Apparatus and method for producing dried pasta

Abstract

A method for producing dry pasta is disclosed, comprising the following steps: preparing a dough having a moisture content between 25% and 35% from hard wheat flour or soft wheat flour and water; placing the dough in a chamber, creating a vacuum between 0.1 bar and 0.5 bar in the chamber; pushing the dough through a stretching device by applying a pressure between 80 bar and 110 bar to the dough to obtain edible pasta (P) in the form of long pasta units or short pasta units; conveying and transferring the pasta (P) to a dryer (3, 4); drying the pasta (P) in the dryer (3, 4) until the moisture content of the pasta (P) is no more than 12.5%, the drying comprising heating the pasta (P) in the dryer (3, 4) to a set temperature and keeping the pasta at the set temperature for a set period of time; removing the dried pasta (P) from the dryer (3, 4); wherein the heating is obtained by passing the pasta (P) in an oscillating electromagnetic field with a frequency between 10 MHz and 100 MHz. Disclosed is an apparatus (1; 1a) for producing dry edible pasta (P), comprising: a kneading and stretching device (2) configured to produce both long pasta and short pasta; a first dryer (3) configured to dry the long pasta produced by the kneading and stretching device; a second dryer (4) configured to dry the short pasta produced by the kneading and stretching device; the first dryer (3) and the second dryer (4) are equipped with a plurality of pairs of electrodes (23, 24), between which an electromagnetic field oscillating at a frequency between 10 MHz and 100 MHz is generated by a generator (54) of an oscillating electromagnetic field.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for producing dried food pasta, in particular to a method and an apparatus for drying food pasta produced with durum wheat flour, or with soft wheat flour, or with a mixture of durum wheat flour and soft wheat flour. Background Art

[0002] Drying methods for food pasta are known from the prior art, the purpose of which is to gradually remove part of the initial moisture from the product by heating, thereby reducing the humidity of the product. Reducing the humidity means reducing the enzyme activity, thereby minimizing fermentation.

[0003] Drying can be provided in equipment provided with suitable heat sources which heat a large volume of air which is then sent into contact with the pasta to be treated in order to heat the pasta and thereby gradually evaporate the moisture contained therein.

[0004] The hot air drying process usually has three steps: a first pre-drying step, a second proper drying step, and a third stabilization step.

[0005] In the first pre-drying step, the pasta coming from the kneading device and stretched by the stretching device is in a plastic state, which therefore presents the possibility of deformation. In this first step, the pasta is heated quickly under the action of a large amount of heat in order to reach the maximum obtainable value of the Q / t ratio without damaging the pasta, where Q / t is the amount of moisture removed from the pasta per unit weight per unit time.

[0006] The pre-drying step may be provided with a continuous pre-drying device, wherein the pasta moves at a constant speed inside the device and is impacted by a continuous flow of hot air with low humidity coming from a heat exchanger. The hot air flow causes heating of the pasta to evaporate the moisture contained in the pasta and transfer it to the air flow.

[0007] Heat is transferred to the pasta in two ways: by convection from the hot air flow to the surface of the pasta and by conduction from the surface of the pasta to the interior.

[0008] Furthermore, the transfer of moisture from the pasta to the hot air stream flowing over the pasta occurs in two different ways: by diffusion from the inner layers of the pasta to the surface and by evaporation from the surface of the pasta to the hot air stream.

[0009] At the end of the pre-drying step, the pasta is no longer in a plastic state, but in an elastic state. This means that temperature differences inside the pasta can lead to internal tensions, which, when high, can cause permanent deformation and breakage of the pasta.

[0010] In order to avoid excessive tension in the mass of the pasta, during the drying step, the transfer of heat from the hot air flow to the pasta occurs more slowly, so that no excessively high gradients are created within the pasta. This means that moisture is removed more slowly from the pasta than in the pre-drying step. If Q1 / t indicates the amount of moisture removed from the pasta per unit weight per unit time during the drying step, this amount is less than the amount Q / t removed in the pre-drying step, i.e. Q1 / t<Q / t.

[0011] The drying step can also be provided in a continuous drying device, which usually extends in height. The pasta moves from top to bottom inside the device, while a hot and dry air flow moves from bottom to top.

[0012] In order to avoid drying defects, it is important that the velocity of the air inside the drying device is as constant as possible.

[0013] The drying step is considered finished when the residual moisture of the pasta does not exceed 12.5%, which is the maximum moisture value for dried pasta set by law.

[0014] At the end of the drying step, the pasta undergoes a so-called stabilization step, making the moisture percentage uniform throughout the pasta mass so that, although the total residual moisture is not greater than 12.5%, the possibility of having areas in the pasta mass with a residual moisture greater than said value is avoided.

[0015] During the stabilization step, the pasta is kept at a temperature above ambient temperature for a set time, at the end of which possible moisture gradients within the pasta mass are zeroed.

[0016] Finally, the pasta is cooled to room temperature before being packaged.

[0017] It should be noted that the transfer of moisture from the pasta to the hot air flow, when the pasta is still in a plastic state, i.e. in the initial step of the drying process previously defined as the pre-drying step, depends essentially on the internal conditions of the drying apparatus, i.e. the speed, temperature and humidity of the air flow impinging on the pasta. On the other hand, when the pasta passes from a plastic state to an elastic state, at the end of the pre-drying step, the transfer of moisture from the pasta to the hot air flow depends essentially on the diffusion rate of moisture inside the pasta mass.

