A decrease in milk acidity may be due to increased content urea, which may be the result of excess protein intake from green feed, exceeding the consumption standards for urea as a nutritional nitrogen supplement, or high content nitrogenous fertilizers on pasture. Due to low acidity, such milk curdles more slowly rennet and resulting

The curd is less easily processed when making cheeses.

pH (active acidity) - the concentration of hydrogen ions, depending on the composition of the milk, varies within narrow limits - from 6.55 to 6.75. With titratable acidity raw milk above 18oT, when lactic acid is already formed, the pH decreases slightly. This is explained by the presence of a number of buffer systems in milk - protein, phosphate, citrate, bicarbonate lactate, etc. The buffer capacity of milk is understood as the amount of 1 N solution of acid or alkali that must be added to 100 cm3 of milk to shift the pH by one. Fresh buffer capacity normal milk for acid it is 1.7 - 2.6, and for alkali - 1.2 - 1.4. Buffer properties components milk has great importance for the functioning of lactic acid bacteria. The minimum pH value for the development of thermophilic lactic acid rods is 3.5 - 4.25, for lactococci - 4.75. Due to the buffering properties of milk, the pH of kefir at the end of ripening at a titratable acidity of 75 - 80oT is only 4.85 - 4.75, and the pH of cottage cheese at an acidity of 58 - 60oT is 5.15 - 5.05.

Such pH values ​​allow the development of lactic acid streptococci, which accumulate aromatic substances.

During production hard cheeses pH cheese mass is 5.2 - 5.6 with very high titratable acidity up to 200oT, which is associated with a significant buffer capacity of proteins.(2)

Density of milk. The density or volumetric mass of milk at 20 ° C ranges from 1027 to 1032 kg/m3. The density of the harvested milk is 1028.5 kg/m or 28.5 hydrometer degrees. The density of milk depends on temperature (decreases as it increases) and on chemical composition(decreases with increasing fat content and increases with increasing protein, sugar and salt content). The density of milk should be determined no earlier than 2 hours after milking, since the density of freshly milked milk is lower due to the content of gases in the milk and changes in the density of milk fat.

Colostrum and milk obtained from animals with mastitis differ significantly in density from normal milk. The density of milk changes when adulterated - it decreases when water is added and increases when cream is raised or diluted with skim milk.

The density of dairy products depends on their composition: cream 8 - 10% fat - density 1024, cream 20% fat - 1018, cream 35% fat - 998, sweetened condensed milk - 1270 - 1295, whey 1019 - 1027, skim milk - 1032 – 1035, buttermilk 1031 – 1033.(16)

Table 2. Average amount of vitamins in milk.

Vitamins
A (retinol)
D (antirachitic)
E (tocopherol)
K (antihemorrhagic)
B1 (thiamine)
B2 (riboflavin)
B6 (adermin)
B12 (anti-anemic)
PP (nicotinic acid)
B3 (pantothenic acid)
C (ascorbic acid)
N (biotin)

Regulation of milk secretion. It has been established that the nervous and endocrine system. Afferent impulses are due to the presence of a rich receptor apparatus - mechano-, thermo- and chemoreceptors are widely represented in the mammary gland. The afferent impulse generated in the receptors of the mammary gland enters the spinal cord, where a short reflex arc is formed - the interaction of the sensitive and effector neurons develops, as a result of which the so-called segmental reflex to the mammary gland occurs.

At the same time, afferent impulses reach the medulla oblongata and hypothalamus through the spinal cord conduction system - the dorsal longitudinal fasciculus and spinothalamic tracts. The mammary gland has a wide representation in the hypothalamic structures, which are responsible for the production of releasing factors (liberins) and inhibitory factors (statins), which determine the production of lactogenic hormones. From the hypothalamus, excitation goes to the cerebral cortex, where a community of nerve centers is formed that control the intensity of the lactation process and a special state of the body “lactation dominant” is created.

1.3 Rules for milking cows. Hygiene of dairy equipment

Milk is not excreted spontaneously, but only in the presence of certain specific effects on the gland - sucking or milking. The secretion of secretion components in the alveolar epithelium occurs cyclically - the phases of the secretory cycle, including the transport of precursors, the synthesis and design of the sector product and its removal outside the cell, are completed in a period of time that takes from 55 to 70 minutes. During the time between suckling or milking, several secretory cycles can occur in the secretory epithelium, and when excess amounts of milk accumulate in the alveolar epithelium, inhibition of the secretory process is observed.(5)

It is customary to divide the milk in the capacitive system of the organ into cisternal and alveolar portions. The alveolar portion of the secretion fills the cavity of the alveoli and small interalveolar ducts and makes up from 25 to 48% of the single milk yield. By the time of milking, the tank contains about 25% of the milk yield, but with full pre-milking preparation, massage, and washing of the udder, the bulk of the milk (85 - 97%) moves into the tank. This rather conventional division of milk yield is necessary to describe the phases of the milk ejection reflex: nervous and neurohumoral.

