WO2008017308A1

WO2008017308A1 - Package having one or more compartments and a method of preserving food in a package

Info

Publication number: WO2008017308A1
Application number: PCT/DK2007/000370
Authority: WO
Inventors: Anders Thorbjørn JENSEN
Original assignee: R. Faerch Plast A/S
Priority date: 2006-08-10
Filing date: 2007-08-10
Publication date: 2008-02-14

Abstract

The invention involves a package (1) having one or more compartments (7) adapted for storing heat-treated food, said food preferably containing one or more polyunsaturated fatty acids, wherein the package comprises a thermoformed multilayer laminate foil having at least one layer made of a polymeric material, and wherein the package comprises at least one closure part (2) which is removable by peeling. Such a package is suitable for replacing metal cans as a means of packaging for long term storage of food and is generally more conveniently handled by the end-user, e.g. when opening the package.

Description

Package having one or more compartments and a method of preserving food in a package

The present invention relates to a package having one or more compartments adapted for 5 storing heat-treated food. The invention further relates to a package for at least one type of food and a method of preserving at least one type of food in a package.

Background

10 Canned food has been known for many years. The types of canned food range over a wide variety such as fish, meat, pate, vegetables etc. The food may be pre-cooked or raw when filled into metal cans, after which a closure is attached hermetically in order to protect the content against the entry of micro-organisms and/or germs during and after heat processing. The can is heat treated at a relatively high temperature, in the range of 90-

15 140⁰C, in order to destroy micro-organisms, which may otherwise cause deterioration of the food. The heat treatment process is adjusted to the actual product in order to obtain Commercial sterility, which implies that the product is free from micro-organisms and/or germs capable of growing in the food at temperatures at which the food is likely to be held during distribution and storage. Heat treatment is typically done in an autoclave or retort.

20 During a heat treatment the product can be sterilised or pasteurised depending on whether or not germs will be destroyed.

It is also known to preserve e.g. pre-cooked meals, also known as TV-dinners, in a plastic package wherein the food is heat treated at a relatively low temperature, such as at 70- 25 100⁰C, after which the package is stored at around 5 degrees Celsius or less, to obtain a shelf life of up to a month. Longer shelf life may be obtained by storing the products at a temperature well below zero degrees, such as deep freezing.

Canned food may be stored at room temperature for months and some even for years.

30

Cans are also widely used because of their ability to withstand the over and under pressure in the package, which happens during the heat treatment process, zero permeability and the ability to close the can very securely and thereby preventing the package from opening ■ during the heat treatment. During the years producers of autoclaves and retorts have

35 improved the control system of the heat treatment equipment, which has allowed thinner gauge cans, and the use of plastic as a packaging solution for food. Some disadvantages are related to the use of cans. The price of the actual can and the timeframe and costs to design and produce new cans are long and costly. Cans are not consumer friendly as they often are difficult to open and the end consumer need to transfer the food from the can to another container if they need to keep the food in for example a refrigerator after opening the can because of the chemical reaction taking place when the metal is subject to atmospheric air. Can producers have tried to solve this issue by using different types of lacquers, but it is difficult for the end user to know if they need to transfer the food to another container and some of the lacquers used have been questioned because of migration/off-taste issues. By using plastic containers some of these issues can be prevented. A new container design is easily done and tools for new thermoformed containers are relatively cheap and can be produced within a few weeks. To the end-user it is easier to open a package composed of a plastic container and a sealable film and the food can be stored in the same container after it has been opened.

Glass jars are used for some applications, typically with a screwed on metal closure. A major disadvantage of glass is the required thickness and thereby the weight of an actual container as well as the risk of glass fragments in the food.

The environmental impacts of using cans are a subject with different views and beliefs. In Denmark incineration is used to dispose of waste from households and metal cans are therefore not a good solution. Plastic containers, unlike metal cans, are a very good waste component as it helps the incineration process. Different plastic solutions are present in the market today. Widely used solutions are packages made from polymers like PP (Poly propylene), PS (Poly styrene), PE (poly Ethylene) or APET (Amorphous Poly Ethylene Terephthalate) in combination with typically an EVOH (Ethylene Vinyl Alcohol) layer in a co-extruded or laminated multilayer structure. Some of these structures are normally only suitable in applications where in which the food is not heat treated in the package. This involves foods like rice, nuts, dried pasta, spices etc.

