Generally known method of production of cheese consists in making of coagulum in processed milk by addition of rennet, and cutting the coagulum to a grain of size depended on the planned degree of separation of whey during a period of time specific for particular type of cheese. Cut to the grain coagulum is maintained as a suspension in whey formed in result of synereza, by continuous stirring with mechanical stirrers of different shapes, adjusted to the changing properties of the drained grain. To prevent from agglomeration and deposition at the bottom of cheese-making boiler, stirring has to be intensified as the draining progresses. Usually, the temperature of curd slurry is gradually increased during draining of the grain, to intensif the process.

This stage of cheese production is associated with significant expenditure of both mechanical and thermal energy. Beside, part of the grain is often disintegrated, and in subsequent stages of production it passes to the whey.

The necessity of keeping grain as a suspension in large amount of curd slurry, while maintaining losses low, results in constructing of boilers with complicated constructions of stirrers. The drained in the sltury grain is separated from whey by sedimentation at the bottom of the partitioned part of cheese-making boiler, and removing of whey from the upper part; pumping over to a press with perforated bottom; pumping over to a pre- pressing column in which the grain settles down, and the whey continuously flows out by an overfall. Pre-pressed texture curd, after cutting, is often transferred to individual cheese forms, in which it is pressed imder gradually increased pressure for several hours. Next, cheese is removed from forms, manually or mechanically using compressed air. The pressed cheese is usually salted by immersing in brine for several days.

From the Polish patent P. 286569 there is known constructional solution of a unit for production of cheese according to which the entire teclmological process of production of pressed cheese is performed in one hermetic tank.

The system is composed of stationary heat boiler in a form of a drum motmted on colins. The boiler has a conical head equipped with flushing valve, and is closed by a cover, which can be lifted and moved rotationally on an outrigger. On the cover, there is positioned rotary stirrer introduced into the working space of the boiler through an opening. The stirrer has a moving blade with sliding cutters of the coagulum. The upper part of cheese- making form is attached to the cover. The bottom of the form is a mobile one, and is moved inside the boiler by hydraulic servos. The mobile bottom of the cheese-making form is covered by a cloth dripped with colloid solution. The heating elements are placed under mobile bottom of cheese- making form, in a space filled by technological water. Agitation inside the apparatus is achieved by moving the curd slurry up inside working space of rotating and simultaneously oscillating blade. Cutting of coagulum is carried out by spirally moving, horizontally positioned blade with cutters sticking out. Pressing of cheese is done by moving up the grain deposited at the bottom of the form, and introducing it to the form positioned under the cover. The stirrer must be first removed from the boiler.

Production line for continuous production of cheese consists of horizontal, tubular coagulator, in which rennet treated processed milk is warmed up and solidify, while moving towards stationary cutters, where it is cut to the form of bands. Next, grain is transferred to a grain draining tank equipped with horizontal helical agitator, and continuously agitated moves towards curd slurry outlet. From this place, the slurry is pumped to whey separation and pre-pressing column. In the lower part of the column there is a damper and texture curd cutter. Portions of the mass are put into forms, which are next transported by drawing conveyor to pneumatic presses, and next to a pressure device, where the cheese is blew out of the fonns.

The method according to the present invention comprises in dissolution of carbon dioxide, in amount from 0.08 to 0.9 percentage by weight, in cheese milk inoculated by suitable bacterial cultures. Then, coagulum is formed in the milk, using a known and specific for particular type of cheese method. Alternatively, milk with already formed, and disintegrated only in result of pumping coagulum, is saturated with carbon dioxide by applying high pressure until its given above concentration is attained. Next, the pressure is lowered, that results in isolation of carbon dioxide in form of gas bubbles, in the entire mass of the coagulum. The bubbles disrupt coagulum, and remain in the formed in this manner curd slurry.

Frothed curd slurry has, in the initial phase of the process, much bigger volume than coagulum before frothing. Double increase in volume is advantageous.

The formed very fine grains give a very fast syneresis, and the bubbles of carbon dioxide prevent the grains from sedimentation and agglomeration.

Moreover, the bubbles preserve penneability of microgaps for whey, which, as the draining process proceeds, flow down under the froth. The smallest particles of cheese are filtered through microgaps, and stopped on bigger particles, in result the separated whey is clear.

Curd grains constantly move a little towards each other, due to their constantly diminishing volume, and existence of changing structure of bubbles among them. If the process is conducted under steadily diminishing pressure, constant separation of carbon dioxide occurs in the curd slurry, and the gas additionally obstructs aggregations of grain, open microgapes, and combine into bigger bubbles, which flow out to the surface of the froth.

