General technology of dietary fermented milk products. Coursework: Technology of liquid fermented milk products and drinks
Fermented milk products are produced by thermostatic and reservoir methods. (Tverdokhleb G.V., 1991)
reservoir method. The technological process for the production of beverages by the reservoir method consists of the following technological operations: acceptance and preparation of raw materials, quality assessment, normalization, homogenization, pasteurization and cooling, fermentation, fermentation in special containers, curd cooling, curd maturation (kefir, koumiss), packaging.
For the production of fermented milk drinks, milk of at least the second grade is used, with an acidity of not more than 19 °T, and a density of at least 1027 kg / m 3. Powdered milk is pre-reconstituted. Skimmed milk, buttermilk, cream, condensed and powdered milk, sodium caseinate, fruit and berry and vegetable fillers must be of good quality, without foreign tastes and odors and defects in texture.
Sour-milk drinks are produced with different mass fractions of fat, so the original milk is normalized to the required mass fraction of fat. Normalization of milk is carried out in a stream on separators-normalizers or by mixing. Some products are made from skimmed milk. When normalizing raw materials by mixing, the mass of products for mixing is calculated according to the formulas of the material balance or determined according to the recipe.
The scheme of the technological line for the production of fermented milk drinks by the tank method is shown in Figure 1.
Rice. 1. 1 -- installation for dissolving milk powder; 2 -- container for the normalized mixture; 3 -- centrifugal pump; 4 - balancing tank; 5 - pasteurization and cooling unit; 6-- centrifugal milk cleaner; 7 - homogenizer; 8-- holder; 9, 14 -- containers for fermented milk drinks; 10-- starter; 11 -- dosing pump; 12 -- screw pump; 13-- plate cooler. (Bredikhin S.A., 2001)
The normalized mixture is subjected to heat treatment. As a result of pasteurization, microorganisms in milk are destroyed and conditions favorable for the development of the starter microflora are created. The normalized mixture is pasteurized at a temperature of 92 ± 2 ° C with an exposure of 2 ... 8 minutes or at a temperature of 85 ... 87 ° C with an exposure of 10 ... 15 minutes; UVT treatment is possible at 102 ± 2 °C without exposure. For the production of fermented baked milk, the mixture is pasteurized at 95...98 °C with an exposure of 2...3 hours. High pasteurization temperatures cause denaturation of whey proteins, while increasing the hydration properties of casein. This contributes to the formation of a denser clot that retains moisture well, which, in turn, prevents the separation of whey during storage of fermented milk drinks.
The heat treatment of the mixture is usually combined with homogenization at a temperature of 60...65 o C and a pressure of 15...17.5 MPa.
After pasteurization and homogenization, the mixture is cooled to the fermentation temperature, after which it enters the fermentation tank. Starter is added to the cooled mixture, the mass of which is usually 5% mass of fermented mixture. Direct fermentation is used.
The fermentation of the mixture is carried out at the fermentation temperature. During fermentation, the ferment microflora multiplies, acidity increases, casein coagulates and a clot is formed. The end of fermentation is judged by the formation of a sufficiently dense clot and the achievement of a certain acidity.
After fermentation, the product is immediately cooled.
Kefir produced with maturation is cooled down to 14...16 °C after fermentation and ripens at this temperature. The duration of maturation of kefir is at least 10 ... 12 hours. During maturation, yeast is activated, alcoholic fermentation occurs, as a result of which alcohol, carbon dioxide and other substances are formed in the product, giving this product specific properties. In the production of fruit kefir, fillers are added after maturation before packaging.
Sour-milk drinks are packaged in heat-sealed bags, boxes, cups, etc.
thermostatic method. The technological process for the production of fermented milk drinks by the thermostatic method consists of the same technological operations as in the production of the tank method, carried out in the following sequence: preparation of raw materials, normalization, pasteurization, homogenization, cooling to the fermentation temperature, fermentation, packaging, fermentation in thermostatic chambers, cooling clot, clot maturation (kefir, koumiss).
The scheme of the technological line for the production of fermented milk drinks by the thermostatic method is shown in Figure 2.
Rice. 2. 1 -- container for raw milk; 2 -- pump; 3 -- balancing tank; 4 - pasteurization and cooling plant; 5 - control panel; 6-- return valve; 7 - separator-normalizer; 8 -- homogenizer; 9 -- container for keeping milk; 10-- container for fermenting milk; 11 - car for packing milk; 12 -- thermostatic chamber; 13 -- refrigerating chamber; 14 -- storage room for finished products. (Bredikhin S.A., 2001)
Acceptance and preparation of raw materials, normalization, heat treatment, homogenization of the normalized mixture and its cooling to the fermentation temperature are performed in the same way as in the tank production method. Next, the normalized mixture is fermented in a container. After fermentation, the mixture is packaged in consumer containers and sent to a thermostatic chamber, where a temperature is maintained that is favorable for the development of the microflora of the starter. The end of fermentation is judged by the acidity and density of the clot. After fermentation is completed, the product is sent to the refrigerator for cooling, and kefir for maturation.
The tank method for the production of fermented milk drinks has a number of advantages compared to the thermostatic method. Firstly, this method makes it possible to reduce production areas by eliminating bulky thermostatic chambers. At the same time, the removal of products from 1 m 2 of the production area increases and the consumption of heat and cold decreases. Secondly, it allows for a more complete mechanization and automation of the technological process, reducing manual labor costs by 25% and increasing labor productivity by 35%.
Defects of dairy products
Defects in fermented milk products arise as a result of the use of low-quality raw materials, the action of bacterial starter cultures in case of violation of the technological regimes of production or non-compliance with the conditions for cooling and storing finished products.
Defects of taste and smell. Unexpressed (fresh) taste - is caused by low acidity, weak aroma and insufficient density of the clot. Such a defect appears when using low-quality starter (poor acid formation) or at too low fermentation temperatures.
Feed flavors that have passed from milk to fermented milk products (wormwood, silage). Ammonia and bready flavors appear when milk is kept in a poorly ventilated barn for a long time.
A bitter taste may appear as a result of the development of peptonizing bacteria in the case of long-term (up to two days) storage of raw milk at low temperatures, as well as in cottage cheese when excessive doses of pepsin are added.
A metallic taste appears in products when they are stored for a long time in poorly tinned dishes.
Excessively sour taste is detected as a result of delayed cooling after ripening or due to the long time of ripening itself, as well as during storage at unacceptably high temperatures.
Acetic acid and butyric taste depend on the activity of the corresponding extraneous microflora that has entered milk or sourdough.
A greasy taste in sour cream may appear as a result of oxidative processes of fat during long-term storage or direct sunlight on the surface of sour cream. (Kastornykh M.S., 2003)
Consistency defects
A flabby clot is the result of using starter cultures with weakened cultures or aging the product at low temperatures, as well as violations of the temperature regime of pasteurization (at low temperatures and without aging).
A viscous consistency is formed with a significant predominance of mucous races of lactic acid bacteria in the leaven.
Isolation of whey - the main defect of fermented milk products produced by the tank method - is a consequence of the unsatisfactory quality of raw materials (low solids content), deviations from the normal mode of homogenization and pasteurization of milk during the fermentation of the product.
The swollen consistency is caused by infection of the starter with gas-forming bacteria, and also appears at low fermentation temperatures. (Shepelev A.F., 2001)
In accordance with GOST R 52090-2003 “Drinking milk. Specifications» drinking milk subdivided depending on the raw milk used: from natural milk, from normalized milk, from reconstituted milk, from recombined milk, from their mixtures; depending on the heat treatment mode: pasteurized, melted, sterilized, UHT (ultra high temperature)-treated, UHT-treated sterilized; according to fat content: low fat (0.1%), low fat (0.3; 0.5; 1.0% fat), low fat (1.2; 1.5; 2.0; 2.5% fat), classic (2, 7; 3.0; 3.2; 3.5; 4.0; 4.5% fat), fatty (4.7; 5.0; 5.5; 6.0; 6.5; 7.0 % fat), high fat (7.2; 7.5; 8.0; 8.5; 9.0; 9.5% fat).
Pasteurized milk. Milk subjected to heat treatment under certain temperature conditions (up to 100 0 C) and then chilled. The technological process for the production of drinking milk at the factories is carried out according to the scheme: cleaning, normalization, homogenization, cooling, bottling with packaging and storage.
Milk homogenization(homogeneous - homogeneous). In the process of homogenization, large fat globules are crushed and uniform in size are obtained with an average diameter of about 1 micron. From one fat ball with a diameter of 6 microns, more than 200 small ones, with a diameter of 1 micron, are formed. In homogenized milk, there is practically no settling of cream.
sterilized milk. The production of sterilized milk at factories can be carried out according to two schemes: with one-stage and two-stage sterilization mode. With a single-stage scheme, milk is sterilized once before or after packaging at a temperature of 130-150 0 C with a holding time of 2-3 s. This mode is accompanied by the least changes in the native properties of milk. Such milk can be stored for up to 2 months from the date of release from the factory at a temperature of 1 to 20 0 C. In a two-stage mode, milk is sterilized with an exposure for 20 seconds, and then in bottles with steam at a temperature of 116-118 0 C for 12-15 min. Double sterilization causes deeper changes in the components of milk, but at the same time ensures its high stability - it can be stored in unrefrigerated rooms for more than a year.