A co-extruded or laminated PP/EVOH/PP structure has been used for containers for applications where heat treatment is needed. In this solution the PP layers provide sufficient rigidity at the temperatures typically used in an autoclave or retort to prevent significant deformation during the autoclave process. The rigidity of PP is commonly explained by the stiffness of PP above tg (Glass transition temperature). A precise control of the autoclave or retort is mandatory in order to prevent the package from opening during the process and to prevent excessive deformation of the package. The EVOH layer is used because of its good oxygen barrier properties. A known sealing film for a container made of PP/EVOH/PP is made of a film having the same PP/EVOH/PP structure. The disadvantage of a PP/EVOH/PP or a similar solution is the off-taste/migration of PP and the influence of water on the EVOH. To determine migration of the final container migration tests are carried out under test conditions specified in the Directives 85/572/EC, 82/71 I/EC and its amendments 93/8/EC and 97/48/EC under the following conditions:

- 2 hours at 100⁰C followed by 10 days at 40⁰C in 3% acetic acid

- 2 hours at 100⁰C followed by 10 days at 40⁰C in 15% ethanol

- 2 hours at 121°C followed by 10 days at 40⁰C in olive oil

The migration results of PP are typically within the limits of the directives but especially tests in olive oil can show results varying from no migration above 1.0 mg/dm2 detected, up to the maximum or even above the limit of 13 mg/dm2. The migration is depending on the raw material chosen, whether it is a co or homo polymer, colour master batches and degradation during the extrusion process. PP is commonly known to cause off-taste on the food in the package, which is observed by some food producers. The oxygen barrier properties of PP relatively poor with typical permeability co-efficients of 1500-4500 (cm³ x 25 μm) / (m² x 24h x Bar) measured at 23 degrees Celcius and 0% relative humidity according to ISO 2556, DIN 53380. The barrier properties of EVOH are significantly better with values ranging from 0.25 to 1.5 depending on the actual grade and supplier of the EVOH. The disadvantage of EVOH is that EVOH is hygroscopic and water is acting as a plasticizer decreasing the barrier properties of EVOH, but the material may however still be useable. The barrier properties are also depending on the relative humidity in the storage environment.

Summary of the invention

An object of the invention is to overcome the disadvantages in use of the known types of packagings for preserved foods, such as metal cans and known plastic solutions. Another object is to provide a package suitable for storing food under ambient temperatures well above 5 degrees Celsius. A further object is to provide a method of preserving food for storage under such temperatures. A yet further object is to provide package for preserved food which is easily opened by hand. Other objects appear from the following description and claims.

One aspect of the invention involves a package having one or more compartments adapted for storing heat-treated food, said food preferably containing one or more polyunsaturated fatty acids, wherein the package comprises a thermoformed multilayer laminate foil having at least one layer made of a polymeric material, and wherein the package comprises at least one closure part which is removable by peeling. Such a package is suitable for replacing metal cans as a means of packaging for long term storage of food and is generally more conveniently handled by the end-user, e.g. when opening the package.

Another aspect of the invention involves a package containing food, where the package and the food has been heat treated at a temperature above 70 degrees Celsius, preferably above 100 degrees Celsius, and where the package comprises a container part comprising a food receiving opening, said container being made of a first foil suitable for contact with food, which is arranged to face the food, said first foil including at least one layer comprising at least 70% polyethylene terephthalate of which at least 15 percent is in crystalline state (CPEET) and having a thickness of at least 200 μm, and where the container part of the package is made by a method including a step of shaping the foil by thermoforming,

