WO1999053749A1

WO1999053749A1 - Apparatus and method for producing mozzarella cheese

Info

Publication number: WO1999053749A1
Application number: PCT/EP1999/002507
Authority: WO
Inventors: Giovbattista Inversini
Original assignee: Giovbattista Inversini
Priority date: 1998-04-22
Filing date: 1999-04-14
Publication date: 1999-10-28
Also published as: ITTO980340A1; AU3816299A

Abstract

An apparatus for producing mozzarella cheese, comprising a citric or lactic curd introduction station (2) provided with curd chopping means (7), hot stretching means (9) and kneading/plasticising means (14) to transform the curd into a flow of pasta filata, forming means (23) providing mozzarella cheese portions from the pasta filata, primary packaging means (44), cooling means (45) and a mozzarella cheese outlet station. The apparatus consists of a single compact workstation (1) having a reduced horizontal size, provided with a computerised control system enabling the plasticising stage to be performed under a predetermined humidity and the forming stage to be carried out in a controlled fashion, so as to warrant only small deviations with respect to the chemical-physical characteristics of the desired final product, through a closed-circuit plant, with a pasteurization effect and a quick temperature lowering, thus providing mozzarella cheese having a high micro-biological standard.

Description

1

"Apparatus and method for producing mozzarella cheese"

***

Background of the invention The present invention is related to production of mozzarella cheese, i.e. pasta filata cheese, starting from a citric or lactic curd mass.

Traditionally the production of mozzarella cheese includes the steps of curd chopping, hot stretching and kneading/plasticising to transform the chopped curd into a ribbon of pasta filata, forming mozzarella cheese portions from the ribbon of pasta filata, and then cooling and packaging the portioned mozzarella cheese.

Conventional apparatuses performing the above production cycle comprise, as a rule as far as the hot stretching stage is concerned, one or more screws immerged within a heating water solution bath, and as far as the kneading or plasticising stage is concerned, a mechanism consisting also of a screw or of paddles sometimes provided with plunging arm finishing elements by means of which the stretched curd, still maintained immerged within a liquid phase, is plasticised. An example of conventional apparatus of the above-referenced type is disclosed and illustrated in European Patent Application EP-A-0186795.

Downstream of the kneading and forming stages, the mozzarella cheese is then as a rule cooled following immersion into a tank of cold water, such as disclosed for instance in US-A-4,848.219.

These conventional apparatuses are generally designed to provide a minimum production of 500-600 Kg. of mozzarella cheese per hour, and are thus suitable to be employed on an industrial scale within the frame of dairy plants. On the other hand, the massive use of liquid employed in the stretching and kneading stages, along with the necessary heating, purifying and discharging plants and related control units, involve installation of these apparatuses at a properly equipped industrial environment.

Moreover the remarkable horizontal encumbrance of these known apparatuses and the need of installation thereof in as far as possible sterile environments, owing to the fact that over the major part of the production stages the product is exposed to the surrounding environment, do not allow contemplating applications of these known apparatuses other than the industrial ones.

Summary of the invention

The primary object of the present invention is to provide an apparatus for producing mozzarella cheese designed so as to afford managing thereof in an handicraft scale, namely by a single operator-transformer artisan, without however excluding an industrial use and also provided with a functionally autonomous arrangement requiring no specific equipment or auxiliary plants.

A further object of the invention is to provide a controlled-process apparatus so as to carry out certified transformation of the curd into packaged mozzarella cheese having a predetermined chemical analysis and a high micro-biological standard.

Still another object of the invention is to provide an apparatus for producing mozzarella cheese wherein the hot stretching and plasticising stages are performed under predetermined humidity. A further object of the invention is to provide an apparatus for producing mozzarella cheese which is adapted for installation within restricted environments and without any particular expedients to ensure sterility while preventing any risks of contamination of the final product.

A further object of the invention is to provide an apparatus for producing mozzarella cheese designed to perform a the pasta filata pasteurization stage.