Reconstituted milk is produced by complete or partial dissolution of dry whole or skimmed milk in drinking water at a temperature of 38-42 0 C, followed by its purification, homogenization and normalization in terms of fat.
protein milk contains an increased amount of dry skimmed milk residue. It is produced from milk, normalized in terms of fat content, with the addition of dry or condensed whole or skimmed milk.
Baked milk- a specific product with certain taste properties and a pronounced color shade. It is produced from normalized and homogenized ordinary milk, which is heated to a temperature of 96-98 0 C and kept at this temperature for 3-4 hours. As a result of prolonged exposure to high temperatures, physical and chemical changes in milk proteins and lactose occur, so the finished product has a pronounced taste boiled milk and acquires a cream color with a brown tint.
Dairy products produced by fermentation of milk and cream with pure cultures of lactic acid bacteria (sourdough). Most of the fermented milk products have not only high nutritional, dietary, but also medicinal properties. Acidophilus bacillus, as well as yeast used in the production of fermented milk products, are capable of secreting significant amounts of antibiotics such as nisin, lactolin, lactomine, etc. Scientifically based human nutrition standards provide that 40-50% of all milk intended for consumption, it is desirable to use in the form of fermented milk products, which are absorbed by the body much easier and faster than milk.
Producing dairy products:
1) liquid and semi-liquid consistency (yogurt, kefir, etc.);
2) high in fat (sour cream);
3) with a high protein content (cottage cheese, curd mass, curd products).
Depending on the type of fermentation, fermented milk products are distinguished, obtained only using lactic acid fermentation and accumulation of lactic acid (curdled milk of all kinds, yogurt, acidophilus and acidophilus milk, the Snezhok drink, and products obtained by joint lactic acid and alcoholic fermentation, when lactic acid, ethyl alcohol and carbon dioxide accumulate (kefir, koumiss, acidophilic yeast milk, etc.). In the manufacture of fermented milk products, starters are used, which are prepared on pure cultures of the corresponding types of microorganisms. In the process of fermentation, biochemical and physico-chemical changes occur in almost all components of milk.
The use of lactic acid microorganisms in various combinations makes it possible to obtain a large number of types of fermented milk products. The dairy industry produces various fermented milk products: yogurt of all kinds, yogurt, kefir, acidophilic products, koumiss, sour cream, cottage cheese, etc.
The production of fermented milk products consists of the following processes: receiving and sorting milk, normalization, pasteurization, homogenization, cooling, fermentation, fermentation, cooling, maturation, storage, sale.
Liquid fermented milk products are prepared by thermostatic and reservoir methods. The thermostatic and reservoir methods have the same initial technological operations, including fermentation.
thermostatic method the production of sour-milk drinks is a method in which the fermentation of milk and the maturation of drinks is carried out in bottles in thermostatic and cold chambers.
tank method production of liquid sour-milk drinks - a method in which fermentation, fermentation of milk and maturation of drinks is carried out in one container.
Butter and cheese making
Oil - high-calorie food product, which is a concentrate of milk fat. The raw material for the preparation of butter is cream, which is subjected to the process of whipping. It consists mainly of a fatty part and water. The quality of butter and its stability during long-term storage largely depend on the quality of milk and cream. Particular attention should be paid to the defects of milk fat, as they increase in butter (20-25 kg of milk is used to produce 1 kg of butter). The best is milk with a high fat content, which has large fat globules, obtained from cows whose diets were complete in terms of general nutrition, protein, and minerals. With an increase in the fat content of milk, its costs for the production of butter decrease and relatively less fat remains in by-products - skimmed milk and buttermilk.
There are two ways to produce butter:
1) churning cream;
2) conversion of high-fat cream.
Cream churning method provides for the production of butter grain from cream of medium fat content (30-35%) and its subsequent mechanical processing. Oil by this method can be produced in butter makers of periodic action (roller and rollerless) and continuous action.
Process for converting high fat cream(82% fat or more) consists in thermomechanical action on high-fat cream in special devices.
Carrying out separate operations when obtaining butter by the method of churning cream. Cream normalization. For sweet cream butter, the optimal fat content of cream is 32-37%.
Pasteurization. Normalized cream of the I grade is pasteurized at a temperature of 85-90 0 C without aging, of the II grade - at 92-95 0 C, to destroy the microflora and the lipase enzyme.
Cooling and physical ripening of cream. After pasteurization, the cream is quickly cooled to 4-6 0 C. At this temperature (physical ripening), mass crystallization of milk fat glycerides occurs: it passes from a liquid state to a solid state, which makes it possible to form an oil grain during subsequent churning.
At physical maturation the fat globules become more elastic, their protein shell thins out, the viscosity of the cream increases, and the fat globules are able to form lumps to a greater extent. The lower the temperature, the shorter the ripening time of the cream. With deep cooling (0-1 0 C) and intensive mixing, the ripening period of cream is reduced to several minutes, which makes it possible to create in-line technological lines for butter production.
Biochemical maturation used in the manufacture of sour cream butter. Its essence lies in the fermentation of cream with starters (the same as in the preparation of sour cream). Biochemical maturation contributes to a greater thinning of the shell of fat globules and the release of fat from them.
Filling the oil maker. The buttermaker is filled with cream by about 35-40% of the volume. The temperature of the cream in the spring-summer period should be 7-12 0 C, in the autumn-winter period 8-14 0 C.
Whipping cream. When cream is churned into butter, the shell of fat globules is destroyed and they are combined into a butter grain. At the heart of the process of churning butter is the flotation theory, which consists in the fact that when churning cream, air bubbles (foam) are formed. Fat globules accumulate (float) on the surface of the air bubbles. Under the action of mechanical shocks, the air bubbles burst and the fat globules are interconnected by bare areas into conglomerates.
Removal of buttermilk and washing of butter grains. When the grains are ready, the buttermilk is removed by filtering it through a sieve in order to retain small grains. Then the grains (oil) are washed 2 times. Waters take 50-60% of the amount of cream. The temperature of the first washing water is equal to the temperature of the cream, the second is lower by 1-2 0 C. In the manufacture of sour cream butter, it is washed less intensively, using only 15-20% of water by weight of the cream, to preserve the specific taste and smell.
Oil processing. The goal is to connect the oil grain and get a layer of uniform consistency, give the oil a certain structure, marketable appearance, evenly distribute salt and moisture throughout the mass, and disperse water drops to a minimum size. Processing is carried out by passing oil between the rollers of the oil maker. Its rotation speed is 3-5 rpm. The duration of treatment in summer is 20-30 minutes, in winter 30-50 minutes. In the finished oil, on the cut and on the surface, there should be no noticeable drops of moisture.
Butter production by converting high-fat cream. This method allows you to create in-line production. Its essence lies in the fact that first milk is separated on a conventional separator, cream with a 35-40% fat content is obtained, then they are pasteurized at a temperature of 85-90 0 C. Pasteurized cream is separated at a high temperature on a special separator in order to obtain high-fat cream (84- 85%), normalize them to the required fat content and send them to the oil former, where they are cooled and turned into oil.
Oil classification. In accordance with the requirements of the standard, butter is divided into the following types: unsalted, salted, Vologda, amateur, peasant, melted, etc.
unsalted And salty butter is made from pasteurized cream with or without the use of pure cultures of lactic acid bacteria (sweet cream or sour cream). When making salted butter, table salt is added.
Vologda unsalted butter is made from sweet cream that has been pasteurized at high temperatures and has a nutty taste and smell.
amateur butter is made from pasteurized cream with or without the use of pure cultures of starter cultures (sweet cream or sour cream), with or without the addition of table salt (salted or unsalted).
Peasant butter unsalted butter is produced from pasteurized cream with or without the use of pure cultures of lactic acid bacteria (sweet cream or sour cream), and peasant sweet cream salted - from fresh pasteurized cream.
Ghee Butter is rendered milk fat with its specific taste and aroma. Each type of oil is characterized by a certain chemical composition.
When determining the quality of the oil, its chemical composition and organoleptic evaluation data are taken into account, which is performed on a 100-point scale. The results of the assessment for taste, smell, consistency, color, salting, packaging and labeling are summarized and the grade of oil is determined by the total score: the highest (more than 88 points) and the first (more than 80 points).
Cheese making. Cheese- a highly valuable food product obtained from milk by enzymatic coagulation of proteins, isolation of cheese mass, followed by its processing and maturation. According to the International Dairy Federation, more than 500 types of cheeses are produced in countries with developed dairy farming that are members of the federation.
classify cheeses on a number of grounds, primarily on the features of technologies. Cheeses are divided mainly into rennet and sour-milk. Processed or processed cheeses are also produced.
Each type of cheese is characterized by a certain shape, organoleptic properties, chemical composition, which must comply with the standard.
Cheese technology consists of a number of operations that can be performed differently, which determines the characteristics of a particular type of cheese or a group of cheeses. In general, the process of production of natural rennet cheeses is carried out according to the following scheme: 1) Determination of the quality of milk and its sorting; 2) Preparation of milk for processing; 3) Coagulation of milk; 4) Processing curd and curd; 5) Cheese molding; 6) salting cheese; 7) Cheese maturation; 8) Preparation of cheese for sale; 9) Storage and transportation.