a closure part made from a second foil including at least two layers, where at least one barrier layer is made of a material selected from a group comprising aluminium, aluminium oxide (AIOx), aluminium alloy, ethyl vinyl alcohol (EVOH), modified polyester with improved barrier properties, polyvinylidene chloride (PVDC), polyamide (PA) and silicium oxide (SiOx), and at least one base layer suitable for contact with food and preferably comprising at least 90% polyethylene terephthalate (PET), said base layer being arranged to face the food, and where the closure part is arranged to close and seal the receiving opening of the container part, and where at least part of the closure part is removable from the container part by peeling. The first foil is including at least one layer comprising at least 70% polyethylene terephthalate. The remaining up to 30% of the at least one layer of the first foil and the remaining up to 10% of the base layer, when PET is used, are additives which are added in order to accelerate the crystallisation process, to improve the impact resistance properties, to change the colour, etc. The first foil may be made in an extrusion or co-extrusion process, or a plurality of layers may be laminated together to form a suitable foil.

Such a package is suitable for replacing metal cans as a means of packaging for long term storage of food and is generally more conveniently handled by the end-user, e.g. when opening the package. Also, it is possible to make at least part of the package transparent, whereby the contents are better displayed.

In a preferred embodiment the first foil comprises at least two layers, at least a first layer of polyethylene terephthalate of which at least 15 percent is in crystalline state and at least a second layer of amorphous polyethylene terephthalate (APET), where said second layer is arranged to face the food. Improved sealing capability may hereby be obtained than by using only non-amorphous PET.

In another embodiment the second foil includes one layer of aluminium or aluminium alloy with a thickness between 2 μm and 50 μm. By such a thickness the layer is easily pliable during opening and still provides a sufficient oxygen barrier. The second foil may also include one layer of polyethylene terephthalate with a thickness between 12 μm and 60 μm to provide sufficient strength to avoid accidental rupture.

In a further embodiment the food contains one or more polyunsaturated fatty acids. This may include that the food comprises fish, in particular salmon, herring, mackerel, eel or other type of fish containing one or more polyunsaturated fatty acids, or fish oil. PET and CPET are especially suitable for use where polyunsaturated fatty acid is present. Other types of plastics may interact with food components, causing off-taste and/or migration of various compounds from the plastic into the food in the package.

In a still further embodiment the reception opening may have a lateral extent substantially corresponding to at least half a lateral extent of the container part and preferably substantially corresponding to the lateral extent of the container part. This convenient when food is filled into the package, but do also lead to a relatively large closure part. This is advantageous, when the material used for the closure part is a better oxygen barrier than the material used for the container part.

A preferred embodiment may involve the container part being adapted to have sufficient stability to function as a dinner plate, serving plate or serving tray for the food, when the closure part is absent. This is convenient when the food is e.g. a ready meal, because the PET material may withstand the temperature present when the food is heated in an oven, a microwave oven or a steamer.

The food may preferably comprise at least one animal substance, including poultry, fish or meat, including meat from a wild, farmed or livestock animal.

It may be preferred that the food has been pre-cooked or otherwise processed prior to being introduced into the package.

The package and the food may have been heat treated to a temperature between 70 degrees Celsius and 121 degrees Celsius, preferably between 105 to 120 degrees Celsius or 108 to 118 degrees Celsius. The temperature is selected high enough and for an adequate time in order to destroy the types of micro organisms and germs present or potentially present, for health reasons. On the other hand, too high temperature may deteriorate the quality of the food.

The package has preferably been subjected to an external pressure above atmospheric pressure while being heated in order to counteract deformation of the package, said external pressure being below 5 Bar, preferably below 3 Bar or below 2 Bar. The pressure is suitably selected to prevent bursting of the package as well as to counteract undesired, possibly permanent deformation.

However, the selection of suitable temperatures, pressures and time is a matter which must be found in situ dependent on the food type, the characteristics of the package, such as size, material etc., as well as on the machinery actually used for the heat treatment process.

During the sealing process gas may be introduced around the package and the food while the closure part were attached to close the package, said gas comprising carbon dioxide, preferably comprising carbon dioxide and nitrogen resulting in a defined gas composition in the closed package.

