WO2014191799A1

WO2014191799A1 - Radiofrequency apparatus for unfreezing food products

Info

Publication number: WO2014191799A1
Application number: PCT/IB2013/060161
Authority: WO
Inventors: Manlio Cavestro
Original assignee: Stalam S.P.A.
Priority date: 2013-05-29
Filing date: 2013-11-15
Publication date: 2014-12-04
Also published as: ITVR20130131A1; ES2643717T3; EP3005832A1; EP3005832B1

Abstract

A radio frequency apparatus (1) for thawing food products, through the use of an oscillating electromagnetic field, comprises a continuous conveyor belt (2), on which the food products are positioned, elements (3) for supporting and for moving the conveyor belt (2) forward, an inlet section (4), for the introduction of the food products to be thawed, a central section (5), defining a tunnel in which the food products are thawed, an outlet section (6), from which the thawed food products come out, at least one oscillating voltage generator (9), for generating the oscillating electromagnetic field, and elements (21) for washing and/or sanitizing the conveyor belt (2) and/or the inlet section (4) and/or the central section (5) and/or the outlet section (6).

Description

"RADIOFREQUENCY APPARATUS FOR UNFREEZING FOOD

PRODUCTS"

Designated inventor: Manlio Cavestro

TECHNICAL FIELD OF THE INVENTION

The present invention refers to a radio frequency apparatus for thawing food products in a short time through the use of electromagnetic fields

In particular, the present invention refers to a radio frequency apparatus of the linear type, i.e. an apparatus in which the food products transit on a transportation line entering frozen or deep frozen and coming out completely thawed.

STATE OF THE ART

Industrial types of radio frequency apparatuses are known for thawing food products in a short time.

Such apparatuses have a linear structure and comprise a transportation device, for example a conveyor belt, on which the food products to be thawed are positioned, the conveyor belt is then actuated by means of conventional type motor means, for example motorised rollers.

The products to be thawed are then moved forward through a tunnel provided in the apparatus itself and are subjected to an electromagnetic fields, emitted by emitting devices, obtaining a continuous machining process along the apparatus itself.

The thawing process, thus obtained, requires a machining time that is much shorter than conventional thawing methods, based upon the use of steam or hot air or similar means.

As it is known, by reducing the thawing time it is possible to avoid an excessive development of the bacterial load on the food products thus preserving the integrity thereof.

Through such known types of apparatuses, moreover, it is possible to thaw, in an easy manner, large amounts of frozen food products.

The desire to improve the performance of such apparatuses, with particular reference to the possibility of overall ensuring a high level of hygiene of the apparatus itself, and in particular of the surface on which the food products to be thawed are positioned and moved forwards, is felt in the field.

The liquids possibly released from the food products during thawing - leachate - can come into contact with the conveyor belt or drip through it, if the latter has a grid structure, thus dirtying portions of the apparatus that are adjacent to the conveyor belt itself. Such a leachate, following the electromagnetic radiations inside the tunnel of the apparatus, could dry up and thus become difficult to remove.

The dried up leachate, moreover, is a contaminating agent for the food products that must undergo thawing cycles, subsequently rested on the belt.

If, on the other hand, the food products to be thawed are contained inside packages, like for example cartons, the leachate could contaminate them, deteriorate them and, in some cases, come out from them.

In the case in which the packages are waterproof the leachate, formed during the thawing process, would be held inside them causing heat alteration in the food products when being thawed.

The leachate or its dried residues, indeed, are sensitive to the electromagnetic radiations and, in some portions of the products with which they are placed in contact, can determine areas of over- heating such as to locally deteriorate the food products, causing them to be only partially cooked and/or burnt.

For such a reason, in the case of food products to be thawed positioned directly on the conveyor belt, it is foreseen for there to be a sanitization of both the conveyor belt and the entire apparatus at predetermined intervals, which can vary as a function of the volumes and of the type of frozen products so as to overall ensure a high level of hygiene thereof. However, such operations can be carried out exclusively when there are no food products inside the apparatus, so as to prevent these from becoming contaminated by the detergent products used during the cleaning process.

In consideration of what has been described above, it is necessary for there to be idle time of the machines in order to clean the apparatuses, thus reducing the productivity thereof.

In order to allow the external cleaning of conventional types of thawing apparatuses, the radio frequency emitting devices are separate from the apparatus itself and, possibly, located in a different room so as to prevent them from being damaged, for example, following contact with the detergent liquid and/or foam used during sanitization .