Another object of the invention to provide an apparatus for producing mozzarella cheese which can warrant automatic and continuous conformity certification of the final product at the apparatus outlet.

These and further objects are achieved, according to the invention, by means of an apparatus of producing mozzarella cheese such as defined in its essential terms in claim 1 and which may be additionally provided with the secondary features defined in sub-claims 2-27.

The invention is also directed to a method for producing mozzarella cheese whose novel and unique features are defined in claims 28 through 39. Some of the fundamental concepts of the invention can be briefly summarised as follows: -the processing steps of stretching-plasticising-forming and primary packaging are carried out within a closed circuit, along subsequent sections mutually connected so as to prevent any contact between the product and the surrounding environment, and thus any contamination risks; -provision of vacuum in the plasticising stage so as to enable transportation, filtration and/or extraction of volatile substances by means of low-temperature boiling;

-employ in the plasticising stage of a flexible tube system which is cyclically deformed by outer mechanical stresses so as to provide both transportation and kneading of the product, even with the aid of a downstream vacuum source and/or an upstream overpressure source;

-suppression of heating by hot-water immersion and provision, as a heating source in the stretching plasticising stages, of heating systems of generally electrical type.

By virtue of provision of these concepts, as well as of additional features which will become apparent in the following, the invention provides an apparatus for transforming curd into mozzarella cheese which is capable to satisfy the needs of the target client, i.e. the artisan/transformer of the product, with relatively limited investments and a drastic simplification in terms of logistics.

A typical example of an apparatus for producing mozzarella cheese according to the invention may thus be provided in practical terms with the following arrangement: -one single block into which the curd lumps are fed and from which mozzarella cheese comes out as a finished product;

-production capability adapted to be handled by a single operator (typically between 50 and 100 Kg/hour of finished product);

-no auxiliary plant servicing production, since the single block is exclusively supplied with electrical power (foreseen demand lower then 30 Kw/h) and drinkable water (foreseen need less than 1000 liters/day);

-warranty of high hygienic standard of the product;

-ISO 9000 certified process;

-computer-assisted process control, possibly with a connection to a centralised production database, so as to ensure a high micro-biological standard of the product. 4

Brief description of the drawings

An exemplary embodiment of the invention, specifically referred to an apparatus whose configuration is corresponding to the above, shall now be disclosed with reference to the accompanying drawings purely provided by way of non limiting example, in which: -Figure 1 is a perspective and diagrammatic view of a single block which constitutes an apparatus for producing mozzarella cheese according to the invention,

-Figure 2 is a diagram showing by way of a simplified scheme the essential functional components of the apparatus shown in figure 1,

-Figure 3 is a sectioned and enlarged view of a part of figure 2, -Figure 4 is an enlarged cross sectioned view along line IV-IV of figure 3,

-Figure 5 is an enlarged cross sectioned view along line V-V of figure 3,

-Figure 6 shows in a larger scale a detail of figure 3, and

-Figure 7 is an enlarged cross sectioned view along line VII- VII of figure 6.

Detailed description of the invention Referring to figure 1, an apparatus for producing mozzarella cheese according to the invention consists of a single block 1 having a reduced horizontal size and grouping, in a single compact workstation, all the operative components for the mozzarella cheese production cycle, confined between a citric or lactic curd introduction station, generally designated as 2, and a mozzarella cheese outlet station 3. The introduction station 2 and the outlet station 3 are placed at the outside of the front side of the block 1, and are thus directly and conveniently accessible by the operator. Moreover the front side of the block 1 can be provided with one or more visual check windows 4 of the operative components of the apparatus.

As it will be further explained the following, the apparatus according to the invention is provided with an electronic system controlling the mozzarella cheese production process, which is managed by a computer unit 5 for instance directly carried at the outside of the block 1.