A further aspect of the invention involves a method of preserving food in a package, said method comprising:

- placing the food in a thermoformed container part comprising a food receiving opening, said container being made of a first foil suitable for contact with food, which is arranged to face the food, said first foil including at least one layer comprising at least 70% polyethylene terephthalate of which at least 15 percent is in crystalline state (CPET) and having a thickness of at least 200 μm,

- closing and sealing the receiving opening of the container part with a peelable closure part to form a closed package, said closure part being made from a second foil including at least two layers, where.at least one first layer is a barrier layer made of a material selected from a group comprising aluminium, aluminium oxide (AIOx), aluminium alloy, ethyl vinyl alcohol (EVOH), modified polyester with improved barrier properties, polyvinylidene chloride (PVDC), polyamide (PA) and silicium oxide (SiOx), and at least one second layer is a base layer suitable for contact with food and preferably made of polyethylene terephthalate, said other layer being arranged to face the food, and heat treating the package including the food to a temperature above 70 degrees Celsius, preferably above 100 degrees Celsius. Brief description of the invention

The following is a detailed description of examples of embodiments of the invention. The figures are merely included as information given as examples to a skilled person as to how the invention may be carried out.

- Figure 1 displays a perspective view of one packaging according to the invention.

- Figure 2 displays a perspective view of another package according to the invention.

- Figure 3 displays a perspective view of a further package according to the invention.

Figure 1 displays a package containing food. The package comprises a container part 1 made of an extruded foil including at least one layer containing crystalline polyethylene terephthalate (CPET). The foil is suitable for contact with food under elevated temperatures and following storage. The CPET material may face the food in the container or a further layer of APET may face the food, or another layer of a suitable material. When CPET is used, at least 15 percent of the layer is in the crystalline state. The foil has a total thickness between 200 μm and 1300 μm. The container part 1 of the package is made by a method including a step of shaping the foil by thermoforming. A food receiving opening 7 is adapted to receive the food. The package further comprises a closure part 2 made from a second foil, which includes at least one barrier layer made of a material selected from a group comprising aluminium, aluminium oxide (AIOx), aluminium alloy, ethyl vinyl alcohol (EVOH), modified polyester with improved barrier properties, polyvinylidene chloride (PVDC), polyamide (PA) and silicium oxide (SiOx), and at least one base layer which preferably is made of polyethylene terephthalate, where the base layer is facing the food. The closure part 2 is arranged to close and seal the receiving opening 7 of the container part 1. The container part 1 may have a rim 4 adapted to receive the closure part 2, such that a sealing film can be sealed to the rim 4 without contact to the unshown food in the package. After one or more food products are filled into the container part 1, a closure part 2 is applied to close and seal the package. After closing the package is heat treated in order to obtain long shelf life of the contained food. The heat treatment may be performed in any known process per se, e.g. retort, autoclave to achieve a pasteurised or sterilised product. Care must of course be taken to avoid too high pressure in the package, which is dependent on the composition of the food, water content and the possibilities to adjust the parameters of the autoclave or retort. A protruding lip 3 is arranged on the closure part 2 in order to facilitate easy opening of the package. The closure part 2 is removable from the package by peeling. Fig. 2 and 3 show other embodiments of packages. In Fig. 3 is four container parts 1 connected in regions 5 and 6 in order to have a package with four separate rooms.

In all the examples of Figs. 1-3 the reception opening 7 is having a lateral extent substantially corresponding to the lateral extent of the container part 1. The reception opening 7 may also be smaller, but is preferably between half of the lateral extent and full lateral extent of the container part 1.

CPET is a preferred material for the container part of packages for several applications. It may be used as a container for ready meals where the food is raw or precooked. It may be used where the food needs to be heated afterwards in a microwave oven or a normal oven.