[0018] The diffusion rate of moisture inside the pasta decreases as drying progresses, which necessarily requires a longer drying time.

[0019] In the drying processes known from the prior art using a hot air stream, in order to reduce the drying time, it is proposed to increase the temperature of the hot air stream to about 100° C. However, this leads to the risk of damaging the proteins and amino acids contained in the pasta, resulting in a reduction in the nutritional value of the pasta, which is greater the higher the temperature of the air used to dry the pasta.

[0020] By using high drying air temperatures comprised between 90°C and 115°C, the drying time can also be reduced to only 2-3 hours, but due to changes in gluten, protein and amino acids caused by the high drying temperatures, a pasta with low nutritional quality is obtained.

[0021] Pasta of high nutritional quality is obtained by slow drying at a temperature not higher than 60° C., which does not destroy the gluten, protein or amino acids contained in the pasta. However, this requires a long drying time, even a drying time of the order of 24-36 hours.

[0022] The methods known from the prior art for drying edible pasta using hot air require considerable energy consumption, which is necessary for heating the air, and have low energy efficiency, ranging between approximately 10% and 35%.

[0023] Furthermore, the table pasta is not dried uniformly throughout the pasta mass because the heating of the whole pasta is not uniform, as the outermost parts of the pasta are subjected to more intense heating than the innermost parts, resulting in a non-uniform character of the final product.

[0024] Finally, it should be noted that drying edible pasta by hot air requires different drying equipment for long and short pasta, significantly increasing the cost of manufacturing equipment that can produce both long and short pasta. Summary of the invention

[0025] An object of the present invention is to provide a method for producing dried pasta obtained from durum wheat flour, soft wheat flour or a mixture of durum wheat flour and soft wheat flour, which method makes it possible to reduce the time required for drying the pasta without modifying the gluten, proteins and amino acids contained in the pasta, so as to obtain pasta of high nutritional quality at low temperatures not exceeding about 60° C. in a time significantly shorter than that required for hot air drying.

[0026] Another object of the present invention is to provide a method for drying edible pasta that makes it possible to obtain a product having homogeneous characteristics throughout the mass of pasta to be obtained.

[0027] A further object of the present invention is to provide a method for drying table pasta which makes it possible to reduce the energy consumption required per unit mass of drying table pasta.

[0028] Yet another object of the present invention is to provide an apparatus for producing dry pasta according to the method of the present invention, which apparatus can be used to produce both long and short pasta and reduces operating costs.

[0029] The object of the invention is achieved by a method for producing dry pasta according to claim 1 and by a device for producing dry pasta according to claim 11 .

[0030] Thanks to the invention, it is possible to dry the pasta in a short time by keeping the temperature of the pasta at values ​​that do not destroy the gluten, proteins and amino acids contained in the pasta.

[0031] It is also possible to obtain substantially uniform heating throughout the pasta mass, which makes it possible to eliminate the stabilization step required in hot air drying equipment.

[0032] Thanks to the present invention, the energy consumption per unit mass of dried pasta can be significantly reduced, resulting in significant savings in production costs.

[0033] Furthermore, the heat dissipation to the environment surrounding the device for producing pasta according to the invention is low and smoke, water vapor and noise are absent in this environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, which are given by way of example only and are non-limiting, with reference to the accompanying drawings, in which:

[0035] Figure 1 is a plan view of a first embodiment of an apparatus for producing dry pasta according to the present invention;

[0036] Figure 2 is from Figure 1 Observed from the side indicated by arrow F1 Figure 1 A front view of the device in FIG.

[0037] Figure 3 is based on Figure 1 The line AA Figure 1 A cross-sectional view of the device in FIG.

[0038] Figure 4 is a top view of a second embodiment of an apparatus for drying dry pasta according to the present invention;

[0039] Figure 5 is from Figure 4 Observed from the side indicated by arrow F2 Figure 4 A front view of the device in FIG.

[0040] Figure 6 is based on Figure 4 The line BB Figure 4 A cross-sectional view of the device in FIG.

[0041] Figure 7illustrates a first type of electrode in a device for producing dried pasta according to the invention, which electrode is used to apply a radiofrequency magnetic field to edible pasta to be dried;

[0042] Figure 8 illustrates the effect of applying a radio frequency magnetic field to an element of edible pasta to be dried;

[0043] Fig. 9 is a wiring diagram of a power supply circuit for an electrode of the present invention;

[0044] Fig.10 A second type of electrode that can be used in the device for producing dry pasta according to the invention is illustrated. DETAILED DESCRIPTION

[0045] Hereinafter, for the sake of brevity, edible pasta may be referred to as pasta.

