WO2007039676A1 - Method and device for cooking food products with microwaves in a tray-type packing, and packaging obtained by carrying out the invention - Google Patents

Abstract

The invention concerns a device for cooking food products with microwaves, comprising a tray-type recipient (1) having a hollow part forming a container (4) for receiving the product to be cooked and an upper edge (3) for hermetically fixing a covering film (2), characterized in that the upper edge of the tray is provided with an degassing opening (7) fitted with a valve or flapper (8) placed on the lower face or outer face of the edge, and in that the edge (3) of the tray (1) is preferably slanted toward the portion of the tray forming the container (4), at least one area bordering the upper opening (5) of the container (4), and in that the degassing opening (7) is provided in the slanted surface of the edge (3).

Description

Method and device for cooking food products in microwaves, in a packaging of the tray type, and packaging obtained by their implementation.

The present invention relates to a method and a device for microwaving food products in a packaging of the tray type. It also applies to cooked food packages, obtained by the practice of this method and this device, and to a microwave cooking apparatus arranged for the implementation of said method and of said device.

More specifically, the invention relates to the field of packaging consisting of a container or tray made of a semi-rigid plastic material containing a precooked food product and sealed with a flexible film sealed on the upper rim of said container. Many food products or culinary preparations are currently marketed under such packaging, including a large number of vegetables. These packages prepared by agri-food processors, upstream of the retail channels, allow conservation of products without health risk for a period of the order of a few weeks, usually about twenty days, before consumption.

According to the traditional methods of producing the packaging of the aforementioned kind, the raw food product, fresh or frozen (vegetable or other culinary preparation), is introduced into the tray which is then hermetically closed by a flexible plastic opercular film provided with an orifice degassing device provided with a valve, for example a valve of the type described in documents FR-2,796,924, FR-2,656,280, FR-2,698,082 or EP-0,023,703. This is done after cooking the product thus conditioned, for example by passing through an autoclave.

During cooking, the steam coming from part of the water contained in the products or in the sauce accompanying the cooking preparation, under the action of heat, creates a pressure inside the packaging which causes the opening of the degassing orifice and the evacuation of part of this vapor, through this orifice. At the end of cooking, the degassing orifice is sealed by means of the valve and the packaging can be routed to a control and shipping station.

However, the filling of the packaging, at the end of cooking, occurs at a temperature much lower than 100 °, so that condensation of the remaining vapor inside the packaging can not be avoided. entry of a volume of air into the latter, before the hermetic closure of the packaging, the presence of this volume of air confined in said packaging constituting, of course, an oxidation factor of the product.

On the other hand, the positioning of the degassing valve on the shrinkable opercular film, has a risk of irremediable leakage, which would inevitably lead to recontamination and deterioration of the treated product.

The invention proposes to remedy these drawbacks.

According to the process of the invention:

raw products, fresh or frozen, are housed in a tray-type container having a flange provided with a degassing orifice provided with a valve or valve disposed on the underside or outer face of said flange;

the upper opening of the tray is sealed hermetically by means of a barrier film;

the product thus conditioned is then cooked or treated by passing the packaging through a microwave tunnel oven equipped with an outlet trap, so that, during cooking, the pressure resulting from the vaporization of the water contained in the product or in the culinary preparation, under the effect of heat, causes the opening of the valve and rapid evacuation of the steam generated inside the packaging;

- Finally, the degassing valve is closed during the passage of the conditioning in the exit trap of the microwave oven-tunnel, at a temperature greater than 85 °, for example at a temperature of about 100 °, so that immediately after cooking, a re-condensation of the vapor occurs inside the sealed package resulting in the creation of a vacuum air that sucks the barrier film cover until it comes to press against the products contained in the tray.

The cooked products are thus vacuum-packed when they leave the cooking appliance.

According to an implementation of the invention, introducing a metered quantity of water, flavored or not, into the tray, before sealing the packaging by means of the cover film and passage into the cooking appliance.

