EP1353860B1

EP1353860B1 - Heatable food package with venting means

Info

Publication number: EP1353860B1
Application number: EP01995818A
Authority: EP
Inventors: Robert Jan Colenbrander
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-12-22
Filing date: 2001-12-27
Publication date: 2006-06-14
Anticipated expiration: 2021-12-27
Also published as: EP1353860A1; DE60120763T2; ATE329854T1; DE60120763D1; ES2266306T3; NL1016978C2; WO2002051716A1

Abstract

Device (1) for the packaging and preparation of food, (20), provided with a dish-shaped container (4), which is provided at the topside with a take out opening, closed by at least two layers of film (8,10) which are placed above each other, whereby at least the bottom film is provided with perforations (18), whereby means are provided to allow for the escape of vapour during use between the bottom film and a film placed above it.

Description

The invention concerns a device for the packaging and preparation of food. Such a device is known from EP 0971849.
This known device, particularly suitable for use in a microwave oven, comprises a plastic container, closed at the topside by means of a film sealed onto the container. In the film a part is made which functions as a valve. During heating of food present in the container, a vapour pressure will develop in the container, by means of which the pressure within the container will rise to above atmospheric pressure. Therefore the temperature in the container will easily rise to above 100 °C, by which food can be prepared in a particularly fast manner, while all the wanted food properties are retained. The valve is adjusted thereby such that vapour can escape through the valve at a desired pressure so that too high pressures and temperatures will be prevented.
This known device has the advantage that food can be packaged and transported in it easily, whereby the food stays fresh, is protected against influences from the outside and moreover it is prevented that moisture can leak away from the container. Moreover, the food can be prepared in it fast, with retention of, for example, aroma, texture, vitamins and such, while too high pressures are prevented. However, the disadvantage of this device is that a relatively expensive valve has to be applied.
Moreover, the fastening of such a valve (one single or multiple valves per device) is complex and time-consuming, particularly because this has to carried out with great care. After all, when the fastening is inaccurate, vapour could leak away along the valve and or the valve or the film could come apart because of which the device as such cannot function properly anymore, with all dangers this entails.
Another disadvantage of this known device is that the valve can become clogged up with food, as a result of which no vapour or at any rate only a limited amount of vapour can escape. A further disadvantage is that the device has to be opened by the user rather quickly after heating since otherwise the device will be compressed together because of the pressure differences. When opening the container the risk exists that the user thereby gets into contact with the hot vapour which is still present.
EP 0 661 219 discloses a layered film for closing food containers, which layered film comprises two layers of film bonded to each other over a large part of the surface which, during use, closes the take out opening of the container, prior to closing the container. Venting channels are provided between said layers of film, whereby venting opening are provided at the edge of the film in the form of rip valves.
EP 0 967 160 discloses a similar layered film of at least two layers of film bonded to each other over most of the surface extending over the take out opening of a container.
It has been proposed to provide such a device whereby an opening, closed by a sticker is made in the film instead of a valve.
This sticker should be removed by the user before heating. Disadvantage of it is that no quick pressure build-up takes place in the device and the user firstly has to manipulate the device before use.
It is an object of the invention to obtain a device of the kind described in the above, whereby the disadvantages of the known devices are avoided, while retaining the advantages of it. Thereto a device according to the invention is characterised by the measures according to claim 1.
A device according to the invention offers the advantage that the layers of film can be fastened in an easy manner, whereby during use a desired overpressure in the packaging can be obtained automatically and can be maintained, for example a pressure between 1.0 and 4.0 bar and preferably between 1.3 and 1.9 bar, as a result of the means for allowing the mentioned vapour to escape.
Vapour will only be able to escape when a certain, increased vapour pressure has been obtained. Because no valves are necessary, the above mentioned disadvantages are prevented. The films can easily be fed in from a roll and be cut to size, by which also various sizes of containers can be applied easily. Moreover, in this way always a suitable combination of films and containers can be chosen, for example depending on the food to be packaged and prepared. Preparation should be understood in this context as at least preparing for consumption, including heating.