[0046] According to the present invention, there is provided a method for drying edible pasta made from durum wheat flour or a mixture of durum wheat flour and soft wheat flour, the method comprising the following steps:

[0047] Prepare a dough having a moisture content between 25% and 35% from hard wheat flour or soft wheat flour and water;

[0048] placing the dough in a chamber in which a vacuum comprised between 0.1 bar and 0.5 bar is created;

[0049] Obtaining edible pasta P in the form of long pasta units or short pasta units by applying to the dough a pressure comprised between 80 and 110 bars in order to push the dough through a stretching device;

[0050] conveying and delivering the pasta unit to dryers 3, 4;

[0051] Drying the pasta P in the dryers 3 and 4 until the moisture content of the pasta P is no more than 12.5%, wherein the drying comprises heating the pasta P to a set temperature in the dryers 3 and 4 and maintaining the pasta at the set temperature for a set period of time;

[0052] Extracting the dried pasta P from the dryers 3, 4;

[0053] Characterized in that said heating is obtained by moving said pasta P in an oscillating electromagnetic field having a frequency between 10 MHz and 100 MHz.

[0054] During the first drying step, the pasta P is heated to a temperature comprised between 55° C. and 80° C., for a set time that may be approximately 1 hour.

[0055] After said first drying step, a second drying step may be provided, wherein the pasta is kept at a temperature comprised between 45°C and 65°C for a further set period of time of about 30 minutes.

[0056] During the first drying step and the second drying step, air at ambient temperature may be passed to the pasta P to remove moisture generated by evaporation of water in the pasta P.

[0057] After the second drying step, the pasta P may be cooled by a cooling air flow until the temperature of the pasta is the same as the ambient temperature.

[0058] Before drying the pasta P, the pasta P is preferably kept at a temperature above ambient temperature for a set time, so that the residual moisture inside the pasta P is distributed as evenly as possible throughout the mass of the pasta.

[0059] In the case of the production of long pasta, before the first drying step begins, the pasta P is preferably subjected to an aeration step which sends onto the pasta P a stream of air having a temperature comprised between 35°C and 45°C.

[0060] The ventilation serves to dry the surface of the pasta P to reduce its plasticity, in order to prevent the pasta from being excessively stretched due to its own weight.

[0061] In one form of the method according to the invention, the pasta P is heated in an environment generating a vacuum between 0.2 and 0.7 bar in order to be able to dry the pasta P at a temperature comprised between 40 and 55° C., lower than the drying temperature at atmospheric pressure.

[0062] Drying in an environment at subatmospheric pressure allows operating at reduced temperatures, keeping the organoleptic properties of the pasta intact and further reducing drying times.

[0063] exist Figure 1 , Figure 2 and Figure 3 In the figure, an apparatus according to the invention is illustrated for producing long pasta (such as spaghetti, bucatini, mafalde, candele or any other type of long pasta) and short pasta (such as maccheroni, penne, fusilli, conchiglie and any other type of short pasta).

[0064] Reference Figure 1The device 1 according to the present invention comprises: a kneading and stretching device 2, which is capable of producing both long pasta and short pasta; a first dryer 3, which is used to dry long pasta; a second dryer 4, which is used to dry short pasta; a first ventilation device 5, which is arranged after the outlet of the first dryer 3 and is used to dry the long dry pasta leaving the first dryer 3; a second ventilation device 6, which is arranged at the outlet of the second dryer 4 and is used to dry the short dry pasta leaving the second dryer 4.

[0065] The kneading and stretching device 2 comprises a decanting cyclone 9 into which the durum or soft wheat flour is conveyed. The decanting cyclone supplies a volumetric dosing device 10 which conveys the durum and / or soft wheat to a centrifugal pre-kneading device 11 in which the durum or soft wheat is mixed with water to obtain a dough from which the pasta is obtained. The dough is made by mixing durum or soft wheat, typically with a relative humidity of between 9% and 14%, with hot water at between 30° C. and 45° C., in an amount sufficient to bring the relative humidity of the product to a value between about 28% and about 35%.

[0066] From the centrifugal pre-kneading device 11, the wet dough enters a kneading machine 12, in which the hard wheat flour or soft wheat flour completely absorbs the water to obtain a dough from which the pasta will be obtained. Kneading lasts for a period of about 20 minutes, at the end of which the obtained dough is sent through an airtight valve 13 to a vacuum tank 14, where the air is removed from the dough by a suction pump that maintains a pressure between 0.1 bar and 0.5 bar in the tank 14, so that the pasta is shiny and without defects after stretching.

[0067] The dough can be sent from the vacuum tank 14 to the first compression device 15 ( Figure 2 ), the first compression device provides a first stretching device 16 for producing long pasta, or the dough can be sent to a second compression device 28 ( Figure 3 ), the second compression device provides a second stretching device 29 for producing short pasta.

[0068] For the production of long pasta, in the first compression device 15, the dough is pushed at a pressure between about 80 bar and about 110 bar through a stretching device, by means of which a curtain of pasta units is formed, which are sent to a so-called tensioning device, in which the pasta units are stretched and positioned on supporting and conveying elements 18, for example in the form of rods or barrels, on each of which a plurality of pasta units are loaded. The supporting and conveying elements 18 are loaded on a first conveying device 19, by which the supporting and conveying elements 18 with the pasta units are conveyed to the first dryer 3, and the supporting and conveying elements 18 are loaded on a second conveying device 22, which conveys the supporting and conveying elements 18 with the pasta units along a first drying channel 21 obtained inside the first dryer 3.

