Continuation of lek No. 2
Technology of cottage cheese, curd products and sour cream
Cottage cheese is a protein fermented milk product, the main part of which is casein, which contains all the essential amino acids. Full-fat cottage cheese contains almost equal amounts (18%) of proteins and fat, as well as milk vitamins. Cottage cheese is rich in calcium, phosphorus, magnesium and other valuable minerals. Among the fermentation products of milk sugar, cottage cheese contains lactic acid and aromatic substances, giving it a specific sour taste and sour-milk smell. Cottage cheese contains the same amount of protein as meat, and its cost is much lower. In addition to direct consumption, cottage cheese is used for preparing various dishes, culinary products and a wide range of cottage cheese products. Adding sugar increases the calorie content of curd products and improves their taste.
Cottage cheese and curd products are produced from pasteurized milk using mesophilic lactic acid bacteria as a starter culture. It should have a clean, delicate fermented milk taste and smell, and a delicate consistency. The consistency of cottage cheese depends on the production technology; it can have a layered structure or be a homogeneous homogeneous mass. The fat content in full-fat cottage cheese is at least 18%, in semi-fat cottage cheese - at least 9%; moisture content of fat - no more than 65%, semi-fat - 73, low-fat - 80%. The acidity of high-fat premium grade cottage cheese is 200, grade I is 225° T; Bold premium grade -210, Grade I - 240° T; premium low-fat cottage cheese - 220 and first grade - 270° T.
There are two ways production of full-fat and semi-fat cottage cheese: regular - from normalized milk and separate - from skim milk, followed by enrichment of the low-fat cottage cheese with cream. Below is a technological scheme for the production of cottage cheese.
Separate method has a number of advantages. Fat loss in production is significantly reduced; the fat savings per 1 ton of full-fat cottage cheese is 13.2, half-fat - 14.2 kg. The separation of whey from the curd is facilitated, creating a greater opportunity to mechanize technological operations and, consequently, increase labor productivity. Finally, an important advantage of the separate method of producing cottage cheese is the improvement in the quality of the product as a result of reducing acidity: adding fresh pasteurized cream to low-fat cottage cheese reduces its acidity, and at the same time, cooled cream reduces the temperature of the cottage cheese, which prevents a further increase in the acidity of the finished product.
The listed advantages of the separate method make it economically more profitable, despite the need for additional operations (separation of milk and mixing low-fat cottage cheese with cream).
Normalization of milk by fat and protein titer. It is performed only when producing full-fat cottage cheese from whole milk; with the separate method, this operation is replaced by separating the milk and then mixing the resulting cream with low-fat cottage cheese.
Pasteurization of milk. Pasteurization temperature 72-74°C, holding time 20 s. In this mode, whey proteins do not undergo noticeable heat denaturation and, during the production of cottage cheese, are completely converted into whey.
Pasteurization at a temperature of 78-80°C with a holding time of 20-30 s increases the reliability of pasteurization of milk and the cottage cheese obtained from it and slightly increases the yield of the product due to thermolabile whey proteins coagulating at this temperature.
Fermentation of milk. Ferment from pure cultures of mesophilic streptococci is added to milk in the cold season at a temperature of 30-32°C (calculating possible cooling), and in the warm season - at 28-30°C. With the accelerated ripening method, when a mixture of cultures of mesophilic and thermophilic streptococci is used, the milk temperature is set at 38 and 35 ° C, respectively.
The use of streptococcal starter in the production of cottage cheese is based on the fact that its acid-forming ability guarantees the production of a finished product with acidity within the requirements for a premium product, i.e., no more than 200°T. Excessive acidity reduces the quality of cottage cheese, it is transferred to grade I or becomes non-standard.
However, despite the use of only streptococcal starter, heat-resistant lactic acid rods are found in the finished product. They are constantly present in cottage cheese and cause the most common defect of fresh cottage cheese - excessive acidity. The source of contamination of cottage cheese with lactic acid rods is the transfer starter.
To eliminate the cause of this defect, it is recommended that when fermenting, add not 5% (to the volume of milk) of secondary, but 2% of primary streptococcal starter into milk. In this case, during the entire process of cottage cheese production, lactic acid streptococci (1.4-2 billion/g) predominate in the fermented milk and curd, and the number of heat-resistant sticks barely reaches 30 million/g and cannot significantly (beyond the highest grade standards). ) increase the acidity of the cottage cheese.
To improve the quality of cottage cheese, it is also proposed to use directly laboratory starter (prepared with sterilized milk) in an amount of only 0.8%. In this case, a significant slowdown in the ripening process is not observed, but a high quality product is guaranteed.
With the rennet-acid method For the production of cottage cheese, in addition to bacterial fermentation, rennet is added to milk at the rate of 1 g/t of milk. Rennet reduces the acidity of the curd and increases its density at the time of processing. Simultaneously with the rennet, a 40% solution of calcium chloride (500 g of anhydrous salt per 1 ton of milk) is added to the fermented milk. After adding rennet and calcium chloride, the milk is left alone until completely ripened.
Fermentation of milk. In fermented milk, as a result of the vital activity of lactic acid microorganisms, acidity increases. The chemistry of the effect of lactic acid on the caseinate calcium phosphate complex of milk during the process of fermentation of milk during the production of cottage cheese is similar to that described earlier in the technology of fermented milk products. But during the production of cottage cheese, the added rennet enzyme also acts in parallel, so a joint acid and rennet coagulation of casein occurs. The partial conversion of casein to paracasein by rennet essentially precedes acid coagulation. Since casein, when converted to paracasein, shifts its isoelectric point from pH 4.6 to 5.2, curd formation occurs at a lower titratable acidity than with purely acidic precipitation, which ultimately leads to a lower acidity of the resulting curd. In addition, the formation of the curd structure during the rennet-acid precipitation method involves calcium bridges formed between paracasein particles, as occurs during rennet coagulation in the production of rennet cheeses. The presence of calcium bridges, which strengthen the structure of the curd, leads to the formation of a denser curd, which in turn prevents its dispersion during mechanical crushing, to a certain extent having a positive effect on increasing the yield of curd.
With the rennet-acid method of producing cottage cheese, the ripening process lasts 4-6 hours from the moment the starter is added to the milk, with the accelerated method using an active acid-forming starter - 3-4 hours, and with preliminary acidification of milk with whey - 3-3.5 hours. Acidity milk in the production of full-fat and semi-fat cottage cheese reaches 66-70, low-fat - 58-60°T. The end of milk fermentation is determined by the break test and by the type of whey released from the curd. If, when separating the clot with a spoon or spatula, smooth break edges with shiny smooth surfaces are formed, then the clot is ready for further processing. The serum released at the fracture site should be transparent and light green in color.
Curd processing. It is very important to correctly determine the end point of milk fermentation before starting processing. When processing an insufficiently fermented curd, curd losses increase, since part of it in the form of “dust” passes into the whey. The fermented curd produces sour cottage cheese with a spreadable consistency. When milk is properly fermented, a clot is formed in the form of a dense gel that spontaneously releases whey (the process of syneresis). Cutting the clot, increasing its surface, speeds up the release of whey.