In an advantageous embodiment a device according to the invention is characterised by the measures according to claim 3.
By making at least one film, particularly the top film, gastight and liquid tight, the advantage is obtained that pressure can build up relatively fast between the bottom and the mentioned gastight and liquid tight film, whereby moreover also a fast build up of pressure to the desired level in the container is achieved.
In an alternative embodiment multiple perforated films are envisaged, whereby in the direction away from the bottom layer the film or each film located above it has perforations with a total permeability surface which is smaller than that of the bottom film.
In a particularly advantageous embodiment a device according to the invention is characterised by the measures according to claim 5.
In such a device vapour, entrapped between the two films can escape because the second film comes loose, at any rate partly, when the pressure between the films surpasses a certain increased preselected pressure. Such a device can be manufactured particularly easy, while an automatic action is achieved immediately, whereby allowable overpressures can be set easily by the choice of the mentioned connections.
In an alternative embodiment the film or each second film is implemented such that it tears when a certain pressure is surpassed to allow the release of the overpressure.
Use of a closed, gastight and liquid tight film above the perforated bottom film for a device according to the invention offers the advantage that in a closed condition it is prevented that moisture can leak away to the outside through the perforations, while moreover an airtight sealing can be obtained. This implies that, for example, also a modified atmosphere can be created within the container prior to or during packaging, for example for the preservation of packaged food. The gas in such an atmosphere can only escape when the films separate from each other or at any rate partly separate.
It is preferred that the perforations in the bottom film are relatively small, for example round with a diameter between 50 and 5000 µm, preferably between 100 and 750 µm or openings with a different shape but with a comparable surface. A dimension between 200 and 500 µm is particularly suitable. A favourable flow-through resistance for vapour is obtained with it, while such perforations can be manufactured relatively accurate.
In a device according to the invention, the bottom film preferably is manufactured from a thermic stable laminate, particularly a laminate manufactured from polyester and polypropylene. The bottom film or each film placed above the bottom film thereby preferably is a heat-sealable plastic film, particularly polyester, which can be peeled off. Yet also other film materials, consisting of one or more layers could be chosen, depending on the application, which choice will be immediately obvious for a skilled worker.
The invention further concerns a method for the manufacture of a device for the packaging and preparation of food, characterised by the measures according to claim 14.
Such a method offers the advantage that a packaging can be manufactured in a particularly quick and easy manner in which food can be packaged, transported and prepared. In such a method various films put on top of each other can be fed in, for example as a laminate, prior to the joining thereof with the container, while the films furthermore can be fed in separately from each other. The films, for example, can be fed in from a roll and directly be cut to size prior to or during the positioning. In this way a particularly great freedom of design can be obtained, whereby packaging of various sizes can be manufactured in an easy way.
The invention further concerns a method for the preparation of food, characterised by the measures according to claim 18.
With such a method the advantage is achieved that packaged food can be put directly into an oven, particularly a microwave oven or steam oven, in which the food can be heated and prepared quickly, without the quality of it being influenced negatively. On the contrary, with a method according to the present invention the quality of the food is retained in a particularly favourable manner. Particularly, it is prevented that the packaged food, for example, is drying out or is losing texture, colour, aromas or such, or at any rate that these qualities are influenced in an undesired way. Moreover, vitamins are retained in this manner.
In the following claims more detailed advantageous embodiments are presented of a device or method according to the invention.
To clarify the invention, examples of embodiments of a device and method according to the invention will be illustrated in more detail by way of the drawing. The drawing shows:

Figure 1, an exploded schematic perspective view of a packaging device according to the invention;
Figure 2, a side view of a cross-section of a packaging according to figure 1, in closed condition;
Figure 3A - C, heating of food in three consecutive steps of a packaging according to the invention;
Figure 4, schematically an alternative embodiment in side view of a cross-section of a packaging according to the invention.
Figure 5, schematically a detail of an edge of a container with films; and
Figure 6, a corner of an alternative embodiment of a packaging device according to the invention.