Referring now in better details to figure 2, the curd introduction station 2 includes a feeding hopper 6 above which a curd chopping device may be conveniently arranged, normally consisting of a motor-driven chopper 7 of a generally conventional 5 type. The curd, for instance consisting of 25 Kg blocks or lumps, is introduced into the chopping device 7 and broken down into the supply hopper 6.

A motor-driven screw 8 is arranged at the base of the supply hopper 6 for transferring the chopped curd to a hot stretching assembly generally designated as 9. Actually, the screw 8 itself performs a first hot stretching stage of the curd and, therefore, is part of assembly 9.

As shown in better details even in figure 3, in addition to the first screw 8 the stretching assembly 9 further comprises a second and a third motor-driven screws 10,11 arranged in a superimposed condition and designed to advance and stretch the curd along mutually opposed directions.

According to a first feature of the invention, heating for the stretching action is furnished to the curd by heating sources preventing that such heating takes place exclusively through contact with a heating liquid, i.e. -differently from the conventional knownapparatuses for producing mozzarella cheese- without any circuit arranged at the outside of the apparatus for heating a liquid employed as the curd heating source. These contactless heating sources, diagrammatically indicated as 66, 12 and 13, may be constituted by electrical heating resistors, or microwave generators, or high frequency e.g. radio-frequencies generators, or by direct ohmic treatment devices or pulsed electrical field generators. Each heating source 66, 12,13 is normally arranged at the outside of the housing of the respective stretching screw 8, 10,11 and is connected to the supply mains.

These outer heating sources may also be applied, if necessary, to the aim of indirectly heating the outside of the related stretching screws 8, 10,11 through an oil bath provided within an annular interspace sorrounding the screw. Provision of outer heating sources enables performing re-hydration of the curd itself in a controlled way and thus obtaining a finished product having a pre-set analysis.

Actually, since known are both the chemical analysis of the curd introduced into the apparatus and the analysis of the desired final product, the computer 5 shall be able to calculate the physical conditions for managing the system to provide re-hydration of the curd so as to obtain a mozzarella cheese final product whose analysis is within the set standards. In order to allow the above, to the connection 54 between the outlet of the first screw 8 at the base of the supply hopper 6 and the second screw 10 of the stretching assembly 9 a tube 55 is connected for inletting a re-hydration liquid supplied by means of a pump 56 or a pulse counting device having the same function. Motorisation of the first hot stretching screw 8 may be conveniently operable at a variable speed, so as to enable adjustment both of the stretching rate and of the curd advancement. Even variable may be the speed of the motor driving the second stretching screw 10 and of the third stretching screw 11.

The outlet of the third hot stretching screw 11 is connected to the base of a plasticising assembly 14, whose arrangement constitutes a further peculiar feature of the invention.

The plasticising assembly 14 essentially comprises a vertically extended support and containment structure 15 along which a flexible duct 16 is arranged, for instance made of rubber or elastically deformable plastic material, which delimits a closed-circuit flow path for the curd. Kneading/plasticization of the curd within the duct 16 is provided by the cyclic press and release motion of the duct 16, substantially according to a functional peristaltic principle. In other words, cyclic deformation of the duct 16 is carried out by virtue of mechanical outer strains applied by a motor-driven presser system, generally designated as 17. This system 17 comprises an endless chain 18 an a pair of respectively lower and upper sprocket wheels 19 and 20, one of which is motor- driven and the ascending branch of which is movable along a vertical guide 21 facing towards and adjacent to duct 16. As shown in better detail in figures 4 through 7, the rollers 22 of the chain 18 are arranged in rolling contact over a track 23 of the guide 21 and each pair thereof carries a respective presser roll 24 placed in rolling contact with the wall of the flexible duct 16. In practice thus the ascending branch of the chain 18 and the corresponding presser rolls 24 are subjected, upon circulation of the chain itself, to a reciprocating motion in a transverse direction with respect to the flexible duct 16, while these presser rolls 24 move parallely to the longitudinal direction of the duct itself.

