WO2003076302A1

WO2003076302A1 - Microwaveable vacuum package

Info

Publication number: WO2003076302A1
Application number: PCT/SE2003/000300
Authority: WO
Inventors: Joel Haamer; Claes Martinsson
Original assignee: Micvac Ab
Priority date: 2002-03-13
Filing date: 2003-02-25
Publication date: 2003-09-18
Also published as: AU2003206576A1; ES2253660T3; DE60302772T2; EP1483174A1; DE60302772D1; ATE312774T1; SE0200740D0; SE0200740L; EP1483174B1; SE519320C2

Abstract

A package is designed to contain food products (3), preferably food products (3) intended to be heated in a microwave oven, said package comprising a tray (1) and a plastic film arranged to cover the tray (4). A second plastic film (2) is arranged between the tray (1) and said first plastic film (4), said second plastic film (2) intended when in use to adapt its shape to that of the food product (3) upon evacuation of the space between said first (4) and said second (2) plastic films in which the food product (3) is contained. A method of packaging food products (3) in a package as defined above, said method comprising the steps of: arranging said second plastic film (2) inside said tray (1); positioning food products (3) inside the tray (1) on said second plastic film (2); arranging said first plastic film (4) on top of the food product (3) positioned inside said tray (1) on said second plastic film (2); and evacuating the space between said first plastic film (4) and said second plastic film (2), said space holding said food product (3). Drawing figure to be published: Fig 1

Description

MICROWANEABLEVACUUMPACKAGE

Technical field of the invention

The present invention relates to a package designed to contain food product, preferably food product intended to be heated in a microwave oven, said package comprising a tray and a plastic film arranged to cover the top face of the tray during use. The invention likewise relates to a method of packaging food product in a package in accordance with the invention.

Technical background of the invention

When ready-cooked dishes are produced in accordance with the method described in WO 00/0365, the food product is placed in a tray, whereupon a plastic film having a valve formed therein is arranged on top of the food product and the tray. The package with the food product contained therein are then inserted into a microwave tunnel for cooking of the food product to the ready-to-eat state, and during this cooking process vapor is produced. Napor exits through the valve, which preferably is a oneway valve, when the pressure inside the package exceeds the atmospheric pressure. When the cooking process is completed, the valve closes and the package is introduced into a cooling tunnel, in which vacuum is created inside the package automatically as a consequence of the condensation that takes place therein. One problem encountered in packages presently on the market is however, that if the tray is too soft, the appearance of the package will change as it is being evacuated, this change of appear- ance of the package being due to the uneven distribution on the tray of the food product as it is being placed thereon. In addition, it is desirable that the tray can be used as a plate, which a soft tray cannot do. This problem may, however, be overcome by a stiffer tray. Also a stiff tray is deformed considerably as a consequence of the evacuation process and for this reason a tray of this kind causes problems in storage and handling.

Another common way of packaging food products is to deep-freeze them to obtain a longer shelf life. However, deep-frozen food products require strict handling in order to guarantee that they remain deep-frozen until the time when they reach the consumer. In this case, the packages often consist of non-transparent bags or card- board boxes. The bag and the cardboard box are also used for presentation of information on their contents. Because of the formation of ice on the food it is likewise desirable that the food is not visible through the package. Although it is inexpensive to use bags and cardboard boxes to package foodstuff, bags are more difficult to handle, and one reason therefore is that they do not lend themselves to stacking. By instead packaging food product in trays covered by a plastic film the handling process is greatly facilitated. As a rule, trays thus covered by a plastic film are subsequently enclosed inside a paper package to improve their aesthetic appearance. On the other hand, the use of an external paper package increases the consumption of material and also a further packaging step is added to the production process.

Summary of the invention

The object of the present invention thus is to provide a package that solves the above referred-to problems . Another object of the invention is to provide a method of packaging foodstuff in a package in accordance with the invention.

These objects are achieved in accordance with the teachings of the invention by means of a package and a method possessing the characterizing features defined in claims 1 and 8, respectively, preferred embodiments being defined in the subsequent dependent claims 2-7 and 9-10, respectively.

In addition to a tray and a plastic film the inventive package also comprises a second plastic film ar- ranged between the tray and said first plastic film, said second plastic film intended when in use to adapt its shape to that of the food product upon evacuation of the space between said first and said second plastic films in which the food product is contained. The advantage of this solution is that the second plastic film deforms as a vacuum is being created in said space without such evacuation affecting the external appearance of the package. As a result, the package retains its appearance and consequently it may be stacked. A package of this kind is suitable for use together with ready-cooked as well as fresh food, whether intended for deep-freezing or refrigeration. A further advantage is the improved appearance of the package, also when a transparent plastic material is used, and the additional paper package conventionally used may be dispensed with. The provision of an additional plastic layer thus makes it possible to eliminate the subsequent paper package, which thus saves money as well as time.

In order to simplify the process of heating food products, particularly ready-cooked dishes, in a microwave oven, a valve preferably is provided on said first plastic film. Preferably, the valve is arranged to open when a predetermined excess pressure generates inside the package, i.e. in the space between the two plastic films. The heat is distributed inside the package as the latter is being heated as a result of the vapor created during this process spreading inside the package. When the food product then is sufficiently hot, pressure builds up from the vapor inside the package and finally the valve opens. When the valve opens it preferably, emits a sound signal as vapor flows out from the valve, thus indicating that the heating up of the food product is complete. Preferably, the valve consists of an adhesive layer, which may be applied on the uppermost plastic film. The adhesive layer is placed on top of a slit formed in the plastic film. The application of the adhesive layer could take place e.g. in conjunction with the application of the plastic film on the tray on top of the food product. A considerable advantage of a valve of this kind, in addition to the low costs, is that it does not add to the size of the package, i.e. it does not take up any space. In order to prevent deformation of the tray during the evacuation or heating processes one or several openings preferably are provided leading into the space between the plastic film positioned closest to the tray and the tray itself. The plastic film closest to the tray moves somewhat away from the tray during the evacuation process, and thus in the absence of an opening^' vacuum is created, which may cause deformation of the tray.

