Soxhlet boiling extraction method for rapid determination of crude fat content in grain and oil

Soxhlet boiling extraction method for rapid determination of crude fat content in grain and oil

According to the national standards of the People's Republic of China, the crude fat content in grain and oil is determined by Soxhlet extraction. After long-term operation practices, this method has certain drawbacks, such as long operation time, labor intensity of test personnel, and high energy consumption of water and electricity. It takes more than 8 hours for Soxhlet extraction to determine the extraction time of a sample. The entire test requires about 12 hours from start to finish, and the work efficiency is extremely low. In order to solve these problems, we have conducted long-term explorations and repeated tests. The test results show that Soxhlet boiling extraction method is used to determine the crude fat content in grain and oil. The results are very satisfactory. The results of the extraction method are very close. This method is worth promoting.

1 Sox boiling extraction method

The Soxhlet boiling extraction method is based on the Soxhlet extraction method. According to the principle that the ether can accelerate the dissolution of fat after being heated, the dried sample is rapidly extracted in a boiling ether solvent and then subjected to a Soxhlet extractor. After 2 hours of extraction, all crude fat was extracted. After recovery of ether, the extracted bottom flask was baked to constant weight, and the measured crude fat content was calculated.

2 Instruments and reagents

2.1 Instruments

Analytical balance: Sensitivity 0.000 1g; Electrothermal Incubator; Electrothermic Water Bath; Crusher; Mortar; Dryer with Discolored Silicone; Filter Cartridge; Soxhlet Extractor (All parts must be washed, with 105 °C temperature drying, wherein the extraction bottle bake to constant weight); wide mouth bottle; skim line; absorbent cotton; skim sand; crude fat analyzer (SZF-06A, SZF-06B can be two models).

2.2 Reagents

Anhydrous ethyl ether (A1R).

3 Sample preparation

(1) Cereal grains and legumes (excluding peanuts) 30-50g of the net sample containing impurities was removed, ground, and placed in a wide-mouth bottle using a 110mm diameter round-hole sieve.

2 The small sample of oil, such as sesame, rapeseed, flaxseed, etc., was divided into 20 g of the net sample for removal of impurities and placed in a wide-mouth bottle for use.

3 Large-grain oil samples such as peanut fruit, castor bean seed, sunflower seed, tea seed, etc. were taken from 30 to 50 g samples, and after removing impurities, the shells were peeled off and the kernels and shells were individually weighed to calculate the total amount of kernels, and then the kernels were added. Cut into pieces or slice into a wide-mouth bottle for use.

4 Operation method

4.1 Sample dressing

From the spare sample, accurately weigh the sample 2-5g with a clean constant-weight baking box, measure the moisture according to the regulations, and bake at 105°C for 30min, then pour it into the mortar and add about 2g. Grinding with anhydrous degreasing fine sand. After polishing the sample and fine sand to oil, cleanly transfer to the filter paper tube (stuff one layer of absorbent cotton at the bottom of the tube and bake at 105 °C for 30 min). Purge the sample on the mortar with a small amount of ethyl ether. And fat, incorporated into the filter paper tube, and then inserted into the upper part with absorbent cotton, pressed the sample, and finally tied with a degreasing line, the filter paper tube may not exceed the height of the siphon tube, the diameter is less than the diameter of the extraction tube, the wrapped sample shall not Too tight.

4.2 Extraction and Drying

The Soxhlet extractor is properly installed, then the filter paper tube with the sample is placed in a known constant weight extraction bottle, and anhydrous ether is added until the filter paper tube is completely immersed (or not more than half of the bottle volume). , At the same time, connect the extraction tube and the condensing tube, connect the condensate, heat and boil for 30min in a water bath, lift the refluxing extraction tube, and lift the filter paper tube from the extraction bottle with tweezers until the ethyl ether is not dropped. Carefully place the filter paper tube into the extraction tube (note that the filter paper tube does not come into contact with the bottle mouth, droplets do not drip outside), rinse the bottle and tweezers with a small amount of ether, into the extraction bottle, connect the extractor, Continue extraction for 1 to 2 hours until the ethyl ether in the extraction cylinder is inspected for no trace of oil with glass slides. Take out the filter paper tube, recover the ether, remove the condenser tube and extraction tube, heat to remove the residual ether in the extraction flask, use the absorbent cotton wool to evaporate the outside of the extraction flask, and then extract the extraction flask at 105°C. 90min, bake for another 20min, bake until constant weight (before and after the quality difference is within 01000 2g is considered as constant weight), the quality of extracted bottles is the quality of crude fat.

5 result calculation

Crude fat wet basis content, dry basis content, and standard water miscellaneous content are calculated according to equations (1), (2), and (3), respectively: