After the sample is extracted with anhydrous ether or petroleum ether, the substance obtained by evaporating the solvent is called fat or crude fat in food analysis. Because in addition to fat, it also contains pigments and volatile oil, wax, resin and other things. The fat measured by extraction method is free fat.
2 reagent
2. 1 anhydrous ether or petroleum ether.
2.2 Sea sand: Determination of moisture in food
Three kinds of instruments
Soxhlet extractor.
4 operation method
4. 1 sample processing
4. 1.65438+
4. 1.2 liquid or semi-solid sample: weigh 5.0 ~ 10.0g, put it in an evaporating dish, add about 20g sea sand, evaporate it in boiling water bath, then dry it at 95 ~ 105℃, grind it, and transfer it to a filter paper tube. Wipe the evaporating dish and the glass rod containing the sample with absorbent cotton stained with ether, and put the cotton into the filter paper tube.
4.2 extraction
Put the filter paper cylinder into the extraction cylinder of the fat extractor, connect it with the receiving bottle which has been dried to a constant amount, add anhydrous ether or petroleum ether from the upper end of the condenser tube of the extractor to 2/3 of the internal volume of the bottle, and heat in water bath to continuously reflux the ether or petroleum ether for extraction, generally 6 ~ 12h.
4.3 Weighing
Take down the receiving bottle, recover the ether or petroleum ether, and when 1 ~ 2ml of ether remains in the receiving bottle, evaporate it in water bath, then dry it at 95 ~ 105℃ for 2h, and put it into a dryer to cool it for 0.5h and then weigh it.
4.4 calculation
m 1-m0
x =──────× 100
The second part of money supply
Where x refers to the content of fat in the sample,%;
M 1—— mass of receiving bottle and fat, g;
M0—— quality of receiving bottle, g;
M2—— the mass of the sample (if it is a sample after moisture determination, it shall be calculated according to the mass before moisture determination), g. 1 principle.
After acid hydrolysis, the sample was extracted with ether, and the total amount of free and bound fat was obtained by removing the solvent.
2 reagent
2. 1 hydrochloric acid
2.2 95% ethanol.
2.3 ether.
2.4 petroleum ether.
Three kinds of instruments
100 ml measuring cylinder with stopper.
4 operation method
4. 1 sample processing
4. 1. 1 solid sample: accurately weigh about 2g, put it in a 50mL test tube, add 8mL of water, mix well and then add 10mL of hydrochloric acid.
4. 1.2 liquid sample: weigh 10.0g, put it in a 50mL test tube, and add 10mL hydrochloric acid.
4.2 Put the test tube into a water bath at 70 ~ 80℃ and stir it with a glass rod every 5 ~ 10 min until the sample is completely digested.
Stop, about 40 ~ 50 minutes.
4.3 Take out the test tube, add 10mL ethanol and mix well. After cooling, transfer the mixture into a 100mL measuring cylinder with a plug and mix with 25 ml b.
Wash the test tube several times with ether, and then pour it into the measuring cylinder. After all the ether is poured into the measuring cylinder, add the stopper and shake it for 65438 0 minutes. Carefully open the plug and let it go.
Exhaust the gas, plug it again, let it stand for 12 minutes, carefully open the plug, and clean the plug and the accessories at the barrel mouth with the same amount of petroleum ether-ether mixture.
Fat. Let stand 10 ~ 20min. After the upper liquid is clarified, suck out the supernatant from the constant conical flask and add 5mb.
Put the ether into a measuring cylinder with a plug, shake it evenly and let it stand. Still suck out the upper ether and put it into the original conical bottle. Put the conical flask into the water bath.
Evaporation, drying in an oven at 95 ~ 105℃ for 2h, taking out, cooling in a dryer for 0.5h, and weighing.
4.4 1 calculation, principle:
(1) Adding ammonia water (concentrated ammonia water) to milk destroyed the colloidal properties of protein in milk, and made casein calcium salt in milk generate soluble ammonia salt.
(2) 95% ethanol was added to separate lipids from non-lipids in milk.
(3) Adding diethyl ether to extract lipids.
(4) adding petroleum ether to remove the water in the ether. (5) the ether and petroleum ether in the ether outlet layer volatilize; The remaining fat is the fat in milk.
2, detection steps:
(1) Accurately weigh 10g uniform milk sample in Shi Mao liposuction bottle with electronic balance (1g milk powder is dissolved in 9 ml distilled water and washed several times).
(2) Add 2ml of concentrated ammonia water and mix thoroughly.
(3) Add 10 ml of 95% ethanol, add 2 drops of Congo red and mix thoroughly.
(4) Add 25ml of ether, shake 1 min, 100 times/1 min, deflate 1-2 times during shaking, and rinse the cork with the mixed solution.
(5) Add 25ml petroleum ether, shake well for half a minute, deflate 1-2 times when shaking well, clean the cork with mixed solution, and let it stand for half an hour.
(6) Carefully pour the ether layer after standing into a triangle bottle (after washing and drying 1.5 hours, the balance room is dust-free, naturally cooled 1 hour, and weighed m 1), and wash the bottleneck with mixed reagents.
(7) Add 5ml ethanol into Shi Mao liposuction bottle and shake well.
(8) Add 15ml ether, shake 100 times/1min, and clean the cork with mixed reagent. Add 15ml petroleum ether, shake well for half a minute, clean the cork with mixed reagent, and let it stand for half an hour.
(9) After standing, pour the ether layer into the triangular flask and rinse the bottleneck with mixed reagent.
(10) Volatilize the ether solution extracted twice in a water bath at 30-60℃ (in a triangular flask), and remove the ether and petroleum ether in a fume hood.
(1 1) Bake the triangle bottle with fat in the oven at 98- 100℃ for 1.5 hours until it reaches a constant weight. After taking it out, naturally cool it in the balance room 1 hour, and weigh m2.
3. Calculation:
m2-m 1
Fat content% =-× 100.
M
Where m2—— refers to the fat and weight of an empty triangular bottle (g)
M1-weight of empty triangular bottle (g)
M—— Weighed milk quality (g)
Determination of FT 120 (omitted)
Sudan three identification method
(1) Cut the material into pieces of 1MM with a slicer and move it to a clean slide.
(2) Drop 2-3 drops of Sudan III dye solution with a dropper, dye for 2-3 minutes, then absorb the dye solution with absorbent paper, wash off the floating color with 1~2 drops of 50% alcohol, and then absorb the alcohol.
(3) Drop 1~2 drops of distilled water, cover with glass and observe under a microscope.
(4) Small orange particles are fat.
A new technology applied to fat determination: ultra-micro filter bag technology
Because of the popularization of filter bag technology (FBT) used for batch analysis of fiber content in feed, Ancombe technology enjoys a worldwide reputation. As early as 1993, ANKOM fiber analyzer has been widely used all over the world, which can accurately determine acidic detergent fiber (ADF), neutral detergent fiber (NDF) and crude fiber (CF). Based on the experience gained in fiber analysis, ANKOM Technology recently developed an accelerated batch extraction (ABE). ANKOM fat analyzer is a new technology developed by ANKOM technology, which uses common solvents to quickly extract food and feed fat.