How to determine the acidity of milk, fat content of milk. The fattier the milk, the more valued it is. The best cows are not only those that give the most milk - show high milk yields - but also those whose milk is the fattest. The acidity of milk indicates its freshness - the lower the acidity, the fresher the milk.
Acidity of milk.
Acidity characterizes the freshness of milk, so it is always determined in non-canned samples. Fresh, just milked milk has an acidity of 17–18°, but after two hours (if the milk has not been cooled) the acidity increases. With an acidity of 22°, milk is on the verge of fresh and sour. Acidity increases as a result of the activity of bacteria, which convert milk sugar into lactic acid.
Acidity is determined as follows: pipette 10 ml of milk into a flask or glass, add 20 ml of distilled water and 3 drops of phenolphthalein (2% alcohol solution). The contents of the flask are titrated with 0.1 normal sodium hydroxide solution (NaOH) to a faint pink color. The amount of alkali spent on milk titration is multiplied by 10. The result shows the titratable acidity of the milk in degrees.
Table. Average ratio of pH to titratable acidity.
Determination of milk fat content.
To determine the fat content in milk, the following equipment and reagents are required: a centrifuge, butyrometers (butyrometers) with rubber stoppers, a bath for heating the butyrometers, an 11 ml pipette, automatic pipettes (in extreme cases, pipettes) of 1 and 10 ml, sulfuric acid of specific gravity 1 .81–1.82 and isoamyl alcohol.
The procedure for determining the amount of fat in milk is as follows:
- Automatically pour 10 ml of sulfuric acid into a clean and dry butyrometer;
- pipette exactly 11 ml of well-mixed milk, directing the stream onto the wall of the butyrometer and without mixing the milk with the acid;
- using a machine or a pipette, pour in 1 ml of isoamyl alcohol, avoiding wetting the neck of the butyrometer;
- wrap the butyrometer in a napkin and close it with a rubber stopper so that the end of the stopper comes into contact with the liquid;
- shake the butyrometer until the milk proteins are completely dissolved, and then turn it over several times, making sure that the liquid is mixed and homogeneous;
- Place the butyrometer with the plug facing up for 5 minutes. in a water bath at a temperature of 65°;
- remove the butyrometer from the bath, wipe it and insert it into the centrifuge cartridge with the narrow end towards the center; in the case of an odd number of butyrometers, it is necessary to install a butyrometer filled with water for symmetry and balance;
- screw on the centrifuge lid and, gradually accelerating the rotation of the handle, bring the centrifuge rotation speed to 800–1000 rpm, which corresponds to 60–70 revolutions of the handle; continue centrifugation for 5 minutes;
- Place the butyrometer with the plug down again in a water bath at 65° for 5 minutes;
- count the fat on the butyrometer scale, adjusting the fat column in relation to the scale by screwing in or unscrewing the plug.
The butyrometer reading corresponds to the number of grams of fat in 100 ml of milk. The volume of 10 small scale divisions corresponds to 1 g of fat.
In accordance with GOST 5867–90, 3 methods are used to determine the fat content of milk and dairy products:
- acid method,
- optical (turbidimetric),
- extraction.
(GOST 5867–90 Milk and dairy products. Methods for determining fat. — download).
Determining the percentage of fat content without special equipment is quite difficult. However, this can be done at home and get an approximate result. This is done very simply. You need to take the milk sample to be tested, shake it, pour it into a measuring cup and leave it overnight. In 6–8 hours, the milk cream will rise to the surface in the form of a denser layer.
For example, we poured 100 ml of milk into a measuring cup and after 8 hours we saw that the cream had formed a layer with a volume of 4 ml. This means the fat content of this milk is approximately 4%. This method is often given on various sites, but it is always worth considering that the result may contain an error depending on density, temperature and other various factors.
Video.
At the end of the video there is a training video for technologists who will work in a laboratory examining milk samples. What milk tests are performed, what equipment and reagents are used? - learn from the video.
Water results in a decrease in density of approximately 0.003 for every 10% added water. Skim milk has a higher density than non-skimmed milk (1.033-1.037), due to its lower fat content and relatively higher mineral content.
Determination of fat content in milk
Fat is determined by the acid method using butyrometers in accordance with GOST 5867-69.
The method is based on the separation of fat from milk under the action of concentrated sulfuric acid and isoamyl alcohol in the form of a continuous layer, the volume of which is measured in the graduated part of the butyrometer. Butyrometers are manufactured in accordance with the requirements of GOST 1962-66.
Determination technique. Into a dry butyrometer, being careful not to wet the neck, add 10 ml of sulfuric acid with a density of 1.81-1.82 g/cm3 in a cylinder. Then pipette 10.77 ml of the test milk. Having tilted the pipette at an angle of 45° and placing it on the inner wall of the butyrometer neck, allow the milk to slowly drain so that it does not mix with the sulfuric acid, but is layered on it. When the last drop of milk drains from the pipette, hold for 7 seconds without removing the pipette from the butyrometer. The drop remaining in the tip of the pipette is not blown out. Next, add 1 ml of isoamyl alcohol. It is necessary to follow the specified sequence of adding liquids, since if you break it and add milk first, then the clots of coagulated protein that form in the narrow part of the device will make it difficult to determine. Mixing acid and milk leads to strong heating of the mixture, so it is necessary to keep the butyrometer in a stand while adding the reagent.
The butyrometer is closed with a stopper, turned over several times until the proteins are completely dissolved, while wrapping it in a towel and supporting the stopper with the index finger. Then the butyrometers are placed in a water bath with a temperature of 65±2°C for 5 minutes with the plugs down, after which they are inserted symmetrically into the centrifuge nests. In case of an odd number of butyrometers, add another one filled with water. Butyrometers should be placed with the graduated part towards the center (in a horizontal centrifuge) or upward (in vertically placed cartridges). Centrifugation duration is 5 minutes at a rotation speed of 1000-1200 rpm.
During centrifugation, the temperature of the mixture in the butyrometers decreases, and since the butyrometer scale is calibrated at a temperature of 65°C, after centrifugation they are again placed in a water bath with a temperature of 65°C for 5 minutes. Then, maintaining the vertical position of the device, remove it from the water, wipe it with a towel, supporting the stopper, and measure the fat content. To do this, set the lower limit of the fat column at any division of the scale, from which the number of divisions is then counted to the lower point of the concave meniscus of the fat column.
The instrument scale should be at eye level. The butyrometer readings correspond to the fat content in milk as a percentage: large divisions mean whole percentages of fat, small divisions mean tenths. The discrepancy between the butyrometer readings during parallel determinations should not exceed 0.1%.
Determination of milk moisture content
Drying to constant weight according to GOST 3626-73 (arbitration method).
Determination technique. 20-30 g of well-washed calcined sand are placed in a glass with a glass rod and kept for 30 minutes in a drying cabinet at a temperature of 102-105°C. Then close the glass with a lid, cool in a desiccator and weigh (without a lid with an accuracy of 0.001 g). Pipette 10 ml of milk, close and weigh again. Thoroughly mix the milk with sand and heat in a water bath with frequent stirring of the contents until a crumbling mass is obtained. Then the glass is placed in a drying cabinet (102-105°C) and dried for 2 hours. Cover with a lid, cool in a desiccator and weigh. Drying is continued and the cup is weighed every hour until the difference between the last two weighings is less than 0.004 g. The moisture content is calculated as a percentage.
The discrepancy between parallel determinations should be no more than 0.2% (absolute).
Determination of dry residue content by calculation method (GOST 3626-73)
where 4.9 is a constant coefficient;
D420 - density of milk in degrees of lactodensimeter;
0.5 - correction for density.
Determination of milk acidity by arbitration method
One of the important indicators of the quality of milk is its acidity, which is mainly determined by the presence in it of acid salts, partly proteins, 3 organic acids (citric, lactic) and products of the hydrolytic breakdown of certain compounds, such as fat.
The acidity of milk is expressed in degrees Turner, meaning the number of milliliters of decinormal alkali spent to neutralize acidic substances contained in 100 ml of milk.
The acidity of milk is determined according to GOST 3624-67.
Determination technique. Pipette 10 ml of milk into a conical flask with a capacity of 150-200 ml, add 20 ml of freshly boiled cooled distilled water and 3 drops of phenolphthalein. The mixture is thoroughly mixed and titrated with 0.1 N. solution of sodium hydroxide (potassium) until a pink color appears that does not disappear within 1 minute.
The discrepancy between parallel determinations should not exceed 1°T.
In accordance with the requirements of GOST 13277-67, the acidity of pasteurized cow's milk should not exceed 21°T; freshly milked milk usually has an acidity in the range of 16-18°T. Milk with an acidity above 22°T can coagulate into small flakes when boiled for a long time; with an acidity above 30°T, milk immediately coagulates into flakes when heated.
Determination of protein content in milk
In addition, the yield of dairy products such as cheese, cottage cheese and other products depends largely on the amount of proteins in the original milk. Therefore, determining the protein content in milk should be one of the main operations of technological control of dairy product production processes. Currently, accelerated methods for determining protein in milk and dairy products are being used. There are 2 methods described in this manual: refractometric and formol titration methods.
Refractometric method. This method is based on establishing the difference between the refractive indices of the milk under study and the solution obtained after precipitation of proteins with a solution of calcium chloride during boiling.
Determination technique. Pipette 5 ml of milk into a test tube, add 5-6 drops of a 4% calcium chloride solution. The test tube is capped and placed in a boiling water bath for 10 minutes. The contents of the tube are then filtered through a pleated filter. In the transparent filtrate, as well as in the original milk, the refractive index is determined on an IRF-22 refractometer at 20°C. The protein content in milk (%) is calculated using the formula:
nDm - refractive index of milk at 200C;
nDc is the refractive index of serum at 200C;
0.002045 is a coefficient that allows you to express the resulting difference in refractive indices, % of the total protein.
Material balance.
Let us determine the need for raw materials for the production of 1000 kg of pasteurized milk with a fat mass fraction of 2.5%.
Based on the mass of the finished product, we determine the mass of normalized milk, taking into account milk losses during acceptance, processing and packaging according to the formula:
Mn - mass of normalized milk, kg;
Mgp - mass of the finished product, kg;
P - consumption rate of normalized milk per 1 ton of product, kg/t.
.
Let's calculate the mass fraction of fat in normalized milk:
Zhn=Zhgp+0.05=2.5+0.05=2.55%.
Zhn, Zgp - fat content of normalized milk and the finished product,%.
Since the mass fraction of fat in normalized milk is less than in whole milk, it is necessary to carry out the process of normalization with skim milk by mixing according to the formula:
where Zhc is the fat content of whole milk, 3.6%;
Jo - fat content of skim milk, 0.05%;
Mts - mass of whole milk, kg.
We determine the required mass of skim milk using the formula:
Let us determine the mass of whole milk to obtain 598.4 kg of skim milk as a result of separation using the formula:
Zhs - fat content of cream, 21%.
Bibliography
1. Technology of milk and dairy products / G.V. Solid bread. - M.: Agropromizdat, 1991. - 463 p.
2. Golubeva L.V. Design of dairy industry enterprises with the basics of industrial construction // L.V. Golubeva, Glagoleva L.E. - St. Petersburg, GIORD, 2006. - 288s.
3. Falunina Z.I. Laboratory workshop on general food production technology. M., Agropromizdat, 1981.
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Currently, two methods are used to determine the fat content in milk and dairy products: acid and gravimetric.
1) Gravimetric method determination of fat content is based on its extraction (extraction) with organic solvents and subsequent determination of the amount of fat in the extract. For fat extraction, solvents with low boiling points are used, from which fat removal is not difficult. The most commonly used are petroleum, ethyl, diethyl, sulfuric and other ethers, as well as chloroform and dichloroethane. Petroleum ether has advantages over other solvents, since it extracts less substances associated with fats.
Several modifications of the gravimetric method are known: according to Rose-Gottlieb, according to Schmidt-Bondzinsky - Raclaw, according to Mojognier, the express method.
2) Sulfuric acid or standard method (Gerber method) GOST 5867 - 90. The determination is carried out in a butyrometer (butyrometer), showing the fat content as a percentage. To determine the fat content in milk, it is necessary to free the fat globules from the protein shells. Concentrated sulfuric acid is used as a solvent.
The following schematic reaction occurs:
NH 2 R (COOH) 4 + H 2 SO 4 ð Ca SO 4 + NH 2 R (COOH) 6
(COO) 2 Ca Precipitated Protein,
Protein-Calcium Conc. sulfuric sulphate transferred
calcium acid complex (gypsum) in solution
For a more complete release of the fat freed from the protein membranes, isoamyl alcohol is used.
H 2 SO 4 + 2 C 5 H 11 OH = 2H 2 O + (C 5 H 11) 2 SO 4
Sulfuric Isoamyl Amyl sulfur ether,
acid alcohol promotes fat fusion
Deviations in the volume of the pipette are allowed no more than ± 0.04 ml (subject to holding for 6 seconds (counting up to 6) after the main part of the water has flowed out; 4) measure 1 ml of isoamyl alcohol with a dispenser and pour into the butyrometer without soaking the neck. If the neck of the butyrometer becomes wet, it must be carefully wiped with filter paper.
butyrometer←10 ml H 2 SO 4 ← 10.77 ml milk ← 1 ml isoamyl alcohol
5) close the butyrometer with a well-fitted and dry stopper so that the stopper touches its contents; To prevent the plug from becoming wet and to ensure that the plug holds securely, it is better to rub the plug with chalk before screwing it into the butyrometer. If the contents of the butyrometer are insufficient, add a few drops of distilled water to it. Previously, before the adoption of the new GOST in 1990, it was recommended to add sulfuric acid to the butyrometer in such cases;
6) wrap the butyrometer in a napkin, mix the contents thoroughly and place in a water bath with the stopper down at 65 ± 2 o C for 5 minutes;
7) remove the butyrometer from the bath (wipe the wet butyrometer), place it in a centrifuge, being sure to maintain symmetry (if one butyrometer is used in the centrifuge to determine fat, it is necessary to place another butyrometer symmetrically), centrifuge for 5 minutes, at a centrifuge rotation speed of 1000-1200 rpm minute;
8) after centrifugation, place the butyrometer again in the bath for 5 minutes, with the stopper down; measure the percentage of fat in milk using the butyrometer scale. To do this, use a rubber stopper to align the lower limit of the fat column with a whole division of the butyrometer scale. The upper border of the column is considered to be the lower edge of the concave meniscus. Each small division of the milk butyrometer corresponds to 0.1%, and each large division corresponds to 1%.
When making parallel determinations with two butyrometers, a discrepancy in readings of no more than 0.1% is allowed.
When determining fat using the Gerber method, the following should be taken into account:
1) the temperature when measuring milk and sulfuric acid should be 20±2 o C;
2) the internal diameter of the pipette drain hole must be such that water in a volume of 10.77 ml flows out within 8 - 12 seconds;
3) do not collect a sample of mixed milk above marks at 1 cm;
4) wipe the outside of the pipette;
5) do not touch the end of the pipette to the sulfuric acid, since at the tip of the pipette some of the milk may coagulate and the clot may prevent the liquid from flowing out completely;
6) a drop of milk remaining in the tip of the pipette (after counting 6) do not blow;
7) the water level in the bath should be slightly higher than the level of the fat column in the butyrometer;
8) the fat column should not be moved along the scale, otherwise the butyrometer must be put back into the bath before the countdown;
9) fat should be counted quickly so that the contents do not cool;
10) the column of fat should be transparent, light yellow in color. Cloudy or dark-colored fat indicates a misidentification.
Cloudy whitish layer results from the use of too weak sulfuric acid, a very low temperature of the acid or milk when measuring, or incomplete mixing of them.
Dark fat obtained as a result of using too strong sulfuric acid; adding more acid than necessary; high temperature of acid and milk when measuring; quickly adding milk to sulfuric acid; long break between mixing and centrifugation. Sometimes a loose fluffy sediment appears at the bottom of the fat column. This may be due to insufficient centrifugation (in terms of the number of revolutions of the centrifuge and the time of its rotation) or a small amount of isoamyl alcohol poured into the butyrometer. The appearance of a dark-colored “plug” under a column of fat, interfering with the count, occurs when an excessive amount of preservatives is added to milk samples. To prevent the formation of plugs, it is recommended to add a drop of formalin to the butyrometer.
Butyrometry (from the Greek butyron - oil and metreo - I measure) is a method for determining the amount of fat in milk and dairy products using a special device - a butyrometer (butyrometer). Strong sulfuric acid is used as the main reagent, which converts insoluble calcium salts of milk into a soluble sulfuric acid casein compound. The latter sharply reduces the amount of adsorption of fat globules and thereby promotes their fusion.
In the USSR they produce: a) butyrometer for milk and dairy products (GOST 1962-50);
b) butyrometer for cream (GOST 1963-51);
c) butyrometer for skim milk, buttermilk and whey (GOST 1964-53).
Butyrometer for milk and dairy products (Fig., a) is used to determine the amount of fat in milk, curdled milk, acidophilus milk, acidophilus kefir, koumiss, milk ice cream and cheese. Each long line on the scale represents 1 g and each small line represents 0.1 g of fat per 100 g of milk.
