GB2369341A - A heat responsive food product container - Google Patents

Abstract

A food product container comprises a container 10 and a closure 24 which define a sealed cavity 32 for housing a food product. The closure 24 is adapted to opening in response to heating either by heating of the food product as in microwave cooking or by external heating of the container 10 as in conventional oven cooking. The closure 24 preferably comprises material that is adapted to peel, curl, contract, shrink, expand or otherwise change shape when heated, it is also adapted to remain in association with the container 10 after opening. The container 10 is preferably in the form of a tray and lid which may include a heating means which is adapted to transfer heat energy to the food product, this heating means is preferably a dielectric layer.

Description

Packaging for Food Products

The present invention relates to the packaging of food products and in particular to the packaging of a microwaveable food products.

It is increasingly common for the provision of self service hot food facilities to be provided in such locations as petrol station forecourt shops. Typically such facilities comprise a microwave oven and storage means for a selection of food products a prospective purchaser can select for heating in the oven. Purchasers avail themselves of these facilities in between regular cleaning of the of the oven and storage means and the products may be handled by more than one purchaser prior to a selection being made. Accordingly it is imperative in the interest of hygiene that the food products are packaged in a manner which does not allow direct contact with the oven and storage means before or during heating, and which prevents direct handling by numerous purchasers. In the interests of consumer convenience, it is desirable that, once heated, the food products are readily accessible for consumption.

One solution is to provide individually wrapped food products, for example sausage rolls, which the user removes from the wrapping prior to the placing in the microwave oven. However, it is possible for a user to attempt to heat the product without removing the wrapping, which may possibly render the heated product inedible or at least lead to a reduction in the quality of the heated product. Also, where the wrapping is removed prior to heating, there exists the possibility of the food product becoming microbiologically contaminated or coming into contact with the interior of the oven before or during heating. Further there must be provided means to carry the heated product from the oven after heating, for example disposable plates, the supply of which needs replenishing periodically.

An alternative solution is to provide a food product within two layers of packaging, for example a cardboard container which is initially wrapped in plastic. The plastic serves to prevent contact with the food product and must be removed before heating, while the cardboard container prevents the food product coming into contact with the interior of the microwave oven. However, as noted above, it is possible for a consumer to attempt to heat the product without removing the plastic wrapping and there is still a risk of microbiological contamination before or during heating.

According to an aspect of the present invention there is provided a food product container having a closure, the container and closure defining a sealed cavity for a food product, wherein the closure is adapted to open in response to heating.

The closure may be adapted to open in response to heating of the food product, for example by microwave cooking wherein heat energy from the food product is transmitted to the container by conduction, convection and/or radiation. Alternatively, the closure may be adapted to open in response to external heating of the container by conduction, convection and/or radiation, for example where the container is heated in a conventional oven.

In a preferred embodiment the closure is adapted to open so as to allow venting of the container. In such a manner moisture generated by the food product during heating thereof is allowed to escape and thereby not compromise the quality of the heated food product. The closure may also be adapted to open so as to enable access to the heated food product, and preferably to allow removal of the heated product from the container without the need for further container opening operations to be conducted.

Advantageously the closure may be arranged so as to be retained in association with the container after opening thereof. In such an embodiment a portion of the closure may be integral with the container, permanently attached by means of adhesive or permanently attached by means of a mechanical connection such as welding.

The closure may comprise a material adapted to peel, curl, contract, shrink, expand or otherwise change shape and/or size when heated. Alternatively the material of the closure may exhibit shape memory characteristics when heated. The closure may be manufactured from a plastics material. Other suitable materials include cellophane, and paper and cardboard treated so as to curl when heated.

The closure may be attached to the container by any appropriate means. In one embodiment the closure is attached to the container at least in part by adhesive. In such an embodiment the container and closure may be provided with facing flanges which are held together by said adhesive. The adhesive may be adapted to lose its adhesive properties when heated so as to enable the closure to be opened. In one embodiment the closure is partially attached to the container by a first adhesive adapted to lose it's adhesive properties when heated, and in the remaining part by a second adhesive which does not exhibit such a property. In such an embodiment the degradation of the first

adhesive enables the closure to be opened, while the second adhesive retains the closure in association with the container. The closure may be retained in association with the container by a mechanical connection, for example by the embossing, debossing or punching of common flanges of the container and closure. Alternatively, a flange of the closure may be extended so as to permit it to extend around a corresponding flange of the container and be secured to the underside of said container flange.