[0069] Before entering the first drying channel 21, the pasta P passes through the third ventilation device 20, in which the pasta is ventilated with air having a temperature between about 35° C. and 45° C. to slightly dry the outer surface of the pasta P, thereby reducing its plasticity, so as to prevent the pasta P from being excessively elongated due to its own weight.

[0070] In the first drying channel 21, the electrodes 23 and 24 are distributed in a substantially uniform manner ( Figure 7 ), an electromagnetic field is generated between these electrode pairs, the electromagnetic field oscillating at a frequency between about 10 MHz and about 100 MHz. The pasta P is heated by passing through the electromagnetic field between the pair of electrodes 23 and 24. The power applied to the electrodes to generate the oscillating magnetic field is adjusted so that the pasta is heated to a temperature between 55° C. and 75° C.

[0071] After a set period of time of about one hour, the power applied to the electrodes is reduced so as to reduce the temperature of the pasta P to a value between about 45° C. and about 65° C., the pasta being kept at this temperature for a further set period of time of about another 30 minutes, at the end of which the pasta is dry, i.e. with a moisture percentage not greater than 12.5%, as required by legal standards. The expressions "about one hour" and "about 30 minutes" mean that the set period of time and the further set period of time may vary according to the size and thickness of the pasta P. In particular, the set period of time is equal to 1 hour ±10% and the further set period of time is equal to 30 minutes ±10%.

[0072] At the end of drying, the pasta P leaves the first dryer 3 and is conveyed through a first ventilation device 5 in which the pasta P is cooled to ambient temperature.

[0073] Subsequently, the pasta P is conveyed to the removal and cutting device 7, in which the pasta unit is removed from the support and conveying element 18 and cut into a standard length for packaging equal to approximately 260 mm. The pasta P is then conveyed from the removal and cutting device 7 to a packaging device (not shown).

[0074] To produce short pasta, the dough from the vacuum tank 14 is sent to a second compression device 28, into which the dough is pushed, passes through a second stretching device 29 at a pressure between about 100 bar and about 105 bar, and leaves the second stretching device, where the dough is cut into a plurality of short pasta units by a cutting device not shown. The stretching device 29 is interchangeable, depending on the type of short pasta to be produced.

[0075] The short pasta thus produced is sent to a screening device 27, called "trabatto", in which the short pasta units are separated from each other and fall onto a fourth conveying device 33, with the help of which the short pasta units are conveyed to the entrance of the second dryer 4, where they move to a fifth conveying device 35, which transports the short pasta units through a second drying channel 34 obtained inside the second dryer 4.

[0076] Also in the second drying tunnel 34, the pairs of electrodes 23, 24 are distributed in a substantially uniform manner, between which an electromagnetic field is generated, which oscillates at a frequency between about 10 MHz and about 100 MHz. The pasta P is heated by passing through the electromagnetic field between the pairs of electrodes 23, 24. The power applied to the electrodes to generate the oscillating magnetic field is adjusted so that the pasta is heated to a temperature between 55°C and 80°C.

[0077] The pasta P is kept at the above-mentioned set temperature for a period of about one hour, at the end of which period the pasta P is dried and stabilized, with a moisture percentage not greater than 12.5%, as required by legal standards. The expression "about one hour" means that the setting time may vary slightly according to the size and thickness of the pasta P, and in particular, the setting time may be equal to 1 hour ± 10%.

[0078] If a special pasta type has to be produced (such as bird's nests or lasagna), the following process is followed.

[0079] In the case of bird's nest noodles, the pasta leaving the stretching device is sent to the so-called "bird's nest forming" device 30, from which the pasta leaves in the shape of a simulated bird's nest. Subsequently, the pasta thus produced is dried by the same method as disclosed above for long pasta.

[0080] In the case of lasagna, the pasta leaving the stretching device is sent to the so-called "lasagna" device 31, from which the pasta leaves in the form of lasagna. The pasta thus produced is then dried by the same method disclosed above for long pasta.

[0081] The advantage of heating the pasta by microwaves during the drying process is that a very rapid and uniform heating of the pasta is obtained, with a gradient of about 1°C / s. Furthermore, unlike hot air drying equipment, no preheating of the environment is required, in which drying must take place until the drying temperature is reached.

[0082] Furthermore, no pasta stabilization step needs to be performed at the end of drying.

[0083] A short drying time of almost one hour can be obtained, keeping the drying temperature not exceeding 80° C., in order to minimize the degradation of the nutritional and organoleptic properties of the pasta and to obtain high quality pasta.

[0084] Finally, the energy efficiency of the drying device according to the invention is between about 65% and about 70%, compared to the energy efficiency of hot air drying devices according to the prior art between about 10% and 35%. This allows considerable savings in operating costs of the device according to the invention.

[0085] exist Figure 4 , Figure 5 and Figure 6 In FIG. 1 , a variant 1a of a drying device 1a according to the invention is illustrated.

[0086] The drying device 1a according to the present invention is Figure 1 , Figure 2 and Figure 3 The illustrated apparatus 1 differs in that the first drying channel 21 and the second drying channel 34 are kept under vacuum. In order to keep the first drying channel 21 under vacuum, the first dryer 3 is equipped with at least one first vacuum pump 40. The second dryer 4 is equipped with at least one second vacuum pump 48 to keep the second drying channel 34 under vacuum.