By using CPET the end-user does not need to transfer the food into another container for heating but can use the container in which is was bought. CPET is a known polymer, which has the ability to crystallise during thermoforming. CPET is available from different raw material suppliers like Voridian™, Advansa™, Wellman™ etc. Different additives can be added during extrusion of the sheet for the following thermoforming process. Additives which may be added are:

Additives to accelerate the crystallisation process - Additives to increase the number of crystallisation nuclei Additives to improve the impact resistance properties Additives to change the colour Additives to increase the modulus of elasticity

The level of crystals in a CPET container ranges typically between 15% to 30%, depending on the measurement method, additives and production parameters. Thermal stability of the container is dependent on the level of crystallinity. The higher the level of crystallinity the better is the thermal stability. A thermoformed CPET container may be able to withstand temperatures up to 240 degrees Celsius while maintaining its shape and dimensions. The crystals in CPET have a melting point of 249-255 degree Celsius.

The oxygen barrier properties of CPET are well suited for applications involving food and has permeability co-efficients between 66 up to 110 (cm³ x 25 μm) / (m² x 24h x Bar) measured at 23 degrees Celsius and 0% relative humidity, according to ISO 2556 or DIN 53380 and depends on the level of crystallinity and additives.

The actual permeability of any gas is inversely proportional to the thickness, i.e. doubling the thickness halves the permeation of any gas. Materials with oxygen permeability coefficients below 150 (cm³ x 25 μm) / (m² x 24h x Bar) measured at 23 degrees Celsius and 0% relative humidity, according to ISO 2556 or DIN 53380 is believed to be sufficient for many food applications if the heat tratment process has been carried out successfully and so-called Commercial sterility has been achieved.

A CPET container does allow some oxygen to permeate. Hence, CPET as a general solution for food with a shelf life up to 2-10 years may not be achievable, but as a solution where shelf life up to 2 years is obtainable.

The wall thickness of a thermoformed container is important as direct consequence of the above-mentioned issues. The thickness of the container is depending on the thickness of the sheet and technology used in the thermoforming process. The wall thickness of a container typically ranges between the thickness of the foil used and down to approx. 20% of the thickness of the foil. A wall thickness of 130 μm at the thinnest point of a CPET container is believed sufficient to achieve shelf life up to 2 years.

The seal ability of the CPET container can be improved by co-extrusion of an APET top- layer on a CPET foil and is preferred in order to achieve good sealing properties of the container.

The actual values of barrier properties needed for a specific application may be found by testing, such as the minimum barrier property needed of the container part and the closure part in order to achieve a certain shelf life at a certain temperature at a certain relative humidity.

Definitions

Whenever mentioned in the present context, the following abbreviations are to be understood as:

"PE" is Poly Ethylene

"PP" is Poly Propylene

"PET" is Poly Ethylene Terephthalate

"CPET" is Crystalline Poly Ethylene Terephthalate

"APET" is Amorphous Poly Ethylene Terephthalate "EVOH" is Ethylene Vinyl Alcohol

"PVDC" is Polyvinylidene Chloride

"PA" is Polyamide

"AlOx" is Aluminium Oxide

"SiOx" is Silicium Oxide "μm" is micro-meters, equivalent to 10^"6 metres or 0.000001 metres or 0.001 millimetres

Example 1

A package for food may include a container part made of CPET foil having a thickness of 5 200 μm up to 1300 μm with or without an APET top-layer for improved seal ability.

Example 2

A package for food may include a closure part made of a foil composed of a layer of polyester sealing film designed for sealing on APET or CPET with a thickness 12 μm up to 10 60 μm, a layer of aluminium with a thickness of 2 μm up to 50 μm or a film with similar barrier sealing properties as aluminium, such as EVOH or modified polyester with improved barrier properties, such as Kurarister™ , or PVDC or PA or AIOx or SiOx, and optionally an additional polyester film with a thickness of 2 μm up to 50 μm to protect the barrier layer.

15 Example 3

A package for food may include a closure part made of a foil with a total thickness between 20 up to 80 μm and preferably between 20 μm and 50 μm. The thickness of the foil has great influence on the total permeation/transmission of oxygen into the package. To compensate for the barrier properties different layers may be added through a laminating

20 or co-extrusion process. A preferred structure may be:

- a top layer for protecting a barrier layer and to provide heat stability towards the heated sealing head in a sealing machine. The top layer may be made of an oriented PET but PA or oriented PA could be used as well. PA is used especially in

25 cases where improved impact strength is needed. The use of PA may avoid the use of a specific barrier layer since PA has better barrier properties than PET, but with decreased shelf life as a result.

