WO2004089623A1

WO2004089623A1 - Packaging for food product

Info

Publication number: WO2004089623A1
Application number: PCT/GB2004/001599
Authority: WO
Inventors: Chris Barker; Chris Martin
Original assignee: H.J. Heinz Frozen & Chilled Foods Limited
Priority date: 2003-04-14
Filing date: 2004-04-13
Publication date: 2004-10-21
Also published as: GB0308598D0; AU2004228447A1

Abstract

Provided is a healable packaging for a food product, which packaging comprises an outer layer (1) situated on a substrate (2), wherein: (a) the substrate (2) comprises a heat absorbent layer (5) and a carrier layer (6); and (b) the outer layer (1) comprises a transparent layer (3) and a design layer (4); wherein the design layer is situated between the substrate and the transparent layer.

Description

PACKAGINGFORFOODPRODUCTS

The present invention concerns packaging for a food product, in particular packaging for a food product that can be cooked in the packaging, and which is printed and flexible. The invention also concerns a method for packaging a food product, and food products packaged using the packaging and methods of the invention.

Convenience food products, such as frozen or chilled bread based products and pizzas, are a popular consumer food product which may be conveniently stored in freezer or fridge until consumption is required. Typically, the product is then removed from the fridge or freezer and cooked or reheated in an oven. In the case of frozen products, to avoid an inconvenient delay for defrosting, they are preferably cooked or reheated directly. However, because of the low temperature of the product when it is removed from the fridge or freezer, a relatively long cooking time is required compared to a fresh product in order to bring the centre of the product through the latent heat zone up to the necessary temperature for palatability and bacteriological safety. This effect is exacerbated with heavily topped products, such as deep pan pizzas. The disadvantage of this is that the product must be removed from the packaging for cooking or reheating, since high quality printed flexible packaging is not able to withstand the heating process, which is inconvenient for some products and consumers.

A number, of attempts have been made to provide improved packaging for these products, which is capable of withstanding the cooking or reheating process. These efforts have generally met with limited success. It is known to provide packaging for a food product, having a paper layer attached to a heat absorbent layer formed from metal, which in turn is attached to a carrier layer. The carrier layer is formed from a polymer and serves to carry the food product. The outer paper layer is printed with an ink layer displaying the product attractively for marketing purposes. However, such packaging has a number of disadvantages. The paper layer has to be designed to withstand high temperatures, but the paper that needs to be used tends to allow the ink layer to run, resulting in poor product appearance. In addition, the paper layer does not provide an excellent barrier to the exterior of the packaging, resulting in a lower than desirable product shelf life. Moreover, the packaging layers generally are less robust than desirable, making transport of the product more difficult. This is a particular problem for snack products, which are preferably available from a wide variety of shops and outlets, such as vending machines, petrol stations, etc. and therefore typically need to be transported longer distances than other food products. Finally, the known packaging also suffers from poor ability to withstand water, which is significant for frozen and chilled products which are stored in a freezer or fridge, where condensation or water (e.g. from defrosted ice) may easily come into contact with the packaging.

The present invention aims to overcome the disadvantages of the prior art methods and products, and in particular to provide an improved packaging for a food product, which allows the food product to be cooked or reheated in the packaging, whilst mamtaining the high quality of the food product, and ensuring that the packaging is also flexible and printed to a high quality. Cooking in the packaging is particularly desirable for snack products, which are often eaten on the move, since they can then be eaten directly from the packaging.

It is also an aim of the present invention to improve the shelf-life of the food product, and to improve the resistance of the packaging to water. It is a further aim of the invention to improve the look of the packaging for marketing purposes, and to provide packaging that can perform effectively through the supply chain, from factory to cold store, to supermarket and finally to the consumer, and be able to withstand the rigours of transportation effectively.

The present invention therefore provides a heatable packaging for a food product, which packaging comprises an outer layer and a substrate, wherein:

(a) the substrate comprises a heat absorbent layer and a carrier layer; and

(b) the outer layer comprises a transparent layer and a design layer; wherein the design layer is situated between the substrate and the transparent layer.