The acidity of milk is used to judge its freshness. Acidity must be known to establish the type of milk, as well as to determine the possibility of pasteurization and processing of milk into dairy products. Acidity can be determined using a pH meter (active acidity). Active acidity milk is in the range of 6.5 - 6.7. Typically, titratable acidity is determined in conventional degrees or Turner degrees (o T).

Under Turner's Degree the amount of milliliters is implied to be 0.1 N. alkali solution used for neutralization (titration) 100 ml of milk, diluted twice with distilled water, with phenolphthalein as an indicator.

Titratable acidity fresh milk is within 16 - 18 o T and is determined by:

1) acidic nature of proteins (5-6 o T);

2) phosphoric acid, citric acid salts and citric acid(10-11 o T);

3) dissolved carbon dioxide (1-2 o T).

1) Titration method. The method is based on the neutralization of acids contained in the product with an alkali solution (NaOH, KOH) in the presence of the indicator phenolphthalein.

Determination technique. Using a measuring pipette, measure 10 ml of milk into the flask, add 20 ml of distilled water and 2 - 3 drops of a 1% alcohol solution of phenolphthalein. When determining, water is added in order to more clearly detect the pink tint during titration. Then, while slowly shaking the contents of the flask, a decinormal (0.1 N) solution of alkali (caustic soda) is poured from a burette until the color is slightly pink, corresponding to the control color standard, and does not disappear within 1 minute. The amount of alkali used for titration (measured according to the level of the lower meniscus), multiplied by 10 (that is, recalculated per 100 ml of milk), will express the acidity of the milk in degrees Turner. The discrepancy between parallel determinations should be no more than 1 o T. If distilled water is not available, the acidity of milk can be determined without it. In this case, the reading results must be reduced by 2 o T.

2) Maximum acidity of milk. The method for determining the limiting acidity allows for sorting during mass acceptance of milk into standard (up to 19 - 20 o T) and non-standard (over 20 o T). The method is based on the neutralization of acids contained in the product with an excess amount of alkali (NaOH, KOH) in the presence of the indicator phenolphthalein. In this case, the excess of alkali and the intensity of color in the resulting mixture are inversely proportional to the acidity of the milk.

Determination technique. To prepare a working solution of alkali, measure into a 1 liter volumetric flask required quantity(table) 0.1 n. alkali solution (NaOH), 10 ml of 1% phenolphthalein solution and add distilled water to the mark.

Determination of the limiting acidity of milk

10 ml of sodium hydroxide (potassium), prepared to determine the corresponding degree of acidity, is poured into a series of test tubes. 5 ml of the test milk is poured into each test tube with the solution and the contents of the test tube are mixed by inverting. If the contents of the test tube become discolored, the acidity is higher than that corresponding to the solution.

Instead of the above NaOH solution, you can use another solution. To do this, measure 10 ml of distilled water into test tubes, add 2-3 drops of phenolphthalein and 0.1 N. NaOH solution corresponding to a certain acidity of milk, in the following quantity:

1.1 ml NaOH corresponds to an acidity of 22 o T

1.0 ml NaOH corresponds to an acidity of 20 o T

0.95 ml NaOH corresponds to an acidity of 19 o T

0.90 ml NaOH corresponds to an acidity of 18 o T

0.85 ml NaOH corresponds to an acidity of 17 o T

0.80 ml NaOH corresponds to an acidity of 16 o T

In large factories, the method of establishing the maximum acidity of milk is used to automatically sort it in the flow into fresh and sour.

3) Boiling test. This test is used to distinguish truly fresh milk from mixed milk, to which milk has been added. increased acidity. The freshness of milk is determined by boiling small portion in vitro. Usually, milk curdles when boiled if its acidity is above 25 o T. But a mixture of milk with an acidity of 27 o T and 18 o T will also curdle when boiled, although the titratable acidity of such a mixture may not exceed 22 o T. Due to the simplicity of this method, it is desirable when assessment of milk quality. delivered to dairies.

4) Acid-boiling test. It is used to judge both the acidity and the state of milk proteins.

Determination technique. To 10 ml of normal fresh milk you can add up to 0.8 - 1 ml of 0.1 N. solution of sulfuric acid, hold the mixture for 3 minutes in boiling water, and it will not curdle. If milk curdles when less acid is added, it means that the protein in it has changed mainly under the influence of microflora.

