EP0299237A1 - Package with a lid for food products - Google Patents

Abstract

The package comprises a tray (1) having a lid (3) made from plastic-coated cardboard or from plastic material, comprising a face (4) whose contours are adapted to those of the upper edge (5) of the tray, and a continuous lateral wall (6) which is first drawn in and then flared out in the form of a skirt. The face (4) is provided with projecting bulges acting as spacing and centring studs for the tray. The lid (3) acts as a bain-marie for the regeneration of the foods in microwave ovens. …<IMAGE>…

Description

The present invention relates to a packaging for food products comprising a metal tray and a removable cover adapted to the tray.

Food products of the frozen meal type are generally found in metal trays, for example aluminum. The trays are closed by a cover, for example an aluminum foil or cardboard and placed in an overwrap carton. To cook or reheat the product, remove the lid and place the tray in an oven. Other culinary products, for example intended for the easy preparation of quiches, pies or pies based on flan, salted or sweetened, can consist of a base of precooked dough already placed in a metal tray and a sachet containing ingredients of the filling, for example in dehydrated form. To prepare the dish, the housewife can simply add to the dehydrated ingredients the necessary quantity of liquid, for example milk and egg, preferably mixed beforehand, then bake the product in the oven. The metal trays are perfectly suited for conventional convection ovens or infrared radiation, but have serious drawbacks vis-à-vis 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 for example even more convenient.

There are several problems:
- The traditional metal tray is opaque to microwave radiation and is not suitable in microwave ovens because there may be arcing in the oven cavity, which can damage the walls of the oven, or return of radiation towards the magnetron, which can damage it if the protection is insufficient, for example in ovens of relatively old design.
- The cooking of certain products is very uneven because the metals in conductive sheet are not transparent to microwaves and the heating intervenes from the top to the bottom. Consequently, the upper layer preferentially undergoes the action of the wave, which is also weakly penetrating, with excessive heat production and evaporation of the water. This leads, in particular for frozen products, to inhomogeneous cooking with a cold bottom layer and also still frozen while the top layer is dried out, or even burnt. In the specific case of preparation of a blank, the use of a microwave oven leads to a movement of the product which is detrimental to correct coagulation of the blank. It is not smooth but its texture is more like that of scrambled eggs.
- Cooking is not only heterogeneous but greatly slowed down.

Some development work in the packaging industry in conjunction with microwave cooking has addressed the problem of selective cooking of multi-component meals in which the individual components of the meal require different amounts of microwave energy. waves.

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 cooked to different degrees, which container is opaque to the microwave radiation 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 .

Other work has focused on the production of trays which are supposed to allow both homogeneous regeneration or cooking and the protection of materials, for example cardboard or plastics in household or microwave ovens equipped with infrared grills. -red. For example, US Patent No. 4,351,997 relates to a tray of material transparent to microwave radiation, the inner surface of the side wall or corners and the upper part thereof constituting the horizontal edge are covered with '' a metallic material opaque to microwave radiation. The realization of such a tray is complicated.

Finally, U.S. Patent No. 4,439,656 relates to a microwave-safe material utensil in which a metal tray is placed and which, once filled with water, provides protection microwave oven and even heating of a food. The consumer does not always have such a utensil sold independently of the food. In addition such a utensil can not be adapted to all forms of trays, so it would take several.

The invention makes it possible to solve the problems associated with known devices by simple means, sold together with the food and constituting part of its packaging.

The packaging according to the invention is characterized in that the cover is made of a material transparent to microwaves, that said cover constitutes a receptacle for a microwave absorbing fluid, so as to surround the tray of said fluid during reheating or cooking, once the lid is turned over and the tray placed inside.

According to the invention, a tray can be in the form of a truncated pyramid with a rectangular or square base, as well as a frustoconical with a circular or oval base.

The following description provides a better understanding of the invention with reference to the drawings which illustrate preferred embodiments thereof.