As a consequence the duct 16 is cyclically depressed and released elastically, such as depicted in detail in figures 5 and 4, respectively. Due to this cyclical deformation, the curd within the tube 16 is advanced upwardly as a continuous flow or ribbon, while simultaneously it is kneaded with its fibres continuously aligned along the longitudinal direction, and with the certainty that each portion of the curd is subjected to the same plasticising effect over the same period, without dead areas.

An intermediate heating unit, also consisting of non-traditional heating means such as electrical resistors, micro-waves or radio-frequency generators, etc., not shown in the drawings, may be possibly associated to the plasticising assembly 14.

Transportation and plasticisation of the curd along the duct 16 performed by the presser system 17 may be enhanced on one hand by the thrust applied by the stretching assembly 9, and on the other hand also by a vacuum source connected to the upper outlet of the duct 16. Still referring in detail to figure 3, the outlet of the duct 16 is connected to a horizontal tubing 25 in turn connected to a stripping and homogenizing boule 26 whose interior is kept under vacuum by means of a vacuum pump 27. The vacuum pump 27 is actually connected to the boule 26 via a drainage container 28, having a level gauge 29 associated therewith, in turn connected to the interior of a discharge vessel 30 through which a pierced section 31 of the tubing 25 is extending.

The function of the boule 26 is to strip, i.e. remove from the plasticised curd any excess of liquid along with undesired substances in connection with organoleptic characteristics of the finished product, as well as to homogeniee the pasta filata ribbon. These effects are also achieved by maintaining the product stirred by means of a mixer 32 driven by a motor 33. The combined action of the mixer 32 and of the vacuum within the boule 26 enables enhancing vaporisation of any excess of liquid, through boiling thereof at a relatively low temperature. To further aid this action, the amount of heat released to the product within the boule 26 may be increased by means of an outer heating device 34, also consisting of heating resistors or similar systems.

In case the stripping stage of undesired substances and/or evaporation of any water excess in not required, the block 1 may be provided without the stripping boule 26 and related condenser. In this case the outlet of duct 16 shall be directly connected to the discharge vessel 30, vertically arranged, through a vertically extending pierced section 31 of the tubing 25 directly connected to the controlled forming assembly generally designated as 36.

Reverting to the shown embodiment, a continuous extraction screw 35 is arranged at the base of the stripping boule 26, which is conveniently also driven by the motor 33 and by means of which the pasta filata ribbon is delivered to a controlled forming assembly generally designated as 36 for portioning thereof.

The controlled forming assembly 36 comprises a vertical forming unit 37 of a generally conventional motor-driven rotary plate type, including two or more forming cylinders 38 and associated pressor piston 39. The forming assembly 36 is however provided of a few peculiar features, according to a further aspect of the invention, distinguishing it over the traditional apparatuses: this assembly is actually equipped with devices capable to verify conformity of the finished product through the checking of physical parameters of the forming process. These devices consist of a thermometer 40, positioned at the outlet of the stripping boule 26 (or directly on the tubing 25), a detector 41 associated to the pressor piston 39 for measuring the filling time of the forming cylinders 38, and a scale 42 for controlling the product weight arranged at the outlet of the vertical forming assembly 37.

To the scale 42 a diverter unit generally designated as 43 is operatively associated, by means of which the finished product is selectively delivered to a primary packaging assembly 44 or to a refuse container 65.

The primary packaging assembly 44 is of a generally conventional type, and therefore it shall not be disclosed in detail: it provides automatically packaging the product within a film envelope or a tray, with the addition of certain amount of preserving liquid. The outlet of the primary packaging assembly 44 is connected, for instance by means of a mechanical arm, with a cooling unit generally designated as 45. Differently from the conventional apparatuses, wherein mozzarella cheese cooling is performed by immersion into cold water contained within open-top tanks, according to a further peculiar feature of the invention the unit 45 provides cooling by exposing the mozzarella cheese to a flow of liquid nitrogen or CO₂. To such effect the cooling unit 45 comprises a series of endless transportation belts 46, which are mutually superimposed and conveniently provided with receptacles, by which the portioned mozzarella cheese is advanced downwardly within a tunnel environment at a temperature comprises between - 20 and -40°C, towards an exit connected to the outlet station 3. A further manually operated or mechanised secondary packaging station may possibly be associated to the outlet station 3.