Requirements for milk for the production of cheese. Milk with defects in organoleptic characteristics is unsuitable for cheese production. In the finished cheese, the defects of taste and smell are more pronounced than in milk. The yield of cheese depends on the content of fat and casein in milk. For the production of cheese, milk is used only 7-10 days after calving and 7-10 days before the start of cows, since the admixture of colostrum or old-fashioned milk with normal milk reduces the quality of the cheese. The milk of cows suffering from mastitis is unsuitable for cheese making. Milk should contain a sufficient amount of calcium and phosphorus, especially calcium, which is in a soluble state. For cheese making, milk with an acidity of not more than 20 0 T is used, since high-quality cheese cannot be obtained from milk with high acidity.
Cheese suitability of milk is estimated by the duration of its coagulation by rennet. Milk that coagulates slowly under the influence of rennet is considered non-chewy or rennet. To improve cheese suitability, calcium chloride, an increased dose of bacterial starter are added to milk, and the temperature of milk clotting is also increased. So-called "mature" milk is used to make cheese. Freshly milked milk cannot be processed into cheese, as it does not coagulate well with rennet. Exposure (ripening) of high-quality milk for 10-15 hours at 8-10 0 C leads to the development and accumulation of lactic acid microflora, enlargement of casein micelles, and an increase in acidity by 1-2°T. The changes that take place (ripening) have a positive effect on the quality of the cheese.
Pasteurization. In cheesemaking, pasteurization of milk is used at 71-72 0 C, higher temperatures of pasteurization lead to the loss of the milk's ability to coagulate.
Curdling of milk. To coagulate milk, an enzyme preparation is used - rennet powder, obtained at special factories from the mucous membrane of the abomasum of suckling calf lambs. Pepsin, obtained from the gastric mucosa of adult animals, is also used to coagulate milk. Before curdling, bacterial starter, calcium chloride, chemically pure potassium or sodium nitrate (to suppress the development of Escherichia coli), and paint are added to cooled milk. After that, the required amount of rennet is set to coagulate the milk.
Clot processing. Clot processing is carried out in order to partially remove whey from the curd and cheese grain, as well as to create optimal conditions for microbiological and biochemical processes in the curd, grain and cheese in the first period of its ripening. To speed up and more complete release of whey, the clot is subjected to cutting, kneading the resulting cheese grain, and second heating. The clot is cut with the help of cheese lira and knives. Cutting the clot and grinding it to the required size is called setting the curd.
Plastovanie cheese grain- carried out in order to connect the cheese grain into a solid monolith.
Cheese molding. To give the cheese an appropriate shape characteristic of a particular type, the cheese mass is molded. To do this, the cheese layer is cut into pieces corresponding to the forms (45x10 cm) and laid in these forms.
Cheese pressing. Cheeses are pressed to give them shape, firmness and to remove whey residue. The duration of pressing is 2-3 hours at a press pressure of 30-40 kg per 1 kg of cheese mass, the air temperature should be 15-18°C.
Cheese salt. Salting gives the cheese certain taste qualities, with the help of salting the development of microbiological processes is regulated, it affects changes in the physico-chemical properties of the cheese rind, cheese dough and cheese yield.
Cheese maturation. This is a complex of sequential complex biochemical changes in the substances of the cheese mass. Ripening gives the cheese pronounced organoleptic properties characteristic of this type, primarily taste and smell, as well as color, texture, pattern, which distinguish mature cheese from fresh cheese mass. The duration of ripening is up to 2.5 months or more (depending on the type of cheese).
Waxing and packaging of cheese. Ripened cheeses are thoroughly washed, rinsed in a lime solution, dried, factory stamped and waxed to prevent shrinkage during their long-term storage. Some types of polymer films are also used to protect cheese from shrinkage and the development of aerobic microflora on the surface of the cheese head.
Storage and transportation of hard cheese. During transportation, cheeses must be protected from high and extremely low temperatures. They do not undergo changes at temperatures from plus 10 to minus 6 0 C. If cheeses are transported at high temperatures, the cheese dough softens, fat is released, resulting in a deterioration in taste and texture. When cheese freezes after thawing, it becomes crumbly, and its taste is empty, unexpressed. On refrigerators for long-term storage of cheese, the air temperature should be from 0 to 2 ° C, for short-term storage - 2-8 0 C. Hard rennet cheeses are stored for up to 8 months, soft - up to 4 months, Swiss - up to a year or more. Each type of finished cheese is characterized by a certain shape, chemical composition, organoleptic properties. The organoleptic evaluation of hard cheese is made on a 100-point scale. Depending on the overall assessment and assessment for taste and smell, the cheese is classified as the highest (more than 87 points) and the first (more than 75 points) grade. Cheeses that do not meet the requirements of the standard in composition or have received a score of less than 75 points are subject to processing into processed cheeses.
Processed cheese production. Both non-standard cheeses and cheeses of various degrees of maturity and grade are used as feedstock. In addition, "specific" processed cheeses are produced from natural high-quality cheeses of the same type. These cheeses are named after the cheese from which they are made (processed Kostroma, Russian processed, etc.).
The technological scheme for the production of processed cheese includes the following operations: 1) selection, cleaning and grinding of cheese; 2) preparation of a mixture for melting and the introduction of melting salts; 3) maturation of the mixture; 4) cheese melting; 5) packaging; 6) Processed cheese cooling and storage.
An important process in the production of processed cheeses is the addition of melting salts (dibasic sodium phosphate, sodium metaphosphate, tartaric salt, etc.) to the crushed cheese mass. The introduction of melting salts into the cheese mass significantly reduces the release of moisture from the cheese mass when it is melted (heated to 95 ° C), the mass turns out to be plastic, viscous, with increased swelling. Upon cooling, a gel is formed, the properties of which largely depend on the selection of the melting salt.
Processed cheeses are packaged in the molten state in aluminum foil, plastic molds. The shelf life of processed cheeses is 3-6 months at 5-8 0 C. The assortment of processed cheeses is the most diverse. They produce smoked processed cheese, sterilized processed cheese, pasteurized processed cheese, sweet processed cheeses, plastic (chocolate, coffee, with fruits, with nuts) cheeses, powdered processed cheeses, etc.
In the production of fermented milk drinks, two methods are used: thermostatic and reservoir. With the thermostatic method for the production of fermented milk drinks, the fermentation of milk and the maturation of drinks is carried out in bottles in thermostatic and cold chambers.
With the tank method of production, fermentation, fermentation of milk and maturation of drinks occur in one container.
Fermented milk drinks produced by the reservoir method, after maturation and mixing, are poured into glass or paper containers, therefore, their clot is disturbed compared to the thermostatic method - having a homogeneous creamy consistency.
To obtain a product with a dense homogeneous consistency, it is necessary to maintain the fermentation temperature that is optimal for this product. The duration of milk fermentation depends on the type of fermented milk products obtained and ranges from 4 to 16 hours. The end of fermentation is determined by the nature of the clot and by acidity, which should be slightly lower than the acidity of the finished product.
Cooling and ripening is carried out at a temperature not higher than 6 for several hours (6-8). During this time, milk proteins swell, which leads to the formation of a denser clot, the lactic acid process weakens or completely stops.
In the production of mixed fermentation products, during cooling and maturation, the development of lactic acid microorganisms is suspended, but yeast develops, as a result of which alcohol and carbon dioxide accumulate in these fermented milk drinks.
Finished products are controlled for the presence of bacteria of the Escherichia coli group and according to a microscopic preparation from one or two batches at least once every 5 days.
Equipment that comes into direct contact with the product during the production process requires special attention. Before starting the technological process, a thorough sanitization of such equipment should be carried out. If the sanitary indicators of the finished product deteriorate, a thorough analysis and additional control of the technological process is carried out to establish the causes of secondary contamination of the product, the quality of the starter culture, as well as the sanitary and hygienic condition of the workshop are checked.
Fermented milk products are also produced with fruit and berry fillers and fortified. The control of finished products is carried out according to the methods adopted for fermented milk drinks with fruit and berry fillers. In the production of fermented milk drinks with fillers, you need to be especially careful to avoid the production of products of non-guaranteed quality.
Tank method for the production of fermented milk products
Description of the general operations of the technological process.
Acceptance of milk is carried out in accordance with GOST R 52054-2003. The milk is cooled down to 4 °С in order to prevent the development of microflora and spoilage of milk. Milk reservation should not last more than 12 hours. Before cleaning, the milk is heated to 40 ... 45 ° C. Normalization of milk according to the mass fraction of fat is carried out in a stream or by mixing. Normalized milk is homogenized in order to exclude fat sludge and obtain a product with a uniform consistency. Pasteurization is carried out at a temperature of 90 ... 95 ° C with an exposure of 2 to 8 minutes. The pasteurized normalized mixture is cooled to the fermentation temperature. Fermentation is carried out with specially selected starter cultures from thermophilic or mesophilic lactic acid bacteria, bifidobacteria. Depending on the type of product and starter culture, the fermentation time is 4…12 hours, the fermentation temperature is 20…43 °C.
For kefir, which contains yeast, additional maturation is required for 12-14 hours, during which the formation of a specific taste of the product takes place. The finished product is cooled and sent for bottling.
The production of sour-milk dietary products - kefir, acidophilus, acidophilus milk, acidophilic yeast milk, Snezhok, Yuzhny drinks, yogurt and others - has increased tenfold.