Butyrometers: a - for milk and dairy products; b - for cream; c - for skim milk, buttermilk and whey; 1 - head; 2 - neck; 3 - body; 4 - neck.
The butyrometer for cream (Fig., b) is used to determine the amount of fat in cream, sour cream, cottage cheese, curd products and ice cream. It is designed basically like a milk butyrometer.
The butyrometer for skim milk, buttermilk and whey (Fig., c) is designed like the previous ones, with the only difference that the volume of its working part is twice as large as that of milk and cream butyrometers. The neck of the butyrometer is elongated in the form of a tube with a very narrow diameter, and the scale has divisions indicating tenths and hundredths of a gram. The amount of fat in the products for which this device is designed to study is very small. Therefore, for analysis they take much more than whole milk, and the butyrometer scale must be calibrated more accurately.
Determination of fat in milk. The butyrometer is placed on a stand, 10 ml of H 2 SO 4 (pl. 1.81 -1.82) is poured in, then, slightly tilting the device, 11 ml of well-mixed milk (t° 20°) is carefully layered on the acid along its wall, avoiding mixing milk with H 2 SO 4; add 1 ml of isoamyl alcohol.
The described procedure for introducing liquids into the butyrometer is strictly observed, being careful not to wet the neck of the device. The milk pipette is designed for free flow of liquid; the remaining drop of milk is not blown out. Close the butyrometer with a stopper, screwing it in so that the circular protrusion on the stopper fits into the thread of the neck. The cork must be dry. Having wrapped the butyrometer in a towel (the liquid and the device are very hot), take it by the neck and, holding the plug with your finger, shake it several times until a homogeneous mass without flakes is obtained in the butyrometer. Place the butyrometer (with the plug down) for 5 minutes. in a water bath with water temperature 65-70°. Having taken the butyrometer out of the bath, wipe it dry, transfer the released fat to the neck of the device by screwing or unscrewing the cap, insert the device into the centrifuge sleeve with the cap facing the circumference and centrifuge for 5 minutes. at a speed of at least 1000 rpm. The butyrometer is removed from the centrifuge, grasping it by the neck, and again placed in the bath under the same conditions. After taking it out of the bath, wipe it dry and count the released fat on a scale. The butyrometer is held with your left hand, vertically and against the light, and the plug of the device is held with your right hand. If the fat column is outside the scale, it is moved with a stopper until the lower border of the column coincides with any long line of the scale; count the number of divisions from this line to the lower point of the meniscus of the fat column. The eye should be at the level of the upper border of the column. If the fat is not clearly separated from the rest of the liquid, which happens due to insufficient heating in the bath or insufficient centrifugation, the determination should be repeated.
Determination of fat in yogurt, acidophilus milk, acidophilus kefir and kumis. 10 ml of H 2 SO 4 (pl. 1.81 -1.82), 5 ml of the mixed product are poured into the milk butyrometer; the pipette from under the taken product is washed with 6 ml of water, which is poured into the device, and 1 ml of isoamyl alcohol is added. The further course of the analysis is the same as when determining fat in milk. The result of the fat reading on the butyrometer scale is multiplied by 2.2.
Determination of fat in cream, sour cream, cottage cheese and curd products. Use a butyrometer for cream. A sample of 5 g is taken in the butyrometer itself, 5 ml of water is added, rinsing the neck of the device with it, carefully pour in 10 ml of H 2 SO 4 (pl. 1.81 -1.82; for sweet curd products, take acid pl. 1.80 -1.81). The further course of the analysis is the same as in the study of milk. Before centrifugation, the butyrometer is heated, shaking frequently, until the protein substances are completely dissolved. The volume of two divisions on the butyrometer scale corresponds to 1% fat in 100 ml of product.
Fat in cream can also be determined using a milk butyrometer. To do this, the cream is diluted with water at a temperature of 40° (at the rate of 5 ml of cream per 50 ml of water), mixed thoroughly, cooled to 20° and fat is determined in the same way as in milk. The value obtained on the butyrometer scale is multiplied by the dilution factor.