According to a preferred implementation of the process of the invention, the products are introduced into a tray having a rim inclined towards the center of the tray, so that an annular space is formed between the cover film and the surface. said inclined flange and that the creation of an air gap inside the packaging obtained at the outlet of the cooking apparatus has the effect of pressing the cover film along the inclined plane constituted by this rim and, therefore, to obstruct, from the inside, the degassing orifice, thus reinforcing the safety of closing the packaging in the event of failure of the valve located on the outer face or lower face of said flange.

The device according to the invention comprises, on the one hand, a container of the container type comprising a hollow part forming a container or receptacle intended for receiving a raw product, fresh or frozen, and an upper rim, and on the other hand, a cover barrier film, intended to be sealed on said rim, this device being remarkable in that the rim of the tray is provided with a degassing orifice provided with a valve or valve disposed on the lower face or outer face of said flange.

According to a preferred implementation of this device, the edge of the tray is inclined towards its container part, at least in a zone bordering the upper opening of said portion, and the degassing orifice is formed in the inclined surface of said flange.

According to another characteristic arrangement, the inclined edge of the tray is bordered by a flat surface on which is sealed the cover barrier film.

According to another important feature of the invention, the side wall of the tray is constituted by one or more convex surfaces, preferably by a spherical surface or by spherical surface portions.

The convex, preferably spherical, shape of the tray significantly improves its resistance to deformation when successively subjected to pressure and depression during the cooking and cooling phases, respectively. This allows to advantageously reduce the diameter of the degassing hole and, consequently, to increase the temperature during cooking and, after cooking, to hermetically close the tray at a temperature above 85 °.

The cooking apparatus for implementing the method according to the invention comprises a microwave tunnel oven equipped with an exit trap, and this apparatus is remarkable in that means allowing the automatic closing of the valve. degassing are installed in said outlet trap.

Thanks to the invention, it is possible to cook and vacuum packaging and continuously many products (various vegetables) or food preparations (ready meals), at rates and under conditions of remarkable safety.

In addition, the invention allows the reheating of the content by the consumer, without changing the container, the latter, depending on the qualities and specificities of the content that can be adapted to reheat by microwave or convection. The above and other objects, features and advantages will become more apparent from the following description and accompanying drawings, in which:

Figure 1 is a perspective representation, in an exploded top view, of a first exemplary embodiment of packaging type tray according to the invention.

Figure 2 is a top view of an example of packaging obtained by means of this package, before cooking.

Figure 3 is a bottom view of Figure 2.

Figure 4 is a side view, and in vertical section of the package.

Figure 5 is a partial view from below, on a larger scale, of the rim equipped with a degassing valve, according to the invention.

Figure 6 is a sectional view along the line 6-6 of Figure 5, showing the valve in the closed position.

Figure 7 is a view similar to Figure 6, showing the degassing valve in the open position.

Figures 8 to 12 are front views, schematic, illustrating different phases of Ia implementation of the packaging method according to the invention.

Figure 13 is a detail view, on a larger scale, and in section, showing the double sealing of the degassing orifice by the movable tongue of the valve and the cover film, at the end of cooking.

FIG. 14 is a perspective view of a second advantageous embodiment of the cooking and packaging tray according to the invention, shown at the end of the treatment.

Figure 15 is a top view of this tray, before the treatment, the dotted line showing the concave shape obtained after treatment. Fig. 16 is a sectional view taken along line 16-16 of Fig. 15.

Referring to the drawings to describe examples of interest, although not limiting, implementation of the method and embodiment of the packaging and the microwave cooking apparatus according to the invention.

The packaging used for the implementation of the invention is of the tray type, essentially comprising:

- On the one hand, a container or container 1 made of any rigid or semi-rigid material, transparent to microwaves, impervious to water and able to withstand the heat released by the microwave cooking ovens designed for the industrial preparation of precooked food products, that is to say practically at least equal heat and generally above 100 °, not causing any deformation or migration of their components to food or water contained in the packaging made; the trays may be advantageously obtained by thermoforming any semi-rigid food plastic material fulfilling the aforementioned requirements, such as, for example, polypropylene (PP) or polyethylene terephthalate glycol (PET).

- On the other hand, a cover film 2 also transparent to microwaves and having barrier properties (liquid and gas tightness), this film may be constituted by a transparent film of plastic material, for example polyethylene, PVC, polyethylene terephthalate (PET) polyolefin anti-fog, or the like, having the qualities required for their use such as flexibility, extensibility, compliance with food regulations, resistance to heat released by microwaves, resistance to pressure generated by steam, etc.