Kefir is the most popular among the population, so it has taken a dominant position in the production of fermented milk drinks produced in Kazakhstan. The birthplace of kefir is the North Caucasus, where for a long time it was made in wineskins or in wooden tubs. The technology of its production in the villages is simple - kefir fungi are poured with fresh milk, cooled to 18-20 ° C, during the fermentation and maturation process, the product is periodically shaken. When kefir ripens due to increased aeration, yeast actively develops, which affects the taste and consistency of the product: the consistency becomes liquid, creamy, the taste becomes specific, sour, and becomes sharp.
In Russia, kefir was produced back in 1866-1867. in an artisanal way on fungi brought from the Caucasus in a dry form. Kefir fungi were revived in boiled chilled skim milk and used to make starter cultures. Milk for kefir was heated up to 16-23°C and fermented with starter directly drained from fungi. After obtaining a clot, the bottles were shaken to speed up the process of forming a drink and kept indoors at a temperature of 14 - 16 ° C for a day, and sometimes for a longer time.
The same technology was used to produce kefir at city dairies, while pasteurization of milk and bottling of the drink into bottles with hermetic seals were used. As a result of the length of the technological process, the laboriousness of many operations, the production of kefir was limited and the demand from the population for it was not satisfied, so the technology of kefir was changed: they began to produce it, in an accelerated way, which later received the name thermostatic.
Milk used for the production of kefir began to be fermented at high temperatures in thermostats without shaking and the corresponding accumulation of yeast fermentation products. As a result of a change in technology, instead of a soft but consistency of a semi-liquid drink with a characteristic refreshing taste, factories began to produce a product with a dense clot that tastes like yogurt.
As a result of a number of research works, VNIMI has developed a tank method for the production of kefir, which is currently a generally recognized progressive method that is being widely introduced into the dairy industry.
The main stages of the technological process are the following:
- - heat treatment and homogenization of milk used for the production of kefir;
- - fermentation of milk, cooling and maturation of kefir in tanks;
- - bottling of high-viscosity drink into paper bags and glass bottles.
In the production of kefir by the tank method, milk is pasteurized at 85 ° C and kept. As the pasteurization temperature increases, the holding time decreases. An obligatory operation is the homogenization of milk: it prevents the sludge of whey in the finished product and gives it a homogeneous creamy consistency. Milk is homogenized under a pressure of at least 125 atm, the optimum homogenization pressure is 175 atm. Milk is fermented at a temperature of 20-25°C in double-walled tanks specially designed for the production of fermented milk drinks. The starter is introduced in a stream or in any other way with continuous mixing of the milk in the tank. The end of fermentation is determined when the acidity of the clot reaches 85-90 ° T. Water at a temperature of 1-3 ° C is supplied to the interwall space of the tank to cool the clot to the maturation temperature, and then turn on the stirrer to stir it and leave it alone for maturation.
In the process of maturation, kefir acquires a specific taste, different from the taste inherent in curdled milk.
The method of cooling depends on the scheme of the technological process adopted at this enterprise.
In the production of kefir, mixing and cooling it when serving for bottling is of great importance. The stirrer should not shake, and not cut it into layers and cubes, but smoothly and evenly mix the entire mass of kefir. Partial agitation or cutting of the curd results in whey separating (syneresis), just as churning kefir with a stirrer results in foaming, resulting in whey sludge. To preserve the quality of kefir, you should not use pumps that foam kefir and break the product. Chilled kefir is packaged in small containers (bottles and paper bags). Before being released into the distribution network, the finished product is cooled in the chamber to 6-8 ° C.
Below is the main technological scheme for the production of fermented milk drinks by the tank method (in two versions - with cooling in tanks and cooling in a stream on a plate heat exchanger), developed by VNPLSH and providing for mechanization and automation of main and auxiliary operations.
According to this scheme, milk is pumped through pipes, and the packaged finished product is transported internally (chain and belt conveyors, etc.).
In heat exchangers, milk and drinks are subjected to heat treatment (heating and cooling) to a predetermined temperature. Milk is purified from mechanical impurities in inline separators and processed in homogenizers to obtain the appropriate dispersion of fat and improve the viscosity of the drink.
The beverage in the tank is agitated by a powered agitator. The drink is packaged in bottles or paper bags on filling machines and automatic machines. Labour-intensive processes of washing equipment are carried out with the help of irrigation and jet devices.
Control of the technological process and its management are automated.
The peculiarity of this scheme lies in the fact that after fermentation and reaching the desired acidity, kefir is mixed and cooled in the same tank, after which it enters the bottling and is fed into the chamber for post-cooling.
The process of cooling fermented milk drink in a double-walled tank lasts 3.5 - b hours. In the production of fermented milk products on thermophilic cultures, acidity rises very quickly. To stop the rapid increase in acidity after reaching 85-90 ° T, the product is fed from the tank to a plate cooler with the help of a low-speed pump, where the duration of the cooling process is reduced to 1 hour.
Another variant of the basic scheme of the technological process for the production of fermented milk drinks by the tank method with in-line cooling is shown in Fig. 2.
A feature of this technological mode is that the milk is fermented in a double-walled tank or in a conventional milk storage tank 13 equipped with driven tubular "mixers", and when the acidity reaches 85-90 ° T, the drink is supplied to the cooler 15 using a low-speed pump 14 from the tank 13. Drink cools in a thin layer very quickly. Then it enters the intermediate tank 16, and then goes by gravity to machines such as "Yudek", OR-6U, I2-ORK-6, I2-ORK-3 for packaging in glass bottles or to an automatic machine of the type AP-1N, AP-2N for packaging in paper bags. The packaged drink is transported by a conveyor to the storage room for further cooling.
The advantages of the production of fermented milk drinks by the tank method are as follows:
- - manual labor is almost completely eliminated as a result of mechanization and automation of the technological process;
- - improving the skills of workers serving the line; Reduce labor costs and increase productivity
- - the cost of 1 ton of product is reduced by 4 rubles. 46 k.; production areas are reduced, since the finished product matures and cools in the same tanks in which it is prepared, and not in thermostatic rooms; reduced heat and cold consumption.
The practice of operating equipment for the tank method of obtaining drinks has shown that lines assembled from machines and apparatus specially designed for the tank method for the production of fermented milk drinks are cost-effective in operation and ensure the production of high quality products.
If equipment for the production of drinking milk is used in the lines for the production of fermented milk drinks in a tank way, then it works intermittently.
At present, all the main machines and devices for completing a standard line are mass-produced (heat exchangers of the OPL-5 and OPL-10 types, A1-OGM homogenizers, automatic machines AP-1N, AP-2N, double-walled tank tanks and filling lines I2-OL2- 6 and I2-OL2-3. The line for the production of sour-milk drinks, completed from double-walled tanks, is universal, since it can produce drinks according to two options for the technological scheme after adding a pump and a plate pasteurizer to it.
MINISTRY OF YOUTH EDUCATION AND SPORTS
TECHNICAL UNIVERSITY OF MOLDOVA
Department of Technology and Public Catering
Course work
According to the technology of milk processing on the topic:
"Technology of liquid fermented milk products and drinks"
Performed:
Student gr. TL-052
Checked:
Senior Lecturer Popescu L.
Chisinau 2009
Introduction
1. Assortment of liquid fermented milk products.
Terms and definitions…………………………………..3
2. Finished product quality indicators………….5
3. General technology………………………………………….8
4. Theoretical foundations of production………………10
5. The influence of various factors on the production process..14
6. Vices……………………………………………………… 17
Bibliography.
Introduction
The national fermented milk product is a fermented milk product that has a historically established name in the country, depending on the type of starter culture and specific technology.
Fermented milk products include liquid fermented milk products and drinks, as well as cottage cheese and curd products and sour cream. Liquid fermented milk products and drinks include the following products.
1. Assortment of liquid fermented milk products .
curdled milk - a national fermented milk product made by fermenting milk with pure cultures of lactococci and / or thermophilic lactic streptococci, the total content of which in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, without the addition of non-dairy components.
Mechnikovskaya prostitute - a national fermented milk product made by fermenting milk with pure cultures of thermophilic lactic acid streptococci and lactic acid bulgarian sticks, the total content of which in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, without the addition of non-dairy components.
Ryazhenka - a national fermented milk product made by fermenting baked milk with pure cultures of thermophilic lactic streptococci, the total content of which in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, without the addition of non-dairy components.
Varenets - a national fermented milk product made by fermenting milk sterilized or heat treated at a temperature of (97 ± 2) ° C for 40 to 80 minutes with pure cultures of thermophilic lactic streptococci, the total content of which in the finished product at the end of the shelf life is at least 107 CFU in 1 g of the product, without the addition of non-dairy components.
Kefir - a national fermented milk product of mixed lactic acid and alcoholic fermentation, made by fermenting milk with sourdough prepared on kefir fungi without the addition of pure cultures of lactic acid bacteria and yeast, the content of lactic acid microorganisms in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, and yeast not less than 104 CFU per 1 g of the product, without the addition of non-dairy components.
acidophilus - a national fermented milk product made by fermenting milk with pure cultures of lactic acidophilus bacillus, lactococci and sourdough prepared on kefir fungi in equal proportions, the total content of lactic acid microorganisms in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, without the addition of non-dairy components.