The finished curd is cut with wire knives into cubes about 2 cm in size along the edge; first cut along the length of the bathtub into horizontal layers, then along the length and width into vertical ones. The clot cut in this way is left alone for 1 hour to increase acidity, which promotes the most complete release of whey.
Separating the whey from the curd. It is known that in the isoelectric state, protein substances have a minimum solubility and a minimum of swelling. Spontaneous separation of whey from the curd during syneresis occurs most actively at pH 4.6-4.7, i.e. at the isoelectric point of casein, and for paracasein (during rennet coagulation) at pH 5.0-5.2. With the mixed rennet-acid method of cottage cheese production, the isoelectric point of the curd is shifted towards paracasein and the optimal pH value is about 4.7-5.0.
When the freely released serum as a result of syneresis is removed, part of it is retained in the clot. To finally separate the whey from the curd and obtain curd with a standard moisture content, self-pressing and then forced pressing are used. Self-pressing of the curd, laid out from the bath into bags made of synthetic fabric (lavsan), calico or gauze, is carried out on press carts, which also have a device for forced pressing. Self-pressing continues for at least 1 hour, during which the bags of cottage cheese are transferred. The room temperature should not be higher than 160C. After self-pressing, the bags with the product for final pressing of the cottage cheese are evenly laid out on the bottom of the press cart and covered with a metal perforated plate, which through a special frame receives pressure from the press screw.
This method is the simplest, but also the most time-consuming. Currently, cottage cheese makers with a pressing bath are mainly used.
The curd maker (Fig. 1) is intended for fermenting milk, obtaining a curd curd, cutting it, removing freely separated whey and final pressing of the curd mass. It consists of double-walled baths with a tap for releasing whey and a hatch for unloading curd. A pressing bath with perforated walls is mounted above the curd bath, onto which a filter cloth is placed; Inside this bath there is a pipe for pumping out the serum.
The milk is poured into a bath for fermentation, the starter and enzyme are added. The resulting curd clot is cut, as indicated above, and after some time, part of the released whey is drained using a separator lowered into the bath. After draining the whey, the sampler is removed and the hydraulic drive is turned on, lowering the pressing bath down at a speed of 2-4 mm/min.
In this case, the whey passes through the filter fabric and the perforated lining inside the bath, from where it is periodically pumped out by a pump. At the end of the process, the pressing bath is raised, the hatch is opened and the curd is unloaded into a cart.
The use of cottage cheese makers with a pressing bath, compared to the conventional method of pressing in bags, provides a great economic effect: labor costs are reduced, the process is mechanized, and the need for production space and filter material is reduced. All this ultimately increases labor productivity and reduces product costs.
Recently, continuous production of cottage cheese has been developed by separating fermented milk using a special curd separator (Fig. 2). The working part of the separator is a drum with a set of conical plates (52 pcs.). The drum is covered with a protective spherical casing, supported through an intermediate casing on an annular bowl that serves to catch the curd ejected from nozzles with a diameter of 0.5 to 0.7 mm. The drum rotates at a speed of 5500 rpm.
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It was previously indicated that the most favorable conditions for the separation of whey from the curd occur at a pH value close to the isoelectric point of casein, when the most complete connection and compaction of its particles occurs. When separating fermented milk, sediment particles that are in an electrically neutral state, under the influence of centrifugal forces, can form a mass of dense consistency in the peripheral part of the drum, which will not be thrown out through the separator nozzles, and rapid clogging of the nozzles is inevitable. To avoid this, during ripening it is necessary to cross the boundary of the isoelectric state of casein towards a more acidic reaction. It has been experimentally established that whey should have a pH in the range of 4.5-4.3.
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In this case, the casein particles, the size of which is calibrated by the mesh filter (Fig. 3), begin to acquire a positive charge, i.e., opposite to the charge of the casein particles in fresh milk. When similarly charged particles come into contact with each other, they do not form a dense mass and therefore are easily removed from the separator drum without clogging the nozzles.
Cooling the cottage cheese. The pressed cottage cheese must be immediately cooled to 3-8°C to stop lactic acid fermentation with an increase in excess acidity. Cooling, depending on the type of technological equipment used for the production of cottage cheese, is carried out using various methods.
When using the method of placing the curd in bags, pressing can be combined with cooling by placing the pressing carts in the refrigerating chamber. For this purpose, a special press cooler is also used, which is a tubular drum into which bags of curd mass are loaded and cooled brine is passed through the pipes; When the drum rotates slowly, the bags move, and the whey is simultaneously separated and the curd is cooled.
When using a curd maker with a pressing bath, cooling of the curd is combined with pressing: for this, a refrigerant is passed into the interwall space of the bath. The finally finished cottage cheese is cooled in a refrigerator or on a special cylindrical cooler. In a cooler designed by Loktyukhov, brine at a temperature of -7°C circulates inside the cylinder. A thin layer of cottage cheese is applied to the surface of the cylinder on one side through a gap of 0.4-0.5 mm with a roller; on the opposite side of the cylinder, the cooled layer of cottage cheese is cut from the surface with a knife and falls into a trolley, in which it is served for packaging.
More advanced are the one- and two-cylinder curd coolers OTV-500 and OTD-650 (Fig. 4).
The cooled curd is continuously removed by knives from the surface of the cylinder and, moved by two screw turns of the drum, enters through a hole in the cylinder cover. Brine circulates in the cylinder jacket through a spiral channel.
The cottage cheese cooled from 28 to 10°C is supplied for packaging.
Packaging, packaging and storage of cottage cheese. Full-fat, semi-fat and low-fat cottage cheese for retail sale is packaged in bars weighing 250, 500 and 1000 g. The temperature of the cottage cheese sent for small packaging should not exceed 6°C. It is packaged using OFZ machines (Fig. 5) and semi-automatic packaging machines with forming attachments. Cottage cheese bars, wrapped in parchment or colorless cellophane, are placed in cardboard or wooden boxes. Packaged cottage cheese is cooled and stored until sale in refrigeration chambers at a temperature around zero, but not higher than 4 ° C.
It should be borne in mind that at the specified storage temperature, the quality of the cottage cheese decreases due to enzymatic processes and further breakdown of lactose and protein substances. As is known, the activity of enzymes does not stop even at low positive temperatures. Therefore, after two to three days of storage at 4-6 ° C, cottage cheese is transferred from the highest grade to the first; with prolonged storage, its quality deteriorates even more.
For long-term storage and reserve of summer cottage cheese, it is frozen. The reversibility of this process is most complete if freezing is carried out at low temperatures. Under these conditions, the water in the cottage cheese freezes in the form of small crystals without disturbing its structure. In contrast, slow freezing is accompanied by a redistribution of moisture in the curd with the formation of large crystals. When quick-frozen cottage cheese is defrosted, its original consistency and structure are restored. Moreover, some deficiencies in the consistency of the cottage cheese (for example, coarseness) are eliminated during defrosting. This is explained by the fact that small ice crystals formed during freezing inside grains of cottage cheese destroy them, creating a fine-grained structure that tastes like a homogeneous mass.
Cottage cheese in small packaging (0.5 kg) and in blocks (10 kg) is frozen in freezers at a temperature of ° C or in quick-freezers.