Thus, the packaging of the present invention comprises a transparent outer layer, preferably a polymeric layer, which serves to protect the layers beneath. Such a layer is particularly advantageous, since it can withstand the temperatures required for cooking or reheating, whilst additionally being able to receive a printed ink layer on its underside (reverse printing) which serves as the design layer. Because of this, it is possible to dispense with a paper layer for printing the design layer, thus removing many of the disadvantages associated with the paper layer in the known packaging. The polymer layer also adds robustness to the packaging, improving transport capabilities, whilst simultaneously providing a barrier to the elements, thus increasing shelf-life and improving resistance to water.

Although a paper layer is not required, if desired such a layer may be present. The paper need not be the same paper as in the known packaging, but by virtue of the presence of the outer polymeric layer, paper more suitable for printing (if the paper is to be printed), or more able to withstand heating, can be selected. In this case, there is no requirement to consider the other properties of the paper, which could not be ignored in known packaging. Thus the paper layer may be a polymeric-type paper or a wood-based paper.

It is a particular advantage of the present packaging that the food product may be cooked or heated in the packaging, without the need to remove the packaging and place the product on a plate or cooking dish. As a result, the product can be cooked and eaten using the packaging to handle the product whilst eating. Typically, such as in the case of food products that do not comprise a high proportion of water, such as bread-based products, cooking or heating can take place whilst the packaging is still sealed. Typically, the food product used in the present invention is a snackfood product.

The present invention further provides a method for forming a heatable packaging for a food product, which method comprises:

(a) forming a design layer on at least a portion of a transparent layer;

(b) applying an adhesive to at least a portion of the transparent layer, on the same side as the design layer; and

(c) laminating the transparent layer to a substrate, comprising a heat absorbent layer and a carrier layer, at a temperature of from 40°C to 55°C, to form the heatable packaging.

Typically the substrate layer is formed first, using standard lamination techniques known in the art, and then the transparent layer, with its design layer and adhesive, is laminated to the substrate, as defined above. Typically, the transparent layer is a polymeric layer. In a particularly preferred embodiment, the temperature employed in step (c) is from 47°C to 53 °C, more preferably about 50°C. The heatable packaging to be produced in the method is typically any of the heatable packaging defined herein. Thus, the transparent layer, the design layer, the heat absorbent layer and the carrier layers preferred in the packaging of the present invention, as described below, are all preferably employed in the method of the present invention.

The present method has particular advantages over known methods. In known methods, heatable packaging could not be produced having a transparent outer layer, since attempts to produce such packaging had failed because of delamination of the outer layer during heating. However, in the present invention this problem has been solved by applying the adhesive to the transparent layer and using a lower lamination temperature of from 40-55°C. In known methods, typical lamination temperatures of 70°C were employed, and the adhesive was generally applied to the upper layer of the substrate (usually a paper layer). Without being bound by theory, it is believed that the present method prevents adhesive being absorbed into the substrate layer in two ways: first by applying the adhesive to the less porous transparent layer, and second by using a lower temperature to increase the viscosity of the adhesive during lamination. It is believed that these measures lead to more adhesive remaining on the surfaces being laminated, instead of being absorbed, which creates a stronger bond, and avoids the delamination seen in known products.

The present invention will now be described in more detail by way of example only, with reference to the following Figures, in which:

Figure 1 shows a schematic of the basic packaging, depicting the outer layer (1), the substrate (2), the transparent layer (3), the design layer (4), the heat absorbent layer (5) and the carrier layer (6); and

Figure 2 shows a schematic of a multilayer packaging including further optional layers, depicting the outer layer (1), the substrate (2), the transparent layer (3), the design layer (4), the heat absorbent layer (5), the carrier layer (6), a heat seal layer (7), an adhesive layer (8) and another adhesive layer (9). The present invention will now be described in more detail.