• la figure 1 est une vue avec demi-coupe d'une barquette à base rectangulaire avec couvercle avant étuyage,
• la figure 2 est une coupe longitudinale de la barquette avec couvercle de la figure 1 dans un étui,
• la figure 3 est un schéma d'utilisation du couvercle de la figure 1 pour la préparation d'un aliment, en vue de sa consommation,
• la figure 4 est une vue de dessous du couvercle de la figure 1
• la figure 5 est une perspective en coupe selon AA de la figure 4
• la figure 6 est une vue partielle avec demi-coupe selon AA de la figure 7 d'une barquette à base ronde avec son couvercle,
• la figure 7 est une vue de dessous du couvercle selon la figure 6 et
• la figure 8 est une perspective d'une variante de couvercle pour une barquette à base rectangulaire.

In the drawings:

• FIG. 1 is a half-section view of a rectangular-based container with cover before casing,
• FIG. 2 is a longitudinal section of the container with the lid of FIG. 1 in a case,
• FIG. 3 is a diagram of the use of the cover of FIG. 1 for the preparation of a food, with a view to its consumption,
• Figure 4 is a bottom view of the cover of Figure 1
• Figure 5 is a sectional perspective along AA of Figure 4
• FIG. 6 is a partial view with half-section along AA of FIG. 7 of a round base tray with its lid,
• FIG. 7 is a bottom view of the cover according to FIG. 6 and
• FIG. 8 is a perspective view of a variant cover for a tray with a rectangular base.

In the drawings, the tray 1, made of aluminum, optionally coated on the outside, containing the frozen food 2 is provided with a cover 3, made of material transparent to the microwave. The cover 3 can be manufactured by folding or forming, for example cardboard covered with a layer of plastic material on its internal face. It can be obtained by injection or thermoforming of a plastic material or a cardboard and plastic composite material. The plastic is preferably polyethylene or polybutylene terephthalate, a polyolefin, for example polybutylene, polymethylpentene, polypropylene or high density polyethylene, polyetherimide, polystyrene, polyvinyl chloride, polycarbonate, or combinations materials.

The cover includes a face 4 whose rounded contours are adapted to those of the upper edge 5 of the tray and a continuous side wall 6 connected to the face 4. In the embodiment shown, this side wall follows at its beginning the side wall 7 of the tray, so is slightly reentrant. This configuration allows the cover to be snapped onto the tray. The start of the side wall can also be substantially perpendicular to the face 4. The side wall is extended by a flared skirt up to the level of the bottom of the tray. This skirt defines a sufficient enveloping volume to avoid the formation of undesirable electric arcs in the case where the metal tray is close to other metallic objects such as for example the wall of the oven or another tray, during the preparation, as it will be explained later. In the particular embodiment shown, the side wall 6 has a line of rillage 8 or perforations at the change of direction of the wall. The wall 6 has pre-cut 9 or perforation lines at the angles from the rillage line 8. Thus precut, the end of the wall defines lateral gripping ears 10 serving at the same time as flexible tongues to hold the tray in the cardboard case 11, which reduces the risk of deformation during handling.

The cover 3 is provided with protruding reliefs which constitute studs 12 for spacing the bottom and centering studs 13 for the tray. In a variant not shown, a sheet of embossed paper capable of absorbing water is inserted between the studs 12 against the bottom of the cover. Its thickness is such that it reaches the upper level of the studs 12.

When you want to heat or cook the food in a microwave, remove the cover and turn it over. Water is then poured into the bottom (a), up to the upper level of the studs 12, for example 20 to 200 ml, then place the tray (b) between the studs 13 and place the assembly in the oven. The lid defines a space enveloping the tray and then plays the role of double boiler. Once the heating or cooking is finished, the flexible tabs can advantageously serve as gripping ears to remove the food from the oven. The rillage line 8 allows the tongues to be folded outwards to facilitate gripping without the risk of burns. If an absorbent sheet is placed against the bottom of the cover, there is no risk of spilling hot water when the dish is removed from the oven.

If using a convection or infrared oven, simply remove the cover and place the tray in the oven.

As shown in Figures 6 and 7, the cover 14 of a tray 15 with a round base includes a bottom 16 of diameter adapted to that of the upper edge of the tray. The tray contains a precooked crust 17 and a sachet 18 containing a dehydrated mixture constituting the filling. The tray containing the base of dough, the bag and its cover are placed in a cardboard case 19. The case 19 can alternatively be replaced by a bag, for example made of polyethylene.

