EP0024605A1 - Package for food products - Google Patents

Abstract

The invention relates to a packaging for food products intended for the controlled heating or cooking of dishes prepared in hot air, convection ovens, household ovens and microwave ovens. The package comprises a tray (1) having a bottom (2) and an upwardly extending peripheral wall (3) which is curved outward at its upper part, defining a peripheral edge (4) extending horizontally, said peripheral wall and edge being in, or at least their inner surface being covered with a material (5) reflecting it or opaque to microwave radiation and said bottom (2) being made of a material transparent to micro radiation -waves or can be easily removed. The packaging is specially adapted for cooking in microwave ovens fitted with infrared grills.

Description

The present invention relates to a package for the controlled heating or cooking of food prepared in hot air, convection, household and microwave ovens.

The rapid growth in the sale of microwave ovens to households and the development of industrial catering have changed the conditions for making ready meals, bringing benefits as well as problems. The advantages are obvious and linked to rapid heating by microwaves, which makes frozen products even more convenient to use.

• - La barquette métallique traditionnelle est opaque au rayonnement micro-ondes et ne convient pas dans les fours à micro-ondes dépourvus de protections pour le magnétron, car il peut y avoir formation d'arc dans la cavité du four, ce qui peut endommager le magnétron.
• - La cuisson de certains produits est très inégale du fait de la faible profondeur de pénétration des micro-ondes, parce que les métaux ne sont pas transparents aux micro-ondes et le chauffage intervient depuis le haut vers le bas. Cela conduit, en particulier pour les produits surgelés, à une cuisson inhomogène avec une couche du dessous froide et également encore congelée tandis que la couche supérieure est trop cuite et inacceptable (sèche ou brûlée).

There are mainly two problems:

• - The traditional metal tray is opaque to microwave radiation and is not suitable in microwave ovens without protections for the magnetron, as there may be arcing in the oven cavity, which can damage the magnetron.
• - The cooking of certain products is very uneven due to the shallow penetration depth of the microwaves, because the metals are not transparent to the microwaves and the heating takes place from the top to the bottom. This leads, in particular for frozen products, to inhomogeneous cooking with a cold bottom layer and also still frozen while the top layer is overcooked and unacceptable (dry or burnt).

Most of the recent development work in the packaging industry in connection with cooking microwave have addressed the problem of selective cooking of multicomponent meals in which the individual components of the meal require different amounts of microwave energy.

For example, U.S. Patent No. 3,865,301 describes a container with openings, suitable for several ingredients of a sandwich-type food product, which must be heated or baked to different degrees, which container is opaque to radiation microwaves excluding windows transparent to radiation.

U.S. Patent No. 4,081,646 illustrates a tray made of microwave-transparent material and having several compartments, a cover formed of microwave-transparent material and suitable for the tray, and a box with openings having microwave-opaque walls and openings at predetermined locations, into which the tray and the lid are inserted, so that a control is obtained of the amount of radiation received by each of the individual components of the meal.

In previous developments, very little attention has been paid to the problem of inhomogeneous cooking of a dish prepared in a package comprising a single compartment or a tray in a microwave oven.

Aluminum trays are used without problems in household ovens but are not suitable for microwave ovens.

Trays of other materials are also used (plastic, cardboard covered with material plastic) and cooking, e.g. in a cardboard tray, allows a much more homogeneous cooking and a better quality result in a microwave oven.

But not all of these packages are completely satisfactory, because the cooking is still inhomogeneous because of the particular shape of the products and, for example. the cardboard trays covered with polyester do not resist surface browning, which is important for many types of prepared products. In addition, most modern microwave ovens are now equipped with grills. When the cardboard tray is exposed to grill temperatures (above 200 ^o C) in household ovens or in microwave ovens with an infrared grill, the cardboard will dehydrate and deteriorate, becoming brown and brittle. The current situation is therefore problematic, because the existing trays cannot be used satisfactorily at the same time in microwave ovens and in conventional household ovens.

The main object of the present invention is to provide a packaging in the form of a tray which can be used in hot air, convection ovens, in household ovens at temperatures up to 300 ° C. and also in all types. microwave ovens. Another object of the present invention is to provide a package in the form of a tray which gives excellent temperature distribution and minimizes the effects of arcing and sparking.

The invention relates to a packaging for food products intended for the controlled cooking or heating of food prepared in hot air, convection, household and microwave ovens, comprising a tray consisting of a bottom. and a peripheral wall risk extending upwards, said wall being curved towards the outside in its upper part, thus defining a peripheral edge extending horizontally, the wall or at least its internal surface or the upper part thereof constituting the horizontal edge as well as the parts of it situated in the corners being in or covered with a material reflecting / / opaque to microwave radiation and said bottom being made of a material transparent to microwave radiation or capable of being remove easily.