On the other hand, in such a way, there is an overall increase of the bulk of the thawing apparatus and, moreover, means for conveying the electromagnetic radiation up to the thawing area must be foreseen. Such embodiments of thawing apparatuses do not make it possible to precisely control the energy radiated to the products during the thawing process.

Therefore, it is difficult to ensure and to obtain a homogeneous thawing treatment of the products.

PURPOSES OF THE INVENTION

One purpose of the present invention is therefore that of improving the state of the art.

A further purpose of the present invention is to propose a radio frequency apparatus for thawing food products that makes it possible to maintain a high level of cleanliness of the support and forward movement means, on which the food products are positioned, ensuring, at the same time, that the apparatus itself is highly operative.

Another purpose of the present invention is to propose an apparatus for thawing food products the overall cleaning of which is easy to carry out, so as to ensure a high hygiene level thereof.

In accordance with one aspect of the present invention it is foreseen for there to be a radio frequency apparatus for thawing food products according to claim 1.

The dependent claims refer to preferred and advantageous embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention shall become clearer from the detailed description of a preferred, but not exclusive, embodiment of a radio frequency apparatus for thawing food products that is illustrated as an indication, and not for limiting purposes, in the attached drawing tables, in which:

figure 1 is a front perspective view of a radio frequency apparatus for thawing food products according to the present invention;

figure 2 is an exploded front perspective view of the radio frequency apparatus according to figure 1;

figure 3 is a rear perspective view of a detail of the radio frequency apparatus according to figure 1;

figure 4 is a perspective view of some details of the radio frequency apparatus according to figure 3;

figure 5 is a front perspective view of a detail of the inlet section of the radio frequency apparatus according to figure 1;

figure 6 is a front perspective view of a detail of the outlet section of the radio frequency apparatus according to figure 1;

figure 7 is a perspective view from below of a portion of the radio frequency apparatus according to the present invention;

figure 8 is a schematic perspective view of the radio frequency apparatus according to the present invention .

EMBODIMENTS OF THE INVENTION

With reference to the attached figures, a radio frequency apparatus, of the line type, for thawing food products in a short time is wholly indicated by 1.

As it is known, radio frequency apparatuses of the industrial type for thawing food products comprise an electric generator that is suitable for producing an oscillating voltage with set frequencies, through international standards, equal to 6.78 MHz, 13.56 MHz, 27.12 MHz or 40.68 MHz, and at least one applicator comprising electrodes for transforming the oscillating voltage into an electric or magnetic field as a function of the characteristics of the product to be thawed.

According to one version of the present invention the frequency of the oscillating electromagnetic field applied to the food products to be thawed is comprised in a range of between 1 MHz and 1 GHz.

With reference to the embodiment illustrated in figure 1, the radio frequency apparatus 1, which has a structure of the line type, comprises a continuous conveyor belt 2, on which the food products to be thawed (not illustrated) are positioned, means 3 for supporting and moving the conveyor belt 2 forward, an inlet section 4, for introducing the food products to be thawed, a central section 5, and an outlet section 6, from which the thawed products come out.

The thawing of the food products occurs through the application of an electromagnetic field of the oscillating type, to the food products along the central section 5.

The central section 5 comprises at least one thawing module 7.

With reference to the embodiment illustrated in figures 1, 2 and 8 the central section 5 comprises three thawing modules 7.

However, the central section 5 can comprise a greater or a smaller number of thawing modules 7 with respect to what is shown above without for this reason departing from the scope of protection of the present invention .

Each thawing module 7 mainly comprises a frame 8, at least one oscillating voltage generator 9 and a control circuit, not illustrated, of the at least one oscillating voltage generator 9.

The at least one oscillating voltage generator 9 and the relative control circuit are installed above the frame 8.

The frame 8 defines a central tunnel along which the food products to be thawed are moved forward.

The frame 8 has, along the opposite side walls, openings 10 for accessing the central tunnel and the lower part of the apparatus 1, for example for being able to carry out in an easy manner the ordinary or extraordinary maintenance of the radio frequency apparatus 1 and for cleaning inside the part of tunnel and the lower part of the apparatus 1.

The openings 10 are sealingly closed through corresponding mobile panels 11.

The mobile panels 11 are foreseen for shielding and confining the oscillating electromagnetic field radiated to the product to be thawed inside the tunnel of the radio frequency apparatus 1.