The cover film 2 being hermetically fixed by heat sealing on the upper edge of the tray 1, said film and said tray must be made of materials compatible with such a method.

The container may have various forms: parallelepiped, frustoconical, truncopyramidal, cylindrical, and others; it can be realized under the shape of a disposable plate, circular, square, hexagonal or other. However, according to an advantageous embodiment described hereinafter, the side wall of the container 2 consists of one or more convex surfaces and, preferably, a spherical surface or portions of spherical surfaces. Its volume may vary, but it must remain compatible with microwave cooking. Depending on the qualities and specificities of the products, the container must be made of a material allowing the heating of the contents by microwaves or by convection.

The tray 1 has an upper flange 3 inclined toward its hollow central portion 4. This inclined flange may be more or less wide for presentation reasons and it forms, for example, an angle α of the order of

165 ° with the plane P-P in which is included the upper opening 5 of the hollow part of the tray (Figure 4).

According to an advantageous embodiment, the inclined flange 3 is bordered by a flat surface consisting of a narrow peripheral strip 6 for fixing the cover film 2 after introduction of the food product to be cooked.

In this way, when the cover film 2 has been sealed, for example by heat-sealing, on the peripheral flat surface 6, an annular space E is formed between said film 2 and the upper surface of the inclined flange 3.

According to a characteristic arrangement of the invention, a degassing orifice 7 is provided in the flange 3 and this orifice is provided with a valve or valve 8 disposed on the outside or bottom side of the container. This hole 7 may have a diameter of the order of one to a few millimeters, for example of the order of 3.5 mm. The valve or valve 8 may be constituted by a self-adhesive tab 8a of flexible material firmly fixed under the flange 3 via one of its ends and the remaining movable portion may be adhesively bonded to the outer surface defining the degassing hole, so as to seal it, or be spaced from said hole so as to allow rapid evacuation of the steam generated inside the tray, during cooking. Preferably, the degassing hole 7 and the valve 8 are arranged near the connecting line of the inclined flange 3 and the flat peripheral surface or beach 6.

According to the process of the invention:

- raw, fresh or frozen food products A, such as, for example, various vegetables (potatoes, carrots, leeks, green beans, artichokes, asparagus, cauliflower, corn on the cob, zucchini, aubergines, endives, broccoli) , etc., or a mixture of these products), preparation of cooked meal, or other, are housed in the hollow portion 4 of the tray 1 (Figure 8);

the upper opening of the tray is hermetically sealed by means of the cover barrier film 2 fixed by heat-sealing to the flat peripheral region 6 of the container (FIG. 9);

the product is cooked or treated by passing the packaging in a microwave tunnel oven equipped with an outlet trap, so that, during cooking, the pressure resulting from the vaporization of the water contained in the product or in the tray, under the effect of heat, causes the swelling of the cover film 2 due to the expansion of the space enclosing the products A, the opening of the valve 8 and the rapid evacuation of the steam generated inside the package (Figure 10);

- The degassing valve 8 is then automatically closed and kept closed for a few seconds (for example for a period of the order of 1 to 5 seconds), during the passage of the packaging in the exit trap of the microwave tunnel furnace. wave (FIG. 11) at a temperature greater than 85.degree., for example at a temperature of about 100.degree., at the end of cooking, a condensation of the vapor occurs rapidly inside the hermetically sealed package, immediately at its temperature. leaving the cooking apparatus, causing the creation of an air gap which holds the valve 8 in the closed position and sucks the barrier film cover 2 towards the bottom of the tray, until he comes to flatten himself against the products contained in it (figure 12). At the outlet of the cooking appliance, the degassing valve 8 is securely welded, for example by heat-welding or ultrasound on the underside of the rim 3 of the tray, which makes it possible to avoid any risk of contact. cooked products contained in the latter with the outside.

According to this method, the closing of the degassing valve takes place automatically without stopping the movement of the tray between its entry into the cooking appliance and its exit from the latter.