The following description will make the invention easier to understand with reference to the drawings which illustrate preferred embodiments.

• - la figure 1 est une perspective cavalière d'une première forme d'exécution de l'emballage sans couvercle,
• - la figure 2 est une coupe d'une partie de la forme d'exécution de l'emballage, de la figure 1 avec un premier couvercle,
• - la figure 3 est une coupe d'une partie d'une variante d'exécution de l'emballage avec un deuxième couvercle,
• - la figure 4 est une vue de dessus d'une partie de l'emballage de la figure 3 montrant une partie du bord de la barquette sans couvercle,
• - la figure 5 est une coupe d'une partie d'une seconde variante d'exécution de l'emballage avec le couvercle de la figure_' 3 et
• - la figure 6 est une vue de détail et en perspective d'une troisième variante d'exécution de l'emballage sans couvercle.

In the drawings:

• FIG. 1 is a perspective view of a first embodiment of the packaging without cover,
• FIG. 2 is a section of part of the embodiment of the packaging, of FIG. 1 with a first cover,
• FIG. 3 is a section through part of an alternative embodiment of the packaging with a second cover,
• FIG. 4 is a top view of part of the packaging of FIG. 3 showing part of the edge of the tray without a lid,
• - Figure 5 is a section through part of a second alternative embodiment of the packaging with the cover of Figure _' 3 and
• - Figure 6 is a detail and perspective view of a third alternative embodiment of the packaging without cover.

In the figures, the tray is produced for example by stamping in a PEERLESS machine or for example by folding a transparent material in the microwave, such as for example. cardboard or cardboard covered with a layer of plastic. It can also be obtained by injection or thermoforming of a plastic material or a cardboard and plastic composite material, preferably a polyester, for example polyethylene or polybutylene terephthalate, a polyolefin, for example polybutylene, polymethylpentene or polypropylene, or suitable combinations of these materials.

The tray comprises a bottom 2 and a peripheral wall 3 ending in a horizontally extending edge 4. The edge 4 is partially covered (Fig. 4) or completely (Fig. 5) with a material reflecting them or opaque to micro -waves such as aluminum foil. The peripheral wall 3 is covered with a layer of material 5 which can be placed in different ways, provided that it acts as a reflector of the microwave radiation towards the center of the tray. Thus the wall 3 can be completely covered (Fig. 1) or partially, for example in a region surrounding each of the corners (Fig. 6, number 5) of a material 5. The metal sheet can be laminated or fixed to the material transparent to microwaves or applied when stamping the tray or after stamping or folding the tray.

The tray can be closed with an aluminum cover 6 as shown in Figure 2. In this case, the cover is removed just before cooking, for example by means of a conventional pull-out pull tab or not shown.

Figures 3 and 4 show an alternative embodiment of the packaging, in which the tray comprises cardboard walls 2 and 3 covered with a polymer sheet 7 on their inner surface, which is partially laminated with a sheet of aluminum 5. Only part of the horizontal edge 4 is covered with aluminum, the external part 8 serving as a welding surface. The outer part 8 of the edge 4, where the aluminum sheet 5 ends, is provided with a line of peripheral perforations 9, so that the outer part of the edge is connected to the tray only by narrow bridges of matter. The tray is closed by a cover 6, which is made of cardboard 10 covered with a polymer film 11. Alternatively, the cover may be a sheet of polymer. The edge 12 of the cover 6 is thermally sealed to the outer part 8 of the edge 4. When the packaging is opened, the outer part 8 of the edge 4 is torn off at the same time as the cover 6, the cover preferably being provided with 'a tear-off tab not shown in the drawing. This leaves a protective layer of material 5 over the entire horizontal edge 4. It is obvious that the perforation must have an exact design, so that the tray once opened has clean edges and that it can be opened easily. The tray must also have satisfactory strength and rigidity.

FIG. 5 shows a second alternative embodiment of the packaging which differs from that of FIG. 3 in that the entire surface of the horizontal edge is covered with aluminum foil 5, for example laminated, the metal part then also being provided with a line of perforations 9. In this case, the cover 6 may be made of cardboard covered with a polymer sheet, for example of the ionomer type (SurlynG9), laminable on an aluminum sheet.

Although the drawings show rectangular shaped packages, these could be square or circular. Also, the outer surface of the wall of the tray and the peripheral edge can be covered with aluminum to prevent them from deterioration by heat and to contribute to the rigidity of the carton.

Alternatively, the packaging can be entirely metallic, for example stamped in a single aluminum sheet and have a bottom which can be easily removed, for example. by means of an easy opening.

In this case, the cover is removed and the bottom torn off, for example. by means of a tear strip formed by lines of weakness just before cooking and the packaging containing the food placed on a ceramic plate or tray for cooking.