[0087] Device 1a and Figure 1 , Figure 2 and Figure 3 The corresponding elements of the illustrated device 1 are identical to the elements of Figure 1 , Figure 2 and Figure 3 The same reference numerals used in the drawings are used to mark the same reference numerals used in the drawings.

[0088] Reference Figure 5 , Figure 5Referring to the part of the device 1a intended for producing long pasta, the pasta unit supported on the support and conveying rods 18 and coming from the third ventilation device 20 is introduced into the loading chamber 36 of the first dryer 3. The loading chamber 36 is equipped with a first sliding baffle 38 placed at the entrance of the loading chamber 36 and a second sliding baffle 39 placed at the exit of the loading chamber 36. The first sliding baffle 38 is movable between an open position, in which it places the loading chamber 36 in communication with the external environment at atmospheric pressure, and a closed position, in which it isolates the loading chamber 36 in an airtight manner from the external environment. The second sliding baffle 39 is movable between an open position, in which it places the loading chamber 36 in communication with the first drying channel 21, and a closed position, in which it isolates the first drying channel 21 in an airtight manner from the loading chamber 36. The second sliding baffle 39 is normally in the closed position so as to keep the first drying channel 21 of the first dryer 3 under vacuum. The loadlock chamber 36 is also equipped with a third vacuum pump 37 , which is intended to create a vacuum inside the loadlock chamber 36 .

[0089] The support and conveying elements 18, each carrying a plurality of long pasta units, are introduced into the loading chamber 36 in groups, each group G1 comprising, for example, 10 to 30 support and conveying elements 18. During the introduction of the support and conveying elements 18 into the loading chamber 36, the first sliding shutter 38 is in the open position to enable the rods 18 to be introduced, while the second sliding shutter 39 is in the closed position.

[0090] After the group G1 of supporting and conveying elements 18 has been introduced into the loading chamber 36, the first sliding baffle 38 moves to a closed position, hermetically sealing the loading chamber, and the third vacuum pump 37 starts to generate a vacuum in the loading chamber 36 comprised between 0.2 bar and 0.7 bar, which is approximately the same as the vacuum generated and maintained by the first vacuum pump 40 in the first drying channel 21 of the first dryer 3.

[0091] When the pressure in the loading chamber 36 is the same as the pressure in the first drying passage 21 of the first dryer 3, the second sliding shutter 39 is opened to convey the group G1 of supporting and conveying elements 18 to the first drying passage 21. After conveying the group G1 of supporting and conveying elements 18 to the first drying passage 21, the second sliding shutter 39 is returned to the closed position to seal the first drying passage 21, air is then conveyed to the loading chamber 36 to restore the pressure therein to be equal to the atmospheric pressure, and the first sliding shutter 38 is brought to the open position to enable conveying to the loading chamber 36 a new group G1 of supporting and conveying rods 18 with corresponding pasta units.

[0092] The pasta P inside the first drying tunnel 21 moves between the pair of electrodes 23, 24, and an electromagnetic field is generated between the pair of electrodes, which oscillates at a frequency between about 10 MHz and about 100 MHz. The pasta P is heated by passing through the electromagnetic field between the pair of electrodes 23, 24. The power applied to the electrodes to generate the oscillating magnetic field is adjusted so that the pasta is heated to a temperature between 40°C and 55°C. Since the vacuum maintained in the first drying tunnel 21 promotes the evaporation of moisture contained in the pasta, it is possible to dry the pasta P at a temperature lower than that of the pasta P in the first drying tunnel 21. Figure 1 , Figure 2 and Figure 3 The drying temperature in the drying device 1 shown dries the pasta P at a significantly lower temperature, which allows the organoleptic properties of the pasta to remain substantially unchanged, since the temperature used during the drying of the pasta in the first drying tunnel 21 is below 60° C., which is the temperature at which the gluten, proteins and amino acids of the pasta begin to degrade. This allows very high quality pasta to be obtained.

[0093] The residence time of the pasta P in the first drying tunnel 21 is about one hour, in particular 1 hour ±10%, at the end of which time the pasta will be dried and stabilized, with a moisture percentage not greater than 12.5%, as required by legal standards.

[0094] The first dryer 3 is equipped with an unloading chamber 41 at the outlet of the first drying passage 21, through which the dried pasta P can be unloaded from the first drying passage 21 into the external environment under atmospheric pressure.

[0095] The unloading chamber 41 is equipped with a third sliding baffle 43 placed at the entrance of the loading chamber 41 and a fourth sliding baffle 44 placed at the exit of the unloading chamber 41. The third sliding baffle 43 is movable between an open position, in which the third sliding baffle places the first drying passage 21 in communication with the unloading chamber 41, and a closed position, in which the third sliding baffle hermetically isolates the unloading chamber 41 from the first drying passage 21. The fourth sliding baffle 44 is movable between an open position, in which the fourth sliding baffle places the unloading chamber 41 in communication with the external environment, and a closed position, in which the fourth sliding baffle hermetically isolates the unloading chamber 41 from the external environment. The third sliding baffle 43 is usually in a closed position to maintain the vacuum inside the first drying passage 21. The unloading chamber 41 is also provided with a fourth vacuum pump 42, which is intended to generate a vacuum inside the unloading chamber 41.