Figure 1, schematically in exploded perspective view, a packaging device 1 according to the invention.
This packaging device 1 comprises a dish-shaped container 4, for example manufactured from heat-sealable plastic, known from practice and suitable for use in a magnetron or steam oven. This dish-shaped container 4 is provided at the topside with a take out opening 2, surrounded by a flat edge 6 which extends outwards. This packaging device 1 further comprises a first bottom film 8 and a second, top film 10. Bottom should be understood in this context to be closest to the take out opening 2, top film as the film or each film at the side which is turned away from the take out opening 2 of the bottom film 8. In the embodiment shown, two films 8, 10 are provided, with a surface size approximately matching the topside of the container 4 as is determined by the lengthwise edge 6. The films 8, 10 are manufactured from a material that can be fastened by means of heat sealing on the lengthwise edge 6. The bottom film thereby preferably is manufactured from a thermic stable heat-sealable laminate, the top film 10 of a heat-sealable plastic, preferably a heat-sealable plastic which can be peeled off. Figure 5 shows films 8, 10, above the lengthwise edge 6. The bottom film 8 thereby consists of, for example a laminate manufactured from a first layer 14 of polypropylene with a thickness of for example between the 60 and the 120 µm and particularly 90 µm and a second layer 12 of polyester on top of it with, for example, a thickness between the 10 and 15 µm, particularly 12 µm. The top film 10 thereby is manufactured, for example, from polyester with a thickness of approximately 25 µm, preferably 20 µm heat-sealable polyester which can be peeled off. The materials and dimensions mentioned here are only presented as examples and should not be explained as being limiting as regards the scope of the invention.
As is shown by figure 1, the bottom film 8 is provided with a perforation pattern 16, in the embodiment shown are a number of perforations 18 with mainly circularly shaped cross sections. This perforations have, for example, a diameter between 50 µm and 5000 µm, particularly between 200 and 500 µm, so that water droplets or at any rate vapour can pass through it when sufficient pressure exists within the container 4, as will still be described in more detail.
During use a quantity of food 20 is placed, as is shown, for example, in figure 2, in the dish-shaped container 4, after which the first, bottom film 8 is fastened all around with the aid of first sealing means 22 onto the lengthwise edge 6. The first sealing means 22 are schematically shown here by the hatching. It will be clear that any desired, suitable sealing method can be applied, for fastening of the first, bottom film 8 onto the lengthwise edge 6, or at any rate onto the container 4. In the embodiment shown in figure 2, the second film 10 is fastened onto the bottom film 8 with the aid of second sealing means 24, in the embodiment shown directly above the first sealing means 22 and the lengthwise edge 6. The first sealing means 22 and second sealing means 24 thereby are chosen such that the bottom film 8 is joined relatively tight with the lengthwise edge 6. This connection, formed by the first sealing means 22, is stronger than the connection between the bottom film 8 and the second film 10, formed by the second sealing means 24. The purpose for this will be elaborated on later in this document. It will be clear that in the drawing the thicknesses of the films 8, 10, the first and second sealing means 22, 24 and the dish-shaped container 4 are not shown in relation.
When food 20 is packaged in the manner shown in figure 2 in the packaging device 1 then it can be transported and stored in the device, while the packaging 1 with the food 20 can be placed in the closed condition in a microwave (magnetron) or steam oven or such. When the respective oven thereafter is switched on, the food 20 can be prepared with a method according to the invention, explained in more detail on basis of figure 3A - C. Preparation should be understood in this context as at least comprising the preparation for consumption, included heating up.
Figure 3A schematically shows the packaging 1 according to the invention in a relatively cold condition. In the inside space of the dish-shaped container 4 a relatively low temperature T₀ (for example room temperature or lower) is present and a relatively low pressure P₀ for example comparable to the atmospheric pressure P_A outside the container 4. Possibly a protective gas can be contained in the inside space of the container 4 to obtain a modified atmosphere. In occurring cases, the food 20 is still better protected by it.
After the oven is switched on, the food 20 is heated, by which moisture present in the food 20 and possibly added moisture is heated and will evaporate. Because of it, the pressure in the container 4 will rise to a relatively high pressure P₁, whereby the temperature will also increase to a relatively high temperature T₁. As a consequence of the increase of pressure, vapour will be forced through the openings 18, as shown by the arrows 25. This vapour will flow between the bottom film 8 and the top film 10, but will be prevented from escaping by the second sealing means 24. Thus, the pressure will rise between the bottom film 8 and the top film 10 to a relatively high pressure P₂, whereby the temperature will also increase somewhat to a temperature T₂. When the pressure P₂ surpasses a top limit, at any rate a part of the second sealing means 24 will be broken, as shown in figure 3C, by which vapour between the bottom film 8 and the top film 10 can flow away, to the surroundings, and because of which equalising of pressure will occur to approximately atmospheric pressure P_A. The space within the container 4 under the bottom film 8 will expand thereby, while the pressure will equalise to a pressure P₃, which is at maximum, while the temperature will rise to a relatively high temperature T₃. The temperature T₃ will be, for example, higher than 100 °C, in view of the relatively high vapour pressure P₃. This means that the food 20 will be heated relatively quickly, whereby the quality of the food will be retained, particularly does not dry out, being unwanted, and / or the texture, colour or taste changes, while moreover, for example, vitamins will be retained in a particularly suitable manner. Because the second sealing automatically, or at any rate partly is broken when the pressure P₂ between the layers of films 8, 10 increases, automatically a desired pressure is set, depending on for example, the amount of heating, the amount of vapour which develops, the inside volume of the container 4 under the bottom film 8 and the total permeability surface of the permeability openings 18 in the bottom film 8.