The nature of the transparent layer used in the present invention is not especially limited, provided that it is capable of withstanding the cooking or reheating procedure. The layer is generally a polymeric layer. Preferably the polymer employed for the layer comprises a polyester, a polyimide and/or a regenerated cellulose polymer. When the polymer is a polyimide, it is preferred that nylon is employed. However, most preferably, the polymer comprises a polyester, such as Mylar, Melinex® 800, Melinex® 813, Melinex® 850 and/or

Melinex® 852 (all available from Dupont/ICI Europe). Most preferably Melinex® 800 or

Melinex® 850 is employed. The thickness of the layer is not especially limited, provided that this does not affect the cooking of the product or its appearance. Typically the layer has a thickness of from 10 μm to 40 μm.

The design layer may comprise any type of layer that is suitable for the purposes of displaying the product according to marketing requirements. Typically the layer comprises ink. Preferably the design layer is a full colour layer, and the method of printing and surface for printing is determined based upon the type of design and design layer employed. The design layer is preferably reverse printed on the underside of the transparent layer. In an alternative embodiment, the design layer may be printed on the upper side of a paper-based, or other material, layer, situated directly beneath the transparent layer.

The type of ink employed is not particularly limited, and any ink commonly used on packaging or for other marketing materials may be employed. Inks that can be used in the present invention include nitro-cellulose based ink systems, PVB-based ink systems, urethane-based ink systems, cap ink systems and/or acrylic ink systems. Any convenient method of printing may be used to apply the ink, including, but not limited to, screen printing, flexographic printing, gravure printing, pad printing and heat transfer printing.

The heat absorbent layer serves to aid in the cooking or reheating of the food product. The heat absorbent layer may be formed from any material provided that the material does not hinder the ability of the layer to aid in the cooking or reheating of the product. It is particularly preferred that the heat absorbent layer is arranged for absorbing microwave radiation such that the resultant heat is imparted by conduction to the surface of the contained food product, preferentially heating it, evaporating moisture from its surface and crisping it. The heat absorbent layer may also be termed a receptor layer, since such technology is also known in the art as receptor technology. It is preferred that the heat absorbent layer comprises a metal. The most preferred metal for use in this layer is aluminium, but other metals may be employed to achieve similar effects if desired, such as iron and/or stainless steel.

In a preferred embodiment, the heat absorbent layer comprises a support layer. This layer is preferably present, because when the heat absorbent layer is heated in a microwave, it may otherwise cause layers that it is in contact with to wrinkle and/or shrink, depending upon the materials used in the respective layers. A support layer serves to prevent this. The support layer may be made from any material that effectively serves this function. Preferably, however, the support layer comprises board, paper, cellulose or a combination of these. When there is a support layer present, typically particles of the heat absorbent material (such as aluminium particles) are applied to the supporting layer to form the heat absorbent layer.

In a preferred embodiment of the present invention, the heat absorbent layer exhibits an optical density which is favourable for heat absorption when heating occurs using microwave radiation. Preferably the heat absorbent layer has an optical density of from 0.15-0.35 nm. More preferably, the optical density of the heat absorbent layer ranges from 0.20-0.30 nm and most preferably from 0.25-0.30 nm. The optical density of the layer can be optimised for the type of food product to be used in the packaging. For example, for a wet food product (one containing a relatively large proportion of water, an optical density at the lower end of the range is preferred, e.g. from 0.18-0.20 nm, whilst for drier products an optical density at the higher end may be preferred, e.g. from 0.30-0.32 nm. The optical density of the layer is an optical density measured according to standard methods known in the art using a Tobias Densitometer.

The carrier layer of the present packaging serves to hold the food product. It is also preferable that the food product is prevented from direct contact with the heat-absorbent layer, in order to prevent uneven heating, and to avoid contamination of the food product. This is required when the heat absorbent layer comprises a metal, for food standards compliance. Thus, the carrier layer is typically situated internally from the heat absorbent layer and comprises a material suitable for separating a food product from the heat absorbing layer. The material from which the carrier layer is formed is not especially limited, provided that its function is not impeded, but it is preferred that a polymer is employed. Preferably the polymer employed for the layer comprises a polyester, a polyimide and/or a regenerated cellulose polymer. When the polymer is a polyimide, it is preferred that nylon is employed.