Preferably the container of this embodiment is in the form of a tray and the closure takes the form of a lid. In an alternative embodiment the container may be of a unitary construction wherein the closure is defined by a line of weakness. In such an embodiment the line of weakness is adapted to be breached during heating and thereby permit the container to be opened.

In one embodiment the container may be formed from a non-metallic material, for example plastic or cardboard. The container may be provided with heating means adapted to transfer heat energy to a food product supported thereupon and to the facing flanges which are held together by said adhesive. Said heating means may take the form of a dielectric layer. The dielectric layer may be formed integrally with the container. Alternatively the dielectric layer may be separate from the container and be attached thereto by any appropriate means such as adhesive. In one embodiment the dielectric layer may be omitted from a flange of the container so as to ensure that adhesive present on said flange is not heated when the container is subjected to microwave radiation.

In a further embodiment the container may be formed from a non metallic material such as plastic or cardboard. In such an embodiment the dielectric layer may be omitted and the adhesive between the facing flanges adapted to lose it's adhesiveness when heated in either a conventional or microwave over, or by steam generated by the food product when heated. In yet a further embodiment adapted solely for use in a conventional oven the container may be formed from a metallic material such as aluminium alloy. As before, the adhesive between the facing flanges is adapted to lose adhesiveness when heated or is contacted by steam generated by the food product when heated.

According to another aspect of the present invention there is provided a food product in a container according to the first aspect of the invention or any of the subsidiary clauses relating thereto.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which : Figure I shows a perspective view of a container according to an embodiment of the present invention in a closed position; Figure 2 shows a perspective view of the container of figure 1 in an open condition; Figure 3 shows a cross-sectional side view of the container of figure 1; Figure 4 shows a cross-sectional side view of an alternative container embodiment; and Figures 5 and 6 show perspective views of a container according to a further embodiment of the present invention in respective closed and open positions.

Referring firstly to figures 1 to 3 there is shown a food product container, generally designated 10, within which is contained a portion of a food product 32, for example a slice of pizza. The container 10 comprises a tray 12 having a rectangular base 14 and a peripheral wall 16 extending therearound to define a tray cavity 18 having a depth of about 20 millimetres. In the embodiment shown, the wall 16 extends both upwardly and outwardly from the base 14 such that the tray 12, when inverted, has the form of a truncated four sided pyramid. The upper edge of the peripheral wall 16 comprises a flange 20. The tray 12 is formed from a rigid non-metallic material such as cardboard or a plastics material. Provided on the base 14 within the tray cavity 18 is a dielectric layer 22. In the embodiment shown the dielectric layer overlies the base 14. In an alternative embodiment the dielectric layer 22 may be incorporated into the base 14, for example during manufacture of the tray 12.

Overlying the tray 12 is a lid 24 defined by a shaped layer of material. In the embodiment shown lid 24 has substantially the same shape as the tray, i. e. that of a truncated four sided pyramid, having a top 26 and a peripheral wall 28 having a flange 30. The lid 24 is secured to the tray 12 by the provision of adhesive between the respective flanges 20,30. The join between the tray 12 and lid 24 hermetically seals the food product 32 so as to prevent dehydration thereof during storage.

In use, the sealed container 10 is stored, for example in a refrigerated cabinet, until it is desired to heat and consume the portion of food product 32 contained therein. To heat the portion of food product 32 the container is placed in a microwave oven. As is well known in the art, microwave energy is absorbed by water molecules within the food product 32 to cause heating thereof. Additionally, the microwave energy is absorbed by the dielectric layer 22 which itself is heated, and which imparts heat energy to the

underside of the food product 32 in contact therewith. Steam is typically generated as a result of such microwave heating and it is necessary to vent the container 10 in order that the steam does not affect the quality of the food product, for example by rendering it soggy.

