;
the sum of standard moisture and standard impurities of a sample, %. M standard
×100...(3)
The allowable difference between the two test results is: grain and oilseeds shall not exceed 0.4%, and soybeans shall not exceed 0.2%. The average is the test result. The test result shall be rounded to the first decimal place. If the crude fat content of shelled oilseeds is to be determined, the formula (4) and formula (5) must be used for conversion respectively: N×A
Crude fat of shelled oilseeds (wet basis %)=
Crude fat of shelled oilseeds (dry basis %)=
Wet basis content of crude fat of shelled oilseed kernels, %; Where: N
A——Percentage of total kernel output of shelled oilseeds, %; M—Moisture content of shelled oilseeds, %.
. (5)
Note: If there is no filter paper tube available, take a 28 cm long and 17 cm wide filter paper, use a 2 cm diameter test tube, and roll it into a tube along the lengthwww.bzxz.net
of the filter paper. Pull out the test tube to half the height of the paper tube, flatten the evacuated part and fold it over so that it is close to the outer layer of the test tube, tie it with a degreased thread, fold the lower corner upwards, press it into a round bottom, and pull out the test tube to form a filter paper tube with a diameter of 2.0 cm and a height of about 7.5 cm. 2 Direct drop extraction method
2.1 Instruments and utensils
2.1.1 Direct drop extractor;
2.1.2 Other instruments and utensils are the same as 1.1.
2.2 Reagents
The reagents used are the same as 1.2.
2.3 Sample preparation
The sample preparation method is the same as 1.3.
2.4 Operation method
The instrument treatment is the same as 1.4. When using, put the sample bag into the extraction tube, extract the fat with ether, and after the fat is completely extracted, take out the sample bag, close the reflux glass piston, and continue heating to recover the ether. Other methods are the same as 1.4. Note: The re-production of recovered ether is divided into three steps: ① Removal of peroxide: Pour ether into a separatory funnel, add 10% ferrous sulfate solution accounting for one-fifth of the amount of ether (take 100g ferrous sulfate and dissolve it in 600ml water, add 30ml concentrated sulfuric acid for acidification, and then dilute with water to 1000ml) and mix thoroughly, let it stand to clarify and release the aqueous solution. ② Removal of ethanol: Add 10% potassium hydroxide solution accounting for one-fifth of the amount of ether, shake and wash, let it stand, release the aqueous solution, and repeat the washing 2 to 3 times. ③ Remove moisture and distill: Add an appropriate amount (one tenth to one fifth of the amount of ether) of small-particle anhydrous calcium chloride to the ether bottle, leave it for a day and night, shake it from time to time, take the upper clear liquid for distillation, and collect the fractions between 33 and 37°C. The ether receiver needs to be cooled with ice or cold water. At the same time, connect a safety bottle and discharge the gas in the bottle to the outdoors or into the sewer.
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. It was issued by the National Bureau of Standards on November 2, 1985
Implementation on July 1, 1986
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