According to an implementation of the invention, for example applicable to the cooking of low hydrated products, it is expected to introduce a quantity of water, flavored or not, in the tray 1, before closing thereof by means of cover film 2 and cooking products A.

The invention also applies to a microwave cooking apparatus of the type consisting of a tunnel oven 9 and an exit trap traversed by the packaging moved by a conveyor 12 during the cooking process, this apparatus being remarkable by the fact that means allowing the automatic closing of the degassing valve 8 are installed in said outlet trap. ^•

According to an interesting embodiment, the closing of the valve is performed automatically during the passage of the packaging in the exit trap of the microwave oven-tunnel 9, for example by means of a ramp 11 fixedly installed in said trap outlet, on the path of the packages leaving the tunnel oven 9, this ramp 11 being arranged such that the underside of the rim 3 of the packaging which is equipped with the valve is slid on said ramp which exerts a counter-support allowing press the movable tongue 8a of the valve 8 against the underside of the rim, thus ensuring the closure of the degassing orifice.

Note that under the suction effect created by the vacuum of air, the cover film 2 is pressed against the inner surface of the inclined flange 3 of the tray. It thus obstructs the inside of the degassing orifice 7, as shown in FIG. 13; this double closing of said orifice, reinforcing the safety of the hermetic closure of the packaging in the event of failure of the valve 8. According to a very advantageous embodiment illustrated in Figures 14 to 16, the side wall 13 of the tray is constituted by one or more convex surfaces, preferably by a spherical surface or by portions of spherical surfaces. In this way, the pressure that supports the body of the tray is equal in all points of the body.

According to one embodiment of the method, the bottom 14 of the tray may initially be flat, so that, during cooking, under the effect of the pressure of the steam, it may take a slightly convex shape and then, during the depression caused by the hermetic closure of the degassing valve 8 and the cooling resulting in a re-condensation of the vapor, it may take a concave shape.

Similarly, the body 13 of the tray may initially have, symmetrically, around its periphery, at least two planar faces 15, capable of increasing the physical strength of said tray. These faces can swell with a convex effect, under the pressure of steam, during cooking, then retract with a concave effect, under the effect of the depression caused by the hermetic closure of the degassing valve 8 and the cooling resulting in a recondensation of the steam.

This process makes it possible to advantageously and homogeneously reduce the interior volume of the tray. It avoids, in this way, the tray, after cooking, appear insufficiently filled and deformed. It thus secures the presentation of packaging to consumers.

Advantageously, the rim 3 of the tray 1 is provided with a second orifice 16 preferably disposed diametrically opposite to the degassing orifice. This orifice is closed by a reheating valve 17 constituted by a detachable tongue fixed, by any suitable method, on the underside of the rim 3 under conditions such that this tongue remains in the closed position of the reheat orifice during any the cooking and packaging process; but it can then be easily detached by the consumer when it wants to warm the contents of the tray before consuming it.