In figure 4 an alternative embodiment of a device 1 according to the invention is shown, whereby both the bottom film 8 and the top film 10 are fastened with aid of respectively the first sealing means 22 and second sealing means 24 directly onto the lengthwise edge 6. The advantage is obtained thereby that a particularly good connection is obtained between the second film 10 and the rest of the container 4, also when the top layer of the bottom film 8 is not, or at any rate badly heat-sealable or else does not allow a relatively weak connection in a suitable manner.
In a further alternative embodiment, as shown in figure 6, the top film 10 and the bottom film 8 are fastened directly onto each other, whereby the bottom film 8 is directly fastened onto the lengthwise edge 6. A weakening line 26 is manufactured in the top film 10, which initially is closed. When this packaging 4 with food 20 is put in an oven and is heated, vapour will flow between the first and second film 8, 10, in the manner as shown in figures 3 A and B, the volume in between the films will increase and a pressure P₂ will develop. The tear line 26 will tear open when the limit pressure P₂ is surpassed and vapour can escape to the surroundings. In this embodiment the bottom film 8 and the top film 10 can stay connected to each other and when opening the packaging device 1, can be torn off and discarded together.
In the example of an embodiment shown, a mainly rectangular container 4 is applied. However, it can be preferred to apply a container with, for example, a round or oval shape, with which a more steady heating can be obtained while moreover a more steady distribution of heating and vapour pressure can develop.
In this description is departed from a dish-shaped container since this is known from practice. Such a dish-shaped container is for example manufactured from plastic or plastic laminated cardboard, manufactured by means of, for example vacuum forming, injection moulding or such techniques. In the examples of embodiments shown, a dish-shaped container is applied, manufactured from a material that can be sealed with in itself known sealing methods, particularly heat sealing methods. Such materials which are applicable for it therefore are well-known from practice.
The invention is in no way limited to embodiments shown in the description and the drawings. Many variations thereof are possible within the scope of the invention as outlined by the claims. Thus, the perforations 16, 18 can also be put on in another way, for example in the form of a regular or irregular matrix of openings 18. The number and size of the perforations can be chosen easily, depending on the products to be heated, surfaces, contents of the container and such. Such a choice will be apparent immediately for the skilled worker. More than two films can also be applied, for example two perforated films on top of each other, possibly covered by a closed film, whereby preferably the perforations of the in-between film have a total permeability surface which is smaller than that of the perforations of the bottom film, or at any rate have a flow resistance which is higher than that of the bottom film. In this way pressure can be built up in a stepwise manner. Furthermore, a container can be applied which is divided into various compartments, whereby at least the bottom film is also fastened onto a separation wall of the various compartments. Particularly the perforations in the bottom film can be different thereby for each compartment, for obtaining different pressures and / or temperatures in those compartments. Any suitable material is applicable within a packaging device according to the invention. One or more of the films can also be fastened onto the container in another manner instead of the heat sealing technique, for example under application of a suitable gluing technique, welding technique or such. The top film can also be implemented in such a way that it rips open when a certain or a desired maximal pressure is surpassed, in order to allow the escape of vapour.
Multiple perforated layers of film are envisaged in an alternative non-gastight embodiment of the device according to the invention, whereby, in the direction away from the bottom film, the film or any film placed above it is provided with perforations with a total permeability surface which is smaller than that of the bottom film.
These perforations in the above placed film are, for example, round and having a diameter between 10 and 1000 µm, preferably between 20 and 100 µm and particularly having a diameter between 40 and 60 µm. These perforations are made with a frequency of, for example, 10 to 1000 perforations per m².
The object of this alternative embodiment is to increase the storage life of the food products packaged in the device, particularly that of plant material. Such an assembly of perforated layers of film allow to adjust the O₂ and CO₂ levels during transport and storage.
These and many comparable variations are considered to stay within the scope of the invention as is outlined by the claims.