Furthermore, the mobile panels 11 are foreseen so as to prevent dirt and/or foreign objects from accidentally entering inside the apparatus 1 during the thawing process of the food products. In such a way, the integrity of the food products and the safety of the workers present in the immediate vicinity of the radio frequency apparatus 1 during the operation thereof is ensured.

In the rest of the description by the expression washing liquid or foam we mean to indicate one or more detergent substances, in the form of a liquid or of a foam, that can be used to carry out the washing and/or the sanitization of the radio frequency apparatus 1.

In the radio frequency apparatus 1 it is foreseen for there to be a cover 12 that is suitable for protecting the at least one voltage generator 9 and its control circuit from harmful external agents.

The cover 12 is substantially parallelepiped-shaped and it is suitable for hermetically insulating the voltage generator 9 and its components from the surrounding environment .

In particular, the cover 12 makes it possible to protect the oscillating voltage generator 9, its control circuit and its electrical and electronic components from washing liquids and/or foam used during the washing and/or sanitising operations of the radio frequency apparatus 1.

Moreover, the cover 12 prevents the accidental contact between the workers and the oscillating voltage generator 9 and its components.

In such a way, a high level of safety is ensured to the single workers present in the vicinity of the radio frequency apparatus 1 during the operation thereof and/or during the washing and/or sanitising steps thereof.

The cover 12 is made from thermoacoustic insulation material .

In one embodiment, not shown in the figures, the cover 12 can comprise plastic and/or metal finishings that are applied to the thermoacoustic insulation material .

The radio frequency apparatus 1 is foreseen for a use in serious environmental conditions with reference, for example, to very low environment temperatures, very high percentage of humidity, presence of contaminating agents, such as dusts, vapours, fog of particles, possibly also oily, etcetera.

As a non-limiting example, the radio frequency apparatus 1 can be installed and operate inside a cold room or in a room with controlled thermo- hydrometric conditions, which are set so as to avoid or reduce the proliferation of bacteria, integrated with further pre-existing machines, plants or manufacturing lines for producing food products.

In such a way it is possible to ensure high productivity of the line itself, since it is not necessary to move the food products to be treated through different rooms.

The cover 12, moreover, makes it possible to keep an optimal temperature for the operation of the oscillating voltage generator 9 and of its components inside the radio frequency apparatus 1.

Furthermore, the cover 12 makes it possible to reduce thermodynamic and sound pollution produced by the single or many voltage generators 9 present in the radio frequency apparatus 1.

The presence of the cover 12 makes it possible to safely carry out, the complete external cleaning of the radio frequency apparatus 1, also in the cases in which it is foreseen for washing liquids to be used. Indeed, the voltage generator 9, and its components, are protected and insulated from external agents through the cover 12 itself.

The cover 12 comprises a series of side openings 30, that are hermetically closed through corresponding doors 13 (figure 8).

The. doors 13, which can for example be hinged or removable to or from the cover 12, make it possible to access the inside of the upper portion of the thawing module 7 and, in particular, the access to the generator 9 and to its components.

The means 3 for supporting and moving the conveyor belt 2 forward comprise an idle roller conveyor 14 (figures 2, 3, 5 and 6), that is arranged below for supporting the conveyor belt 2, a first roller 15 and a second roller 16, of which at least one is motorised, substantially parallel to one another, suitable for moving the conveyor belt 2 forward.

The first roller 15 and the second roller 16, both rotating around a horizontal axis, are positioned at the opposite ends of the radio frequency apparatus 1. In particular, the first roller 15 is positioned at the inlet section 4 and the second roller 16 is positioned at the outlet section 6.

In one version of the present invention, the second roller 16 is motorised, whereas the first roller 15 is idle.

However, in a further version of the present invention, not illustrated in the figures, the first roller 15 is motorised whereas the second roller 16 is idle.

Again, in a further version of the present invention both the first roller 15 and the second roller 16 can be motorised.

In this last case it is foreseen for there to be synchronisation means of the known type, not shown in the figures, so as to ensure a correct synchronism in the rotation of the two rollers 15, 16, so as to avoid possible damage to the conveyor belt 2.