The described acid method for determining fat in milk and dairy products was developed more than 60 years ago. It is good, simple and gives accurate results even when studying products containing fat in the range of 0.05-0.1%. However, the method has two serious drawbacks: a) the danger of working with strong sulfuric acid, especially during mass analyses; b) the need to use a special centrifuge. This has necessitated the search for safe and cheaper methods. The essence of the so-called alkaline methods comes down to the conversion of casein-calcium salts of milk into soluble potassium or sodium compounds of casein. Isoamyl alcohol is poorly soluble in alkalis; therefore, during analysis, less of it is taken than in the acid method; it is replaced with isobutyl alcohol or a mixture of alcohols (tartar, etc.).
The mass fraction of fat in milk is determined after destruction of the protective shells of fat globules (Gerber acid method, Rose-Gottlieb extraction method) or without methods using semi-automatic and automatic devices.
The acid method is considered the standard method and is still widely used in our country and a number of other countries due to its accuracy, relative simplicity and availability.
Principle of the method: The method is based on the release and separation of fat from the fat globules of a milk sample under the influence of concentrated sulfuric acid and isoamyl alcohol, followed by centrifugation.
Adding sulfuric acid to the butyrometer will not only destroy the protein shells of fat globules, but also acts on the main protein, calcium caseinate, which precipitates into flakes and dissolves in excess acid. The reaction is accompanied by an increase in the temperature of the mixture to 70-75*C.
When isoamyl alcohol is added, it reacts with the acid to form isoamyl sulfur ester, which diffuses into the excess acid solution and lowers the surface tension at the milk fat/plasma interface and promotes fat release.
Heating and subsequent centrifugation of the butyrometer contents lead to complete separation and combination of fat into a continuous layer, the amount of which is measured on the butyrometer scale.
Instruments: instruments for automatic measuring of sulfuric acid and isoamyl alcohol for 10 and 1 ml, a stand for butyrometers, a butyrometer for milk with measurement limits from 0 to 6% or from 0 to 7%, rubber stoppers for butyrometers, pipettes for 10.77 ml , water bath, centrifuge.
Materials for research and reagents: raw milk, sulfuric acid with a density of 1.81-1.82 g/cm3, isoamyl alcohol 0.811-0.813 g/cm3.
Progress of the analysis: clean, tested butyrometers are placed in a tripod, 10 ml of sulfuric acid is poured into one of them using an automatic pipette, being careful not to lubricate the neck of the butyrometer. Then, use a pipette to measure 10.77 ml of the test milk, placing the tip of the pipette on the inner wall of the butyrometer neck at an angle, and allow the milk to slowly flow down the butyrometer wall so that it does not mix with sulfuric acid, but liquids are layered. The remaining part of the milk in the tip of the pipette should not be blown out, since the volume of the pipette is designed for free flow of liquid. Then 1 ml of isoamyl alcohol is poured into the butyrometer using an automatic pipette, without allowing the neck of the butyrometer to become wet. Then the butyrometer is closed with a special rubber stopper and turned over 3-4 times to mix the liquids, after placing the butyrometer in the cartridge and wrapping it in a napkin, then shake until the proteins are completely dissolved. The butyrometer is placed with the stopper down in a water bath with a temperature of 63-67* C and kept for 5 minutes. Then it is taken out, wiped and placed in a centrifuge cartridge, the butyrometers are set in sevenfold and an even amount, if the butyrometer is not even, the butyrometer is set with water. Close the centrifuge with a lid and turn on for 5 minutes. Then the butyrometer is removed from the centrifuge and placed with the stopper down in a water bath at a temperature of 63-67*C for 5 minutes. The water level in the water bath should be higher than the liquid in the butyrometer. The butyrometer is removed from the bath, wiped and readings are quickly taken from the scale. To do this, holding the butyrometer vertically at eye level, moving the plug up and down, set the lower limit of the fat column at any whole division and count the number of divisions to the lower point of the meniscus of the fat column. If the fat column does not separate sharply from the rest of the liquid, the butyrometer must be shaken and placed in a bath at a temperature of 63-67*C for 5 minutes. Centrifuge and put back into the bath, take readings of the fat content.
Acid method for determining m.d.f. has significant disadvantages: the duration of determination. The use of expensive reagents, increased danger for operating personnel, the inability to control the fat content of the product in the flow, etc.
Semi-automatic and automatic butyrometers developed in recent years do not have these disadvantages. Their action is based on measuring the degree of light scattering by fat globules or the intensity of their fluorescence, as well as measuring the speed of ultrasound propagation in milk, the degree of absorption of infrared radiation by milk components, etc.
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