Grain cottage cheese. This type of cottage cheese has been produced in our country on an industrial scale since 1965. Cottage cheese with cream has a grainy structure and a pleasant sour-milk taste. 100 g of grain cottage cheese contains 16-20 g of protein, 6 g of fat, 0.8-2.0 g of minerals and other substances.
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Rice. 6. Technological scheme for the production of grain cottage cheese with cream:
1- tank for milk; 2- centrifugal pump; 3 - balancing tank; 4- pasteurization unit pump; 5 - pasteurization unit; 6 - cream separator; 7-tank for collecting cream; 8-pump for supplying cream to the homogenizer; 9- homogenizer; 10- pasteurizer for cream; 11 - tank for aging and storing cream; 12 - pump for supplying cream to the automatic dispenser; 13 - bath with stirrer; 14 - pump for supplying grain for drying; 15 - vibration installation for drying grain; 16 - trolleys; 17 - trolley lift; 18 - automatic dispenser for grain and cream; 19 - starter for mother starter; 20 - installation for industrial fermentation; 21 - pump for supplying starter to the bath; 22 - centrifugal pump for water supply; 23 - tank for water preparation; 24 - cooling unit.
Due to the fact that cream, as in the separate method of producing cottage cheese, is added to the low-fat product, it is concentrated on the surface of the grains, and this product tastes like high-fat cottage cheese. The technological process diagram is shown in Fig. 6. Fresh conditioned milk is pasteurized in a plate unit at 72-74°C with a holding time of 18-20 s and separated. A starter culture is added to skim milk in an amount of up to 5%, consisting of homofermentative lactic acid streptococci and flavor-forming cultures. At the same time, rennet is added at the rate of 0.5-1.0 g and a solution of calcium chloride at the rate of 400 g per 1 ton of milk. Two modes of ripening are used: short-term and long-term. In short-term mode, the fermentation temperature is 30-32°C, the process duration is 6-8 hours; for a long time, respectively, 21-23 ° C and 12-18 hours.
The readiness of the clot is determined by the increase in the acidity of the whey. The clot should be strong with smooth edges at the break; the whey is separated in the form of a transparent greenish liquid.
The finished clot is cut with wire knives into cubes measuring 12-13 mm along the edge (first cut along the length into horizontal layers, then across the width into vertical layers), after which they are left alone for 20-30 minutes to release the whey and compact the clot. Then water at a temperature of 46-48°C is added to the bath in such an amount as to increase the level of contents in the bath by 50-60 mm. Water increases the temperature of the curd by 2-3°C and reduces the acidity of the whey from 40-42 to 36-38°T. After adding water, the grain is thoroughly mixed and gradually heated by introducing hot water into the interwall space of the cheese bath; the temperature of the contents in the bath should increase by 1° every 10 minutes and reach 33° C.
Subsequent heating to 48-55°C must be done faster so that the temperature rises by 1° every 2 minutes. Once the specified temperature is reached, the grain is kneaded for an hour to compact it. The finished grain, pre-cooled with tap water, should retain its shape when lightly compressed in the hand. Then the whey is removed and the grain is washed and cooled at the same time. First, add water at a temperature of 16-17°C to the grain, mix it for 15-20 minutes, then drain the water; for the second washing, add water at a temperature of 2-4°C, keep the grain in water for the same time, after which it is drained.
The washed grain is left in the bath for 1-2 hours, and then transferred to carts with a perforated bottom, in which it is placed in a refrigerator for 10-12 hours at an air temperature of no higher than 5-10°C. Cream with a fat content of 20-30% and an acidity of no higher than 17°T is added to the dried grain. The cream is pre-pasteurized at 33-35°C for 20-30 minutes, then cooled to 26-30°C, homogenized at a pressure of 12.5-15.0 MPa, and finally cooled to 2-4°C. Salted cream is added to the total mass of grain or in portions, into each glass when packaging.
Cottage cheese with cream is packaged in small containers - polymer cups with a capacity of 200, 250 and 500 g and in large stainless steel containers or cardboard boxes of 20 kg each with a paper lining coated with a polymer film.
Cottage cheese should be stored at room temperature (16-20°C) for no more than a day, and at 8-10°C for no more than 6 days. The stability of grain cottage cheese during storage is somewhat lower than the stability of ordinary cottage cheese due to the fact that lactic acid, which, as is known, has a preservative property and counteracts the development of putrefactive processes, is removed from the former by thorough washing.
When stored both at room conditions and in the refrigerator, yeast can develop intensively in grained cottage cheese. Long-term storage of grained cottage cheese is possible only in brine (10% NaCl) at 6-8°C for 5 months without a significant change in organoleptic properties.
Curd products
From cottage cheese with the addition of sugar, salt, flavoring and aromatic substances (cocoa, coffee, candied fruits, dry fruits, raisins, caraway seeds, dill, etc.) curd cheeses, curd mass, cakes, creams, as well as semi-finished products - dumplings, cheesecakes, dough are produced for cheesecakes, etc., for which wheat flour, chicken eggs, starch and other products are used as additional raw materials.
The commodity classification of curd products divides them into four groups - with a high fat content (20-26%), fatty (15%), semi-fat (up to 8%) and low-fat; according to flavoring additives - sweet with a sugar content of 13 to 26% and salty with a salt content of 1.5 to 2.5%. Curd cheeses and curd mass of these types can be produced with or without the addition of flavoring substances. The number of individual components included in the composition of curd products is regulated by the recipe for certain types of these products and the requirements of the RTU.
The technological process for the production of curd products consists of preliminary grinding of the curd on roller machines (Fig. 7) to obtain a homogeneous curd mass and its subsequent mixing in kneading machines with the rest of the ingredients. The duration of mixing depends on the design and capacity of the machine, the speed of rotation of the mixer, as well as the temperature and consistency of the incoming components.
Upon completion of processing, the resulting mass is cooled on a cylindrical cooler or in refrigeration chambers to a temperature not exceeding 6 ° C and then sent for packaging.
Curd products, with the exception of glazed cheese curds, cakes, creams, are packaged in parchment or polymer packaging materials; glazed cheese curds - in aluminum or tin foil with a surrounding label; curd cakes - in cardboard boxes, the bottom of which is pre-lined with parchment with patterns on the edges. Curd creams are packaged in cups or tubes made of polystyrene or other polymer materials approved for food packaging.
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Rice. 7. Roller machine:
1- conveyor hopper; 2 - auger; 3 - receiving hopper; 4 - wheel for adjusting the roll gap; 5 - rollers; 6 - bed support.
Finished curd products must meet the requirements of the current RTU in terms of acidity, fat, sugar and salt content, have a clean, fermented milk taste and smell, with a pronounced taste and aroma of added flavoring and aromatic substances, a homogeneous consistency, tender, moderately dense, white in color, with a creamy tint or due to the addition of flavoring substances, for example cocoa, chocolate, uniform throughout the mass.
The most common taste defects in cottage cheese and curd products include an excessively sour taste, which occurs when excess lactic acid accumulates, and a yeasty taste, especially in sweet curds and curds, which appears as a result of alcoholic fermentation caused by yeast. Bitterness in the product is the result of contamination of the product with putrefactive bacteria. The acetic acid taste and smell are caused by the development of acetic acid bacteria. The breakdown of fatty substances under the influence of both putrefactive bacteria and molds also leads to the appearance of taste defects.