5) Determination of milk freshness. The freshness of milk is expressed in degrees, which is the sum of the degrees of acidity and the coagulation number of the milk. Coagulation number- number of milliliters 0.1 n. sulfuric acid solution required to curdle 100 ml of milk.

Degree of freshness normal milk should not be lower than 60. If changes have occurred in the milk, mainly under the influence of putrefactive bacteria, then less acid will be needed to curdle the milk. This milk will have less degree of freshness than normal milk.

Example. When determining acidity, 1.8 ml of 0.1 N was consumed. NaOH solution, that is, the acidity is 18 o T. 3.0 ml of 0.1 N was used to precipitate casein (10 ml of milk + 20 ml of water). sulfuric acid solution, therefore, the clotting number is 30.

Degrees of freshness 18 + 30 = 48, which means that the milk is of poor quality, since with low titratable acidity, relatively little acid was required to precipitate casein.

The acidity of milk from individual animals can vary within fairly wide limits. It depends on the state of metabolism in the animal’s body, which is determined by feed rations, breed, age, physiological state, individual characteristics of the animal, etc. The acidity of milk changes especially strongly during the lactation period and when animals become ill.

So, in the first days after calving, the acidity of milk is increased due to the high content of proteins and salts, then, after a certain time (40-45 days), it decreases to the physiological norm. Milk before the end of cows' lactation has low acidity.

When animals become ill, the acidity of milk usually decreases. It changes especially sharply in animals with mastitis.

Although titratable acidity is a criterion for assessing the freshness and naturalness of milk, it should be remembered that milk may have increased (up to 26°T) or decreased (less than 16°T) acidity, but nevertheless it cannot be considered of poor quality or adulterated, since it is heat-resistant and withstands boiling or gives a negative reaction to the presence of soda, ammonia and admixtures of inhibitory substances. The deviation of the natural (native) acidity of milk from the physiological norm in this case is associated with a violation of feeding rations. Such milk is accepted as varietal based on the testimony of a stall test confirming its naturalness. More precisely, the acidity of milk can be controlled using the pH method.

The observed increase (up to 23-26°T) in the acidity of milk obtained from individual animals and even an entire herd is a consequence of a serious violation mineral metabolism in the body of animals. It is usually caused by an insufficient amount of calcium salts in the feed. Such cases occur when animals are fed large quantities of acidic feed (green mass of cereals, corn, corn silage, beet pulp, stillage) poor in calcium salts. Fresh milk with high natural acidity is suitable for production fermented milk products, cheese and butter.

A decrease in milk acidity is mainly due to increased urea content, which can be caused by excess protein intake from green feed, the use of significant amounts of nitrogen supplements in animal diets or nitrogen fertilizers on pastures. Milk with low acidity is not advisable to process into cheeses - it slowly coagulates with rennet, and the resulting curd is poorly processed.

Active acidity (pH).

Active acidity is expressed by the pH value. It characterizes the concentration of free hydrogen ions (activity) in milk and is numerically equal to the negative decimal logarithm of the concentration of hydrogen ions (H +), expressed in moles per 1 liter.

pH value whole milk averages 6.7-6.5 and ranges from 6.3 to 6.9, which indicates a slightly acidic milk reaction.

Since in current GOSTs and technological instructions acidity is expressed in units of titratable acidity, there are established average ratios for comparing pH readings for milk and basic fermented milk products with them. For example, for prepared milk these ratios are as follows:

There is no complete correspondence between active and titratable acidity, since titratable acidity does not indicate the content of any alkalis in milk, but a shift in pH from 6.3 to 8.2-8.5. This is determined by the appearance of the red color of phenolphthalein added to the milk. Freshly milked milk may have high titratable acidity, but low active acidity, and vice versa. With an increase in titratable acidity as a result of the formation of acid during the development of microorganisms, the pH value does not change for some time due to the buffering properties of milk, characterized by the presence of proteins, phosphates, and nitrites in it. If instead of an acid you add a certain amount of alkali to milk, the pH value will not change, but the titratable acidity will change. Only when the acidic and amide groups of amino acids in proteins are neutralized does a sharp change in active acidity occur.

The pH indicator is of great importance, since the stability of the polydisperse system of milk, the growth conditions of microflora and its influence on the processes of cheese ripening, the speed of formation of components on which the taste and smell of dairy products depend, the thermal stability of milk proteins, and enzyme activity depend on it. The quality of raw milk and dairy products is assessed by pH value.

The acid dissociation of proteins is insignificant, therefore the concentration of hydrogen ions remains constant, while the titratable acidity increases, since when it is determined, both active and bound hydrogen ions react with the alkali.