Curd grains in froth are submitted also to a gentle self-pressing, what results in acceleration of separation of whey, especially in the final phase of draining, when the degree of degassing is significant.

Decrease in pressure is stopped when the pressure reaches a value close or equal to saturated vapor pressure of water at the temperature of the process.

At that time, the pressure of gas inside bubbles comes mainly from vapors of water. This guarantee a removal of carbon dioxide to such extend that its residue will dissolve in texture curd after pressing. The froth separated from the top of whey and containing"drained"grain of cheese is submitted to fast pressing under a pressure sufficient to combine grain into miform texture curd.

Due to the high effectiveness of draining, the process can be conducted isothermally, at temperature typical for coagulation of milk or higher, what results in even faster draining of the grain.

Additional acceleration of the process can be achieved by additional wanning of the frothed curd slurry during the final phase of draining. The additional warming can be accomplished by indirect heating or by injection of preheated whey.

Assuming that the degree of saturation with carbon dioxide is determined, for coagulum characterized by given parameters and comprising bacterial culture of standardized dynamics of souring, and with established procedure of reduction of pressure, the correctness of final parameters of texture curd is determined by selection of appropriate temperature of the process.

Namely, for texture curd of a given contents of water, it is necessary to keep contents of calcium bonded to casein at a level suitable for the given class of cheese. If the dynamics of souring of whey inside grain is bigger than the dynamics of draining, then the calcium in the form of lactate, is transferred to whey to fast. Pressing of grain is done by immediate application of pressure, while according to the traditional technology pressure is used only in the last stage, to achieve blending of grain. Minimal level of pressure depends on its operation period, and degree of dehydration as well as of the temperature of the texture curd.

Bubbles of rarefied gas in curd grain disappear instantly under influence of increased pressure. Steam is liquefied, and like residual amonts of carbon dioxide, the water is absorbed by texture curd. The whey is not drained off during pressing.

In a continuous process, the pressed texture curd can be processed further while moving in tubular form. Texture curd can be melted and stretched to get unification of structure. Next, the texture curd is cooled down, and cut as leaving the molding tube. The end of the molding tube is immersed in brine of a density higher than the density of the texture curd.

Cutt ng of horizontal or slanting band of cheese under the surface of brine results in self-floating of cheese towards the surface.

Apparatus according to the present invention, in its version for a periodic process, essentially consist of hermetic, conical in its bottom part tank equipped with slanting propeller mixer, with an elastic partition separating the bottom, and forming inside an air chamber of variable volume. A float having its upper surface flat is fixed to the elastic partition. The float when released from catches is moved by hydrostatic lift and enters cylindrical, upper part of the tank. At the bottom of the conical part, the tank has milk inlet connection and whey outlet connection, and near the cover there is located deaeration and degasification connector. Air chamber connector is placed at the bottom.

It is necessary that the float has an easy fit in relation to walls of the upper part of the tank, and that its hydrostatic lift is sufficient to raise all of grain above the surface of the whey, in the final phase of draining.

An apparatus according to the present invention, in its version for a continuous process, essentially consists of a~ vertical flow tank which is tapered both in its upper and lower part. In the lower part of the tank there is an expansion valve coming-out by the bottom outlet, and protruding above the level of the bottom. In the upper part of the tank there is an outlet opening with a valve, connected with a vacuum chamber, equipped with a drawing conveyor.

In its upper part the tank is equipped with transverse heating elements, and in its bottom in a whey outlet connector.

The vacuum chamber in its bottom part has a carbon dioxide outlet connector. Besides, in its upper part the chamber has a salt feeder. The vacuum chamber is integrally connected with an expeller in such a way that the drawing conveyor feeds curd grain directly on the expeller working elements. The expeller outlet is connected to the texture curd molding tube, which is equipped with a heating jacket with mixer, and with a cooling jacket.

The tube enters horizontally or aslant into a brine tank, and on its end has a crosswise cutting double cutter, drawn by a servo.

The example of application which follows, shows the method and apparatus according to the present invention, in their version for a periodic process, Fig. 1 presents the top view of the apparatus, and Fig. 2 presents the cross-section of the apparatus.