According to one of the fundamental features of the invention, the duct 16 of the plasticising assembly 14 and the related connection with the stripping boule 26, as well as the connection between the stripping boule 26 and the controlled forming assembly 36, and thus connection between this controlled forming assembly 36 and the primary packaging unit 44, are such as to define a closed circuit flow path to substantially prevent any contact between the product and the surrounding environment. This closed circuit path can advantageously extend also to the hot stretching assembly 9 and to the cooling unit 45 (even if along the latter the mozzarella cheese is already isolated from the outside by the primary packaging), whereby the entire path of the product from the curd introduction station 2 to the mozzarella cheese outlet station 3 can substantially wholly be within a closed circuit.

As already previously pointed out, the apparatus according to the invention is also provided with an electronic control system of the production process, connected to the computer 5. This control system is not shown in detail, since the components thereof and the related connections are well within the technical skill of the practitioner. As far as the present invention is concerned, it is sufficient to clarify that the computer 5 is operatively connected to the variuos sensors and detectors disclosed in the above, provided along the product path during the successive process stages, particularly in correspondence of the controlled forming assembly 36. The computer 5, programmed according to a suitable operative software, provides by means of on/off switchings along the various apparatus stations automatic and controlled management of the transforming process of the citric or lactic curd into packaged mozzarella cheese. Moreover the computer 5 handles by means of suitable procedures checking of the raw material and of the critical process stages, and through comparison between the detected values and the accepted standards it provides in real time certification of conformity of the finished product. In case of non compliance with the conformity parameters, the computer 5 operates activation of the diverter device 43 provided downstream of the scale 42, or of a similar switching system possibly arranged downstream of the cooling assembly 45, so as to reject the non conforming product. Moreover, in case of any deviations from the accepted parameters, the control system is capable to detect the reasons of the deviation and to suggest how to deal with the detected unconformity.

This computerised control system also takes care of the washing stage, activating it in case the temperature and pH values are reached in the proper time and way. In practice the computerised control system embodies a real quality system providing continuously a conformity certification of the product supplied at the outlet of the apparatus according to the invention.

The stages of the production process performed by the apparatus according to the invention shall now be disclosed in the following, with particular reference to those steps provided, as compared with the conventional production methods, novel and unique features: this is namely the case of the plasticising stage under controlled humidity, of the controlled forming stage, and of the pasteurizing stage which shall be disclosed hereinafter..

Plasticising under predetermined humidity has the aim to achieve an analysis of the final product having a quite limited deviation with respect to preset standard. This is accomplished through the apparatus components performing curd introduction (chopping device 7, hopper 6, first stretching screw 8), and by re-hydrating the curd, having a known analysis, with a liquid amount which is calculated by the computer 5 and delivered through the pump 56, connected to the control circuit of the apparatus. This re-hydration is as pointed out performed via the connection 54 provided immediately upstream of the second hot plasticising stage ( screw 10 and heaters 12) and of the third hot plasticising stage (screw 11 and heaters 13). In alternative, re-hydration may also be performed between the second and the third screws 10,12, and also in other areas of the stretching assembly 9. Plasticising under predetermined humidity may also be performed trough the control of the stretching, time and temperature parameters. In this case, being the curd 1 1 analysis known even in any excess conditions of the re-hydratation liquid, the re- hydratation efficiency is directly bound to the mechanical members via the time, which is variable as a function of the speeds of the screws 8, 10, 11, and the stretching temperature, which is set by the heating system 66, 12, 13. Accordingly any liquid in excess, separated from the vertically-arranged discharge container 30, shall be recycled into th hopper 6 through a suitable connecting line.