When assessing the quality of milk, the following are determined: organoleptic indicators (taste, color, smell, consistency), physicochemical indicators (density, acidity, freezing point, heat resistance, SOMO), mass fraction of fat and protein, sanitary and hygienic indicators.

Organoleptic indicators quality of milk. The color, smell, taste and consistency of milk depend on its composition. White color with a yellowish tint and the opacity of whole milk are due to the presence of colloidally dissolved casein compounds with phosphorus-calcium salts and fat in an emulsified state. Carotene and lactoflavin give milk a yellowish tint.

The taste and smell of natural milk are influenced by proteins (tasteless in pure form), lipids, milk sugar, acids, mineral salts, vitamins and other substances. Fat gives tenderness, milk sugar gives sweetness, protein and minerals form the taste of milk. Free low-molecular fatty acids, carbonic compounds, and their oxidation products determine the aroma of milk.

Deviations in organoleptic properties are classified as milk defects, which are of feed, bacterial, technical and physico-chemical origin. Defects of feed origin can be detected immediately after milking. They occur when cows eat sorrel, chamomile, wormwood, colza, garlic, wild onion, and buttercup, which contain large amounts of essential oils. Introduction to cabbage diets large quantities leads to the appearance of cabbage taste and smell in milk.

Milk can adsorb feed odors. Volatile carbohydrates, esters, acids, alcohols found in feed are absorbed by milk and give it feed flavors and odors.

Defects of bacterial origin (viscous milk, blue, red, excessively yellow) are detected during storage. As a result of proteolysis of proteins

Enzymes of putrefactive bacteria in milk create putrefactive, cheesy and musty flavors. Under the influence of enzymes of various microflora, carbohydrates can decompose with the formation of butyric and other carboxylic acids, volatile carbonyl compounds, and alcohols that cause milk defects.

When storing milk, an oxidized taste may appear associated with peroxides and aldehydes formed during the oxidation of unsaturated acids contained in milk fat and phospholipids. Fat is prone to oxidation at high concentrations of copper and iron in milk, as well as when stored in light under the influence of sunlight.

The most common defects in milk consistency are: viscous, slimy, foamy, watery, curdled, sandy. Color defects: blue and cyan, excessively yellow, bloody. Odor defects: ammonia, cabbage, beet, medicinal, acetone, tobacco, butyric acid, sour, yeast, alcohol, putrefactive, musty, barn. Taste defects: bitter, fishy, ​​rancid or tart-salty, brackish, soap, feed, turnips, radishes, garlic, onions, beets, herbs, metallic, taste of petroleum products.

Physico-chemical indicators of milk quality. The most important indicator physical and chemical properties milk - density.

Density. This is the mass of a substance at 20 °C contained in a unit volume (kg/m3). The density of milk determines its naturalness. In our country, the density of whole cow's milk is 1030 kg/m3 with fluctuations from 1027 to 1033 kg/m3. The density of fresh, just milked milk is lower than that which has been cooled and stood for 2-3 hours. This is explained by the volatilization of carbon monoxide in the milk, the transition of fat to a solid state and the hydration of proteins.

The density of milk is determined with a special hydrometer (lactodensimeter) at a temperature of 20 °C. It is permissible to determine density at 15-25 °C, bringing it through an amendment to 20 °C, which is 0.2 °A for each temperature degree. If the temperature is more than 20 °C, the correction will be positive, if less than 20 °C, the correction will be negative. The degree of lactodensimeter (°A) refers to the third and fourth digits of the density indicator. For example, a density of 1029 kg/m3 in degrees lactodensimeter will be 29 °A.

When water is added, the density of milk decreases by approximately 2.5-3 °A for every 10% of water added.

Freezing point. The freezing point is the temperature at which milk turns into a solid state. It is established using a Beckman thermometer. Normal cow's milk freezes at -0.54 °C. Depending on the composition of the milk, this indicator can range from -0.525 to -0.565 °C. The freezing point of colostrum ranges from -0.57 to -0.58 °C. The dependence of the freezing point on the concentration of truly soluble parts of milk can be used in practice to determine the adulteration of milk and calculate the added water. Adding 1% water increases the freezing point by an average of 0.005 °C.

Thermal stability of milk. This is its resistance to high temperatures (up to 140 ° C) without protein coagulation. Under production conditions, the heat resistance group of milk is determined by the formation of protein flakes in a Petri dish when mixing 2 ml of milk with 2 ml ethyl alcohol different concentrations: 80% (I group of heat resistance), 75% (II group), 72% (III group), 70% (IV group), 68% (V group).