Airan - a national fermented milk product of mixed lactic and alcoholic fermentation, made by fermenting milk with pure cultures of thermophilic lactic acid streptococci, lactic acid bulgarian bacillus and yeast, the content of lactic acid microorganisms in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, and yeast is at least 104 CFU per 1 g of the product, without the addition of non-dairy components.
Kumys - a national fermented milk product of mixed lactic and alcoholic fermentation, made by fermenting mare's milk with pure cultures of Bulgarian and acidophilic lactic acid bacilli and yeast, the content of lactic acid microorganisms in the finished product at the end of the shelf life is at least 107 CFU per 1 g of the product, and yeast is at least 105 CFU in 1 g of the product, without the addition of non-dairy components.
Yogurt - a fermented milk product with a high content of skimmed milk solids, produced by fermenting with a protosymbiotic mixture of pure cultures of thermophilic lactic acid streptococci and lactic acid bulgarian sticks, the content of which in the finished product at the end of the shelf life is at least 10 7 CFU per 1 g of the product (adding food additives is allowed , fruits, vegetables and products of their processing).
1.1. Classification of liquid fermented milk products and drinks
Fermented milk drinks, depending on the milk raw materials from which they are produced, are divided into products :
From natural milk;
From normalized milk;
From reconstituted milk;
From recombined milk;
from their mixtures.
Sour-milk drinks, depending on the mass fraction of fat, are divided into products :
Fat-free (m.d.zh.,%, 0.1);
Non-fat (m. d. w.,%, 0.3; 0.5; 1.0);
Low-fat (m.d. w.,%, 1.2; 1.5; 2.0; 2.5);
Classical (m. d. w.,% 2.7; 3.0; 3.2; 3.5; 4.0; 4.5);
Fat (m. f.,%, 4.7; 5.0; 5.5; 6.0; 6.5; 7.0);
High-fat (m. f.,%, 7.2; 7.5; 8.0; 8.5; 9.0; 9.5).
2. Indicators of the quality of the finished product .
According to organoleptic indicators, fermented milk drinks must meet the requirements indicated in Table 1
Table 1
Organoleptic characteristics of fermented milk drinks
According to physical and chemical indicators, fermented milk drinks must meet the requirements specified in Table. 2
table 2
Physico-chemical indicators of fermented milk products
Phosphatase is not allowed in the product.
Table 3
| Indicators | Permissible levels, mg/kg (l), no more |
| Toxic elements: | |
| lead | 0,1 |
| arsenic | 0,05 |
| cadmium | 0,03 |
| mercury | 0,005 |
| Mycotoxins: | |
| aflatoxin M, | 0,0005 |
| Antibiotics: | |
| chloramphenicol | not allowed |
| tetracycline group | not allowed |
| streptomycin | not allowed |
| penicillin | not allowed |
| Pesticides: | |
| hexachlorocyclohexane (a, P, y-isomers) | 0,05 |
| DDT and its metabolites | 0,05 |
| Radionuclides: | |
| cesium-137 | 100 |
| strontium-90 | 25 |
Microbiological indicators of fermented milk drinks are shown in table. 4
Table 4
Microbiological indicators of fermented milk drinks
Product name |
Quantity lactic acid microorganisms, cfu/g, no more |
Product mass (g, cm3), in which are not allowed |
Yeast, molds, CFU/g, no more |
||
| BGKP (coliforms) | Pathogenic incl. salmonella | S. aureus | |||
| Liquid fermented milk products, wt. h. yogurt with a shelf life of no more than 72 hours | - | 0,01 | 25 | 0,1 | - |
| Liquid fermented milk products, including yogurt with a shelf life of more than 72 hours | not less than 1 * 10 7 (not standardized for heat-treated products) | 0,1 | 25 | 1,0 | yeast - 50 (except for drinks made using starter cultures containing yeast), molds - 50 |
| Liquid fermented milk products enriched with bifidobacteria with a shelf life of more than 72 hours | not less than 1*10 7 ; bifidus bacteria - not less than 1 * 10 6 |
0,1 | 25 | 1,0 | yeast - 50 (except for drinks made using starter cultures containing yeast), molds - 50 |
| Ryazhenka | - | 1,0 | 25 | 1,0 | __ |
For the manufacture of fermented milk drinks, the following raw materials are used :
raw cow's milk not lower than the second grade according to GOST E52054; whole milk powder of the highest grade according to GOST 4495; skimmed milk powder according to GOST 10970; cream powder according to GOST 1349; unsalted butter according to GOST 37; starter cultures based on pure cultures of lactic acid microorganisms produced according to TU 9229-369-0019785-04 “Start cultures, bacterial concentrates, yeast and test cultures”; drinking water according to SanPiN 2.1.4.1074 (for recombined or reconstituted milk).
3.General technology of fermented milk products .
Milk and other raw materials are accepted according to the weight and quality established by the quality control department (laboratory) of the enterprise, as well as on the basis of certification documents of supplier firms.
Immediately after taking the milk
1. warm up to a temperature of 35 ... 40 ° C and cleaned on centrifugal milk cleaners or other equipment without heating. To purify raw milk, it is also recommended to use a bacteriophage with a specially built hermetic separator to remove bacteria from the milk.
2. After this milk is sent for processing or cooled to a temperature of (4 ± 2) °C and stored in intermediate storage tanks. Storage of milk, cooled to a temperature of 4 °C, before processing should not exceed 12 hours, cooled to a temperature of 6 °C-6 hours.
3. Selected quality milk normalize by mass fractions of fat and protein in such a way that they in the finished product are not less than provided by the standard.
Normalization, as well as the preparation of butter, the restoration of dry dairy products is carried out in the same way as it was shown in the technology of drinking milk.
4. normalized mixture warm up to a temperature of (43 ± 2) °С and cleaned on centrifugal milk cleaners or filters.
5. Purified milk homogenize at a pressure of (15.0 ± 2.5) MPa at a temperature of 45 to 85 °C. If necessary, it is allowed to homogenize milk at the pasteurization temperature.
Instead of complete homogenization, it is allowed to use separate homogenization of milk. When using separate homogenization, milk normalized for fat and heated in the second regeneration section of the plate pasteurizer to a temperature of 55 ... 65 ° C is separated. In this case, the mass fraction of fat in the resulting cream is from 16 to 20%. The resulting cream is homogenized in a two-stage homogenizer at a pressure: in the first stage from 8 to 10 MPa, in the second - from 2 to 2.5 MPa. The homogenized cream is mixed in-line with the skimmed milk leaving the cream separator and sent to the pasteurization section.
In order to improve the taste of fermented milk drinks, it is also recommended to homogenize the milk intended for their production with a mass fraction of fat less than 2.5%.
6. Purified and homogenized mixture pasteurized at a temperature of (92 ± 2) °C with an exposure of 2 to 8 minutes or (87 ± 2) °C with an exposure of 10 to 15 minutes. Milk can be kept at these temperatures for 30 to 40 minutes. In the production of ryazhenka, milk is pasteurized at temperatures from 95 to 99 ° C with an exposure of 3 to 4 hours until a pronounced light cream color, and Varentsa - at the same temperatures with an exposure of 60 to 80 minutes.
In the production of ryazhenka, it is necessary to take into account the degree of bacterial contamination, composition, thermal stability of raw materials, etc. It is allowed to pre-pasteurize the normalized mixture at a temperature of (76 ± 2) ° С, followed by heating to a temperature of 95 ... 99 ° С with holding from 3 to 4 hours to a pronounced light cream color. Moreover, during heating, the mixture is stirred 1-2 times per hour to prevent the formation of foam.
7. After pasteurization and aging milk chilled to fermentation temperature : (40 ± 2) °С or (30 ± 2) °С in the production of curdled milk; (42 ± 2) °С in the production of Mechnikovskaya curdled milk, yogurt, fermented baked milk, Varenets, etc.; (37 ±2) °С in the production of acidophilic fermented milk drinks; from 18 to 25 ° C in the production of kefir, etc., that is, to a temperature that is optimal for the development of microflora used in the production of a particular fermented milk drink. Storage of the unfermented mixture at the fermentation temperature is not allowed.
With the tank method of production, milk is fermented and fermented in tanks for fermented milk drinks with a cooling jacket, equipped with special agitators that ensure uniform and thorough mixing of milk with ferment and fermented milk clot. To avoid foaming, which affects the separation of whey during the storage of fermented milk drinks, milk is fed into the tank through the lower fitting.
The starter is prepared in accordance with the current technological instructions for the preparation and use of starters and bacterial concentrates for fermented milk products at dairy industry enterprises, approved in the prescribed manner.
The starter is introduced into milk in a stream using a dosing pump simultaneously with milk, or after some time from the start of filling the tank, or after filling the tank. The volume fraction of the starter in relation to the volume of the fermented mixture prepared with sterilized or pasteurized milk is 3...5%. During the introduction of the starter, the milk must be stirred to evenly distribute the starter in the volume of the product and prevent the formation of protein flakes. Milk with added starter is stirred for 10 ... 15 minutes.
With the tank method of production, after mixing, the fermented milk is left alone for fermentation. It is allowed to re-mix in 1...1.5 hours after fermentation.