Thereafter, during the kneading/plasticising stage performed along the station 14, as already explained the curd is indirectly stressed by means of cyclic mechanical deformation of the flexible duct 16, while providing transportation and plasticisation of the product thus transformed into a continuous pasta filata ribbon.

The plasticising stage under predetermined humidity may be completed by the vacuum boule system 26 and associated heater 34, by which as pointed out removal of any undesired volatile substances can be performed at low temperature and the supply temperature value to the forming assembly 36, whose amount shall normally be corresponding to or higher than 65°C, can be warranted.

The aim of the controlled forming stage is to verify conformity of the finished product through checking of the physical elements of the forming process.

The temperature value detected by the thermometer 40 provided at the inlet of the forming assembly 36 constitutes a first check parameter. Downstream of the thermometer 40, the pasta filata is supplied to one of the forming cylinders 38, displacing then the pressor piston 39 upwardly. The filling up time of the volume defined by the forming cylinder 38, detected by the sensor 41, constitutes a second check parameter. As a matter of fact it is known that viscosity of a product at a set temperature is strictly related to the time necessary for that product to travel along a set distance and, in the case of mozzarella cheese, viscosity is affected by the chemical composition of the product.

Upon reaching the set filling up amount, the motor-driven rotary plate 37 rotates so as to displace the filled forming cylinder 38 to the discharge position, whereby the mozzarella cheese portioned therein is placed onto the scale 42 for weight control. The weight of the so portioned mozzarella cheese constitutes a third check parameter. 12

Through the weight of the set volume the specific gravity of the product, which is also affected by the chemical composition thereof, can be accessed.

Taking into account the relationships between specific gravity, viscosity, chemical analysis of the raw material, amount of the liquid supplied into the controlled humidity stretching and plasticising system, or -in case of liquid excess- the plasticising time and temperature, the computer 5 is capable to define with a high precision degree and in a continuous way whether the produced mozzarella cheese conforms the pre-set process analysis or, owing to any operation defects, unconformity occurs which shall have as a consequence discharge of the product into the container 65 instead of delivering it to the primary packaging device 44.

During the step of hot stretching, the curd may also be conveniently subjected to a pasteurization stage to the aim of getting rid of any curd contaminants. To such effect the first stretching screw 8, the second stretching screw 10 and a suitable section of the third stretching screw 11 shall raise the curd temperature up to a value ≥ 72°C , and in the final section of the third stretching screw 11 stay time over > 15 sec at such a temperature shall be ensured. Such a pasteurization stage shall be checked and certified by the computer 5 by means of suitable temperature sensors and the undirect verification of the pasteurization time through the speed control of the stretching screws 8, 10, 11.

In brief summary the invention thus provides an apparatus for producing mozzarella cheese according to a unique method and comprising a citric or lactic curd introduction station provided with curd chopping means, hot stretching means and kneading/plasticising means to transform the curd into a flow of pasta filata, forming means providing mozzarella cheese portions from the pasta filata, primary packaging means, cooling means and a mozzarella cheese outlet station. The apparatus is mainly characterised in that it consists of a single compact workstation having a reduced horizontal size, provided with a computerised control system enabling the plasticising stage to be performed under a predetermined humidity and the forming stage to be carried out in a controlled fashion, so as to warrant only small deviations with respect to the chemical-physical characteristics of the desired final product, through a closed-circuit plant, possibly also with a pasteurization effect, and with a quick temperature lowering, thus providing mozzarella cheese having a high micro-biological standard. 13

Accordingly, the apparatus of the inventuion besides being properly designed to be managed by a single operator-transformer artisan, even if not particularly skilled or experienced in the field, warrants certified transformation of cyclic or lactic curd into packaged mozzarella cheese having a predetermined chemical analysis and high microbiology standard.