Of the consistency defects, the most common is coarseness, indicating a violation of the production and processing technology of cottage cheese.
In all cases, in order to prevent the appearance of defects in the product, it is necessary to maintain a high level of sanitary culture in the production of sourdough and the technological process.
“Health” and acidophilus pastes
Milk-protein paste “Zdorovye” is produced from pasteurized skim milk by fermenting it with a starter prepared on pure cultures of lactic acid bacteria and adding cream, sugar, fruit and berry syrups, vitamin C (in the form of rosehip syrup) and salt. The product is intended for consumption directly as a highly nutritious protein concentrate, or as a seasoning for dishes. It has a pure fermented milk taste with a pronounced aroma of added flavoring substances and the consistency resembles thick sour cream.
“Health” paste is available in several types: 5% fat, low-fat and with fillers - salty (salt 0.2%) and sweet (sugar 10-13%); moisture content from 75 to 85%, depending on the type of paste.
The technological process is as follows. Skim milk is pasteurized at a temperature of 80°C for 20-30 s. Then it is cooled to a fermentation temperature of 36-38°C and 5-8% of the starter prepared from a mixture of cultures of thermophilic and mesophilic races of lactic acid streptococci in a 1:1 ratio is added. Fermentation is carried out to an acidity of 80-85°T for 10-12 hours. The finished curd is cut into cubes about 2 cm in size along the edge. The cut curd is left alone for 40-50 minutes.
Removing the whey and pressing the curd is done using the same methods as when making cottage cheese.
To obtain a uniform consistency, the milk-protein base is passed through a colloid mill, and then syrup, cream, sugar or salt are added to it, depending on the type of paste. The finished product is packaged in various containers: wide-mouth glass jars, bottles or containers made of polymer materials.
Packaged products are cooled to a temperature not exceeding 8°C and stored for no more than 36 hours.
For the production of “Zdorovye” paste, VNIMI has developed a production line, equipped mainly with technological equipment used for the production of cottage cheese.
Acidophilus paste- a medicinal fermented milk product - it is not only a protein, but also a bacterial concentrate of acidophilus bacilli. The paste is produced from whole and skim milk, using pure cultures of acidophilus bacillus as a starter. Sugar and fruit and berry syrups are added to the paste.
They produce sweet acidophilus paste with 8 and 4% fat content and low-fat.
Acidophilus paste is intended for direct consumption. In addition, it is recommended for use as a medicinal product for a number of gastrointestinal diseases.
Paste can be produced in two ways: by pressing the curd obtained by fermenting milk and from pre-condensed milk, as shown in the diagram below.
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Conditioned whole milk is normalized to a fat content of 2.3% for a 4% paste and to 3.4% for a paste with an 8% fat content. Milk (normalized, skim) is pasteurized in pasteurization units at a temperature of 85-90°C, kept in baths for 15 minutes, and then cooled in the same baths to the fermentation temperature (40-42°C).
When producing paste from pre-condensed milk, the pasteurized milk is sent to a vacuum apparatus. Milk is condensed as quickly as possible at a temperature of 50-55°C, increasing it at the end of condensation to 55-60°C. The dry matter content in condensed milk normalized by fat must be at least 29% and in skim condensed milk at least 23%. Condensed milk is cooled to fermentation temperature (38-40°C).
The milk is fermented with a starter prepared on an acidophilus bacillus, taken in an amount of 5% of the weight of the milk. The fermented milk is thoroughly mixed; Fermentation is carried out until a dense clot is obtained. The acidity of the curd from milk normalized for fat should be in the range of 80-90°T and from condensed milk 180-200°T.
The curd is placed in calico or lavsan bags with a capacity of 12-14 liters for self-pressing at a temperature of 6-8°C, and then pressed (in press carts, curd presses) to the required humidity.
Sugar syrup with a concentration of 66% is added to the pressed and condensed paste and mixed in a kneading machine until a homogeneous consistency is obtained.
The paste is packaged in glass jars or containers made of polymer materials and sent to the refrigeration chamber for cooling to 8°C.
The finished product should have the taste and smell of pure fermented milk, for pasta made from condensed milk - with a taste characteristic of condensed milk, a delicate, pasty, homogeneous consistency. The moisture content in sweet paste with 8% fat content is 60%, 4% fat content - 65%, low-fat - 80%; sugar content is 24, 20 and 12%, respectively. Acidity in all cases is not more than 200°T. It is not allowed to contain pathogenic microorganisms in acidophilus paste; the titer of E. coli should be at least 0.3 ml.
Sour cream
Sour cream is a national Russian fermented milk product containing 20, 25, 30 and 36% fat. Diet sour cream contains 10 fat, amateur sour cream contains 40%.
The technological process of sour cream production consists of the following operations: separating milk and obtaining cream, normalizing cream by fat, pasteurization, homogenization, cooling cream to fermentation temperature, adding starter, fermenting cream, cooling and maturing sour cream, packaging and storing the finished product.
Milk is separated at 40-45°C to obtain cream with a fat content of at least 32%; the cream is finally normalized in terms of fat to 31.6%, based on the receipt after adding the starter in the amount of 5% of the finished product with a fat content of 30%. When producing a product with 36% fat content, the cream is normalized to 37.9%. The corresponding calculation is made for other fat contents of sour cream. The cream is pasteurized at 85-95°C with holding time for 15-20 s.
It is recommended to homogenize cream at a temperature of 50-70°C and a pressure of 7.0-8.0 MPa. Sour cream made from homogenized cream has a denser consistency, as do fermented milk drinks produced using the tank method using milk homogenization.
After homogenization, the cream is immediately cooled on a plate or tube cooler to the fermentation temperature (18 ° C in the warm season, and 22 ° C in the cold season). Pure cultures of mesophilic streptococci (Str. lactis, Str. cremoris) and flavoring agents (Str. diacetilactis) are used as starter cultures. The amount of starter added significantly affects the duration of ripening.
The ripening of cream, depending on the temperature, lasts 14-16 hours. In the first 3 hours, the cream is stirred every hour, and then it is left alone until the end of ripening. The end of ripening is determined by the increase in acidity to 65-75°T in summer and 80-85°T in winter.
Freshly prepared sour cream can be packaged in small or large containers; In the same container, the sour cream is cooled and matured. For cooling and ripening, large containers are also used - VDP baths, double-walled tanks, in this case ready-made sour cream is packaged. In any case, cooling is combined with the ripening of sour cream, which continues at 5-8°C for 24-48 hours. The ripening of sour cream, pre-packaged in small containers in a refrigerator at 2-4°C, can be completed within 24-28 h. By quickly cooling the fermented cream to 5-6°C, the ripening process can be reduced to 6-8 hours.
The essence of the ripening process during cooling of sour cream is the crystallization of milk fat glycerides, the hardening of the shells of fat globules and the joint acid coagulation of casein and thermolabile whey plasma proteins denatured during high-temperature pasteurization of cream. These are the main processes of sour cream structure formation, which occurs over time.