Titratable acidity. The acidity of milk determines its freshness. Freshly milked milk has an amphoteric, that is, acidic and alkaline reaction, since proteins contain amine and acid groups. Titratable acidity is expressed in conventional degrees, or Turner degrees. The Turner degree is the number of milliliters of 0.1 N alkali solution (KOH or NaOH) required to neutralize 100 ml of milk diluted twice with distilled water, with phenolphthalein as an indicator. Sometimes titratable acidity is converted to lactic acid. To do this, the number of Turner degrees is multiplied by 0.009 (the number of grams of lactic acid equivalent to 1 ml of 0.1 N alkali).

The titratable acidity of fresh milk is 16-18 °T. During milk storage, microorganisms developing in it ferment milk sugar, which contributes to the accumulation of lactic acid, which increases titratable acidity. The acidity of milk depends on a number of factors: breed, individual characteristics of animals, feeding conditions, stage of lactation of cows. In the first month of lactation of cows it is 20 °T, in the tenth month it is 15-13 °T, sometimes it drops to 6 °T. As cows age, the acidity of milk decreases.

Low acidity of milk indicates that it was obtained from sick animals. Milk with high acidity is unsuitable for making dairy products and may curdle during pasteurization.

In addition to titratable acidity, they also determine active acidity. This indicator is expressed by the value pH, on average it is 6.5 (ranges from 6.3 to 6.9), which indicates a slightly acidic reaction of the milk.

The technical regulations for milk regulate the indicator of dry skimmed milk residue (SMR).

SOMO. This indicator is determined by subtracting the fat content from the dry residue. The dry residue contains all the chemical components of milk (fat, proteins, milk sugar, minerals, vitamins, enzymes, etc.). Depending on the stage of lactation, age, feeding ration and other factors, it can vary significantly - from 11 to 14%. SOMO is a more constant value. It is used to judge the naturalness of milk: if the SOMO is below 8%, then the milk is probably diluted with water.

When assessing the quality of milk, additional indicators not regulated by regulatory documents are also determined: viscosity, surface tension, boiling point, electrical conductivity, specific heat capacity, thermal conductivity, redox potential, refractive index, osmotic pressure. These indicators are determined when determining the naturalness of milk and during its processing.

Sanitary and hygienic indicators of milk quality. They are judged by their purity, bacteria content and somatic cells, the nature of the microflora, the presence of pathogens, chemical pollutants. The technical regulations for milk and dairy products regulate the following milk safety indicators:

Microbiological indicators: number of mesophilic aerobic and facultative anaerobic microorganisms(KMAFAnM), coliform bacteria (coliforms), sulfite-reducing clostridia, S. aureus, pathogenic microorganisms, including salmonella and Listeria monocytogenes,

Toxic elements (lead, arsenic, cadmium, mercury);

Pesticides - hexachlorocyclohexane (a, R\at- isomers), DCT and its metabolites;

Mycotoxins (aflatoxinMO;

Antibiotics (chloramphenicol, tetracycline group, streptomycin, penicillin);

Radionuclides (cesium-137 and strontium-90);

Inhibiting substances.

Requirements for milk safety indicators are given in Chapter 5.

Purity. This indicator characterizes the sanitary conditions for obtaining milk. Contamination of milk with various mechanical impurities (wool, particles of feed or bedding, dust, etc.) indicates a lack of proper care for animals and failure to comply with basic sanitary and hygienic rules. Sources of contamination can be: udder, skin and hair of the animal, barnyard air, dairy utensils and equipment, feed, bedding, and service personnel.

According to the degree of purity, milk is divided into three groups: the first is pure milk, good quality; the second - satisfactory and the third - contaminated.

Microorganisms of raw milk. They can be conditionally divided into three groups: beneficial to human health (lactic acid, widely used in the dairy industry), harmful to health (causative agents of diseases) and worsening the hygienic properties of milk (butyric acid, putrefactive).

The content of bacteria in milk is determined By reductase test. Bacteria that get into milk secrete enzymes, in particular reductase. There is no reductase in fresh, just milked milk. Reductase decolorizes solutions of methylene blue or resazurin added to milk. When a solution of methylene blue is added to milk, the mixture turns blue; when resazurin is added, it turns grayish-lilac, and then becomes discolored under the action of reductase. The color fades faster the more reductase there is in the milk. Having established the duration of discoloration of methylene blue or resazurin, the number of bacteria in it is determined using special tables.

Character of microflora determined by fermentation test. When milk naturally sours, a clot forms. The nature of the clot depends on the predominance of one or another type of bacteria. Based on the quality of the curd, milk is classified into one class or another.

The milk of cows with mastitis has a high bacterial contamination. The content of somatic cells increases in mastitis milk.

Somatic cells. They are represented mainly by leukocytes, the epithelium of the milk alveoli and milk ducts and are common elements of normal milk. When animals become ill with mastitis, the migration of leukocytes to the site of inflammation increases, which leads to an increase in the number of somatic cells in milk. Under production conditions, the number of somatic cells is determined using the surfactant “Mastoprim” using milk-control plates PMK-1, devices “ISKM-1”, “Somatos”, etc.