However, most preferably, the polymer comprises a polyester, such as Mylar, Melinex® 800,

Melinex® 813, Melinex® 850 and/or Melinex® 852 (all available from Dupont/ICI Europe).

Most preferably Melinex® 852 is employed. The thickness of the layer is not especially limited, provided that this does not affect the cooking of the product or its appearance. Typically the layer has a thickness of from 10 μm to 40 μm. More preferably, the thickness of the layer is from 12-30 μm.

In a preferred embodiment, at least a portion of the substrate comprises a heat seal layer, suitable for sealing one portion of the substrate to a further portion of the substrate. In this way the packaging may be sealed with the food product inside, in the manner of a confectionary bar, or similar product. Such products are convenient for consumers and easy to unseal before consumption. Generally the heat seal layer is situated on an internal portion of the carrier layer. The heat seal layer may be comprised of any material suitable for sealing the packaging, provided that the material is able to withstand the cooking or heating procedure. Preferably the heat seal layer comprises a polymer, more preferably an elastomeric polymer. When this material is a polymer, the polymer employed for the layer generally comprises an EVA polymer, a styrene polymer, a polyester, a polyimide, a polyamide, a PVDC polymer, a polyethylene and/or a regenerated cellulose polymer. When the polymer is a polyimide, it is preferred that nylon is employed. However, most preferably, the polymer comprises a polyester. Suitable commercially available products for this purpose include Melinex® and Mylar such as, Melinex® 800, Melinex® 813, Melinex® 850 and/or

Melinex® 852 (all available from Dupont/ICI Europe). Most preferably Melinex® 852 is employed. The thickness of the layer is not especially limited, provided that this ^"does not affect the cooking of the product or its appearance. The thickness of the transparent layer is not especially limited, provided that its function is not impaired. Typically the layer has a thickness of from 0.5 μm to 30 μm, more preferably from 1 μm to 20 μm and most preferably from 2 μm to 14 or 15 μm. In most instances this layer will range from 2-6 μm in thickness.

The heat seal layer may be applied by any means, provided that the function of the packaging is not impaired. Preferably the heat seal layer is applied by employing a direct gravure roller coater using a reverse kiss effect. Typically, the seal will retain its integrity over a temperature range of from 120°C to 220°C.

The packaging of the present invention may further comprise one or more additional adhesive layers, if desired. The adhesive layers may be included if it becomes necessary to hold two or more of the above layers more firmly together. Preferably there is an adhesive layer between the heat absorbent layer and the carrier layer. This typically serves to adhere the heat absorbent layer to the carrier layer, but also to prevent break-up of the heat absorbent layer during the cooking or heating process. The nature of the additional adhesive layer is not especially limited provided that its function is not impaired. In a preferred embodiment (especially for a layer between the heat absorbent layer and the carrier layer) the adhesive comprises an acrylic compound and/or a casein latex compound. Suitable commercially available products for this purpose include wet bond acrylic (available from Henkel), Adcote (available from Rohm and Haas) and foil/paper acrylic (available from HB Fuller).

In a further preferred embodiment, an additional adhesive layer may be situated between the substrate and the design layer. This is particularly preferred when the design layer is reverse printed onto the transparent polymer layer, since otherwise the design layer may interfere with adhesion between the heat absorbent layer and ^"the transparent layer. In some embodiments, this adhesive layer is important for ensuring that the transparent layer does not delaminate from the heat absorbent layer during the heating or cooking process. This was a particular problem in similar known packaging systems which were subjected to heat. This further adhesive layer may be formed from any material, provided that its function is not impaired, such as with the adhesives above mentioned in respect of the first further adhesive layer. Suitable commercially available products for this purpose include Liofoil adhesive (available from Henkel) and Adcote (available from Rohm and Haas). It is especially preferred that in this layer a 2-component adhesive is employed.

In addition to the above embodiments, the present invention also provides a packaged food product comprising a food product packaged with the heatable packaging as defined above.