The motorisation of the first roller 15 and/or of the second roller 16 can be obtained, as a non-limiting example, through an electric motor of the direct- drive type, which is positioned coaxially inside the first roller 15 and/or the second roller 16 or through a transmission comprising an electric motor of the conventional type that is connected through a belt or chain to one end of the first roller 15 and/or of the second roller 16 or, again, through equivalent means that are suitable for motorising the first roller 15 and/or the second roller 16.

In order to keep the conveyor belt 2 under tension, or to recover possible slack that can occur during its operation, it is foreseen for there to be belt- tightening means 17.

In one version of the present invention, illustrated in figure 3 and 4, the belt-tightening means 17 comprise at least one idler cylinder 18, with a horizontal axis, which is positioned at the first roller 15 and/or at the second roller 16.

The idler cylinder 18 is slidingly mounted in a vertical direction on a support 19.

In a further version of the present invention, not shown in the figures, the idler cylinder 18 is slidingly mounted on a support in a horizontal direction.

Therefore, by modifying the position of the idler cylinder 18 along the support 19 it is possible to modify the tension applied to the conveyor belt 2.

The conveyor belt 2 is made from a plastic material 2 that is suitable for coming into contact with the food products.

In particular, such a plastic material is compatible with the electromagnetic fields and, therefore, it can be radiated by them without becoming damaged.

In one version of the present invention, the conveyor belt 2 has a body that is equipped with a double sheet without joints, the resting surface of which is substantially flat.

If there are joints in the conveyor belt 2 it is foreseen for there to be strips of insulating material or similar sealing elements that are placed on the joints themselves.

In such a way possible liquids released from the food products are prevented from dripping inside the joints, avoiding therefore the formation of deposits and the drawbacks previously described.

The conveyor belt 2 has, at the side ends, raised edges 20, that are suitable for holding in possible liquids that are released from the food products during the thawing process.

The raised edges 20 prevent such liquids from dripping at the side of the conveyor belt 2, possibly dirtying the roller table 14 and/or portions of the radio frequency apparatus 1 near to or below the conveyor belt 2.

If they are not removed from the conveyor belt 2 or in general from the radio frequency apparatus 1, such liquids could be a source of bacterial contamination of the food products subsequently positioned on the conveyor belt 2, jeopardising the integrity thereof. Moreover, possible liquids that are not removed from the conveyor belt 2 could dry up during the subsequent thawing processes and cause localised over-heating and/or burning on the surface of the food products.

Consequently, the food products thus altered would not be suitable for subsequent processing and would have to be discarded, thus negatively affecting the overall processing costs.

The radio frequency apparatus 1 comprises washing means 21 (figures 3 and 4) that are suitable for ensuring the correct cleaning of the conveyor belt 2. The washing means 21 can be positioned at the inlet section 4 and/or the central section 5 and/or the outlet section 6 so as to allow it to be washed and/or sanitised.

The washing means 21 comprise a first series of nozzles 22, for emitting washing liquids that are suitable for the use foreseen for the radio frequency apparatus 1, and a series tanks 23 for collecting the liquid emitted by the first nozzles 22 and/or possible impurities present on the conveyor belt 2, as better indicated in the rest of the description.

The first nozzles 22 can be fed through the water mains or through a dedicated washing plant, which is not shown in the figures.

With reference to the embodiment illustrated in figure 3, the collection tanks 23 are positioned below the roller table 14.

The collection tanks 23 can be positioned at the inlet section 4 and/or at the central section 5 and/or at the outlet section 6.

Each collection tank 23, in turn, can comprise a first discharge duct 24.

The first discharge duct 24 makes it possible to convey the washing liquid, possible impurities removed during the washing or the possible leachate held along the conveyor belt 2, outside the radio frequency apparatus 1.

In order to promote the flow and prevent stagnation inside the collection tank 23, the bottom of the latter is suitably shaped and inclined towards the first discharge duct 24 itself.

The single first discharge ducts 24 are aligned along the same side of the radio frequency apparatus 1 or along both the sides thereof.

All the collection tanks 23 and the first discharge ducts 24 have an inclination such as to promote the natural flow by gravity of the collected liquids.

With reference to the embodiment illustrated in figure 4, the first nozzles 22 are positioned inside the single collection tanks 23 and face towards the conveyor belt 2.

Therefore, the first nozzles 22, which are positioned below the conveyor belt 2, make it possible to cleanse the roller table 14 and the lower surface of the conveyor belt 2 itself.