The fat phase of sour cream makes up more than 4/3 by volume; its physical state, associated with crystallization, hardening and the formation of polymorphic structures, is crucial for the consistency of sour cream. Thus, according to Tverdokhleb, preliminary deep cooling of cream to 2-6°C before fermentation and holding for 2-3 hours makes it possible to achieve a high degree of hardening of fat and the formation of metastable forms of glyceride crystals, as happens during the physical maturation of cream in butter making. This kind of processing of cream allows you to improve the consistency of sour cream and reduce the ripening time.
In addition to the hardening of milk fat glycerides during the cooling and ripening process, the consistency of sour cream is also reflected by the degree of dispersion of fat particles. On the developed surface of the shells of fat particles, especially after homogenization, protein substances are included in structure formation. When the environment is acidic, i.e., at a pH below 4.6-4.7, casein again acquires a charge (opposite), colloidal dissolution occurs, the gel structure is disrupted, and the clot is liquefied. In this case, the sour cream acquires a liquid consistency, which increases as the pH shifts from the isoelectric point, which is observed when sour cream is fermented.
In addition, the consistency of sour cream is greatly influenced by the concentration of proteins in the sour cream plasma, which depends on the casein content in the original milk. An increase in casein content even by tenths of a percent can have a noticeable effect on the consistency of sour cream, all other things being equal.
Denatured whey proteins may also participate in the formation of protein stroma during acid coagulation of casein. During the coagulation of protein substances, the resulting structures do not have sufficiently strong bonds, therefore any mechanical impact both at the moment of formation of the structure and especially at the final stage of its completion should be minimized.
Until sale, sour cream should be stored in the refrigerator at a temperature not exceeding 2-40C and a relative humidity of 75-80%.
Sour cream sent for sale must comply with the requirements of the current RTU: taste and smell for the highest grade, pure fermented milk without foreign tastes and odors; for the first grade, weakly expressed flavors of feed, melted butter, containers (wood), and the presence of slight bitterness are allowed; The consistency of the highest grade sour cream is homogeneous, moderately thick without grains of fat and protein (cottage cheese), for the first grade it is allowed to be insufficiently thick, slightly lumpy, with the presence of grains and slight viscousness. Acidity for the highest grade is 65-90, for the first grade 65-110°T.
The assortment of sour cream includes two more varieties - “Dietary” and “Amateur”.
Features of the technology for the production of dietary sour cream are as follows. Fermented with a special starter of lactic acid bacteria capable of synthesizing vitamin B, pasteurized and homogenized cream with a fat content of 10% is poured into wide-neck glass bottles and glasses or into plastic glasses and then fermented in thermostats at 28°C to an acidity of 65-70°T, after which the sour cream is cooled in a refrigerator at a temperature of 5-6°C and kept for ripening for 12-16 hours. Cooling of sour cream is completed when its temperature drops to 8°C, after which it is sent for sale.
For the production of amateur sour cream, the initial cream is obtained with a fat content of at least 44.5%, followed by its reduction with sourdough to 40%. The cream is pasteurized at 87°C for 20 minutes or at 92-99°C for 10-20 minutes, which gives the sour cream a specific, so-called “nutty” flavor. Pasteurized cream is homogenized at 50°C and a pressure of 10 MPa. Ferment for amateur sour cream from strains of mesophilic and thermophilic races in a 1: 1 ratio is added in an amount of up to 10% of the weight of the cream at 45-50°C. Upon reaching the required acidity (not lower than 55°T), the sour cream is cooled on a cylindrical cooler for cottage cheese to 4-6°C and packaged on machines with briquettes weighing 100 g packed in parchment or other material. Sour cream briquettes packed in cardboard boxes are placed in refrigeration chambers at a temperature of 0-6°C and kept for maturation for at least 6-12 hours. The finished product has a dense, uniform consistency, retains the shape of a given briquette, and has a pure sour milk taste with a pronounced taste of pasteurized cream.
Milk acceptance is carried out according to quality and quantity; Quality control and sorting are carried out. After mixing the milk, organoleptic indicators are determined: taste, smell, color, consistency, purity, acidity, density, mass fraction of fat are determined. In case of forced storage of milk before processing, it must be cooled and such conditions must be ensured that the temperature of the milk does not rise above 10°C, the shelf life is no more than 6 hours.
Powdered milk is reduced in water at a temperature of 35-45°C, cooled and left to swell for 3-5 hours. You can dilute milk at 8-12°C and leave it to swell if it is not possible to cool the milk. Swelling is not necessary, but helps to increase yield by 5-10%. MonaMilk mixture No. 14 is added together with dry milk and wheat fiber before swelling. During swelling, it is recommended to pass the mixture through a dispersant or stir with a stirrer.
After swelling, the mixture is normalized by fat using cream or adding melted fat through a dispersant. In this case, the fat is melted to a temperature of 45-55°C, the milk is heated to the same temperature and mixing is performed. After normalization, MonaMilk-mixture No. 1 is added.
It is first diluted in cold water in eight to ten times the amount of water while stirring. It is applied through a dispersant or into a tank.
Temperature treatment
The mixture is pasteurized in a pasteurization-cooling unit at a temperature of 85-95°C for 20 s. At this temperature, the most complete coagulation of whey proteins is obtained, which also helps to increase the yield.
Then the mixture is cooled to a fermentation temperature of 30 ± 2 ° C when using mesophilic cultures and to 35 ± 2 ° when using combined or thermophilic starter cultures and sent to the curd bath. It is not recommended to store pasteurized mixture without fermentation, as this leads to additional contamination of the milk. The cottage cheese may taste sour and yeasty.
The starter is added to the milk, mixed for 10-15 minutes, then calcium chloride and rennet are added. The mixture is stirred for 5-10 minutes.
Then the milk is left alone until a clot forms; the required acidity for skim - 75±2°T, for 5% fat content - 73±2°T, for 9% fat content - 70±2°T, for 18% fat content - 65±2°T T. Cutting with insufficient acidity causes the product to have a rubbery consistency.
The duration of milk fermentation with bacterial starter is 6-15 hours. Formation of a clot. The readiness of the curd is determined by the titratable acidity and density of the curd.
The finished curd is cut with knives into cubes measuring 2.0x2.0x2.0 cm. The cut clot is left alone for 30 to 60 minutes to release the whey. You can heat it up to a temperature of 40°C with a holding time of 30 to 40 minutes. To heat the curd evenly, it is carefully mixed from one wall to the other. It is important not to “cook” the curd, but simply to enhance the separation of whey. Heating should be carried out gradually without sudden changes in temperature to avoid destruction of the curd grain.
Curd processing
When using a UPT brand unit for pressing and cooling cottage cheese, the curd is poured into calico or lavsan bags measuring 40x80 cm, filling them 3/4 full. Place bags in installations. Pressing and cooling of the curd is carried out until the curd reaches the required moisture within 1-4 hours.
The bags containing the curd are tied and placed in a press trolley for self-pressing and pressing. In the press trolley, self-pressing continues for at least 1 hour. To speed up the separation of whey, bags with curd are periodically shaken.
Cottage cheese in bags is pressed in a refrigerator on hangers or on tables at a temperature of 5-8°C. Pressing is continued until the curd reaches the required moisture.
You can press on hangers until the humidity is 3-5% higher than normal, then press in carts. Excessively long storage in bags on hangers leads to the development of foreign microflora, since the product does not cool quickly enough and prolonged contact with the fabric bag also contributes to additional contamination.