- a barrier layer for improving the barrier properties of the foil. Different materials 30 may be used as a barrier, e.g. Nylon, EVOH, PVDC, Kurarister™, aluminium or aluminium applied through a metallization process. A preferred solution is to use an aluminium film when transparency is not needed.

- a base layer comprising a sealing medium. The base layer provides the sealing

35 ability to the container. Typically the base layer is made from bi-oriented PET which is made heat stable through bi-oriented stretching. A sealing medium is often added through a coating process or by co-extrusion. It is preferable that one or more layers in the foil are made of bi-oriented PET because of costs and good heat stability. Normally bi-oriented PET films are heat stable up to approximately 250 degrees Celsius. Typical sealing temperatures are between 180-200 degrees Celsius, but in some cases increased temperatures are needed to compensate for other issues in the sealing process. Therefore it is recommended to use a film which is heat stable up to minimum 220 degrees Celcius. There are several producers of bi-oriented PET films, such as Dupont Teijin Films™ and Mitsubishi

Polyester™ and both of them produce sealing films through coating and co- extrusion. These films which are able to seal to PET and CPCT and are available in different grades depending on the seal strength, how easy they are to peel off, i.e. peel ability, in both cold and hot condition and costs. Basically there are two different solutions available. One is a solid seal where the container part and the closure part are sealed very hard such that an instrument is typically needed to open the package. The solid seal provide a sealing solution which easily can withstand the pressure build-up in the package and the temperatures it gets exposed to during the heat treatment process. Another option is Peel able foils, which makes it easier to open the package by the end-user. This option is normally preferred if possible.

Example 4

A package for food may include a closure part made of a PET/ALUMINIUM/PET layered foil provided by EHRNO FLEXIBLE A/S in Denmark. The foil includes a 12 μm top-layer made of oriented PET, which improves the stiffness of the foil and protects a middle aluminium layer against scratches and corrosion. The middle layer is a 9 μm aluminium film, which improves the barrier properties. The base layer is a 25 μm PET sealing film, which is characterised by its sealing strength and properties. The sealing properties of the base layer on a PET container is characterised as peel-able but it keeps sufficient sealing strength during a heat treatment process and at the temperatures and moisture level typically present during such a process in an autoclave or retort. The base layer allows higher as well as lower pressures in the package without opening the seal between the container part and the closure part during the heat treatment process. The different layers are laminated together and adhesives are used to bond them together.

A container made from a container part according to example 1 and a closure part according to example 2, 3 or 4 may be used for food, which needs to be heat treated in or order to achieve a shelf life from 3 months up to 2 years under room temperature conditions, such as in a supermarket.

It is to be understood that the invention as disclosed in the description and in the figures may be modified and changed and still be within the scope of the invention as claimed hereinafter.

Claims

1. A package having one or more compartments adapted for storing heat-treated food, said food preferably containing one or more polyunsaturated fatty acids, wherein the package comprises a thermoformed multilayer laminate foil having at least one layer made of a polymeric material, and wherein the package comprises at least one closure part which is removable by peeling.

2. A package according to claim 1, wherein the laminate foil is transparent.

3. A package according to claim 1 or 2, wherein the laminate foil is suitable for being heated to a temperature up to less than 200 degrees Celcius.

4. A package according to any of claims 1-3, wherein the closure part is attached by gluing or welding.

5. A package according to any of claims 1-4, wherein the food comprises at least one animal substance, including poultry, fish or meat, including meat from a wild, farmed or livestock animal.

6. A package according to any of claims 1-5, where the package is adapted to have sufficient stability to function as a dinner plate, serving plate or serving tray for the food, when the closure part is absent.

7. A package according to any of claims 1- 6, wherein the closure part is having a lateral extent substantially corresponding to at least half a lateral extent of the package and preferably substantially corresponding to three quarters of the lateral extent of the package, and more preferably to substantially corresponding to the overall lateral extent of the package.

