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Milk fat, as one of the important indicators for national testing of milk quality, has been paid attention to by the majority of manufacturers and consumers. Milk fat content determination method has the weight method and the volume method, the volume method is faster than the weight method determination speed, save time, save effort. Some commonly used methods are Rhodes - Gotri method, Ynihoff alkali method, Gabor method and so on. The most commonly used methods for the determination of milk fat in China are respectively the Ynihoff alkali method and the gaber method (acid method).Cows milk fat
Milk fat with fine spherical emulsion dispersed in the milk, is one of the main components of milk. The fat content in milk varies with the variety and other conditions, and the mass fraction is generally between 3% and 5%. Because the emulsion of milk fat is quite stable, so the determination of milk fat, alcohol, acid, alkali and other chemical treatment methods to destroy the fat bulb membrane, combine into fat layer.
Ynihoff's method of alkali
The required material
Gaiber milk fat meter, constant temperature water bath (can also use aluminum pot with water heating on the electric stove), reagents
Methods the process
Alkali reagent: add 30GnOH to the first beaker and dissolve it in 300ml distilled water; I'm going to add 40 gigaNA to the first beaker. C03, dissolved in 300ml distilled water; In the third beaker, 75GnACl was heated to 65 ~ 70 ° C with water to dissolve. Then mix the ①②③ solution together, inject it into a volumetric flask with a volume of 1000ml, add water to the scale, strain it into the reagent flask with absorbent cotton, plug it tightly and reserve it.
Isoamyl alcohol-ethanol mixture: 130ml of isoamyl alcohol was mixed with 210ml of 960 ethanol, added into the reagent bottle, and sealed for later use.
Put the Gaiber milk fat meter on the test-tube rack, suck 10ml of alkali reagent through a straw, inject into the human milk fat meter, then suck 10ml of shaken milk sample through another milk straw, inject into the alkali reagent, then add the mixture of isoamyl alcohol-ethanol Lml, plug the milk fat meter tightly with rubber plug, mix the contents carefully (oscillate), Until the foam develops and the milk curds dissolve. The milk fat meter was placed in a water bath of 70 ~ 73℃ for 10min, and the water temperature should not drop to less than 70℃ after 5 minutes of oscillation. Then put the milk fat meter upside down with the rubber plug down, and then put it in the water bath at 70 ~ 73℃ for LO ~ 15min (the length of time depends on the extent of foam disappearance). When the straight fat column does not contain foam, take it out, and the reading is the percentage of fat.
Gaber's process (acid process)
The required material
Gaber's Milk Fat Meter, Sulfuric Acid, Isoamyl Alcohol, Scale Straw, Milk Fat Centrifuge
Methods the process
1. Take 10mL of sulfuric acid and pour it into the milk fat meter. Don't wet the neck with sulfuric acid. Draw milk sample with 11mL milk pipet to the scale and add it into the same milk fat meter.
2. Add 1mL of isoamyl alcohol, plug the rubber plug tightly, shake it thoroughly, and dissolve the milk clot.
3. Put the fat meter in a water bath at 65-70℃ and keep warm for 5min. Turn the rubber plug in and out so that the fat column is suitable for the scale part of the fat meter
4. Put it in a centrifuge with centrifugal force =350, rotate for 5min, then put it in a water bath of 65-70℃ for 5min, take it out and read immediately.
Comparing the two methods, the gaber method (acid method) is more convenient and less labor-intensive than the ynihoff method, although the results are certainly different.
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