Requirements for the quality of raw milk, raw skimmed milk and cream intended for processing regulated by Federal Law No. 88-FZ of June 12, 2008 “TR for milk and dairy products”, as well as GOST R 52054-2003 “Natural cow’s milk - raw materials. Specifications", GOST R 53503-2009 "Skimmed milk - raw materials. Technical specifications" and GOST R 53435-2009 "Cream raw materials. Technical conditions".

Standardization and conformity assessment of milk

In accordance with the requirements of the TR, raw milk must be obtained from healthy farm animals in an area free from infectious and other diseases common to humans and animals. It is not allowed to use raw milk for food obtained during the first seven days after calving of animals and within five days before their launch (before their calving) and (or) from sick and quarantined animals.

The manufacturer must ensure the safety of raw milk. It should not contain residual amounts of inhibitory, detergent, disinfectant and neutralizing substances, animal growth stimulants and medicines.

The mass fraction of dry non-fat substances (SNF) in cow's milk should be at least 8.2%. The density of cow's milk, the mass fraction of fat in which is 3.5%, must be at least 1027 kg/m3 at a temperature of 20 ° C or no less than the equivalent value for milk, the mass fraction of fat in which is different.

Indicators of chemical, radiation, microbiological safety, somatic cell content, regulated by TR, are given in Chapter 5.

In TR, the requirements for the quality of raw milk are differentiated depending on its intended purpose. The most stringent requirements are set for the quality of milk intended for the production of products baby food milk based. The purity index must not be lower than the first group, the thermal stability index for the alcohol test - in accordance with the requirements of the national standard - must not be lower than the second group, QMAFAnM must not exceed the level established for raw milk of the highest and first grades, the number of somatic cells - established for milk premium.

Raw cow's milk intended for the production of sterilized milk, including concentrated milk or condensed milk, must correspond to an alcohol test temperature resistance index of at least group three.

Milk intended for cheese production must meet the following requirements: rennet-fermentation test of the 1st and 2nd classes; level of bacterial contamination according to the reductase test of classes 1 and 2; KMAFAnM no more than 1x10 units/cm3; the number of spores of mesophilic anaerobic lactate-fermenting butyric acid microorganisms for cheeses with a low second heating temperature - no more than 13,000 spores/dm3, s high temperature- 2500 spores/dm3; acidity no more than 19 °T; mass fraction of protein is not less than 2.8%.

In milk intended for food production dietary nutrition, KMAFAnM should not exceed 5 * 105 units / cm3, the number of somatic cells - 5 x 105 in 1 cm3, the heat resistance index should not be lower than group 2.

GOST R 52054-2003 applies to natural cow's milk - raw materials produced within the country and imported into Russia, intended for further processing. In accordance with the standard, milk, depending on microbiological, organoleptic and physico-chemical indicators, is divided into grades: highest, first, second and non-graded (Table 14.2).

The basic all-Russian norm established by the standard mass fraction fat in milk is 3.4%, protein 3%.

If inhibitory substances are detected in milk, it is classified as unsorted if in other respects it meets the requirements of the standard. Acceptance of the next batch of milk received from the farm is carried out after receiving the results of the analysis confirming the absence of inhibitory substances.

14.2. Requirements for the quality of raw natural milk raw materials
Index	Milk type	Ungraded milk
higher	first	second
Consistency	Homogeneous liquid without sediment or flakes. Freezing is not allowed	Presence of protein flakes, mechanical impurities
Taste and smell	Clean, without foreign odors and tastes not characteristic of fresh natural milk; weakly expressed feed is allowed in the winter-spring period	Pronounced feed taste and smell
Color	White to light cream	Cream, light gray to gray
Acidity, °T	from 16 to 18	from 16 to 18 from 16 to 20.99	less than 15.99 or more than 21
Cleanliness group, not lower	I	I	II	III
Density, kg/m3, not less				less than 1026.9
Freezing temperature, °C *	not higher than -0.52	above-0.52
*Can be used instead	but definitions	density mo	loka.

Milk with a density of 1026 kg/m3, an acidity of 15 °T or 21 °T is allowed to be accepted on the basis of a control (stall) sample as a second grade, if it meets the requirements of the standard in terms of organoleptic, physicochemical and microbiological indicators.

The standard contains labeling requirements, rules for milk acceptance, control methods, transportation and storage conditions. The following frequency of monitoring quality indicators when accepting milk has been established: organoleptic indicators, temperature, titratable acidity, mass fraction of fat, density, purity group, freezing point, heat resistance group must be determined daily in each batch; bacterial contamination, somatic cell content, presence of inhibitory substances at least once every 10 days; mass fraction of protein at least twice a month.