To that end the lid 24 is adapted to peel from the tray 12 (figure 2) in response to the generation of heat by the food product 32 during microwave heating thereof. To achieve this, the lid 24 is secured to the tray 12 on three sides with an adhesive which loses its adhesive properties when heated, and the lid 24 manufactured from a material adapted to curl away from the tray 12 when heated. The lid 24 is secured on a fourth side with an adhesive which does not lose its adhesive properties when heated and thus the lid 24 cannot fully disassociate itself from the tray 12 during microwave heating. It will be understood that alternative arrangements may be provided to ensure the lid 24 remains secured to the tray 12. For example, the lid 24 may extend around a flange of the tray 12 and be secured to the underside of said flange. Alternatively the lid 24 and tray 12 may be debossed, embossed or punched along a flange so as to provide a mechanical connection.

Once the microwave heating operation has been completed, the now open container 10 can be removed from the heating device, whereupon the heated food product 32 is presented ready for consumption. No further container opening operations are required to gain access to the food product. The material utilised for the tray 12 is sufficiently rigid after heating of the food product to allow the product to eaten from the tray 12.

Figure 4 shows an alternative embodiment of the present invention wherein the dielectric layer 22 extends fully across the inner surface of the tray 12. In this embodiment the dielectric layer 22 present on the flanges is heated, in use, by microwave energy which leads to melting of the adhesive provided on the flanges. As with the embodiment described above, it is highly desirable to have the lid 24 secured to the tray 12 along one side. This may be achieved in a number of ways including the removal of the dielectric layer 22 from one flange of the tray prior to the attachment of the lid 24 thereto. This ensures that the adhesive present on that flange is not heated when the container 10 is subjected to microwave energy and hence the adhesive does not melt. Alternatively, a flange of the tray may be provided with an adhesive having a sufficiently high melting point that it does not melt even when heated by the microwave excited dielectric layer on the flange. Further, as described above, the lid 24 may extend around a flange of the tray 12 and be secured to the underside of said flange.

Alternatively the lid 24 and tray 12 may be debossed, embossed or punched along a flange so as to provide a mechanical connection Referring now to figures 5 and 6 there is shown a further embodiment of a container, generally designated 34, according to the present invention. As before, the container 34 essentially comprises a tray 36 having a base 38 with an upstanding peripheral wall 40 and a lid 42. Again the lid 42 is adapted to open during microwave heating of a food product (not shown) so as to allow steam to escape from the container 34 during heating and to grant access to the heated food product without the need for further opening operations to be undertaken. In this embodiment the lid 42 is formed with lines of weakening 43 which permit the lid 42 to separate into four segments 44,46, 48,50, which curl away from the tray as indicated by the arrows of figure 5.

A suitable material for the lid is a laminate film such as a laminate of Mylar OL and D868 obtainable from DuPont pic. The material comprises a sheet of plastics having a plurality of layers having characteristics which respond differently when heated thereby causing the sheet to change shape and/or size during heating of the food product.

Claims (12)

Claims

1. A food product container having a closure, the container and closure defining a sealed cavity for a food product, wherein the closure is adapted to open in response to heating.

2. A food product container as claimed in claim 1 wherein the closure is adapted to open in response to heating of a food product within the container.

3. A food product container as claimed in claim 1 wherein the closure is adapted to open in response to external heating of the container.

4. A food product container as claimed in any of claims 1 to 3, wherein the closure is be adapted to open so as to enable access to the heated food product, and allow removal of the heated product from the container without the need for further container opening operations to be conducted.

5. A food product container as claimed in any preceding claim, wherein the closure is arranged so as to be retained in association with the container after opening thereof.

6. A food product container as claimed in any preceding claim wherein the closure comprises a material adapted to peel, curl, contract, shrink, expand or otherwise change shape and/or size when heated.

7. A food product container as claimed in any preceding claim wherein the closure is attached to the container at least in part by adhesive.

8. A food product container as claimed in any preceding claim wherein the container is in the form of a tray and the closure takes the form of a lid.

9. A food product container as claimed in claim 8 wherein the container is provided with heating means adapted to transfer heat energy to a food product supported thereupon.

10. A food product container as claimed in claim 9 wherein said heating means take the form of a dielectric layer.

11. In combination, a food product container and a food product, the container having a closure, the container and closure defining a sealed cavity for the food product, wherein the closure is adapted to open in response to heating.

12. A food product container substantially as hereinbefore described with reference to Figs. 1 to 4, or Figs. 5 and 6 of the accompanying drawings.