Furthermore, it can be foreseen for there to be a series of first gutters 25, that are positioned at the side with respect to the radio frequency apparatus 1, for collecting the liquids coming out from the single first discharge ducts 24 and convey them towards a second discharge duct 26 outside the radio frequency apparatus 1.

In such a way it is ensured for there to be a high level of cleanliness of the radio frequency apparatus 1, preventing the possible leachate released during the thawing treatment or washing liquids from contaminating portions thereof.

In the lower portion of the radio frequency apparatus 1, near to the support ground, it is foreseen for there to be second gutters 27, which are transversal with respect to the conveyor belt 2.

Such second gutters 27 are foreseen for collecting and conveying possible liquids towards the first gutters 25.

At the end of the inlet section 4 and/or of the outlet section 6, where the conveyor belt 2 is partially wound around the first roller 15 and/or the second roller 16, respectively, it is foreseen for there to be an inclined plane 28 that is suitable for collecting possible liquids that are present on the conveyor belt 2 and for conveying them towards one of the second gutters 27.

For such a purpose, the inclined plane 28 is suitably shaped so as to. convey the liquids and/or possible residue, which fall by gravity from the conveyor belt 2, towards the second adjacent gutter 27.

Also in this case all the elements 25-28 of the radio frequency apparatus 1, foreseen for collecting and conveying liquids, have an inclination that promotes the natural flow by gravity of the liquids.

The washing means 21 comprise second nozzles 29 that are positioned at the first roller 15 and/or at the second roller 16.

The second nozzles 29 make it possible to cleanse the upper surface of the conveyor belt 2.

With reference to the outlet section 6, illustrated in figures 3 and 4, the second nozzles 29 are positioned at the second roller 16, in a position that is interposed between the conveyor belt 2 and the inclined plane 28.

In particular, the second nozzles 29 are positioned above the inclined plane 28 and below the conveyor belt 2. Therefore, after having been emitted by the second nozzles 29 and having hit the conveyor belt 2, the washing liquid falls by gravity on the inclined plane 28 and is conveyed towards a second gutter 27, that is adjacent to the first inclined plane 28 itself.

In such a way it is possible to keep the conveyor belt .2 clean also during the operation of the radio frequency apparatus 1, i.e. during the thawing treatment of the food products, thus ensuring a high productivity of the radio frequency apparatus 1 itself .

Furthermore, in order to ensure the cleaning inside of the central tunnel of the radio frequency apparatus 1 it is foreseen for there to be a washing plant, not shown in the figures, that is integrated with the control circuit of the at least one voltage generator 9.

The washing plant is installed, at the central portion 5, in the upper portion of the frame 8, above the conveyor belt 2, and comprises a series of nozzles that are fed through the water mains or a dedicated cleaning plant.

The washing plant makes it possible to automatically or semiautomatically or manually wash the entire inner portion of the central tunnel of the radio frequency apparatus 1, i.e. the central portion 5. As an example, the inner washing can be carried out automatically between one thawing cycle and the subsequent one or at predetermined maintenance intervals .

The radio frequency apparatus 1 for thawing food products according to the present invention therefore makes it possible to avoid the drawbacks of the prior art .

In particular, it is possible to cleanse and sanitise the conveyor belt 2 during the thawing process of the food products, without requiring the radio frequency apparatus 1 to be stopped, thus optimising the productivity thereof .

Moreover, the presence of raised side edges 20 along the conveyor belt 2 makes it possible to hold the possible leachate liquid released from the food products during the thawing process, preventing it from coming into contact with and dirtying portions of the radio frequency apparatus 1 adjacent to the conveyor belt 2.

The presence of a series of collection tanks 23, of first and second discharge ducts 24, 26 and of first and second gutters 25, 27 makes it possible to collect and convey the used washing liquids, possible residue removed and/or leachate released from the food products outside from the radio frequency apparatus 1. Moreover, since the entire lower part of the radio frequency apparatus 1 is accessible, also through the openings 10, the collection tanks 23, the first and second discharge ducts 24, 26 and the first and second gutters 25, 27 can be cleaned and sanitised easily, and in an accurate manner.

The presence of a washing plant inside the central tunnel of the radio frequency apparatus 1 makes it possible to clean it completely and effectively.

Therefore, it is possible to ensure a high level of cleanliness and hygiene both inside and outside the radio frequency apparatus 1.

The cover 12 of the oscillating voltage generator 9 and of its components ensures a high level of safety to the worker during the operation of the radio frequency apparatus 1 and during the washing and/or sanitising steps thereof.