The apparatus consists of a tank 1, conical in its lower part and cylindrical in the upper part. The tank is closed by a hermetic cover profiled in such a way that the flat bottom of the cover enters horizontally into the cylindrical space of the tank 1 leaving only a small slot between the cover and the cylindrical wall of the tank. Between this slot and the upper edge of the tank 1, the wall of the cover is moved towards the axis of the tank 1 forming an annular space. At the level of the annular space there is on the tank wall a connector <BR> <BR> <BR> <BR> <BR> 11. The tank 1 has an air chamber formed by a movable partition made of flexible foil, ended with plate 5 and connected by a flange with a flat bottom. The air chamber has a shape of frustum of cone, with the angle of inclination identical with that of conical-part of the tank 1. Diameter of the basis of the air chamber is slightly smaller than that of the tank, so that between the two walls there is a conical space. The horizontal plate 5 of the partition is connected using a spigot with the bottom of the tank 1, in such a manner that it can move towards the bottom, without changing of its horizontal position. The movement of the plate 5 towards the bottom of the tank 1 is caused by a spring 7. A connector 13 is used to introduce or remove air used to move the plate 5 up or down. The spring 7 causes a positive gauge pressure inside the chamber, which keeps the partition 3 <BR> <BR> <BR> <BR> <BR> tensed, and gives to it a conical shape. The conical wall of the tank 1 has a protruding outside, vertical flow-through chamber with a stirrer 8 and connector 12 to supply rennet. The upper, cylindrical part of the tank 1 has a heating jacket. <BR> <BR> <BR> <BR> <BR> <P> An out-put and in-put connector 13 is located in the lower part of the wall of the tank 1. The plate 5 of the partition is equipped with electromagnetic catches, which hold a float 4 and a guiding rot, directing the float 4 into the cylindrical space of the tank 1, after release of the catches 9. The axis of propeller agitator 8 crosses the opposite edge of connection of the conical and cylindrical parts of the tank. The float 4 has a shape of inverted frustum of cone. The float has a small angle of inclination of side wall, and its lower edge is coming out axially. The wall is overlapped by the catches 9. Along its axis, the float has an opening for the guiding rot.

The method according to the present invention can be presented as follows.

The air is introduced by connector 14, to form a positive gauge pressure and a tension of the partition 3.100 liters of warm, partly centrifuged rain milk is <BR> <BR> <BR> <BR> <BR> introduced through the connector 13, while keeping the connector 11 open.

Next, the connector 13 is closed, and the air is blowed under the partition 3 through the connector 14, until the surface of the milk touches the cover 2.

The volume of processed milk can be additionally determined by measurements of the distance between the plate 5 and the bottom of the tank l.

Next, the propeller 8 is switched on, and two liters of cheese leaven is added through the connector 12. The stream of milk from the propeller 8 divides itself into two parts on the edge between the cylindrical and conical parts, what results in a movement of the whole volume of milk and its good mixing.

Heating elements of the jacket 6 are switched on to maintain the temperature of the process at 34 °C. Simultaneously, carbon dioxide is introduced through connector 12 to the tank 1, and dissolves in the milk while the internal pressure is kept at 400 kPa.

After 1 hour the inflow of carbon dioxide is closed, during this time its contents in milk reaches the level of 0.4 %. The pressure inside of the tank 1 is determined by measurement through the connector 14.

After 1.5 hour from the addition of cheese leaven, 20 ml of solution of rennet of normal potency is added through the connector 12, and after 7 minutes the propeller 8 is switched off. After next 18 minutes coagulum is matured enough to be cut. At that moment froth formation and draining of curd grain starts. The process needs 80 minutes, and includes four phases, 20 minutes each.

Phase 1. The air is released from the air chamber of the tank 1 through the connector 14, using a nozzle of a suitable size. Volume of the coagulum rises fast, and the formed inside bubbles of carbon dioxide disrupt the coagulum to small grain. Intensity of the outflow gradually slows down. The <BR> <BR> <BR> plate 5 of partition is falling down to an equilibrium position of the spring 7, next the flexible partition 3 is falling also and tucks under the plate 5. The working capacity of the tank 1 doubles. <BR> <BR> <BR> <BR> <BR> <P>Phase 2. The connector 14 is closed, and the connector 11 is opened to allow release of carbon dioxide, through a nozzle of such a size that the flow of gas ceases in 20 minutes. <BR> <BR> <BR> <BR> <P>Phase 3. The connector 14 is opened through a small diameter nozzle, and carbon dioxide is gradually sucked out through the connector 11. The air enters under the partition 3, until it moves up and becomes conically shaped.

Working capacity of the tank 1 is diminished to 150 liters, under the pressure of 80 kPa. At that moment, the whole frothed, well drained curd slurry is introduced into the cylindrical part of the tank 1.

The float 4 is released from catches 9, and enters the cylindrical part of the tank 1, lifting the whole grain above the whey level. <BR> <BR> <BR> <BR> <BR> <P> Phase 4. Connectors 14 and 11 are connected, and while maintaining the working capacity of the tank constant, the internal pressure is gradually lowered to 25 KPa.

