GB 5512-85 Grain and Oil Inspection Crude Fat Assay
This article describes how to determine crude fat in grain and oil in the national standard. The determination of crude fat in the national standard is a general laboratory method, which we all agree with. However, sometimes, for convenience and speed, we will use the instrument method to directly measure, like the crude fat analyzer: Of course, it has a variety of models, SZF-06A crude fat analyzer, SZF-06B crude fat analyzer, etc. It is an instrument for measuring crude fat.
This standard applies to the determination of crude fat content in commercial grain and oil products.
1 Soxhlet extraction
1.1 Instruments and Apparatus
1.1.1 Analytical balance: Sensitivity 0.0001g;
1.1.2 Electric thermostats;
1.1.3 Electric heating water bath:
1.1.4 Crusher, mortar;
1.1.5 Desiccator with discoloration silica gel;
1.1.6 filter paper tube;
1.1.7 A set of Soxhlet extractors (each part must be washed and dried at a temperature of 105°C, wherein the extraction bottle is baked to a constant weight);
1.1.8 Wide mouth bottle, degreasing line, absorbent cotton, and defatted fine sand.
1.2 Reagents anhydrous ether (AR)
1.3 Sample preparation
1.3.1 For cereals and legumes (excluding peanuts), 30 to 50 g of the net sample to remove impurities shall be collected, ground into a wide-mouth bottle with a 1.0 mm diameter round-hole sieve, and used as a backup.
1.3.2 The small sample of oil, such as sesame seeds, oil seed, flaxseed, etc., is taken to remove 20 g of the net sample for removing impurities, and put into a wide-mouth bottle for use.
1.3.3 Large-grain oil samples such as peanut, castor bean, sunflower seeds, and tea seeds are sampled at 30-50 g. After the impurities are removed, the shells are shell-separated and the kernels and shells are weighed. The total amount of kernels is calculated, and then Cut or slice the kernel into a wide-mouth bottle for use.
1.4 How to operate
1.4.1 Sample Packing: From the standby sample, use a baking box to weigh 2~5g samples, bake at 105°C temperature for 30min, pour hot into the mortar, add about 2g of defatted fine sand and grind together. After the sample and fine sand were ground into an oily form, they were cleanly transferred into a filter paper tube (a layer of absorbent cotton was inserted at the bottom of the tube and baked at a temperature of 105°C for 30 minutes), and the sample on the mortar was rinsed with a small amount of ethyl ether. And fat, into the filter tube, and then use the absorbent cotton into the upper part, press the sample.
1.4.2 Extraction and Drying: The extractor is properly installed, and then the filter paper tube containing the sample is placed in the extraction tube, and at the same time, the ether is injected to the height of the siphon tube. After the diethyl ether is purified, diethyl ether is added. Two-thirds of the siphon height. A small piece of absorbent cotton was gently inserted into the inlet of the condensing pipe, the inlet pipe of the condensing pipe was opened, and heating extraction was started. The temperature of the heating was 120 to 150 drops of ether refluxed per minute, and refluxed seven times or more per hour. The extraction time depends on the oil content of the sample, generally more than 8 hours, and the ether extracted into the extraction tube is inspected with a glass slide (drip test) without oil traces.
After removing the fat, remove the filter paper tube with a long handled tweezers, and then heat the ether to reflux 2 times. Then, recover the ether, remove the condensation tube and extraction tube, and heat to remove residual ether from the extraction bottle. The outer part of the bottle was extracted from the net, and then the extraction bottle was first baked at 105° C. for 90 minutes, then baked for 20 minutes, and then dried until the constant weight was reached. (The weight difference between the front and rear secondary weight is within 0.0002 g, which is regarded as constant weight). The weight added to the extraction bottle is the weight of crude fat.
1.5 Result Calculation
The content of crude fat wet basis, dry base content and standard water miscellaneous content are calculated according to equations (1), (2) and (3) respectively:
W1
Crude fat (moisture basis) = —— × 100 --------------- (1)
W
W1
Crude fat (dry basis %) = ————- × 10000 --------------- (2)
W(100-M)
W1 (100-M mark)
Crude fat (standard water miscellaneous, %) = ─────────── × 100 -------------- (3)
W ( 100 - M)
Where: W1 - crude fat weight, g;
W -- sample weight, g;
M -- Percentage of sample moisture, %;
M mark - the standard sample moisture, the sum of standard impurities,%.
The results of the double test allowable difference: grain, oil does not exceed 0.4%, soybean does not exceed 0.2%, for the average, that is, the determination results. The measurement result is the first decimal place.
If the crude fat content of the shelled oil is determined, it must be converted by formula (4) and formula (5) respectively:
N × A
Shelled oil crude fat (wet basis %) = ─────── -------------- (4)
100 N × A
Shelled oil crude fat (dry basis %) = ─────── --------------- (5)
100 - M
Where: N - the percentage of crude fat wet basis content of shell kernels, %;
A -- Percentage of total kernels with shell oil, %;
M -- Moisture percentage of shelled oil, %.
Note: If no filter paper tube is available, filter paper 28cm in length and 17cm in width may be used. Using a test tube with a diameter of 2cm, roll it into a tube along the long direction of the filter paper, and withdraw the test tube to half of the height of the paper tube, flatten the evacuated part and fold it over. Keep it close to the outer layer of the test tube, fasten it with a degreasing line, fold the lower corner upwards, press it into a round bottom, and withdraw the test tube, make it a filter paper tube with a diameter of 2.0cm and a height of about 7.5cm.
2 straight drop extraction
2.1 Instruments and apparatus
2.1.1 straight drop extractor;
2.1.2 Other instruments and appliances are the same as 1.1.
2.2 Reagents
The reagents used are the same as 1.2.
2.3 sample preparation
Sample preparation method with 1.3.
2.4 How to operate
Instrument processing with 1.4. When used, put the sample bag into the extraction tube and extract the fat with ether. After the fat is extracted, remove the sample bag, close the glass piston that is returning, and continue heating to recover the ether. Other methods with 1.4.
Note: The recycling of recycled ether is divided into three steps:
1 Remove peroxide: Inject diethyl ether into the separatory funnel, add 10% of ferrous sulfate solution which is equal to 5 parts of ether, take 100g of ferrous sulfate dissolved in 600ml of water, acidify with 30ml concentrated sulfuric acid, and dilute with water. To 1000 ml), mix well, stand for clarification, and release the aqueous solution.
2 Remove ethanol: Add 10% potassium hydroxide solution which is one-fifth of the amount of ether. After shaking and washing, let it stand and release the aqueous solution. Repeat washing for 2 to 3 times.
3 Remove water and distillation: Add small amount of anhydrous calcium chloride (a tenth to one-fifth of the amount of ether) in an ether bottle, place it overnight, stir it, and distill the supernatant. Collect the fraction between 33°C and 37°C. The adapter of ethyl ether needs to be cooled with ice or cold water. At the same time, a safety bottle is connected and the gas in the bottle is discharged outside or into the sewer.
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