Claims

Process for cooking microwavable food products in container-type packaging, characterized in that: - raw products, fresh or frozen (A), are housed in a container (1) of the kind of tray having a flange (3) provided with a degassing orifice (7) provided with a valve (8) arranged on the lower face or outer face of said flange (3); - hermetically closing the upper opening of the tray (1) by means of a barrier film (2); - Then the cooking or processing of the product (A) and conditioned by passing the conditioning in a microwave oven (9) equipped with an outlet trap, so that during cooking, the pressure resulting from the vaporization of the water contained in the product, or in the culinary preparation, under the effect of heat, causes the opening of the valve (8) and the rapid evaporation of the steam generated inside said conditioning; the degassing valve (8) is closed and kept closed during the passage of the conditioning in the output trap of the microwave oven-tunnel, at a temperature above 85 °, so that at the exit of said trap of at the outlet, an immediate condensation of the vapor occurs within said hermetically closed package, causing the creation of an air gap which sucks the barrier barrier film (2) until it comes to itself. press against the products (A) contained in the tray (1). 2. Method according to claim 1, characterized in that one introduces a metered quantity of water, flavored or not, in the tray (1), before the hermetic closure of the packaging by means of the cover film (2) and passage in the cooking apparatus (9). 3. Method according to one of claims 1 or 2, characterized in that the products (A) are introduced into a tray (1) having a flange (3) inclined towards the container portion of the tray, so an annular space (E) is provided between the cover film (2) and the upper surface of said inclined flange (3) and that the creation of an air space inside the package at the end of the baking process, has the effect of pressing said film (2) on the inclined plane constituted by this rim and, consequently, to obstruct, from the inside, the degassing orifice (7), thus reinforcing the safety hermetic sealing of the packaging in case of failure of the valve (8) located on the outer face or underside of said flange (3). 4. Method according to any one of claims 1 to 3, characterized in that the raw products, fresh or frozen (A) are housed, initially, in a container (1 ') of the kind trays whose side wall (13) is constituted by one or more convex surfaces, preferably by a spherical surface or by spherical surface portions. 5. Method according to claim 4, characterized in that the raw products, fresh or frozen (A) are housed, initially, in a container (1 ') of the kind trays whose bottom (14) is initially flat, so that when said container is depressed at the end of the cooking process, it takes a concave shape. 6. Method according to one of claims 4 or 5, characterized in that the raw products, fresh or frozen (A) are housed, initially, in a container (1 ') of the kind trays whose periphery (13) has, symmetrically, at least two plane faces (15), so that when said container is placed under vacuum at the end of the cooking process, these faces take a concave shape. 7. Method according to one of claims 1 to 6, characterized in that the tray (1, I ') is provided with a second orifice (16) closed by a detachable heating valve (17) fixed on the tray, under conditions such that the heating valve remains in the closed position of said second orifice (16) throughout the cooking and packaging process, but it can then be easily detached by the consumer when reheating the contents of said tray. 8. Packaging of precooked food products, characterized in that it is obtained by carrying out the method of any one of claims 1 to 7. 9. Device for cooking microwavable food products, comprising a container (1) of the container type comprising a hollow portion forming a container (4) for receiving the product to be cooked and an upper rim (3) intended for fixing hermetic membrane of a cover film (2), characterized in that the upper edge of said tray is provided with a degassing orifice (7) provided with a valve or valve (8) disposed on the underside or outer face of said rim. 10. Device according to claim 9, characterized in that the rim (3) of the tray (1) is inclined towards the portion of said container tray (4), at least in a zone bordering the upper opening ( 5) of said container (4), and in that the degassing orifice (7) is formed in the inclined surface of said flange (3). 11. Apparatus according to claim 10, characterized in that the inclined flange (3) of the tray is surrounded by a flat surface (6) for sealing the cover film (1). Device according to claim 11, characterized in that the degassing orifice (7) and the degassing valve (8) are arranged close to the connecting line of the inclined flange (3) and the peripheral plane ( 6). 13. Device according to any one of claims 9 to 12, characterized in that the side wall of the tray (1 ') is constituted by one or more convex surfaces (13), preferably by a spherical surface or by portions. spherical surface. 14. Apparatus according to claim 13, characterized in that the tray (1 ¹ ) has a flat bottom (14) capable of taking a concave shape at the end of the cooking process. 15. Device according to one of claims 13 or 14, characterized in that the periphery (13) of the tray (1 ') has, symmetrically, at least two planar faces, capable of taking a concave shape at the end. of the cooking process. 16. Device according to any one of claims 9 to 15, characterized in that the tray (1, l ') is provided with a second orifice (16) closed by a detachable heating valve (17) fixed on the tray under conditions such that the heating valve remains in the closed position of said second orifice (16) until the end of the cooking and conditioning process but can then be easily detached by the consumer at the time of reheating the contents of said tray. An apparatus for microwaving products packaged according to the process of any one of claims 1 to 7, and / or a package made according to any one of claims 9 to 16, and comprising an oven microwave tunnel (9) equipped with an exit trap, characterized in that means (11) for closing the degassing valve are installed in said outlet trap. 18. Apparatus according to claim 17, characterized in that the means ensuring the automatic closing of the degassing valve (8) are constituted by a ramp (11) fixedly installed in the outlet trap on the path of the packages exiting the furnace. tunnel (9), this ramp being arranged so that the underside of the flange (3) of said packaging which is equipped with said valve, slides on said ramp (11) during the passage of the latter in the outlet trap.