[0096] In order to unload the group G2 with the supporting and conveying elements 18 of the corresponding dried pasta units from the first drying tunnel 21, the fourth sliding shutter 44 is placed in the closed position, the third shutter 43 is kept in the closed position, and then the fourth vacuum pump 42 is started to generate a vacuum inside the unloading chamber 41 that is equal to the vacuum inside the first drying tunnel 21. When the pressure in the unloading chamber 41 is equal to the pressure in the first drying tunnel 21, the third sliding shutter 43 is placed in the open position, and the group G2 with the supporting and conveying elements 18 of the corresponding pasta units is introduced into the unloading chamber 41. Subsequently, the third shutter 43 returns to the closed position sealing the first drying passage 21, air is delivered to the unloading chamber 41 to restore therein a pressure equal to atmospheric pressure, and the fourth sliding shutter 44 is brought to the open position to enable the group G2 of support and conveying elements 18 with the corresponding dried pasta units to be taken out from the unloading chamber 41 and to send the support and conveying elements 18 to the removal and cutting device 7, where the pasta units are removed from the support and conveying elements 18 and cut into a standard length for packaging equal to about 260 mm. The pasta P is then sent from the removal and cutting device 7 to a packaging device (not illustrated).

[0097] Since the temperature at which the pasta drying occurs is relatively low, the first ventilation device 5 may not be used to dry the pasta P, and the pasta may be allowed to cool naturally. However, the first ventilation device may be used to accelerate the cooling of the pasta.

[0098] Reference is now made to the part relating to the apparatus intended for the production of short pasta. Figure 6 The short pasta from the stretching device 29 is sent to a screening device 27, called a "shaking section", in which the individual short pasta units are separated from each other and fall onto a fourth conveying device 33, by means of which the short pasta units are conveyed to loading devices 45, 46, 47, through which they are conveyed to the second drying channel 34 of the second dryer 4, in which a vacuum between 0.2 bar and 0.7 bar is generated by a second vacuum pump 48.

[0099] The loading devices 45, 46, 47 include a loading bucket 45 into which the short pasta units from the fourth conveying device 33 are conveyed; the loading bucket 45 is connected to a sealed first star valve 46 at the bottom, through which the short pasta units are conveyed to a zigzag chute 47 connected to the second drying channel 34. The short pasta units fall down the zigzag chute 47 that slows down the fall under the action of gravity, and join the fifth conveying device 35 so that the short pasta units are conveyed along the second drying channel 34.

[0100] The short pasta unit moves between the pair of electrodes 23, 24, between which an electromagnetic field is generated, which oscillates at a frequency between about 10 MHz and about 100 MHz. The pasta P is heated by passing through the electromagnetic field between the pair of electrodes 23, 24. The power applied to the electrodes to generate the oscillating magnetic field is adjusted so that the pasta is heated to a temperature between 40°C and 55°C. Since the vacuum maintained in the second drying channel 34 promotes the evaporation of moisture contained in the pasta, it is possible to dry the pasta at a temperature lower than that of the pasta P in the second drying channel 34. Figure 1 , Figure 2 and Figure 3 The drying temperature in the illustrated drying device 1 dries the pasta P at a significantly lower temperature, which allows the organoleptic properties of the pasta to remain substantially unchanged, since the drying temperature of the pasta in the second drying tunnel 34 is below 60° C., which is the temperature at which the gluten, protein and amino acids of the pasta begin to degrade. This allows very high quality pasta to be obtained.

[0101] The residence time of the pasta P in the second drying tunnel 34 is about one hour, in particular 1 hour ±10%, at the end of which time the pasta is dried and stabilized, with a moisture percentage not greater than 12.5%, as required by legal standards.

[0102] The second dryer 4 is equipped with unloading devices 49, 50, 51 which enable the dried pasta to be unloaded from the second drying channel 34 to an environment at atmospheric pressure. The unloading devices 49, 50, 51 comprise an unloading hopper 49 communicating with the second drying channel 34, into which the fifth conveying device 35 conveys the short pasta units currently being dried. The unloading hopper 49 communicates below with a second zigzag chute 50, through which the short pasta units pass under gravity to a second sealing star valve 51, which unloads the short pasta units onto an outlet chute 52 in an environment at atmospheric pressure, for subsequent transfer to a packaging device (not illustrated).

[0103] exist Figure 7 and Figure 8 2 shows an example of a pair of electrodes 23, 24, by means of which an electromagnetic field oscillating at a frequency between 10 MHz and 100 MHz is applied to a pasta unit transported between the electrodes.

[0104] The electrodes are powered by a generator 54 of an oscillating magnetic field, which is connected to the pair of electrodes 23, 24 by coaxial cables 60, which are shielded to avoid interfering with the electromagnetic field generated by the generator 54. The magnetic field lines 53 are Figure 7 and Figure 8 In Figure 8 In FIG. 5 , moisture leaving the surface of the pasta P by the heating effect caused by the oscillating magnetic field is represented by small arrows, which are indicated by reference numeral 55 .