With the thermostatic method of production, milk is fermented in tanks for fermented milk drinks with a cooling jacket, equipped with special agitators that ensure uniform and thorough mixing of milk with ferment. Fermented milk is immediately poured into consumer containers with continuous stirring. Filling from each tank must be completed within 45-60 minutes to avoid the formation of coagulated protein flakes. The mixture is fermented in a thermostatic chamber at the temperature indicated below.
The temperature and duration of fermentation in the production of fermented milk drinks is different depending on the microflora of the used starter. The modes are the same in the production of the same type of fermented milk drink by tank or thermostatic production methods. The end of fermentation is determined by the nature of the clot and its acidity. The clot should be smooth, sufficiently dense and not secrete serum. Temperature and duration of fermentation:
In the production of curdled milk - for 5 to 7 hours at a temperature of (30 ± 2) °С and from 3 to 4 hours at a temperature of (40 ± 2) °С
when using dry bacterial concentrate of lactococci, milk is fermented at a temperature of (30 ± 2) °С from 8 to 10 hours, when using dry bacterial concentrate of thermophilic lactococcus - at a temperature of (40 ± 2) °С from 6 to 8 hours; I in the production of ryazhenka, yogurt, Mechnikov yogurt, varenets, etc. - for 4 to 6 hours at a temperature of (40 ± 2) ° C or when using dry bacterial concentrate - for 8 ... 10 hours at a temperature ( 40 ± 2) °С;
in the production of acidophilic fermented milk drinks - for 7...9 hours at a temperature of (37 ± 2) °C;
in the production of kefir - for 8 to 12 hours at a temperature of 18 to 25 °C. In addition, in the production of kefir, the fermented mixture is matured for 9 to 13 hours at a temperature of (14 ± 2) °C.
Fermented mixtures are fermented until a milk-protein clot and acidity are formed: from 75 to 80 °T in the production of curdled milk; from 65 to 70 °T - in the production of fermented baked milk; from 85 to 100 tons - in the production of kefir, etc.
8. At the end of fermentation in the tank method of production, the supply of ice water with a temperature of (2 ± 2) ° C is included in the interwall space of the tank for partial cooling of the clot to a temperature: in the production of sour milk - 25 ... 35 ° C, in the production of fermented baked milk - (22 ± 5 ) °С; in the production of kefir - (14 ± 2) ° С
In the tank method of production, after a period of 60 to 90 minutes after water supply, the mixer is turned on and the curd is stirred for 10 to 30 minutes, depending on the design of the mixer and the viscosity of the curd, to obtain a uniform consistency of the curd. When storing fermented milk drinks with a heterogeneous, lumpy consistency, whey may be released. Further mixing, if necessary, is carried out periodically, including the stirrer for 5 ... 15 minutes.
In the production of kefir, the milk clot mixed and cooled to a temperature of (14 ± 2) ° C is left alone for maturation for a period of 9 to 13 hours. It is allowed to send a mixed and partially cooled clot for bottling, followed by maturation and cooling of the packaged kefir in a refrigerator. From the moment of fermentation to the end of ripening, at least 24 hours must pass.
2 to 5 minutes - in the production of kefir or within 5 to 15 minutes - in the production of fermented baked milk and curdled milk.
When mixing, pumping and pouring a fermented milk clot, it is recommended to avoid intense mechanical impact (long narrow pipelines, pumps, leading to significant damage to the clot, etc.), air leakage, which adversely affect the quality of the finished product. It is desirable to pour the fermented clot by gravity with a minimum level difference in height.
The mixed clot is fed with a pump designed for viscous liquids for bottling into consumer containers. In the presence of plate coolers, the clot can be cooled to a temperature of (4 ± 2) °C before bottling.
9. The packaging and labeling of fermented milk drinks is carried out in accordance with the requirements of the current standard for this product. The duration of bottling the fermented product from one container should not exceed 2 hours.
The packaged fermented milk drink, if necessary, is additionally cooled in the refrigerator to a temperature of (4 ± 2) °C, after which the technological process is considered complete and the product is ready for sale.
With the thermostatic method of production, after fermentation, the packaged product is placed in a refrigerator and cooled to a temperature of (4 ± 2) °C. In the case of the production of kefir in the refrigerator for 8 ... 13 hours, the milk-protein clot matures. After that, the technological process is considered complete and the product is ready for sale.
4. Theoretical foundations of production
The production of fermented milk products is a complex biochemical process, as a result of which the taste and smell, texture and appearance peculiar only to this fermented milk product are formed. Fermented milk products are obtained by fermenting heat-treated milk, cream, buttermilk, whey, or mixtures thereof.
According to GOST 51917, a fermented milk product is a dairy product made by fermenting milk or cream with kefir fungi and / or pure cultures of lactic acid, propionic acid, acetic acid microorganisms and / or yeast and / or their mixtures. The total content of lactic acid microorganisms in the finished product at the end of the shelf life is not less than 107 CFU per 1 g of the product. After fermentation, the use of food additives, fruits, vegetables and products of their processing is allowed. Bifidoproduct is a product containing bifidobacteria, the amount of which at the end of the expiration date is not less than 106 CFU per 1 g of the product.
The technological process for obtaining fermented milk products includes the following general operations:
- normalization of milk raw materials by fat, in the production of kefir - additionally by protein, yogurt - by mass fraction of milk solids;
- heat treatment,
- homogenization
- fermentation and fermentation,
- cooling
- packaging.
In the production of fermented milk products, both biochemical and physico-chemical processes are carried out
- milk sugar fermentation,
- casein coagulation
- gelation.
BIOCHEMICAL AND PHYSICO-CHEMICAL PROCESSES IN THE PRODUCTION OF FERROUS DAIRY PRODUCTS
Dairy products play an important role in the nutrition of people, especially children, the elderly and the sick. The dietary properties of fermented milk products are primarily that they improve metabolism, stimulate the secretion of gastric juice and stimulate appetite. The presence in their composition of microorganisms that can take root in the intestine and suppress the putrefactive microflora leads to inhibition of putrefactive processes and the cessation of the formation of toxic protein breakdown products that enter the human blood
FERMENTATION OF MILK SUGAR
The most important biochemical process that occurs during the production of fermented milk products is the fermentation of milk sugar caused by microorganisms of bacterial starter cultures. Its speed and direction determine the consistency, taste and smell of finished products according to the nature of milk sugar fermentation, fermented milk products can be divided into two groups. The first group includes products based on the preparation of which is mainly lactic fermentation (yogurt, yogurt, acidophilus, cottage cheese, sour cream), the second group - products with mixed fermentation, in the manufacture of which lactic and alcoholic fermentation occurs (kefir, koumiss, acidophilic - yeast milk).
During lactic acid fermentation, each pyruvic acid molecule formed from a glucose molecule is reduced with the participation of the redox enzyme lactate dehydrogen-1 to lactic acid:
By increasing the acidity of milk during lactic acid fermentation, you can calculate how much milk sugar was fermented. For example, the acidity of milk increased by 60T (acidity of fresh milk was 17°T, after fermentation of milk sugar - 77T). 1˚T corresponds to I cm3 0.1 n. alkali solution or 1 cm30.1 n. lactic acid solution, which is 90 / (10 1000) \u003d 0.009 g of lactic acid. Therefore, 60T will correspond to 600.009 - 0.54 g of lactic acid.
From the total reaction of lactic acid fermentation, it follows that 4 moles of lactic acid are formed from 1 mole of milk sugar, i.e., 4-90 = 360 g of lactic acid is formed from 342 g of lactic acid. Therefore, to obtain 0.54 g of lactic acid, milk sugar was required
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Many lactic acid bacteria during the fermentation of sugar, in addition to lactic acid, form a number of other chemicals that give fermented milk products a specific taste and aroma. These include volatile acids (acetic, propionic, etc.), carbonyl compounds (diacetyl, acetoin, acetaldehyde), alcohol and carbon dioxide.
Depending on the products accumulated during the fermentation process, all lactic acid bacteria are divided into homofermentative and heterofermentative. Lactic acid bacteria (lac. lactis, Lac. cremoris, Lac. diacetilactis, Str. thermophilus, L. bulgaricus, L. acidophilus), which form lactic acid as the main fermentation product, are classified as homo-enzymatic; bacteria (Leuc. cremoris, Leuc. dextranicum, etc.), which, in addition to lactic acid, form other fermentation products in significant quantities, are heterofermentative.
By certain combination of various types of lactic acid bacteria and regulation of the fermentation temperature, it is possible to obtain a product with the desired taste, aroma, texture and dietary properties.
In fermented milk products with mixed fermentation (kefir, koumiss, etc.), along with lactic acid, a large amount of ethyl alcohol and carbon dioxide is formed. The causative agent of alcoholic fermentation in these products is yeast. During alcoholic fermentation, pyruvic acid, under the action of the enzyme pyruvate decarboxylase, which catalyzes the elimination of carbon dioxide, is split into acetaldehyde and carbon dioxide:
Acetic aldehyde with the participation of the redox enzyme alcohol dehydrogenase is reduced to ethyl alcohol:
The ability of yeast to produce alcohol and carbon dioxide depends on many factors: the type of yeast used, the amount of milk sugar in the feedstock, temperature, pH, etc.