Claims

Device (1) for the packaging and preparation of food (20), provided with a dish-shaped container (4), which is provided at the topside with a take out opening, closed by at least two layers of film which are put on top of each other, whereby at least the bottom film (8) is provided with perforations (18), whereby means are provided for the escape of vapour during use between the bottom film (8) and a film (10) placed above it, characterized in that the said bottom film (8) and said film (10) placed above it are connected to each other and/or onto the container (4) by seals (22, 24) exclusively at the circumferential edge (6) of the take out opening (2) of the container (4) whereby essentially the at least two layers of films (8, 10) remain separated from each other over the entire surface area of the take out opening (2) of the container (4) such that when during use the pressure between said two films (8, 10) surpasses a top limit at least part of the seal connecting the top film to said edge is broken and/or said top film (10) is torn for escape of vapor from between said films (8, 10).
Device according to claim 1, whereby the films (8, 10) consisting of at least two layers are sealed onto a lengthwise edge of the container (4).
Device according to claim 1 or 2, whereby at least one film is gastight and liquid tight.
Device according to any of the preceding claims, whereby at least one film (10) placed above the bottom film (8) comprises perforations (18) with a total permeability surface which is smaller than the total permeability surface of the perforations in the bottom film (8).
Device according to any of the preceding claims, whereby the bottom film (8) is connected with the container (4) and the film or a second film (10) is connected with the bottom film (8), preferably along the lengthwise edge thereof, whereby the connection between the bottom film (8) and the container (4) is stronger than the connection between the bottom film (8) and the second film (10) for forming the means for allowing the mentioned vapour to escape, one and other in such a way that gas can flow through the perforations (18) in the bottom film (8) and between the bottom film (8) and the second film (10) during a build up of pressure in the container (4) and the connection between the second film (10) and the bottom film (8) will at any rate break partly, whereby the connection between the container (4) and the bottom film (8) is retained.
Device according to any of the claims 1 - 5, whereby the bottom film (8) is connected with the container (4) and the film or a second film (10) is connected with the bottom film (8), preferably along the lengthwise edge thereof, whereby the connection between the bottom film (8) and the container (4), the connection between the bottom film (8) and the second film (10) and the layer of films is chosen such that gas can flow through the perforations (18) in the bottom film (8) between the bottom film (8) and the second film (10) during a build up of pressure in the container (4) and the connection between the second film (10) and the bottom film (8) will at any rate break partly and / or a opening in the second film (10) will develop for forming the means to allow the escape of the mentioned vapour for a release of the pressure between the films, whereby the connection between the container (4) and the bottom film (8) stays intact.
Device according to any of the preceding claims, whereby the perforations (18) in the bottom film (8) have a diameter between 50 µm and 5000 µm, preferably between 100 and 750 µm, particularly between 200 and 500 µm.
Device according to any of the preceding claims, whereby the bottom film (8) is built up from a thermic stable laminate, particularly a laminate of polyester and polypropylene.
Device according to any of the preceding claims, whereby the film or any film (8) placed at the bottom is a heat-sealable, preferably a heat-sealable plastic film, which can be peeled off, particularly a polyester.
Device according to any of the claims 1- 9, whereby multiple, only perforated layers of film (8, 10) are provided, whereby at least one film (10) which is placed above the bottom layer (8) contains perforations (18) with a total permeability surface which is smaller than the total permeability surface of the perforations in the bottom film.