[0105] exist Fig. 9 , a generator 54 of an oscillating magnetic field is schematically shown. The generator 54 is supplied with direct current by a rectifier 57, which in turn is supplied by a normal alternating current grid 56 (e.g. 220V with a frequency of 50 Hz). The rectifier 57 supplies power to a circuit 58 for generating an oscillating electromagnetic field connected to the pair of electrodes 23, 24. An impedance adapter circuit 59 is inserted between the circuit 58 for generating an oscillating magnetic field and the pair of electrodes 23, 24, which causes the impedance seen by the generator 54 of the oscillating magnetic field to have a set constant value to compensate for possible impedance variations of the load constituted by the pair of electrodes 23, 24 with corresponding coaxial cables 60 and the pasta unit transported between the electrodes 23, 24.

[0106] The electrodes 23, 24 of each electrode pair may be Figure 7 and Figure 8 Example alignment between them, or as Fig.10 Schematically illustrating the staggered arrangement, Fig.10 A series of pairs of electrodes 23, 24 are shown, each pair being staggered relative to each other. The electrode pairs are arranged sequentially along the path of the pasta P either in the first drying tunnel 21 or in the second drying tunnel 34.

[0107] The distance D between each pair of electrodes may be constant or adjustable to suit the thickness of the pasta unit.

Claims

1. A method for producing dried pasta, the method comprising the following steps: - preparing a dough with a moisture content between 25% and 35% from durum wheat flour or soft wheat flour and water; - placing the dough in a chamber and creating a vacuum between 0.1 bar and 0.5 bar in the chamber; - pushing the dough through a stretching device by applying to it a pressure between 80 and 110 bars, so as to obtain edible pasta (P) in the form of long pasta units or short pasta units; - conveying the pasta (P) and transferring it to a dryer (3, 4); - drying the pasta (P) in the dryer (3, 4) until the moisture content of the pasta (P) is no more than 12.5%, the drying comprising heating the pasta (P) to a set temperature in the dryer (3, 4) and keeping the pasta at the set temperature for a set period of time; - removing the dried pasta (P) from the dryer (3, 4); Characterized in that the heating is obtained by passing the pasta (P) inside an oscillating electromagnetic field with a frequency between 10 MHz and 100 MHz, wherein the heating takes place in an environment where a vacuum is created.

2. The method according to claim 1, further comprising: The intensity of the oscillating magnetic field is adjusted according to the set temperature.

3. The method according to claim 1 or 2, wherein: The set temperature is between 55°C and 75°C.

4. The method according to claim 1 or 2, wherein: The set temperature is between 55°C and 80°C.

5. The method according to claim 1 or 2, further comprising: The strength of the oscillating magnetic field is further adjusted so as to bring the temperature of the pasta (P) to a value between 45° C. and 65° C. and the pasta (P) is kept at said temperature value for a set further period of time.

6. The method according to claim 1, wherein: The vacuum is between 0.2 bar and 0.7 bar.

7. The method according to claim 1, wherein: The set temperature is between 40°C and 55°C.

8. The method according to claim 1 or 2, wherein: The time period is equal to 1 hour ± 10%.

9. The method according to claim 5, wherein: The further period of time is equal to 30 minutes ± 10%.

10. An apparatus (1; 1a) for producing dried pasta (P), comprising: a kneading and stretching device (2), the kneading and stretching device (2) being configured for producing long pasta and short pasta; A first dryer (3) configured to dry long pasta produced by the kneading and stretching device; a second dryer (4) configured to dry short pasta produced by the kneading and stretching device, characterized in that the first dryer (3) and the second dryer (4) are provided with a plurality of pairs of electrodes (23, 24), between which an electromagnetic field oscillating at a frequency between 10 MHz and 100 MHz is generated by a generator (54) of an oscillating electromagnetic field, The first dryer (3) is provided with at least one first vacuum pump (40), and a vacuum can be generated inside the first drying channel (21) by means of the at least one first vacuum pump (40); or The second dryer (4) is provided with at least one second vacuum pump (48), and a vacuum can be generated inside the second drying channel (34) by means of the at least one second vacuum pump (48).

11. The device (1; 1a) according to claim 10, wherein The pair of electrodes (23, 24) is distributed along a first drying channel (21) obtained inside the first dryer (3) and along a second drying channel (34) obtained inside the second dryer (4).

12. The apparatus (1; 1a) according to claim 11 further comprises a first ventilation device (5), which is arranged at the outlet of the first drying channel (21) and is configured to cool the pasta (P) leaving the first drying channel (21).

13. The apparatus (1) according to claim 11 or 12, further comprising a second ventilation device (6), which is arranged at the outlet of the second drying channel (34) and is configured to cool the pasta (P) leaving the second drying channel (34).

14. The device (1; 1a) according to any one of claims 10 to 12, further comprising a plurality of supporting and conveying elements (18), on each of which a plurality of long pasta units can be arranged.

15. The device (1; 1a) according to claim 14, further comprising: a first conveying device (19), the first conveying device (19) being used to convey the supporting and conveying element (18) from the kneading and stretching device (2) to the first drying channel (21); and a second conveying device (22), the second conveying device (22) being used to convey the supporting and conveying element (18) through the first drying channel (21).

