Measurement of crude fat content.

related topics . Objective:
fat is widely found in the seeds and fruits of many plants, and the determination of fat content can be used as an indicator to identify its quality. There are many methods for determining fat content, such as pumping, acid hydrolysing, specific gravity, refraction, electrometric and MRI. At present, the method of pumping is widely used at home and abroad, among which Soxhlet extractor method is recognized as a classic method and the standard method of the preferred method of grain and oil division in China. Through the study of this experiment, we can master the principle and operation method of measuring the crude fat content by the Soshi method.2. The original
experiment used the residual method of the Soss extraction method, that is, using a low boiling point organic solvent (ether or petroleum ether) reflow extraction, removing the crude fat from the sample, to the difference between the weight of the sample and residue, to calculate the crude fat content. Because the extract of organic solvents, in addition to fat, but also more or less contain free fatty acids, sterols, phospholipids, waxes and pigments and other lipid-like substances, so the results of the extraction method can only be crude fat., experimental materials, major instruments and
reagents
1. Experimental materials
oil crop species, medium-speed filter paper
2. Instruments:
(1) Sox fat drawer or YG-II. type oil sub-meter
(2)
drying
(diameter 15 to 18cm, color-rich silicone)
(3) stainless steel tweezers (20cm long)
(4)
culture
Dishes
(5) Analysis
balance
(sense 0.001g)
(6) weighing bottle
(7)
constant temperature
water bath
(8) oven
(9) sample sieve (60 items)
3. Reagents
waterless ether or low boiling point petroleum ether (A.R.) , operating steps
1. Cut the filter paper into 8cm×8cm, fold it into an unsealed paper bag, write the sequence numbers in hard pencils, and arrange them in order in a petri dish. Remove the petri dish containing the filter paper bag into the oven at 105±2 degrees C and dry 2h, remove and place in the dryer and cool to room temperature. Each filter paper bag must be weighed (recorded as a) in the same weighing bottle in sequence, and the relative humidity in the room must be less than 70% when weighing.
2. Packing and drying
in the above weighed filter paper bag loaded with 3g or so of fine samples, sealed the bag, put in a 105±2 degrees C oven dry 3h, moved to the dryer to cool to room temperature. The serial numbers are placed in the weighing bottle in sequence (remember b).
3. Pumping
the filter paper bag containing the sample is put into the pump with a long tweezer and injected with a siphon of 1.67 times the amount of waterless ether, so that the sample package is completely immersed in the ether. Connect all parts of the pump, connect the condensate water flow, in the heated water bath for extraction, adjust the water temperature between 70 to 80 degrees C, so that the condensing drop of ether into a bead -like (120 to 150 drops / min or return 7 times / h or more), pumping to the pumping tube ether with filter paper drops to check the oil-free traces (about 6 to 12h). After pumping, remove the filter paper bag with a long tweezer and make the ether volatile at the ventilation area (pumping room temperature is appropriate at 12 to 25 degrees C). The ether in the extraction bottle is recycled separately.
4. Weighing
after the ether has evaporated, place the filter paper bag in a 105±2C oven to dry 2h and place in the dryer until it is cooled to constant weight (remember c)., Results and Calculations : a: Weighing bottle plus filter paper bag weight (g)
b: Weighing bottle plus filter paper bag and drying sample weight (g)
c: Weighing bottles with filter paper bags and drying residue weight (g) 6, note
(1) determination with samples, pumps, extraction of organic solvents need to be dehydrated treatment. This is because: first, there is water in the extraction system, will make the water-soluble substances in the sample dissolved, resulting in high measurement results, second, there is water in the extraction system, then the extraction solvent is easily saturated by water (especially ether, can be saturated about
2% of the water
), thereby affecting the extraction efficiency;
(2) sample weight should be appropriate. The sample powder is too thick, the fat is not easy to draw clean, the sample powder is too fine, it is possible to penetrate
filtration
paper pores with the return solvent loss, affecting the measurement results.
(3) Soch extraction method to determine the biggest deficiency of fat is that it takes too long, if the sample can be returned 1 to 2 times, and then soaked in solvent overnight, the next day and then continue to draw, can significantly shorten the withdrawal time.
(4) YG-II. type oil parts determiner has a large capacity, suitable for the selection of samples more for the identification work, temperature control at about 70 degrees C, 8h can be extracted.
(5) must pay great attention to the safe use of ether. It is strictly forbidden to have an open flame in the pumping room or to heat
with
. Ether must not contain peroxide, keep the pumping room well ventilated to prevent explosion. The inspection method of peroxide in ether is: take the appropriate amount of ether, add potassium iodide solution, shake hard, place 1min, if yellow indicates the presence of peroxide, should be treated before use. The treatment method is: put the ether into the liquid funnel, first wash 2 to 3 times with 1/5 ether amount of thin KOH solution to remove ethanol; SO3 solution, shake, sit, layered and discarded the lower aqueous solution to remove the oxides, and finally washed to neutral, dehydrated with waterless CaCl2 or waterless Na2SO4, and re-distilled., thinking question 1.
1. How to determine the crude fat content in oil crop species by residual method?
2. Why is it necessary to dehydration the sample, the drawer and the organic solvent used in the extraction process?
3. What should I pay attention to when using ether safely during the experiment?
4. What are the requirements for determining the particle weight of the sample?
reference answer
1. Residual method to determine the crude fat content in oil crop species, is to use low boiling point organic solvent (ether or petroleum ether) reflow extraction, remove the sample of crude fat, the sample and residue weight difference, to calculate the crude fat content.
2. There are three reasons for dehydration treatment: first, there is water in the extraction system, which dissolves the water-soluble substance in the sample, resulting in high determination results, second, if there is water in the extraction system, the extraction solvent is easily saturated by water (especially ether, which can be saturated with about 2% of the water), thus affecting the extraction efficiency;
3. It is strictly forbidden to have an open flame in the pumping room or to heat it with an open flame. Ether must not contain peroxide, keep the pumping room well ventilated to prevent explosion.
4. The sample should be suitable for its weight and detail. The sample powder is too thick, the fat is not easy to draw clean, the sample powder is too fine, it is possible to filter the paper pores with the return solvent loss, affecting the measurement results.
.