Obviously, the principle of the invention can be applied to trays having multiple compartments. In this case, the partition walls are made of, or partially or totally covered as indicated above with a reflective material. Microwave radiation.

As a variant, the packaging may include a bottom made of cardboard or of a composite cardboard-plastic material fixed, for example welded to a peripheral wall in the form of a frame consisting solely of aluminum foil.

The packaging according to the invention is preferred For refrigerated or frozen products.

Tests conducted in a conventional household oven at temperatures up to 300 ° C have shown that the walls and the edge are protected by the aluminum foil against browning and deterioration.

• 1) la barquette selon l'invention,
• 2) une barquette conventionnelle en aluminium et
• 3) une barquette en carton recouverte de polyester,

on a obtenu les résultats suivants :

• 1) Distribution régulière de la température avec de légères variations de 65 à 80°C. Produit de bonne qualité sans phénomène de sur-cuisson et l'intérieur du produit suffisamment cuit. La qualité est tout à fait équivalente à celle obtenue dans un four ménager conventionnel.
• 2) La couche du fond est toujours froide avec de la glace résiduelle, cependant que la couche supérieure est trop cuite, brûlée par endroits. Distribution de la température de 0 à 30°C.
• 3) Les coins sont trop cuits et quelque peu brûlés, cependant que la partie médiane des filets de poisson est encore crue. Distribution de la température de 20 à 100°C. La barquette en carton est pratiquement noire sur les bords et détériorée.

When you have cooked in a microwave oven a gratin-type product, comprising a layer of vegetables at the bottom, fish fillets in the middle, a sauce at the top and apple puree of earth distributed around the edge, from a frozen state at (-25 ⁰ C) for 14 min., followed by a browning of 4 min. infrared grill (SHARP RV 1200 E model), in:

• 1) the tray according to the invention,
• 2) a conventional aluminum tray and
• 3) a cardboard tray covered with polyester,

the following results were obtained:

• 1) Regular temperature distribution with slight variations from 65 to 80 ° C. Good quality product without overcooking and the interior of the product sufficiently cooked. The quality is entirely equivalent to that obtained in a conventional household oven.
• 2) The bottom layer is always cold with residual ice, while the top layer is overcooked, burnt in places. Temperature distribution from 0 to 30 ° C.
• 3) The corners are overcooked and somewhat burnt, while the middle part of the fish fillets is still raw. Temperature distribution from 20 to 100 ° C. The cardboard tray is practically black at the edges and deteriorated.

The above results show that the construction of the invention makes it possible to heat the product from above and from the bottom and a relatively higher proportion of the radiation is directed towards the central part thanks to the metal coating on the side walls. Also, the metal coating on the edge protects the cardboard part from deterioration. However, it can be seen that conventional trays are completely unacceptable under the conditions studied.

Claims (7)

1. Packaging for food products intended for the controlled cooking or heating of food prepared in hot air, convection, household and microwave ovens, comprising a tray consisting of a bottom and a wall peripheral extending upwards, said wall being curved outwards in its upper part, thus defining a peripheral edge extending horizontally, the wall or at least its internal surface or the upper part thereof the horizontal edge and the parts thereof situated in the corners being made of or covered with a material reflecting or opaque to microwave radiation and said bottom being made of a material transparent to microwave radiation or capable of being remove easily. 2. Packaging for food products according to claim 1, in which the tray is formed from a cardboard covered with polymer, the peripheral wall and edge of which are covered with a metallic layer, preferably aluminum foil on their inner surface. 3. Packaging for food products according to claim 2, wherein the peripheral wall is partially covered with a metal layer, on its inner surface in a region surrounding each of the corners. 4. Packaging for food products according to claim 1, wherein the tray is provided with a metal cover. 5. Packaging for food products according to claim 1 or 4, wherein the tray is whole metal and its bottom can be easily removed by means of an easy opening. 6. Packaging for food products according to claim 2 or 3, wherein only half of the horizontal edge which is adjacent to the wall is covered with a metallic layer, the part of the edge which extends from the end of the sheet. metallic to the end of the edge being provided with a line of peripheral perforations close to the end of the metallic sheet, so that the outer part of the edge is connected to the tray only by narrow bridges of material, and the tray is provided with a cover consisting of a sheet of cardboard covered with polymer or of a polymer sheet, the edge of the cover being heat sealed or welded to the outside of the edge of the tray. 7. Packaging for food products according to claim 2 or 3, wherein the entire horizontal edge of the tray is covered with a metal layer and is provided in its central part with a line of perforations, the tray being provided with a cover consisting of a sheet of cardboard covered with polymer or of a polymer sheet sealed or welded to the edge thereof.

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