Device according to any of the claims 1-10, whereby multiple, only perforated layers of film (8, 10) are provided, whereby at least one film (10) which is placed above the bottom layer (8) which contains perforations with a diameter between 10 - 1000 µm, preferably between 20 - 100 µm and particularly a diameter between 40 - 60 µm.
Device according to any of the claims 1-11, whereby multiple, only perforated layers of film (8, 10) are provided, whereby at least one film (10) which is placed above the bottom layer (8) contains perforations with a density of 10 to 1000 perforations per m².
Device according to any of the claims 1-12 whereby a container is applied which is divided into various compartments, whereby at least the bottom film (8) is also fastened onto a separation wall of the various compartments.
Method for the production of a device for the packaging and preparation of food, whereby a container (4) is filled with a portion of food (20), after which the container (4) is closed gastight and liquid tight mainly by at least two films (8, 10) placed above each other which are fastened onto the container (4), whereby a film (8) is applied as the bottom film (8) with perforations (18) through which gas, at any rate vapour from the container (4), can flow during use between the films (8, 10), and in such a way that a build up of pressure occurs between the films, characterized in that said at least two films (8, 10) are placed one above the other and are fastened onto said container (4) exclusively at the circumferential edge (6) of the take out opening (2) of the container (4) whereby essentially the at least two layers (8, 10) of films remain separated from each other over the entire surface area of the take out opening (2) of the container (4), such that when during use the pressure between said two films (8, 10) surpasses a top limit at least part of the seal connecting the top film to said edge is broken and/or said top film is torn for escape of vapor from between said films.
Method according to claim 14, whereby a gastight and liquid tight film is applied as the film or as a second film (10) placed on top of the bottom film (8).
Method according to claim 14 or 15, whereby the layers of films (8, 10) are fastened onto the container (4) and / or onto each other, particularly sealed, whereby the bottom film (8) is connected in such a way with the container (4) that this connection is stronger than the connection between the film or each film (10) placed above it and the bottom film (8) and / or the container (4), one and other in such a way that the second film (10) becomes loose or at any rate becomes partly loose during use as a consequence of a build up of pressure between the films (8, 10) without the bottom film (8) becoming loose from the container.
Method for the production of a device for the packaging and preparation of food according to any of claims 14-16, whereby a container (4) is applied which is divided into various compartments, whereby at least the bottom film (8) is also fastened onto a separation wall of the various compartments.
Method for the preparation of food, whereby the food is put into a container (4), which container is closed with at least a perforated bottom film (8) and a second film (10) placed on top of it, wherein said bottom film (8) and said second film (10) are fastened onto said container exclusively at the circumferential edge (6) of the take out opening (2) of the container (4) whereby essentially the at least two layers of films (8, 10) remain separated from each other over the entire surface area of the take out opening (2) of the container (4), after which the container (4) is placed in a closed condition in an oven, particularly a microwave oven or a steam oven, after which the food is heated, in such a way that vapour is developed in the container, which vapour flows at any rate partly between the perforated film and second film and leads to a higher pressure in-between the films, whereby the second film at any rate becomes partly loose and/or rips at near said circumferential edge, in order that the build up pressure is released while the bottom film remains fastened on the container and the pressure in the container is kept at any rate somewhat above the atmospheric pressure.
Method for the preparation of food, whereby the food is put into a container (4) according to claim 18, whereby a container (4) is applied which is divided into various compartments, whereby at least the bottom film (8) is also fastened onto a separation wall of the various compartments.