Next, the texture curd is pressed. This is done by closing the connector 11, rising the pressure in the air chamber to 200 kPa, and maintaining it for 2 hours. The plate 5 moves up, reducing the working capacity of the tank 1 until the gas phase fades completely. This must, however, happen before the plate 5 reaches the extreme upper position. The entire working pressure is than directed to walls of the tank 1.

Heating elements of the jacket 6 are switched off. The pressed cheese is cooled slowly. When the pressing of cheese is finished, the pressure is adjusted to the level of atmospheric pressure, the cover 2 is opened, and cheese is pushed above the edge of the tank 1, by blowing the air into the air chamber.

In the example of method and apparatus according to the present invention, in their version for a continuous process, Fig. 3 presents the cross-section of the installation.

The installation consist of a vertical, tubular coagulator 1, with a heating jacket, which is U bent in its lower part, so it can enter vertically through a bottom to a vertical dryer 2. Inside the dryer, the coagulator is closed by an expansion valve 7. The overfall edge of the valve 7 is significantly above the bottom of the dryer, to assure sufficient volume for continuous collecting and removing of whey through a connector in the bottom. The foam dryer 2, firmly connected with the coagulator 1 has a form of a vertical flow tank with the central part having a cuboid form, with transverse heating tubes 8, and is tapered in its lover part. In its bottom there is a valve 7. The upper part of the dryer 2 tapers gradually, and in the end has a rectangular outlet opening with a valve having a cylindrical working element 15. The side wall of this part of the tank is equipped with air nozzle, which is used in production of"poured"cheese.

The dryer 2 is connected by the outlet opening with a vacuum chamber.

The opposite end of the vacuum chamber is connected through an opening with a vertical screw extruder 4 which tapers in its lower part. The chamber 3 has in its bottom a pit with a connector serving to drain out the whey, and in its upper wall a connector used as carbon dioxide outlet, and a salt feeder 9. Under the grain outlet opening there is an incline drawing bar conveyor, completely obstructing the chamber 3, and guiding the grain through the connection opening to the screw of the extruder 4. The outlet of the extruder 4 is connected with texture curd molding tube. The upper, vertical part of the <BR> <BR> <BR> <BR> tube constitutes a built in mixer comprised of a conical cylinder 11 with a heating jacket, and a conical head 12 inside. The head is positioned towards the wall of the cylinder by a screw gear. Lower part of the molding tube is bonded slantwise, and has a cooling jacket 13, and on its end has a double cutter, moved by a hydraulic servo. The end part of the molding tube 5 is immersed in a brine tank.

The processed milk is cooled to 1 °C, inoculated with a leaven of thermophilous cultures to 8 °SH, andtreatedin a standard way with rennet.

Carbon dioxide is dissolved in the milk under the pressure of 140 kPa, until its contents reaches 0.4 %. Next, keeping the flow constant, the milk is filled into coagulator 1, where it is warmed up and coagulates while moving down, towards the expansion valve 7.

The valve 7 is set to maintain an internal pressure in the coagulator at 320 kPa. Inside the valve 7, coagulum has temperature of 32 °C and is of medium compact. After being forced to the dryer 2, the coagulum froths violently, and disrupts to very fine grain, which moves up under the pressure of 110 kPa. The whey collects near the bottom of the drier, and is removed continuously through a connector. Grain, carried up with the sluury is draine, and when approaching the upper zone is warmed by the moving down whey, which is preheated by tubes 8 to 40 °C. After 40 minutes from the frothing, curd grain pours into the vacuum chamber 3 of internal pressure 20 kPa. Curd grain falls down on lying close bars of drawing conveyor 10, and moves as self-pressing layer to the screw extruder 4.

Salt is spread on the moving texture cur-d from the feeder 9. The salt dissolves in, and enters into the self-pressing, and still undergoing syneresis texture curd. The formed whey flows between bars of the conveyor to the pit of the chamber 3. Texture curd is pressed in the press 4 to 400 kPa, pushed <BR> <BR> <BR> <BR> into the molding tube 5, and next to the mixer, where it is heated up to 70 °C, and spread in the slit between the head 12 and the wall of the cylinder 11. Next, the melted texture curd is pressed into the slant part of the tube 5 and cooled by water in the jacket 13 to 20 °C. Band of texture curd leaves the tube 5 with a constant rate, and is cut under the surface of brine by quick movements of the cutter 14. The pieces of cheese float up to the surface, forced by the uplift force. The formed cheese has a uniform structure, without bubbles, and consistence close to Mozzarella cheese, contents of water is on the level of 50 %.