The cover comprises a continuous lateral face 20 and an edge 21, lateral face and defining edge, at two diametrically opposite points of the gripping ears 22 and providing flow conduits 23 for the water intended to be poured therein as explained above. after. The cover 14 is provided towards the middle part of the bottom with bottom spacing studs 24 in the form of arcs and notches 25 of height greater than that of the studs at the level of the side wall intended for centering the tray.

The use of the cover is as described above in connection with Figure 3, with the difference that there is an additional operation of separate preparation of the filling: after opening the sachet, pour its contents into a bowl with an egg and cold milk, then mix. Once the lid is turned upside down, water is poured up to the upper level of the pads 24, preferably by a conduit 23, then the tray containing the precooked crust is placed between the notches 25 and the constituent mixture of the filling is poured in the tray, then the whole is placed in a microwave oven.

The principle can obviously be applied to trays with multiple compartments. In this case, the cover covers all of the compartments and can, once turned upside down, serve as a double boiler to cook or heat all the food contained in the different compartments.

In FIG. 8, the cover 26 consists of a carton 27 sealed on the inside, for example by impregnation of polyethylene. The cardboard 27 is wrapped around a mattress of absorbent embossed paper 28. On the upper face of the cover, the tabs 29 are pre-cut in the corners. This variant is suitable for heating and cooking frozen prepared meals in aluminum trays. Aluminum can optionally be painted externally.

To prepare the dish, the legs 29 are raised, the amount of water which can be absorbed by the sheet 28 is poured, then the tray is placed between the legs. Then put the dish in the microwave. During reheating or cooking, the steam generated from the absorbed water surrounds the tray and allows a homogeneous reheating or cooking.

Comparative examples 1 to 3 below illustrate the performance of the packaging according to the invention (1), FIG. 1, the lid being turned over, filled with the quantity of water indicated and the tray containing the food being placed at the interior as indicated above, compared with those (2) of the aluminum tray containing the food and (3) of a special glass dish for microwave ovens in which the food is placed once removed from the mold, when heating for 12 min. various frozen ready meals using a Kenwood A414 microwave oven (460 watts returned) with turntable. In case (3), the product is removed from the mold, then placed in the glass utensil either after being stored for 15 min at - 20 ° C, or 15 min at + 20 ° C, or directly. This additional operation is intended to study the impact of the thermal inertia of the tray on the heating of the food. The temperatures are measured as quickly as possible after the treatment in the oven is finished.

In Comparative Example 4 below, the performance of the packaging according to the invention (1), FIG. 6, is compared with that of the aluminum container containing the food (2) in the preparation of a quiche with flan filling. The tray has a volume of approximately 500 cm³.

In case (1), pour the mixture of the dehydrated ingredients of the filling, 200 cm³ of cold milk and a whole egg beaten in the tray containing a crust of precooked dough so as to fill the crust approximately 2/3.

In case (2) the quantity of water indicated is poured into the upturned high density polyethylene cover, the tray containing the crust is placed, then the mixture constituting the filling.

In cases (1) and (2), the food is placed in a microwave oven for 7 min. at the power of 600 Watts restored. Let stand 1 to 2 min. before tasting the quiche.

It can be seen from reading the results in Table 1 that the packaging according to the invention (1) allows better temperature uniformity than in the case of the demolded product placed in a special dish (3) when the temperatures are not all homogeneous in (2).

The evaporation of water from the product is less in (1) than in (2) and (3), and this is particularly noticeable when the amount of water added is greater.

The organoleptic qualities are appreciably better for (1) than for (3) whereas these are insufficient in the case of (2). Table 2 Comparative example 2 Eggplant gratin product of 462 g (1) In a water bath with water (g) (3) Processed immediately (2) 40 50 100 cold 100 hot Tray bottom temperature ° C 56 67.5 77.1 72 77.1 32.5 Temperature in the middle of the tray ° C 61.4 56.9 72.3 61 71.1 55 Tray surface temperature ° C 74 58.4 67.8 60 68.2 63.2 Average temperature ° C 64.7 62.6 74.2 73 76.9 49.3 Evaporation (g) product water 18 11 13.6 16 35 39 added water 13 22.4 9.5 16 - - Aspect Slightly melted cheese Nice appearance Barely melted cheese Cheese rind Gratin texture Slightly chewy cheese Melted cheese Correct Very hard, inedible

The packaging (1) provides a uniform temperature and less evaporation of water from the product. Whether the water added is cold or hot has no major influence on the result. Homogeneity is slightly better with cold water.