Recommended moisture content for low-fat cottage cheese is 79-80%, for 5% fat content - 75%, for 9% fat content - 73%. When using stabilizers to retain moisture, you can make the humidity of the finished product 1-1.5% higher than normal; during storage on the first day it will return to the normal value, since the work of the stabilization systems finally ends after the product has cooled.
Standardization of cottage cheese by moisture (pressing) can be carried out using presses installed in the refrigeration chamber. Bags of cottage cheese are placed in carts in several rows. A press is attached to the top.
After pressing is completed, the curd is shaken out of the bags and mixed; at the end of the process, the finished product is packaged and stored.
Introduction
Cottage cheese is one of the oldest dairy products. It can be assumed that people began to eat it much earlier than cheese and butter. This assumption is quite reasonable, because As a result of the activity of lactic acid bacteria, which are always present in milk, spontaneous souring of milk is possible. In this case, a clot is formed, which becomes denser as a result of natural syneresis. One of the first products that the ancients considered cottage cheese was the product “Hippak” - a clot made from mare’s milk. No less natural is the assumption that in ancient times man also accidentally learned about rennet ripening, using the stomachs of killed animals as containers for milk.
There is information about products such as cottage cheese obtained as a result of sour and rennet ripening of milk in the works of ancient poets, in the works of philosophers and scientists. Homer, Aristotle, Hippocrates, Palladium, and Columella wrote about these products. Columella, who lived in the 1st century AD, wrote in particular detail, indicating practical advice on how to ferment milk and the requirements for its quality.
The works of ancient authors indicate that the remains of coagulated milk from the stomachs of lambs and kids and the gastric mucosa were used for fermentation. Even then, various plant substances and wine vinegar were also used to ferment milk.
Thus, historically there were two main methods of fermenting milk to produce cottage cheese: acidic and acid-rennet. Both of these methods have survived to this day.
In the acid-rennet method of cottage cheese production, pieces of raw and dried stomachs of calves and lambs have been used as rennet for many centuries. Enzyme preparations appeared about 100 years ago, when liquid rennet starters were first sold in France. Dry rennet was obtained at the end of the 19th century.
According to available data, in 1888-1890. began to use pure cultures of lactic acid bacteria.
In industrial conditions, cottage cheese began to be produced at the end of the 18th and beginning of the 19th centuries, which was associated with the organization of urban dairies.
Commercial dairy farming in Russia arose at the end of the 18th century, when large landowner farms organized cheese factories producing not only cheeses, but also melted butter, sour cream and cottage cheese for the market. The first cheese factory was opened in 1975. In the estate of Lotoshchino, district of the same name, Smolensk region.
With the development of capitalism in Russia and the growth of the urban population, the demand for dairy products increases, and therefore dairy farming takes on a commercial, entrepreneurial character. Peasant cooperatives and milk buyers open small artisanal dairies, often in peasant huts, adapted premises, with minimal equipment.
The founder of the scientific approach to dairy farming in Russia was A.A. Kalantar, who worked at the Edimonov school since 1882. and organized the first milk testing laboratory here to conduct scientific research. He has written a number of manuals and popular science guides on dairy farming, cheese making, and butter making.
It should be noted that the further into history the appearance of a product goes, the lower the general technical level of its production at present. This is precisely what can explain the fact that private dairy factories still have primitive production techniques, and the duration of the technological cycle is still long.
Cottage cheese is a protein fermented milk product made by fermenting pasteurized normalized whole or skim milk (mixing with buttermilk is allowed), followed by removing part of the whey from the curd and pressing the protein mass. It is officially customary to classify cottage cheese produced in the traditional way according to its fat content. In accordance with this, a distinction is made between full-fat, semi-fat and non-fat cottage cheese (non-fat cottage cheese is often called low-fat cottage cheese). Cottage cheese from unpasteurized milk is produced in case of high acidity of milk; before consumption, the cottage cheese must be subjected to heat treatment (production of cheesecakes, dumplings, production of processed cheeses). Cottage cheese has a pure fermented milk taste and smell; For the first grade, a weakly expressed taste of feed, containers, and slight bitterness is allowed. The consistency is delicate, homogeneous; for first-grade fatty cottage cheese it is allowed to be somewhat loose and spreadable, for low-fat cottage cheese - crumbly, with a slight release of whey. The color is white, slightly yellowish, with a cream tint, uniform throughout the mass; For first grade fatty cottage cheese, some color unevenness is allowed. The significant content of fat and especially complete proteins in cottage cheese determines its high nutritional and biological value.
When the curd is dehydrated in separators, the curd has a paste-like consistency, which is why it is sometimes classified as non-traditional, although it is traditional in composition and raw materials. Cottage cheese obtained using a separate method, even without the use of separators, is also conventionally called non-traditional.
Non-traditional types include cottage cheese made from buttermilk, whey from dry milk products, as well as grain cottage cheese with cream.
Based on the method of coagulating milk proteins, cottage cheese is divided into acidic and acid-rennet. Acid cottage cheese is usually prepared from skim milk.
In this case, the protein coagulates under the influence of lactic acid, which is formed during the process of lactic fermentation, which develops as a result of introducing starter cultures into milk.
When assessing the quality indicators of cottage cheese, along with the fat content, the moisture content in the finished product, as well as its acidity, is important.
Depending on the acidity of cottage cheese, all types are divided into first and highest grade.
It should be noted that the composition of cottage cheese, and especially its protein part, is certainly influenced by different methods of its production. It can be noted that in acid curd, casein, freed from calcium, predominates, while acid-rennet contains both casein and its calcium salt. The degree of use of milk proteins in the production of cottage cheese also depends on the coagulation methods. The content of calcium and phosphorus salts in cottage cheese is in the ratio most favorable for human absorption
Table 1
The high biological value of cottage cheese is determined by the content of all essential amino acids in it: lysine, histidine, argenine, threonine, valine, mytheonine, isoleucine, leucine, phenylalanine.
It should also be noted that the amino acid content in fatty and low-fat cottage cheese is different. This is explained by the fact that during the production of fatty cottage cheese it includes proteins from the shells of fat globules, which have a slightly different amino acid composition.
Sour cream is produced by fermenting pasteurized cream with pure cultures of lactic acid bacteria, followed by ripening of the resulting curd. Among other fermented milk products, sour cream has high nutritional benefits. Thanks to the changes that occur with the protein part during the ripening process, sour cream is absorbed by the body faster and easier than cream of the same fat content. Some lactic acid bacteria in the process of sour cream ripening are capable of synthesizing B vitamins, so the content of these vitamins is also higher in sour cream compared to milk. Sour cream has a pure fermented milk taste with a pronounced taste and smell characteristic of a pasteurized product. Its consistency is homogeneous, moderately thick, without grains of fat and protein. Sour cream of traditional chemical composition with a mass fat content of 30% is divided into the highest and first grades. For the first grade, mild flavors are allowed: melted butter, container (wood), the presence of slight bitterness. The consistency is allowed to be insufficiently thick, slightly lumpy, grainy, and slightly viscous. Other types of sour cream are not divided into varieties.