Naturally the details of construction and the embodiments of the apparatus may be widely varied with respect to what has been disclosed and illustrated by way of example, without thereby departing from the scope of the present invention such as defined in the appended claims.

Claims

14CLAIMS

1. Apparatus for producing mozzarella cheese, comprising a citric or lactic curd introduction station, provided with curd chopping means (7), hot stretching means (9) and plasticising means (14) for transforming the curd into a flow of pasta filata, forming means (36) providing mozzarella cheese portions from said pasta filata flow, primary packaging means (44), cooling means (45), and a mozzarella cheese outlet station (3), characterised in that said chopping, stretching, plasticising, forming, primary packaging and cooling means (2,9,14,36,44,45) are grouped in a single compact workstation (1) having a reduced horizontal size, and in that at least said stretching means (14), said forming means (36) and said primary packaging means (44) define a closed circuit substantially without any contact with the outer environment.

2. Apparatus according to claim 1, characterised in that said closed circuit is at least in part under vacuum.

3. Apparatus according to claim 1 or claim 2 characterised in that evaluation means (5,54,55,56) of the humidity degree of the pasta filata are operatively associated to said hot stretching means (9) and to said plasticising means (14).

4. Apparatus according to any of claims 1 through 3, characterised in that check means (40,41,42,5) are operatively associated to said forming means (36) to verify in an automatic and continuous fashion conformity and acceptability of the mozzarella cheese.

5. Apparatus according to the claim 4, characterised in that said check means (40,41,42,5) control diverter means (43) to remove any non conforming products from said closed circuit.

6. Apparatus according to claim 1, characterised in that said hot stretching means (9) are provided with curd heating sources (12,13) other than a heating liquid.

7. Apparatus according to claim 6, characterised in that said heating sources include electrical heating resistors.

8. Apparatus according to claim 6, characterised in that said heating sources include micro-wave generators.

9. Apparatus according to claim 6, characterised in that said heating sources include high-frequency generators.

10. Apparatus according to claim 6, characterised in that said heating sources include direct ohmic treatment devices.

11. Apparatus according to claim 6, characterised in that said heating sources include pulsed electrical field generators.

12. Apparatus according to any of claims 6 through 11, characterised in that said stretching means (9) include at least two screw stretching stages (10,11) arranged in series and supply means (56) of a curd re-hydration liquid to said at least two stretching stages (10,11).

13. Apparatus according to claim 12, characterised in that said at least two stretching stages (10,11) are arranged in a side-by-side or superimposed condition.

14. Apparatus according to claim 1, characterised in that said plasticising means (14) operate according to a peristaltic functional principle.

15. Apparatus according to claim 14, characterised in that said plasticising means (14) include an elastically deformable flexible duct (16)and cyclic deformation means (17) acting from the outside on to said flexible duct (16).

16. Apparatus according to claim 15, characterised in that said cyclic deformation means (17) include a presser system (24) operated by an endless motor-driven conveyor (18).

17. Apparatus according to claim 16, characterised in that said presser system includes rollers (24) arranged in rolling contact with said flexible duct (16) and carried by a closed-loop chain (18) having associated therewith a guide (21,23) designed to reciprocate said presser rollers (24) in a direction transverse to said flexible duct (16) while said presser rollers (24) are displaced parallely to the longitudinal direction of said flexible duct (16).

18. Apparatus according to any of claims 15 through 17, characterised in that said flexible duct (16) is vertically arranged.

19. Apparatus according to any of claims 15 through 18, characterised in that said flexible duct (16) is communicating at its outlet with a boule system under vacuum

(26) performing stripping of any undesired volatile substances at a relatively low temperature.

20. Apparatus according to claim 19, characterised in that said boule system under vacuum (26) includes heating means (34).

21. Apparatus according to claim 19 or claim 20, characterised in that said boule system under vacuum (26) further includes stirring means (32) and motor driven extractor means (35) to said forming means (36).