The top plastic film preferably is of a stiffer kind than the intermediate plastic film. During the evacuation process it is essentially the intermediate plastic film that changes its shape while the uppermost one continues to be stretched. The even plastic film offers the advantage of making the package more manageable because it may be stacked. Much time could be gained in packaging ready-cooked dishes if the food may be cooked in a microwave oven immediately after the application on top of the tray-supported food product of the top plastic film in which a valve is formed. When the food product is heated, it emits vapor and when a sufficient amount of vapor has been created the valve opens. Once the cooking is completed, the valve closes and the package is transferred to equipment for refrigeration/cooling, in which equipment evacuation takes place automatically in response to the refrigeration. Brief description of the drawings

The invention will be described in the following in more detail by means of one embodiment with reference to the accompanying drawings, wherein: Fig 1 is a cross-sectional view as seen from the side of a package in accordance with the invention, designed to hold food products.

Figs 2a-2d show the various steps of the packaging process in accordance with the invention up to the point when the top plastic film is applied to the package.

Description of preferred embodiments

The package shown in Fig 1 comprises a tray 1 and a bottom plastic film 2 and an top plastic film 4. Food 3 is located between the plastic films 2, 4. The tray 1 is formed with openings 5 serving to prevent the formation of a below-atmospheric pressure or excess pressure in the space between the bottom plastic film 2 and the tray 1. In accordance with one embodiment of the package a valve 6 is formed in the top plastic film 4. In accordance with one preferred embodiment of the invention, the valve 6 is in the form of a tape, which is positioned on top of a slit formed in the top plastic film 4. The package of Fig 1 is shown in the stage when the food product 3 is pack- aged and the space between the two plastic films 2, 4 is evacuated.

Figs 2a-2d show the composition of the package. Fig 2a shows a tray 1 with openings 5 formed therein. Fig 2b shows the manner in which a plastic film 2 is arranged inside the tray. The plastic film 2 is preferably welded to the edges of the tray 1. Fig 2c illustrates the situation when food product 3 has been positioned on top of the plastic film 2 and Fig 2d the situation when a second plastic film has been applied to the package in a posi- tion wherein it covers the food product and jointly with the bottom plastic film 2 it forms a closed space, in which the food product 3 lies protected. Also the top plastic film 4 preferably is welded to the bottom film 2 and to the edges of the tray 1. The closed space is then evacuated, whereby the bottom plastic film 2 adapts itself to the shape of the food product 3 inside the closed space. The top plastic film 2 preferably is arranged on top of the tray 1 in a manner ensuring that the plastic film 4 is in a stretched condition such that it does not alter its shape as a result of the evacuation process and does not adapt its shape to that of the food product 3. In accordance with a preferred embodiment of the inventive object the top plastic film 4 is of a somewhat stiffer kind than the bottom one to further counteract tendencies of deformation.

As should be appreciated many modifications of the embodiment described above are possible within the scope of protection of the invention as defined in the appended claims. For example as described above, the valve could be an indication of fracture made in the plastic film, the dimensions of which fracture is such as to ensure that it bursts when exposed to a predetermined load. A valve of this kind thus is a single-use valve. In addition, it is possible to design the opening or openings between the tray 1 and the bottom plastic film 2 in other ways than the one shown in the drawing figures. For exam- pie, the bottom plastic film 2 need not be welded to the tray 1 along the entire perimeter edges thereof, in which case the non-welded sections form the openings through which air may exit.

Claims

1. A package designed to contain food products (3), preferably food products (3) intended to be heated in a microwave oven, said package comprising a tray (1) and a plastic film arranged to cover the tray (4) , c h a r a c t e r i z e d in that a second plastic film (2) is arranged between the tray (1) and said first plastic film (4) , said second plastic film (2) intended when in use to adapt its shape to that of the food product (3) upon evacuation of the space between said first (4) and said second (2) plastic films in which the food product (3) is contained.

2. A package as claimed in claim 1, wherein a valve (6) is formed in said first plastic film (4) .

3. A package as claimed in claim 2, wherein said valve consists of an adhesive layer (6)

4. A package as claimed in claim 2, wherein said valve (6) is arranged to emit a sound signal as vapor flows out from the valve (6) .

5. A package as claimed in claim 2, wherein said valve (6) is arranged to open when a predetermined excess pressure is reached inside the package.

6. A package as claimed in claim 1, wherein the tray (1) is formed with at least one opening (5) designed to allow passage-through of air upon evacuation and heating of the food product .

7. A package as claimed in claim 1, wherein said first plastic film (4) is stiffer than said second plastic film (2) .

8. A method of packaging food products (3) in a package as defined in claim 1, said method comprising the steps of: arranging said second plastic film (2) inside said tray (1) ; positioning food products (3) inside the tray (1) on said second plastic film (2) ; arranging said first plastic film (4) on top of the food product (3) positioned inside said tray (1) on said second plastic film (2) ; and evacuating the space between said first plastic film (4) and said second plastic film (2) , said space holding said food product (3) .

9. A method as claimed in claim 8, comprising the step of cooking said food product (3) in a microwave oven prior to the evacuation.

10. A package as claimed in claim 8, wherein said evacuation takes place automatically.