1. Production technology
1.1 Initial technological operations
Cooling essentially determines the behavior of milk during further technological processing. Cooling temperature should be considered the main factor on which such quality indicators of milk as bacterial contamination and acidity depend. The lower the cooling temperature, the longer the quality of the milk remains. During the cooling process, the quality of the raw material does not change. The purpose of cooling is to preserve the original properties. The World Health Organization recommends cooling milk to 4°C no later than one hour after consumption. Maintaining the temperature of chilled milk during packaging prevents the development of microorganisms, and therefore slows down the increase in acidity.
1.1.1 Reception of milk
After milk arrives at the enterprise, it is necessary to ensure the preservation of its native properties and minimal contamination with microflora. To do this, milk after receipt is cleaned of mechanical impurities and cooled. Cleaning is carried out by filtration or using centrifugal separators of milk purifiers. For filtering, you can use gauze-cotton, lavsan filters. Mechanical filtration does not provide complete purification of milk; only large particles are retained; incoming new portions of milk come into contact with contaminated ones in the filtrate and are additionally contaminated with microflora
Each of us has a dream of owning our own business. Someone has already accomplished it, while others are still at a loss as to which direction to move. The dairy industry is a good option. For example, you can start producing cottage cheese. However, not all so simple. First of all, it is necessary to choose the right equipment for the production of cottage cheese, which will be discussed in this article.
About the benefits of cottage cheese
This product is good in all respects. It contains proteins that are very well absorbed. In addition, it contains a lot of calcium, which is necessary for the human body (especially small children). Cottage cheese, in fact, is a unique product; it is often included in various diets. It is always present in a proper nutrition system. The recommended serving is 100 grams per day. To have healthy hair, nails and skin, it is enough to consume this product three times a week.
Production Features
This process follows the following scheme:
1) Acceptance of whole milk and its quality assessment.
2) Preheating and separation of raw materials.
3) Normalization of milk. This is necessary in order to obtain a product of a certain fat content. It should be noted that most often 5% and low-fat cottage cheese is produced (with a mass fraction of fat in the product of 0.5-1%).
4) Pasteurization of the product and its cooling.
5) Adding starter to milk and fermenting it.
6) Cutting the resulting clot and separating the whey.
7) Pressing the clot.
8) Cooling of the finished product.
9) Packaging and labeling of cottage cheese.
Necessary equipment
Let's consider what equipment is needed for the production of cottage cheese:
1) To receive milk, it is necessary to have large tanks in which the product will be stored until the next stage.
2) You will need a pasteurizer-cooler, in which the milk is heated, and a separator for the production of cottage cheese, which separates the cream from the milk.
3) Reservoirs are required for the normalization process.
4) At the stage of pasteurization and cooling, the same pasteurizer-cooler mentioned in the second paragraph is used.
5) Fermentation is carried out in the same tanks (another name for them is baths for the production of cottage cheese) into which the milk enters after normalization.
6) To cut the clot you need a special knife. After this, it is necessary to drain the resulting whey into another tank using a fitting or siphon.
7) To press the cottage cheese, you will need a press trolley covered with serpyanka. Here the cottage cheese is self-pressed for about an hour.
8) Cooling of the finished product is carried out in refrigeration chambers.
9) Packaging and labeling of cottage cheese is carried out by special machines that dose the product, package it and apply special marks.
Automated installations
Today, an automated line for the production of cottage cheese is in great demand. Its significant advantage is that, thanks to the mechanization of the process, only two or three service personnel are enough, and this is a significant saving on labor costs.
Such installations are capable of producing up to 3.5 tons of finished product (in terms of raw materials - 24 tons of milk). Do you want to increase production volume? Such equipment allows the organization of a wide line of several devices, while the flow of the process is maintained.
Thus, in order to begin production of such a valuable product, it is necessary to purchase a number of devices and properly place them on the workshop territory. The easiest way is to purchase a line for the production of cottage cheese, which includes all the necessary machines.
Characteristics of products, raw materials and semi-finished products. Cottage cheese is a paste-like fermented milk concentrated protein product, formed as a result of partial separation of the liquid fraction from fermented milk. Depending on the type of cottage cheese, the mass fraction of dry substances in it is 20...35%, fat - 0.6...18%, proteins - 15...20%.
The specific advantages of cottage cheese as a dietary and baby food product are due to the presence of a relatively large amount of proteins, a favorable combination of minerals, vitamins and microelements, as well as the essential amino acid methionine.
The range of curd products includes the following groups:
– low-fat cottage cheese with a fat mass fraction of no more than 0.6%;
– semi-fat and full-fat cottage cheese (9 and 18% fat);
– soft dietary cottage cheese (9% fat);
– curd pastes and cheeses with various fat contents, fruit fillings and other additives.
The quality of cottage cheese is assessed by physicochemical, organoleptic and microbiological indicators. The composition of cottage cheese must correspond to the standard values for the mass fractions of moisture, fat and proteins, as well as the permissible acidity value. Cottage cheese is not allowed to contain pathogenic microorganisms and harmful chemicals.
The main raw material for the production of cottage cheese is natural cow's milk of at least grade II, with an acidity of no more than 20 °T, or skim milk with an acidity of no more than 21 °T. In the production of some types of cottage cheese, the use of powdered milk and cream obtained as a result of spray drying is allowed.
To ferment milk, starters prepared from pure cultures of lactic acid bacteria and solutions of enzyme preparations made from animal raw materials: rennet or pepsin are used.
Features of production and consumption of the finished product. There are two methods of producing cottage cheese - traditional (ordinary) and separate. The traditional method involves the formation of cottage cheese from a previously prepared normalized milk mixture.
The essence of the separate method is that the milk intended for the production of cottage cheese is pre-separated. From the resulting skim milk, low-fat cottage cheese is produced, to which the required amount of cream is then added, increasing the fat content of the cottage cheese to 9 or 18%. The separate method of producing cottage cheese allows you to speed up the process of whey separation and significantly reduce losses.
Based on the method of curd formation, there are two methods of producing cottage cheese: acid and rennet. The first is based only on the acid coagulation of proteins by fermenting milk with lactic acid bacteria and then heating the curd to remove excess whey. In this way, low-fat and low-fat cottage cheese is made, since when the curd is heated, significant loss of fat occurs into the whey. In addition, this method ensures the production of low-fat cottage cheese with a more delicate consistency. The spatial structure of clots of acid coagulation of proteins is less strong, formed by weak bonds between small casein particles and releases whey worse. Therefore, to intensify the separation of whey, heating of the curd is required.
With the rennet-acid method of milk coagulation, the curd is formed by the combined action of rennet and lactic acid. Calcium chloride restores the ability of pasteurized milk to form, under the influence of rennet, a dense curd that separates whey well. Under the influence of rennet, casein in the first stage turns into paracasein, and in the second, a clot is formed from paracasein. When casein transforms into paracasein, it shifts its isoelectric point from pH 4.6 to 5.2. Therefore, the formation of a clot under the influence of rennet occurs faster, at a lower acidity than when proteins are precipitated with lactic acid, the resulting clot has less acidity, and the technological process is accelerated by 2...4 hours. During rennet-acid coagulation, calcium bridges formed between large particles provide high strength to the clot. Such clots separate whey better than acidic ones, since the spatial structure of the protein is compacted faster in them. Therefore, heating the curd to intensify the separation of whey is not required.