22. Apparatus according to claim 4, characterised in that said forming means (36) include detector means (40) of the pasta filata temperature.

23. Apparatus according to claim 4 or claim 22, characterised in that said forming means (36) comprise a forming cylinder assembly (37,38) to which filling time detector means (41) are operatively associated.

24. Apparatus according to claim 4 or claim 23, characterised in that mozzarella cheese weighing means (42) are provided at the outlet of said forming means (36).

25. Apparatus according to claims 5 and 22 through 24, characterised in that said diverter means (43) are operated through said weighing means (47) in combination with said temperature detector means (40) and said filling time detector means (41) of said forming cylinder assembly (37,38).

26. Apparatus according to claim 1, characterised in that said cooling means include a series of super imposed endless conveyors (46) exposed to a refrigerant fluid flow.

27. Apparatus according to claim 1 or 12, characterised in that said stretching means (9) further include check and control means of the temperature and of the stay time of said pasta filata flow therein designed to provide pasteurization of said pasta filata at a temperature ΓëÑ 72┬░C over a time ΓëÑ 15 sec.

28. Method for producing mozzarella cheese from a citric or lactic curd mass, including the steps of curd chopping, hot stretching and plasticising to transform the chopped curd into a flow of pasta filata, forming mozzarella cheese from said pasta filata, and then primary packaging and cooling of the formed mozzarella cheese, characterised in that at least the steps of plasticising, forming and primary packaging steps are carried out within a closed circuit substantially without any contact with the outer environment. 18

29. Method for producing mozzarella cheese from a citric or lactic curd mass, including the steps of chopping the curd, hot stretching and plasticising to transform the chopped curd into a pasta filata flow, forming mozzarella cheese from said pasta filata, and then primary packaging and cooling of the formed mozzarella cheese, characterised in that at least said stretching step is carried out under vacuum.

30. Method for producing mozzarella cheese from a citric or lactic curd mass, including the steps of curd chopping, hot stretching and plasticising to transform the chopped curd into a flow of pasta filata, forming mozzarella cheese from said pasta filata, and then primary packaging and cooling the formed mozzarella cheese, characterised in that the step of hot stretching includes heating said curd without any contact thereof with a heating liquid.

31. Method according to any of claims 28, 29 or 30, characterised in that it further comprises, downstream of the plasticising step, an extraction stage at a relatively low temperature of any undesired volatile substances.

32. Method according to claim 31, characterised in that said extraction stage consists of a stripping action by means of boiling under vacuum of said volatile substance.

33. Method according to claim 32, characterised in that said stripping action under vacuum is carried out together with a combined stirring and heating action.

34. Method according to claim 30, characterised in that said heating is performed by means of electrical heating resistors.

35. Method for producing mozzarella cheese from a citric or lactic curd mass, including the steps of curd chopping, hot stretching and plasticising to transform the chopped curd into a pasta filata flow, forming mozzarella cheese from said pasta filata, and then primary packaging and cooling of the formed mozzarella cheese, characterised 19 in that the steps of hot stretching and plasticising are performed under predetermined humidity.

36. Method according to claim 35, characterised in that it comprises a controlled supply of a curd re-hydration liquid upstream of said hot stretching step.

37. Method according to any of claims 28, 29, 30 or 35, characterised in that it further comprises the step of continuously checking conformity of the mozzarella cheese during said forming step.

38. Method according to claim 37, characterised in that said checking steps comprise verifying the temperature, viscosity and weight of the formed mozzarella cheese.

39. Method for producing mozzarella cheese from a citric or lactic curd mass, including the steps of curd chopping, hot stretching and plasticising to transform the chopped curd into a pasta filata flow, forming mozzarella cheese from said pasta filata, and then primary packaging and cooling of the formed mozzarella cheese, characterised in that during the step of hot stretching said pasta filata is subjected to a certified pasteurization stage at a temperature ΓëÑ 72┬░C over a time 15 sec.