Requirements for skim milk in terms of taste, smell, appearance and consistency in accordance with GOST R 53503-2009 are similar to the requirements for raw milk. The color should be white with a slightly bluish tint, the mass fraction of fat is not more than 0.5%, the mass fraction of protein is not less than 2.8%, the acidity is from 16 to 21 °T, the density is not less than 1030 kg/m3.

Raw cream according to GOST R 53435-2009, depending on quality, is divided into 3 grades: highest, first and second. Premium cream must have a pronounced creamy, pure, sweetish taste and smell, uniform homogeneous consistency, thermal stability according to alcohol test - the first group, titratable acidity no more than 17-13 °T depending on the mass fraction of fat. 1st grade cream has a sweetish taste, a creamy smell with a weakly expressed feed taste, 2nd grade cream has an insufficiently pronounced creamy smell, not pure enough and (or) with a feed taste, the consistency of cream of both grades is homogeneous, homogeneous or with single lumps of fat, heat resistance of cream of the 1st and 2nd grades, respectively, the second and third groups and the fourth and fifth groups, titratable acidity - no more than 19-14 and 21-15 °T. The color of all types of cream is white, with a creamy tint, uniform throughout the mass, the temperature is not higher than 10 °C. The density of cream (at a temperature of 20 ° C) with a mass fraction of fat from 9 to 20% ranges from

Standardization and conformity assessment of milk

1020 to 1008 kg/m3; from 20 to 30 - from 1008 to 997; from 30 to 40 - from 997 to 987; from 40 to 50 - from 987 to 976 and from 50 to 58% - from 976 to 968 kg/m3.

14.3. Requirements to primary processing,
transportation and storage of raw milk

Raw milk after milking must be free of mechanical impurities. To purify milk, farms use strainer filters or milk separators. In accordance with the requirements of TR, within 2 hours after milking, milk must be cooled to a temperature of (4±2) °C. At this temperature, it is allowed to store raw and raw skim milk by the manufacturer for no more than 36 hours, taking into account the transportation time, and milk intended for the production of baby food products - for 24 hours. To store milk, flasks, tanks, and cooling tanks are used.

The manufacturer can carry out heat treatment, including pasteurization of raw and raw skim milk, in the following cases: its acidity is from 19 to 21 °T, raw cream is from 17 to 19 °T; storing raw milk and cream for more than 6 hours; transportation of dairy raw materials, the duration of which exceeds the permissible storage period, but not more than by 25%. Mode heat treatment must be indicated in the accompanying documentation.

Agricultural producers in the production of raw milk, raw skim milk and raw cream must use equipment and materials approved for contact with dairy products.

During transportation of chilled milk raw materials to the place of processing, its temperature should not exceed 10 °C. Raw milk that does not meet these requirements must be processed immediately.

Milk is transported by specialized vehicles in containers with tight-fitting lids. Vehicles must be equipped with refrigeration systems to maintain temperature.

The storage and transport of raw milk and raw cream must be accompanied by a declaration of conformity and information for consumers. Raw milk, raw cream sold by legal or individuals for processing, must be accompanied by shipping documents containing the following information: name and type of product, identification indicators (except for the mass fraction of milk solids), batch number, name and location of the manufacturer, volume (in liters) or weight (in kilograms) ), date and time (hours, minutes) of product shipment, temperature during shipment.

Raw milk, raw cream, non-industrial milk processing products sold by individuals, including individual entrepreneurs in markets, must be accompanied by information about the place of production, name of the product and date of production.

14.4. Identification and confirmation of milk conformity
requirements technical regulations

Milk identification carried out by the certification body when assessing and confirming compliance with TR requirements, as well as during State control (supervision) by the federal executive body exercising control and supervision functions in the field of veterinary medicine. The State Control (Supervision) Authority pro-

carries out identification in order to establish the compliance of milk with the information contained in the information for consumers, the declaration of conformity. Identification indicators for raw cow's milk are given in table. 14.3.

The acidity of milk is used to judge its freshness. Acidity must be known to establish the type of milk, as well as to determine the possibility of pasteurization and processing of milk into dairy products. Acidity can be determined using a pH meter (active acidity). The active acidity of milk is in the range of 6.5 – 6.7. Typically, titratable acidity is determined in conventional degrees or Turner degrees (o T).

Under Turner's Degree the amount of milliliters is implied to be 0.1 N. alkali solution used for neutralization (titration) 100 ml of milk, diluted twice with distilled water, with phenolphthalein as an indicator.