The food product may be any food product, but preferably is a snack food product. Preferably the food product is a product comprising bread and/or is a bread-based product. However any other food that benefits from the crisping effect of the heat absorbent layer (the receptor layer) may be employed. This includes any food product that may benefit from the application of extra heating to its surfaces, such as pastry products, dough based products, potato products, products coated with batter or breadcrumbs and even meat or fish based products such as burgers, sausages, fillets and any product that can be microwave cooked and benefits from the surface heating effect of the receptor layer.

An example of such a food product preferred for use i the present invention would be a product based on garlic bread, pizza, toast or another bread-based recipe. The pizza or other product may have any topping or filling, and the taste and recipe are selected according to the taste of the consumers to which the product is directed. For such an application, preferred fillings include typically a tomato-based sauce followed by cheese, pepperoni, salami, tomato, mushroom, pineapple, ham, bacon, spinach, egg, peppers, tuna, olives, sausage, or baked beans or any combination of the above. It is important that the filling is distributed evenly within or atop the product. If the filling is unevenly distributed (for instance if it is deposited only into the centre of the base), the product may cook unevenly. Parts covered by too much topping may be undercooked while uncovered parts of the bread base may become overcooked.

It is particularly preferred in the present invention that the food product is a frozen food product.

The present invention also provides a method for cooking a food product as defined above, which method comprises heating the packaged food product in a conventional oven, or in a microwave oven. As explained above, the packaging may remain sealed during heating, but preferably a portion of the packaging seal is opened to allow steam to escape, typically the end seal.

Further provided by the present invention is a method for packaging a food product comprising:

(a) filling with a food product, a packaging as defined above; and

(b) sealing the packaging to package the food product.

The food product may be sealed in the packaging by any method, provided that the function of the packaging and quality of the food product are not impaired. In one embodiment, the food product may be put into the packaging using vertical form fill seal equipment and in an alternative embodiment horizontal flow wrap equipment may be employed. In either case, the packaging is preferably sealed through heat sealing opposing sides of the formed packaging along a back seal and end seals. The relatively greater thickness of the multilayered packaging may sometimes require a greater application of heat than in conventional packaging to effect a good seal that will withstand the rigours of handling and distribution, but this can be effected using conventional sealing apparatus and does not affect the quality of the food product or the packaging..

EXAMPLE

In the following Example, a heatable packaging having the following layer structure was produced:

Polyester - ink - adhesive / paper - adhesive - metal - polyester 852

The polyester - ink — adhesive layer corresponds to the outer layer of the present invention, whilst the paper - adhesive - metal - polyester layers correspond to the substrate layer of the present invention. The outer polyester was a clear Melinex® polyester obtainable from ICI and DuPont, already described above. The metal corresponds to the heat absorbent layer and the polyester 852 to the carrier layer. Polyester 852 is the Melinex® 852 described above. The paper layer is one of the optional layers that may be present. The paper layer employed may be a polymer-type paper, or wood-based paper. Polymer-type paper was used in this Example.

The metal-polyester 852 is obtained commercially as a metalised polyester layer or film. A film width of 700 mm is employed in this Example. In a first lamination step, a film-type adhesive was applied to the metal side of the metalised polyester film. The paper layer was laminated to the metalised polyester layer at a temperature of 20°C using standard laminating apparatus, to form the substrate layer. A temperature range of from 15-30°C is generally preferred for this step.

In a separate step, the outer transparent polyester layer was printed on one side with the ink layer using a desired design. This design was the Heinz 'Bite Me' product design. A 700 mm width polyester film was used. After printing, adhesive 7740 was applied to the printed surface, to form the outer layer.

In a second lamination step, the outer layer was laminated to the substrate layer at a temperature of 50°C using standard laminating apparatus. To complete the heatable packaging, the laminated layers may be cut to size, and then heat sealed together along one side and at each end. One end must clearly remain unsealed, until the packaging has been filled with the food product.

Once the packaging had been formed, the Heinz 'Bite Me' product was sealed inside, and cooked in a microwave oven, with a small opening being placed in an end seal to allow the escape of steam. The packaging was seen to withstand the cooking process without any delamination. In addition the 'Bite Me' product was well cooked throughout, crisp, and when eaten displayed good mouth feel and taste characteristics.