COAGULATION OF CASEIN AND GEL FORMATION
The accumulation of lactic acid during lactic acid fermentation of lactose is essential for the formation of a protein clot that determines the consistency of fermented milk products. The essence of acid coagulation is as follows. The resulting (or added) lactic acid reduces the negative charge of casein micelles, since H-ions inhibit the dissociation of casein carboxyl groups, as well as phosphoric acid hydroxyl groups. As a result, this achieves equality of positive and negative charges and the isoelectric point of casein (pH 4.6-4.7).
With acid coagulation, in addition to reducing the negative charge of casein, the structure of the caseinate-calcium phosphate complex is disturbed (calcium phosphate and structure-forming calcium are split off). Since calcium and calcium phosphate are important structural elements of the complex, their transition into solution additionally destabilizes casein micelles.
In the production of cottage cheese by the acid-rennet method, lactic acid and the introduced rennet are jointly acting on casein.
Under the action of rennet, casein is converted into paracasein, which has an isoelectric point in a less acidic environment (pH 5-5.2).
At the isoelectric point, casein or para-casein particles aggregate upon collision, forming chains or threads, and then a spatial grid, into the cells or loops of which the dispersion medium with fat globules and other components of milk is captured. gelation occurs. In the production of fermented milk products and cheese, the gelation process can be divided into four stages: the stage of latent coagulation (induction period), the stage of mass coagulation, the stage of structure formation (clot compaction) and the stage of syneresis.
In colloidal systems, gelation is affected by the concentration of the dispersed phase, size, shape of particles, temperature, etc. The resulting clot (gel) has certain mechanical properties: viscosity, plasticity, elasticity and strength. These properties are associated with the structure of the system, so they are called structural-mechanical or rheological.
Structural and mechanical properties of clots are determined by the nature of the bonds that arise between protein particles during the formation of the structure. Relationships can be reversible or irreversible. Reversible (thixotropic-reversible) bonds are restored after disruption of the clot structure. They cause the phenomenon of thixotropy (Fig. 1a) ((Greek thixis - touch + trope - change) - the ability of structures after their destruction as a result of some mechanical action to spontaneously recover in time.
Irreversible (irreversibly destroyed) bonds do not have the ability to recover after mechanical action on the clot. They are associated with the phenomenon of syneresis. Syneresis (Fig. 1b) - compaction, contraction of the clot with shortening of the casein threads and displacement of the liquid enclosed between them. Figure 2. The rate of syneresis is determined by the water-retaining capacity of casein and depends on the concentration of solids in the raw material, the composition of bacterial starter cultures, homogenization heat treatment modes, the method of milk coagulation and other factors.
For fermented milk drinks and sour cream, syneresis is an undesirable phenomenon. Therefore, in their production, bacterial starters of the desired composition are used and the technological process is carried out under conditions that prevent the occurrence of syneresis. In the production of cottage cheese, on the contrary, it is required to remove excess whey from the clot. Therefore, such milk processing modes are chosen that would contribute to obtaining a dense, but easily releasing whey clot. To enhance syneresis, grinding, heating of the clot, etc. are also used.
The nature of the bonds in the structure of the clot (product) can be determined by measuring the so-called effective viscosity - the viscosity due to the formation of internal structures in the product. At the same time, the effective viscosity of the undestroyed η n, destroyed ηr and restored ηp structures is determined and compared with each other (Table 5)
As can be seen from Table 5, during the formation of clots of curdled milk and fermented milk drinks, irreversibly collapsing (non-thixotropic bonds) are mainly formed. There are few thixotropic bonds characterized by spontaneous recovery after mechanical action. Sour cream is characterized by a lower loss of viscosity during the destruction of the structure and a large number of thixotropic bonds compared to sour-milk drinks.
Table 5
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BIOCHEMICAL BASES OF PRODUCTION CERTAIN TYPES OF FERROUS MILK PRODUCTS
The quality of fermented milk products produced depends on the nature of the formed clots, as well as the degree of accumulation of flavoring and aromatic substances. The nature of the clots is determined by the level of accumulation of lactic acid, the ability of proteins to form spatial structures, retain moisture, etc. The formation of flavoring and aromatic substances depends on the composition of bacterial starter cultures, the conditions of fermentation, maturation and cooling of products.
fermented milk drinks
The main process that determines the consistency of all fermented milk drinks is gelation. The clots of these products are different: in some cases, the clot is dense (prickly), in others it is even and tender (creamy) or flaky, etc.
When forming the structure of product clots, irreversibly breaking bonds are mainly formed, there are few thixotropic-reversible bonds in them, therefore it is so important to conduct the technological process under such modes that would ensure minimal separation from the whey clot. First of all, this applies to the modes of pasteurization, homogenization and fermentation of milk.
It is known that the syneretic properties of clots depend on the pasteurization temperature of milk. To increase the strength of clots and prevent the release of whey during storage of curdled milk and other fermented milk drinks, it is recommended to use high temperatures for pasteurization of milk (85-87°C with exposure for 5-10 minutes or 90-94°C with exposure for 2-8 minutes).
The duration of fermentation of milk during the development of products is determined by the type of bacterial starter and the fermentation temperature. The end of fermentation is usually set to obtain a sufficiently strong clot and titratable acidity of 75-85°T. In the production of fermented milk drinks by the tank method, it is necessary to obtain a clot with the maximum number of thixotropic-reversible bonds, therefore, before mixing and cooling the clot, the pH (pH) should be controlled: it should be 4.5-4.4 for kefir, 4.7-4.7 for acidophilus. 4.55, ryazhenka - 4.45-4.35. Additionally, the viscosity of the clot is checked by the duration of the flow from a pipette with a capacity of 100 cm 3 at 20 ° C or using a capillary viscometer.
Specific sour-milk taste and smell of products are formed mainly during their fermentation and maturation. Complementing the taste and smell of products are compounds formed during the heat treatment of milk (they play a major role in the production of Varenets and fermented baked milk).
The main flavoring and aromatic substances of fermented milk products are lactic and acetic acids, diacetyl, acetaldehyde (its high concentration is typical for yogurt), etc. Refreshing, slightly spicy taste of koumiss and kefir is given by ethyl alcohol and carbon dioxide. The alcohol retention in beverages is determined by the type of yeast, temperature and length of maturation. In koumiss, it is 1 - H "6, in kefir - 0.01-0.03%. They are also characterized by protein breakdown (proteolysis), so the released amino acids and peptides can take part in shaping the taste of these products.
5 . INFLUENCE OF MILK COMPOSITION, BACTERIAL STARTERS AND OTHER FACTORS ON FERTILIZATION LACTOSE AND CASEIN COAGULATION
The quality of fermented milk products, mainly their consistency, depends on the composition and properties of milk, the type and activity of bacterial starters, the modes of pasteurization, homogenization, fermentation, maturation, and other factors.
- Composition and properties of feedstock
determine the rate of coagulation of milk proteins and the strength of the resulting clots. The development of microorganisms of bacterial starter cultures that ferment milk sugar also depends on them.
The composition and properties of milk change during the year, the stage of lactation, in case of animal diseases, etc. It is known from the practice of dairy plants that in autumn and especially in spring, milk is slowly fermented. This may be due to a decrease in its biological value. For example, in spring the content of vitamins (biotin, niacin, B6, etc.), free amino acids (valine, leucine, phenylalanine, etc.) and microelements (Mn, Co, Fe, etc.), which are necessary for the reproduction of lactic acid bacteria, decrease in milk. bacteria. In addition, the reason for non-fermentation of milk at this time of the year may be the presence of antibiotics and other substances in it that inhibit the development of lactic acid bacteria. Lactic acid bacteria develop poorly in old milk and in milk obtained from cows with mastitis.
In the spring, the technological properties of milk also deteriorate - the rate of formation and density of the acid clot decrease. This is due to a decrease in the content of dry substances in milk, casein, the size of casein micelles, and an increase in the acidity of milk.
· Individual characteristics and breeds of animals
The ability of milk to rennet coagulation is determined by the concentration of proteins, calcium salts and depends on the individual characteristics and breed of animals, feed, stage of lactation and other factors. Milk coagulates poorly at the beginning and end of lactation, as well as when animals are sick.
· Storage time
The properties of milk (and the properties of the clot obtained from it) change during storage. So, after long-term storage of milk (raw and pasteurized) at low temperatures, the viscosity and strength of the acid clot increase, syneresis slows down. Therefore, milk stored at low temperatures should be sent to the production of fermented milk drinks and should not be used. for making curd
· Starter composition.
Not only the taste of fermented milk products, but also their consistency depends on the composition of the starter cultures. The main component of the microflora of starter cultures of all fermented milk products, which ensures the formation of a clot, is lactococcus (Lac. lactis). The inclusion of energetic acid-forming agents in the composition of the starter cultures leads to the production of a dense prickly clot with an intensive separation of whey, and low-energy acid-forming agents - a more delicate clot. Introduction of sourdough Str. thermophilus, Lac. cremoris and thermophilic sticks increases the viscosity of the product, gives the clot elastic properties, prevents the release of whey.
Therefore, by selecting the composition of starter cultures, it is possible to regulate the properties of the clot and ensure the optimal consistency and taste of fermented milk products.
· Heat treatment
Heat treatment of milk affects the rate of clot formation, structural and mechanical properties and syneresis.