16. The device (1; 1a) according to claim 13, further comprising: a plurality of supporting and conveying elements (18), on each of which a plurality of long pasta units can be arranged, and A removal and cutting device (7) is placed after the first drying tunnel (21), the removal and cutting device (7) being configured to remove the long pasta units from the supporting and conveying element (18) and to cut the long pasta units into set lengths.

17. The device (1; 1a) according to claim 12, further comprising: a plurality of supporting and conveying elements (18), on each of which a plurality of long pasta units can be arranged, and A removal and cutting device (7) is placed after the first ventilation device (5), the removal and cutting device (7) being configured to remove the long pasta unit from the supporting and conveying element (18) and to cut the long pasta unit into set lengths.

18. Apparatus (1; 1a) according to any one of claims 10 to 12, further comprising screening means (27) placed between the kneading and stretching means (2) and the second dryer (4).

19. The device (1; 1a) according to claim 18, further comprising: a third conveying device (32), the third conveying device (32) being used to convey the pasta (P) from the kneading and stretching device (2) to the screening device (27); a fourth conveying device (33), the fourth conveying device (33) being used to convey the pasta (P) from the screening device to the second drying channel (34); and a fifth conveying device (35), the fifth conveying device (35) being used to convey the pasta (P) through the second drying channel (34).

20. The device (1; 1a) according to claim 10, wherein The vacuum is between 0.2 bar and 0.7 bar.

21. The device (1; 1a) according to claim 10, wherein The first dryer (3) comprises a loading chamber (36) through which the pasta (P) can be introduced into the first drying channel (21), the loading chamber (36) comprising a first sliding baffle (38) placed at the entrance of the loading chamber (36) and a second sliding baffle (39) placed at the exit of the loading chamber (36), wherein the first sliding baffle (38) is movable between an open position, in which the first sliding baffle (38) places the loading chamber (36) in communication with an external environment at atmospheric pressure, and a closed position, in which the first sliding baffle (38) places the loading chamber (36) in communication with an external environment at atmospheric pressure. The loading chamber (36) is hermetically isolated from the external environment, wherein the second sliding baffle (39) is capable of moving between an open position and a closed position, wherein the second sliding baffle (39) places the loading chamber (36) in communication with the first drying channel (21), and wherein the second sliding baffle (39) hermetically isolates the first drying channel (21) from the loading chamber (36), wherein the second sliding baffle (39) is normally in the closed position, wherein the loading chamber (36) is provided with a third vacuum pump (37), and the third vacuum pump (37) is used to generate a vacuum in the loading chamber (36).

22. The device (1; la) according to claim 21, wherein The first dryer (3) comprises an unloading chamber (41), through which the dried pasta (P) can be unloaded from the first drying channel (21) in an environment under atmospheric pressure, the unloading chamber (41) being provided with a third sliding baffle (43) placed at the entrance of the unloading chamber (41) and a fourth sliding baffle (44) placed at the exit of the unloading chamber (41), wherein the third sliding baffle (43) is movable between an open position and a closed position, in which the third sliding baffle (43) places the first drying channel (21) in communication with the unloading chamber (41), and in which the third sliding baffle (44) is movable between the third sliding baffle (43) and the fourth sliding baffle (44) 3) The unloading chamber (41) is hermetically isolated from the first drying channel (21), wherein the fourth sliding baffle (44) is movable between an open position and a closed position, wherein the fourth sliding baffle (44) places the unloading chamber (41) in communication with an external environment at atmospheric pressure, and wherein the fourth sliding baffle (44) hermetically isolates the unloading chamber (41) from the external environment at atmospheric pressure, wherein the third sliding baffle (43) is normally in a closed position, wherein the unloading chamber (41) is provided with a fourth vacuum pump (42), and the fourth vacuum pump (42) is used to generate a vacuum in the unloading chamber (41).

23. The device (1; la) according to claim 10, wherein The second dryer (4) is provided with a loading device (45, 46, 47), by means of which the pasta unit can be conveyed to the second drying channel (34), wherein the loading device (45, 46, 47) comprises a loading bucket (45), into which the pasta unit can be conveyed, wherein the loading bucket (45) is connected to a sealed first star valve (46) at the bottom, and the pasta unit can be conveyed to a first zigzag chute (47) connected to the second drying channel (34) through the first star valve (46).

24. The device (1; 1a) according to claim 23, wherein The second dryer (4) is provided with an unloading device (49, 50, 51), which enables the dried pasta to be unloaded from the second drying channel (34) into an external environment at atmospheric pressure, wherein the unloading device (49, 50, 51) comprises an unloading bucket (49) connected to the second drying channel (34), into which the currently dried pasta unit can be conveyed, wherein the unloading bucket (49) is connected to a second zigzag chute (50) at the bottom, and the pasta unit reaches a second sealing star valve (51) through the second zigzag chute (50) under the action of gravity, and the second sealing star valve (51) enables the pasta unit to be unloaded to an outlet chute (52) in the external environment at atmospheric pressure.

25. The device (1; 1a) according to any one of claims 10 to 12, wherein: The electrodes (23, 24) of each electrode pair are arranged in alignment with each other or staggered relative to each other.

26. The device (1; la) according to any one of claims 10 to 12, wherein The distance (D) between the electrodes (23, 24) of each electrode pair can be constant or adjustable.

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