Full-fat and semi-fat cottage cheese is produced using the rennet-acid method, which reduces the loss of fat into whey. During acid coagulation, calcium salts are released into the whey, and during rennet-acid coagulation, they are retained in the curd. This must be taken into account when producing cottage cheese for children who need calcium for bone formation.
Ready packaged cottage cheese is stored until sale for no more than 36 hours at a temperature not higher than 8 ° C and a humidity of 80...85%. If the storage period is exceeded, defects begin to develop in the cottage cheese due to ongoing enzymatic processes.
In order to reserve cottage cheese in the spring and summer periods of the year, it is frozen. The quality of defrosted cottage cheese depends on the freezing method. During slow freezing, cottage cheese acquires a grainy and crumbly consistency due to the freezing of moisture in the form of large ice crystals.
With rapid freezing, moisture simultaneously freezes throughout the entire mass of cottage cheese in the form of small crystals, which do not destroy its structure and, after defrosting, the original properties are restored. After defrosting, even the elimination of the undesirable grainy consistency is observed due to the destruction of grains of cottage cheese by small ice crystals.
Cottage cheese is frozen in packaged form - in blocks of 7...10 kg and briquettes of 0.5 kg at a temperature of minus 25...30 °C in thermally insulated continuous freezers to a temperature in the center of the block of minus 18 °C and minus 25 °C for 1.5…3.0 hours. Frozen blocks are placed in cardboard boxes and stored at the same temperatures for 8 and 12 months, respectively. Defrosting of cottage cheese is carried out at a temperature not exceeding 20 °C for 12 hours.
Stages of the technological process. The production of cottage cheese using a separate method consists of the following stages and main operations:
– acceptance of milk, sorting by quality and measuring the amount of milk received;
– cleaning from mechanical impurities and cooling of raw milk;
– heating, separation and purification of milk with its division into cream and skim milk;
– separate pasteurization, cooling and reserving of cream and skim milk;
– preparation and dosing of sourdough;
– dosing of calcium chloride and rennet;
– fermentation and ripening of skim milk;
– stirring, heating and cooling the curd;
– separation of whey and cooling of curd;
– dosing of cream and normalized cottage cheese according to fat content;
– packing cottage cheese into consumer containers.
Characteristics of equipment complexes. The production line for soft dietary cottage cheese begins with a set of equipment for preparing raw milk for processing, including self-priming pumps, flow meters, filters, cooling units and tanks for storing raw milk.
The following set of equipment is designed for milk separation and processing of cream and skim milk. It contains a cream separator, plate pasteurization and cooling units, pumps and cream storage tanks.
The leading equipment is a set of equipment for the formation of soft dietary cottage cheese, which includes an apparatus for fermenting and fermenting skim milk; dispensers for starter, calcium chloride solution and rennet; pumps for curd curd; plate pasteurization and cooling unit for curd, filter and centrifugal separator for curd and skim curd cooler.
The final complex includes dosing pumps for cottage cheese and cream, a mixer and a packaging machine.
The machine and hardware diagram of the production line for soft dietary cottage cheese is shown in Figure 4.8.
Design and operating principle of the line. After checking the quality of milk using centrifugal self-priming electric pumps 1 enters production through a pipeline with a flow meter installed on it 2 and filter 3 . Purified raw milk is cooled in a plate cooling unit 4 and loaded into the tank 5 .
To make curd, milk from the tank 5 pump 6 fed into the surge tank 7 , and from it - with a pump 6 to the recovery section of a plate pasteurization-cooling unit 8 for heating up to 34...40 °C.
The heated milk enters the cream separator 9 , in which it is divided into skim milk and cream with a mass fraction of fat of at least 50...55%. The resulting cream is first fed into an intermediate container. 10 and then pump 11 into a plate pasteurization-cooling unit 12 , where they are pasteurized at a temperature of 85...90 °C with a holding time of 15...20 s, cooled to 2...6 °C and sent to a tank 13 , equipped with a jacket, for temporary storage until mixed with cottage cheese.
Rice. 4.8. Machine and hardware diagram of the production line for soft dietary cottage cheese
Skim milk with a fat mass fraction of no more than 0.05% from the separator 9 enters the plate pasteurization-cooling unit 8 , where it is first pasteurized at a temperature of 75...80 °C with a holding time of 15...20 s. The pasteurization temperature affects the physicochemical properties of the curd, which, in turn, affects the quality and yield of the finished product. Thus, at low pasteurization temperatures, the curd is not dense enough, since whey proteins are almost completely lost to the whey, and the yield of curd decreases. As the pasteurization temperature increases, the denaturation of whey proteins increases, which are involved in the formation of the curd, increasing its strength and enhancing its moisture-holding capacity.
This reduces the intensity of whey separation and increases product yield. By regulating pasteurization and curd processing modes and selecting starter strains, it is possible to obtain curds with the desired rheological and moisture-retaining properties. Pasteurized milk is cooled in the recirculation section of a plate pasteurization and cooling unit 8 to the fermentation temperature (in the warm season up to 26...30 °C, in the cold season - up to 28...32 °C) and sent to the apparatus 15 , equipped with a jacket and a stirrer, for fermentation.
Sourdough for the production of cottage cheese is prepared using pure cultures of mesophilic lactic acid streptococci in a tank 14 and dosed with a pump 11 into the device 15 . Then calcium chloride and rennet are dosed sequentially. All these components are dosed while continuously stirring the milk.
Stirring the milk after fermentation is continued for 10...15 minutes, then the milk is left alone until a clot of the required acidity forms. The end of milk ripening is determined by the active acidity of the curd, which should be within the pH range of 4.4...4.5, or by the titratable acidity of the whey 60...70 °T, or the curd 90...110 °T. When separating a clot with lower acidity, the separator nozzle 19 may become clogged. The duration of ripening is 8...10 hours. The finished curd is thoroughly mixed for 5...10 minutes, then with a pump 16 fed into a plate pasteurization-cooling unit 17 for the curd, where it is heated to a temperature of 58...62 °C for better separation of whey, and then cooled to 25...32 °C, due to which it is better separated into the protein part and whey. From installation 17 clot through a strainer 18 fed under pressure into the separator-curd maker 19 , where it is divided into whey and curd.
To avoid intensive separation of whey from clots during the entire operation of the separator 19 periodically turn on the stirrer in the apparatus 15 .
When producing all types of soft dietary cottage cheese, low-fat cottage cheese must have a moisture content of no more than 80%.
The resulting low-fat cottage cheese is fed with a single-screw pump 20 into the cooler 21 for cooling to a temperature of 12…16 °C. When producing low-fat cottage cheese, the cottage cheese comes from the cooler 21 directly into the receiving hopper of the filling machine 23 bypassing the mixer 22 . Then the packaged cottage cheese is cooled to 4...8 °C. When producing full-fat cottage cheese, the cooled cottage cheese is sent to the mixer 22 , where the dosing pump 11 pasteurized chilled cream is served from a container 13 and everything is thoroughly mixed. Ready cottage cheese is packaged on machines 23 and sent to the refrigeration chamber for further cooling to 1...8 °C.
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