With reference to the washing means 21, the second nozzles 29 make it possible to keep clean the upper surface of the conveyor belt 2, on which the food products to be thawed are rested, also during the normal operation of the radio frequency apparatus 1, i.e. during the thawing process.

Therefore, the integrity of the food products positioned on the conveyor belt 2 itself is preserved in terms of bacterial contamination, of surface appearance and of thawing homogeneity.

Indeed, the absence of dried residues on the conveyor belt 2 makes it possible to avoid, during the thawing process, possible localised overheating and/or burning on the surface of the food products, which could alter the integrity thereof.

Furthermore, the radio frequency apparatus 1 for thawing food products according to the present invention, is foreseen for ensuring a high homogeneity of the thawing treatment along the various sections of the oven, since it comprises at least one thawing module 7, that is provided with a oscillating voltage generator 9, and with relative control components, which are positioned in direct proximity of the conveyor belt 2.

The invention thus conceived can undergo numerous modifications and variants all covered by the inventive concept.

Claims

Radiofrequency apparatus (1) for thawing food products, using an electromagnetic field of the oscillating type, comprising a continuous conveyor belt (2), on which said food products are arranged, means (3) for supporting and moving said conveyor belt (2) forward, an inlet section (4) for introducing said food products to be thawed, a central section (5) , defining a tunnel in which the thawing of said food product occurs, an outlet section (6), from which said thawed food products exit, at least an oscillating voltage generator (9) for generating said electromagnetic field of the oscillating type, characterised by comprising means (21) for washing and/or sanitizing said conveyor belt (2) and/or said inlet section (4) and/or said central section (5) and/or said outlet section (6).

Radiofrequency apparatus (1) for thawing food products according to claim 1, wherein said washing means (21) comprise first nozzles (22), for dispensing a washing fluid, and tanks (23) for collecting said washing fluid, arranged below said first nozzles (22). Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, wherein said washing means (21) comprise second nozzles (29) for cleaning and/or sanitizing the upper surface of said conveyor belt (2).

Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, wherein said first nozzles (22) and said second nozzles (29) are supplied through a water main or through a dedicated cleaning plant .

Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, wherein each of said collecting tanks

(23) comprises at least a first discharge duct

(24) , adapted to convey said washing fluids and any impurity outside said radiofrequency apparatus (1) .

Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, comprising a set of first gutters (25), arranged at the side of said radiofrequency apparatus (1) , for conveying said washing fluids, and any impurity, flowed out from at least one of said first discharge ducts (24), towards at least a second discharge duct (26) . Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, comprising second gutters (27) arranged transversally and below said conveyor belt (2). Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, wherein said support and forward moving means (3) comprise an idle roller conveyor (14), arranged below said conveyor belt (2) to support it .

Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, wherein said support and forward moving means (3) comprise a first (15) and a second (16) horizontal axis rollers, at least one of which being motorised, said rollers (15, 16) being arranged at the ends of said radiofrequency apparatus (1).

Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, comprising an inclined plane (28), arranged below said first roller (15) and/or said second roller (16), respectively, at said inlet section (4) and/or at said outlet section (6), for conveying any fluid dispensed from said food products or any washing fluid towards at least one of said second gutters (27) .

11. Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, comprising at least an element (12) for covering said central section (5) and protecting said oscillating voltage generator (9) and the components thereof.

12. Radiofrequency apparatus (1) according to one of the previous claims, wherein said cover element (12) is substantially parallelepiped- shaped and comprises a number of openings (30), arranged along the sides of said cover (12), for accessing said voltage generator (9) and the components thereof.

13. Radiofrequency . apparatus (1) for thawing food products according to the previous claim, comprising side doors (13), being releasable or hinged to said cover element (12) closing said openings (30) in an hermetic manner.

14. Radiofrequency apparatus (1) for thawing food products according to one of the previous claims, wherein said central section (5) has side openings (10) for accessing said tunnel.

15. Radiofrequency apparatus (1) for thawing food products according to the previous claim, comprising movable panels (11) for sealingly closing said side openings (10) .

16. Radiofrequency apparatus (1) for thawing food products according to the previous claim, wherein said movable panels (11) are made of a heat-insulating material.

17. Radiofrequency apparatus (1) for thawing food products according to one of the previous claims wherein said oscillating electromagnetic field applied to the food products has a frequency ranging from 1 MHz to.1 GHz.