The titratable acidity of fresh milk is in the range of 16 - 18 o T and is determined by: 1) the acidic nature of proteins (5-6 o T); 2) phosphoric acid, citric acid salts and citric acid (10-11 o T); 3) dissolved carbon dioxide (1-2 o T).

1) Titration method. The method is based on the neutralization of acids contained in the product with an alkali solution (NaOH, KOH) in the presence of the indicator phenolphthalein.

Determination technique. Using a measuring pipette, measure 10 ml of milk into the flask, add 20 ml of distilled water and 2 - 3 drops of a 1% alcohol solution of phenolphthalein. When determining, water is added in order to more clearly detect the pink tint during titration. Then, while slowly shaking the contents of the flask, a decinormal (0.1 N) solution of alkali (caustic soda) is poured from a burette until the color is slightly pink, corresponding to the control color standard, and does not disappear within 1 minute. The amount of alkali used for titration (measured according to the level of the lower meniscus), multiplied by 10 (that is, recalculated per 100 ml of milk), will express the acidity of the milk in degrees Turner. The discrepancy between parallel determinations should be no more than 1 o T. If distilled water is not available, the acidity of milk can be determined without it. In this case, the reading results must be reduced by 2 o T.

2) Maximum acidity of milk. The method for determining the limiting acidity allows for sorting during mass acceptance of milk into standard (up to 19 - 20 o T) and non-standard (over 20 o T). The method is based on the neutralization of acids contained in the product with an excess amount of alkali (NaOH, KOH) in the presence of the indicator phenolphthalein. In this case, the excess of alkali and the intensity of color in the resulting mixture are inversely proportional to the acidity of the milk.

Determination technique. To prepare a working solution of alkali, measure the required amount (table) 0.1 N into a 1 liter volumetric flask. alkali solution (NaOH), 10 ml of 1% phenolphthalein solution and add distilled water to the mark.

Determination of the limiting acidity of milk

10 ml of sodium hydroxide (potassium), prepared to determine the corresponding degree of acidity, is poured into a series of test tubes. 5 ml of the test milk is poured into each test tube with the solution and the contents of the test tube are mixed by inverting. If the contents of the test tube become discolored, the acidity is higher than that corresponding to the solution.

Instead of the above NaOH solution, you can use another solution. To do this, measure 10 ml of distilled water into test tubes, add 2–3 drops of phenolphthalein and 0.1 N. NaOH solution corresponding to a certain acidity of milk, in the following quantity:

1.1 ml NaOH corresponds to an acidity of 22 o T

1.0 ml NaOH corresponds to an acidity of 20 o T

0.95 ml NaOH corresponds to an acidity of 19 o T

0.90 ml NaOH corresponds to an acidity of 18 o T

0.85 ml NaOH corresponds to an acidity of 17 o T

0.80 ml NaOH corresponds to an acidity of 16 o T

In large factories, the method of establishing the maximum acidity of milk is used to automatically sort it in the flow into fresh and sour.

3) Boiling test. This test is used to distinguish truly fresh milk from mixed milk, to which milk with high acidity has been added. The freshness of milk is determined by boiling a small portion in a test tube. Usually, milk curdles when boiled if its acidity is above 25 o T. But a mixture of milk with an acidity of 27 o T and 18 o T will also curdle when boiled, although the titratable acidity of such a mixture may not exceed 22 o T. Due to the simplicity of this method, it is desirable when assessment of milk quality. delivered to dairies.

4) Acid boiling test. It is used to judge both the acidity and the state of milk proteins.

Determination technique. To 10 ml of normal fresh milk you can add up to 0.8 - 1 ml of 0.1 N. solution of sulfuric acid, hold the mixture for 3 minutes in boiling water, and it will not curdle. If milk curdles when less acid is added, it means that the protein in it has changed mainly under the influence of microflora.

5) Determination of milk freshness. The freshness of milk is expressed in degrees, which is the sum of the degrees of acidity and the coagulation number of the milk. Coagulation number- number of milliliters 0.1 n. sulfuric acid solution required to curdle 100 ml of milk.

Degree of freshness normal milk should not be lower than 60. If changes have occurred in the milk, mainly under the influence of putrefactive bacteria, then less acid will be needed to curdle the milk. This milk will have less degree of freshness than normal milk.

Example. When determining acidity, 1.8 ml of 0.1 N was consumed. NaOH solution, that is, the acidity is 18 o T. 3.0 ml of 0.1 N was used to precipitate casein (10 ml of milk + 20 ml of water). sulfuric acid solution, therefore, the clotting number is 30.

Degrees of freshness 18 + 30 = 48, which means that the milk is of poor quality, since with low titratable acidity, relatively little acid was required to precipitate casein.