This demonstrates the effectiveness of the packaging of the present invention.

Claims

CLAIMS:

1. A heatable packaging for a food product, which packaging comprises an outer layer situated on a substrate, wherein:

(a) the substrate comprises a heat absorbent layer and a carrier layer; and

2. A heatable packaging for a food product according to claim 1, wherein the transparent layer comprises a polyester layer.

3. A heatable packaging for a food product according to claim 1 or claim 2, wherein the design layer comprises a layer of ink.

4. A heatable packaging for a food product according to any preceding claim, wherein the heat absorbent layer comprises a metal layer.

5. A heatable packaging for a food product according to claim 4, wherein the metal layer is arranged for absorbing microwave radiation.

6. A heatable packaging for a food product according to claim 4 or claim 5, wherein the metal layer comprises aluminium.

7. A heatable packaging for a food product according to any of claims 4-6, wherein the metal layer has an optical density of from 0.20-0.25 nm.

8. A heatable packaging for a food product according to any preceding claim, wherein the carrier layer is situated internally from the heat absorbing layer and comprises a material suitable for separating a food product from the heat absorbing layer.

9. A heatable packaging for a food product according to claim 8, wherein the carrier layer is formed from a polyester.

10. A heatable packaging for a food product according to any preceding claim, wherein at least a portion of the substrate comprises a heat seal layer, suitable for sealing one portion of the substrate to a further portion of the substrate.

11. A heatable packaging for a food product according to claim 10, wherein the heat seal layer is situated on an internal portion of the carrier layer.

12. A heatable packaging for a food product according to claim 10 or claim 11, wherein the heat seal layer comprises a polyester.

13. A heatable packaging for a food product according to claim 12, wherein the heat seal layer comprises Melinex® 10.

14. A heatable packaging for a food product according to any preceding claim, wherein the packaging comprises an additional adhesive layer between the heat absorbent layer and the carrier layer.

15. A heatable packaging for a food product according to claim 14, wherein the additional adhesive layer comprises an acrylic compound and/or a casein latex compound.

16. A heatable packaging for a food product according to any preceding claim, wherein the packaging comprises an additional paper layer between the substrate and the design layer..

17. A heatable packaging for a food product according to any preceding claim, wherein the packaging comprises an additional adhesive layer between the substrate and the design layer.

18. A heatable packaging for a food product according to claim 17, wherein the additional adhesive layer is a 2-component adhesive layer.

19. A method for forming a heatable packaging for a food product, which method comprises

(a) forming a design layer on at least a portion of a transparent layer;

20. A method according to claim 19, wherein the temperature employed in step (c) is

21. A method according to claim 19 or claim 20, wherein the heatable packaging comprises packaging as defined in any of claims 2-18.

22. A heatable packaging for a food product obtainable by a method as defined in any of claims 19-21.

23. A packaged food product comprising a food product packaged with the heatable packaging as defined in any of claims 1-18 and 22.

24. A packaged food product according to claim 23, wherein the food product is selected from a dough-based product, a bread-based product, a potato-based product, a pastry-based product and a batter-based product.

25. A packaged food product according to claim 23 or claim 24, wherein the food product is selected from a filled food product and a topped food product.

26. A packaged food product according to any of claims 23-25, wherein the food product is selected from a product comprising garlic bread, pizza, toast, fries, formed potatoes and extruded potatoes.

27. A packaged food product according to any of claims 23-26, which is a frozen food product.

28. A method for cooking a food product as defined in any of claims 23-27, which method comprises heating the packaged food product in a conventional oven, or in a microwave oven.

29. A method according to claim 28, wherein the packaging has a sufficient portion of the seal opened to vent steam.

30. A method for packaging a food product comprising:

(a) filling a heatable packaging as defined in any of claims 1-18 and 22, with a food product; and

(b) sealing the packaging to package the food product.

31. A method according to claim 30, wherein the food product comprises a food product as defined in any of claims 24-27.