According to VNIMI and VNIIMS, with an increase in pasteurization temperature, the strength of acid and acid-rennet clots increases (Table 6).
Table 6
With an increase in the pasteurization temperature of milk (from 63 to 90" C ) the intensity of separation of whey from the clot decreases. The increase in the strength of clots and the deterioration in the release of whey from them after high temperatures of heat treatment can be explained by an increase in the content of denatured whey proteins in the clot, which increase the rigidity of the spatial structure and the water-holding capacity of casein.
Thus, by adjusting the modes of heat treatment of milk, it is possible to obtain a clot with the desired rheological properties, i.e., improve the consistency of the fermented milk product
· Milk homogenization
When producing fermented milk drinks, it is recommended to homogenize the milk before fermentation (for kefir and yogurt obtained by the tank method, it is mandatory). As a result of homogenization, the dispersion of fat increases, the crushed fat in clots is distributed more evenly, the strength of the clot increases, while the viscosity of the products slightly increases and whey release decreases.
At the same time, homogenization of milk with a high (above 10%) fat content and cream contributes to a significant increase in the viscosity of clots and a decrease in their ability to separate whey. In this case, the increase in the viscosity of the formed clots depends on the pressure and the method of homogenization of the raw material.
Structural-mechanical and syneretic properties of clots significantly depend on the method of protein coagulation
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· Type of coagulation
Clots formed during acid coagulation of proteins are less strong than acid-rennet ones (the spatial structure of acid clots is supported by weak bonds, the structure of acid-rennet ones is additionally stabilized and strengthened by calcium bridges formed between the parts of paracasein); they consist of smaller protein particles and secrete serum worse. However, along with an increase in the strength of acid-rennet clots, their fragility, the degree of dispersion and the ability to separate whey during processing increase.
· Clotting time and temperature
The duration and temperature of curdling (fermentation) of milk are important factors affecting the consistency of fermented milk products. The duration of milk fermentation is usually determined by the increase in acidity, viscosity or strength of the resulting clot. It is especially important to determine the moment of clot readiness in the production of beverages by the tank method. Sometimes there is a liquid consistency of products and whey sludge. This is caused by the wrong choice of the moment of clot mixing. Whey is released when the clot is stirred when it has a minimum viscosity and exhibits slight thixotropic properties.
In addition, the accumulation in the products of substances that give them a certain taste and aroma (volatile acids, diacetyl, acetaldehyde, etc.) depends on the temperature and duration of milk fermentation.
To stop lactic acid fermentation and strengthen the structure of the formed clot, fermented milk products are cooled to 8°C and stored at this temperature. Products of mixed fermentation before cooling are subjected to maturation, for the development of yeast and aroma-forming bacteria. In the process of ripening and keeping in the refrigerator, aromatic substances, alcohol and carbon dioxide accumulate in the products, and partial decomposition of proteins occurs under the influence of proteolytic enzymes of lactic acid bacteria and yeast. At the same time, various soluble polypeptides and free amino acids are formed, which affect the texture, taste and smell of products.
In the production of sour cream, an additional purpose of cooling and ripening is the solidification of fat, which improves the structure and consistency of the product.
5. FAULTS OF FERROUS MILK PRODUCTS .
Bibliography
1 TO. K. Gorbatova "BIOCHEMISTRY OF MILK AND DAIRY PRODUCTS" St. Petersburg GIORD 2004
2.N. A. Tikhomirova "Technology and organization of production of milk and dairy products" 2007 Moscow DeLi print
All types of fermented milk drinks are produced by fermenting prepared raw materials with starters of certain pure cultures. The resulting clot is cooled, and for some products it matures.
To obtain fermented milk drinks, whole and skimmed milk, cream, condensed and powdered milk, sodium caseinate, buttermilk and other dairy raw materials, as well as malt extract, sugar, fruit and berry syrups, jams, cinnamon, etc. are used.
There are two methods for the production of fermented milk drinks - reservoir and thermostatic.
tank method
tank method. The technological process for the production of fermented milk drinks by the reservoir method consists of the following technological operations: preparation of raw materials, normalization, pasteurization, homogenization, cooling, fermentation, fermentation in special containers, curd cooling, curd maturation (kefir, koumiss), packaging.
For the production of fermented milk drinks, milk of at least the second grade with an acidity of not more than 19 ° T is used, which is pre-cleaned. Skimmed milk, buttermilk, cream, condensed and powdered milk, sodium caseinate and fruit and berry fillers must be of good quality without foreign tastes and odors and defects in texture.
Sour-milk drinks are produced with different mass fractions of fat: 6; 4; 3.2; 2.5 1.5; 1 %. Therefore, the original milk is accordingly normalized to the required mass fraction of fat. Normalization of milk is carried out in a stream on separators-normalizers or by mixing. Low-fat foods are made from skimmed milk.
When normalizing raw materials by mixing, the mass of products for mixing is determined by the formulas of the material balance or by the recipe.
Normalized raw materials are subjected to heat treatment. As a result of pasteurization, microorganisms in milk are destroyed and conditions favorable for the development of the starter microflora are created. The best conditions for the development of microorganisms are created if milk is pasteurized at temperatures close to 100 °C. Under these conditions, whey proteins are denatured, which are involved in the construction of the structural network of the clot, the hydration properties of casein and its ability to form a denser clot that retains whey well increase. Therefore, in the production of all fermented milk drinks, except for ryazhenka and Varents, the raw materials are pasteurized at a temperature of 85--87 ° C with an exposure of 5--10 minutes or at 90--92 ° C with an exposure of 2--3 minutes, ryazhenka and Varents - - 95--98 ° C with an exposure of 2-3 hours. In addition, milk sterilization is also used in the production of Varents.
Heat treatment of milk is usually combined with homogenization. As a result of homogenization at a temperature of 55--60 ° C and a pressure of 17.5 MPa, the consistency of fermented milk products improves and whey separation is prevented.
After pasteurization and homogenization, the milk is cooled to the fermentation temperature. When using a starter prepared on thermophilic bacteria, the milk is cooled to 50 - 55 ° C, mesophilic - 30 - 35 ° C and kefir starter - 18 -25 ° C.
In the milk cooled to the fermentation temperature, a starter corresponding to the type of product must be immediately added. It is most rational to introduce the starter into milk in a stream. To do this, the starter is fed continuously through the dispenser into the milk pipeline and mixed with milk in the mixer.
Fermentation of milk is carried out at the fermentation temperature. In the process of fermentation, the sourdough microflora multiplies, acidity increases, casein coagulates and a clot is formed. The end of fermentation is determined by the formation of a sufficiently dense clot and the achievement of a certain acidity.
After fermentation, the product is immediately cooled. Dairy products produced without maturation are immediately sent for cooling.
Kefir, produced with maturation, after fermentation is cooled to 14--16 ° C and ripens at this temperature. The duration of maturation of kefir is at least 10-12 hours. During maturation, yeast is activated, the process of alcoholic fermentation occurs, as a result of which alcohol, carbon dioxide and other substances accumulate in the product, giving this product specific properties.
The technological line for the production of fermented milk drinks by the tank method is shown in fig. 45. Milk from the raw milk tank is fed into the balancing tank, from where it is sent to the recuperative section of the pasteurization-cooling plant, where it is heated to 55--57 °C.
For pasteurization of milk, pasteurization and cooling units for fermented milk products are used, in which pasteurization can be carried out with the necessary exposure and subsequent cooling to the fermentation temperature. Heated milk is sent first to the separator-normalizer, and then to the homogenizer.
Valve-type homogenizers are designed for homogenization. From the homogenizer, milk first enters the pasteurization section, then through the control panel - into the holding tank and returns to the recuperative section and. to the cooling section of the pasteurization-cooling plant, where it is cooled to the fermentation temperature. If, upon exiting the pasteurization section, the milk has not reached the set temperature, then it is sent to the balancing tank for re-pasteurization with the help of a return valve. The cooled milk enters the container for the production of fermented milk drinks, mixing with the starter in the mixer.
Fermentation of milk is carried out in special double-walled vertical containers equipped with automatic mixers.
The mixer is designed in such a way that it does not stir up kefir and cut it into layers and cubes, but evenly and simultaneously mixes the entire mass of kefir. Partial mixing or cutting of the coagulum leads to the separation of the whey, and agitation with a stirrer causes foaming, which in turn causes the separation of the whey.
The automatic device ensures the course of ripening according to a certain cycle: mixing - rest - mixing, and also serves to turn on the cooling system. Cooling is carried out with cold water or brine circulating through the annular gap between the inner and middle tanks. The middle container is provided with thermal insulation lined with a protective casing.
For the production of fermented milk products, containers with a capacity of 2000, 4000, 6000 and 10000 liters are used.
Fermented milk is fermented in a container to the required acidity. The resulting clot is cooled in the same container, and every 30--40 minutes a stirrer is turned on to stir the clot and cool it more quickly. If maturation is required, then the clot is cooled to the maturation temperature and left in a container for maturation.
Product cooling can be done in-line. To do this, the milk is fermented in a container, and when the desired acidity is reached, the product is fed to a plate cooler, where it is cooled in a stream to the required temperature and enters an intermediate container, from where it is sent for packaging.
Sour-milk drinks are packaged in heat-sealed bags or in glass containers on automatic filling machines for liquid dairy products.
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