The texture and appearance according to (2) are completely unacceptable. Table 3 Comparative example 3 Product: fish with Bordeaux sauce of 410 g (1) In a water bath with water (g) (3) Processed immediately (2) 40 50 100 Tray bottom temperature ° C 76.6 78.9 78.4 84 65.4 Temperature in the middle of the tray ° C 76.7 71.4 74.5 79 74.8 Tray surface temperature ° C 77.4 68.1 66.6 68 76.1 Average temperature ° C 77.8 76.7 77 81 73.2 Evaporation (g) product water 20.5 16.1 20.7 40 42.1 added water 8.3 16.9 15.2 - - Aspect Normal Gray, albumin rejection Dull Fish texture Cooked Cooked Not enough cooked

In this case, the temperature differences are attenuated because the fatty sauce drips into the bottom and facilitates heat transfer by convection.

The evaporation of water, the appearance and the consistency of the fish are characteristically different, clearly in favor of (1).

The packaging according to the invention allows the production of products which would be impossible to prepare without it in a microwave oven. It is found in fact that, in the preparation of the sides according to (1), a rise in temperature at full power is much too rapid and causes the filling to boil before it coagulates. The result is the formation of a totally unacceptable scrambled egg-like texture. The use of a reduced power, conventionally obtained in commercial household ovens by sequential emission of waves, would not make it possible to remedy this defect because it would lead to a movement of the lining detrimental to a correct coagulation of the blank: one would obtain also a scrambled egg texture.

On the other hand, the addition of a sufficient quantity of water to the upturned cover, according to (2), makes it possible to increase the load in the microwave enclosure for a fixed quantity of food. This regulates the rate of temperature rise at full power. This allows a better distribution of energy in space. The water layer is mobile and provides a rapid heat transfer in comparison with the slow transfer in the more viscous medium of the lining. The effect obtained is a uniform temperature leading to correct coagulation of the blank before the filling comes to a boil. The derivation by the water of the water bath of part of the microwave energy into conventional heat finally allows the heating of the precooked crust which, because it is dry, is not very sensitive to microwave radiation.

Claims (10)

1. Packaging for food products intended to be reheated or cooked in convection ovens, in infrared ovens or in microwave ovens comprising a metal tray and a removable cover suitable for the tray, characterized by the fact that the cover is made of a material transparent to microwaves, that said cover constitutes a receptacle for a microwave absorbing fluid, so as to surround the tray of said fluid during reheating or cooking, once the cover is turned over and the tray placed inside. 2. Packaging according to claim 1, characterized in that the cover has a face connected to a continuous side wall forming a sealed cavity of geometry similar to that of the tray, so as to delimit with the tray a space surrounding it entirely intended to receive a liquid absorbing microwaves. 3. Packaging according to claim 2, characterized in that the side wall of the cover is extended by a flared skirt in its part remote from said face. 4. Packaging according to claim 2, characterized in that the side wall of the cover is slightly re-entrant in its part close to the face. 5. Packaging according to claim 3 or 4, characterized in that the side wall of the cover has a line of rillage or perforations at the change of direction. 6. Packaging according to claim 5, characterized in that the side wall of the cover has pre-cuts or perforations at the corners in the skirt from the line of rillage or perforations, and that thus the part of the wall remote from the face defines flexible tongues serving as gripping ears. 7. Packaging according to claim 1, characterized in that the cover is provided in its face with projecting reliefs constituting spacing and centering pads for the tray. 8. Packaging according to claim 1, characterized in that the cover is made of cardboard sealed on its internal face. 9. Packaging according to claim 1, characterized in that the cover is made of plastic. 10. Packaging according to claim 1, characterized in that the cover consists of a sealed cardboard surrounding an embossed paper absorbing the fluid, that tabs are pre-cut on one side of the carton and that said tabs, once raised, serve to center the tray and avoid arcing at the corners of the tray.

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