8. Package according to any preceding claim, wherein the food has been pre-cooked or otherwise processed prior to being introduced into the package.

9. A multilayer laminate foil having at least one layer made of a polymeric material and being adapted for use in a package according to claim 1, and wherein the foil has a total thickness of at least 100 μm.

10. A package containing food, where the package and the food have been heat treated at a temperature above 70 degrees Celsius, preferably above 100 degrees Celsius, and where the package comprises:

5 - a container part comprising a food receiving opening, said container being made of a first foil suitable for contact with food, which is arranged to face the food, said first foil including at least one layer comprising at least 70% polyethylene terephthalate of which at least 15 percent is in crystalline state (CPET) and having a thickness of at least 200 μm, and where the container part of the package is made by a method 10 including a step of shaping the foil by thermoforming,

- a closure part made from a second foil including at least two layers, where at least one barrier layer is made of a material selected from a group comprising aluminium, aluminium oxide (AIOx), aluminium alloy, ethyl vinyl alcohol (EVOH), modified

15 polyester with improved barrier properties, polyvinylidene chloride (PVDC), polyamide (PA) and silicium oxide (SiOx), and at least one base layer suitable for contact with food and preferably comprising at least 90% polyethylene terephthalate (PET), said base layer being arranged to face the food, and where the closure part is arranged to close and seal the receiving opening of the container part, and where at least part of

20 the closure part is removable from the container part by peeling.

11. Package according to claim 10, wherein the first foil comprises at least two layers, at least a first layer of polyethylene terephthalate of which at least 15 percent is in a crystalline state (CPET) and at least a second layer of amorphous polyethylene

25 terephthalate (APET), where said second layer is arranged to face the food.

12. Package according to claim 10 or 11, wherein the first foil has a total thickness between 200 μm and 1300 μm.

30 13. Package according to any of claims 10-12, wherein the second foil includes one layer of aluminium or aluminium alloy with a thickness between 2 μm and 50 μm.

14. Package according to any of claims 10-13, wherein the second foil includes one layer of polyethylene terephthalate with a thickness between 12 μm and 60 μm.

35

15. Package according to any of claims 10-14, wherein the food contains one or more polyunsaturated fatty acids.

16. Package according to any of claims 10-15, wherein the food comprises fish, in particular salmon, herring, mackerel, eel or other type of fish containing one or more polyunsaturated fatty acids, or fish oil.

5 17. Package according to any of claims 10-16, wherein the reception opening is having a lateral extent substantially corresponding to at least half a lateral extent of the container part and preferably substantially corresponding to the lateral extent of the container part.

18. Package according to any of claims 10-17, wherein the container part is adapted to 10 have sufficient stability to function as a dinner plate, serving plate or serving tray for the food, when the closure part is absent.

19. Package according to any of claims 10-18, wherein the food comprises at least one animal substance, including poultry, fish or meat, including meat from a wild, farmed or

15 livestock animal.

20. Package according to any of claims 10-19, wherein the food has been pre-cooked or otherwise processed prior to being introduced into the package.

20 21. Package according to any of claims 10-20, wherein the package and the food have been heat treated at a temperature between 70 degrees Celsius and 121 degrees Celsius, preferably between 105 to 120 degrees Celsius or 108 to 118 degrees Celsius.

22. Package according to any of claims 10-21, wherein the package has been subjected to 25 an external pressure above atmospheric pressure, while being heat treated, in order to counteract deformation of the package, said external pressure being below 5 Bar, preferably below 3 Bar or 2 Bar.

23. Package according to any of claims 10-22, wherein gas was introduced around the 30 package and the food while the closure part was attached to close the package, said gas comprising carbon dioxide, preferably comprising carbon dioxide and nitrogen.

24. A package adapted for containing food and for being heated to a temperature above 70 degrees Celsius, preferably above 100 degrees Celsius, while sealed and containing food,

35 the package comprising:

- a container part comprising a food receiving opening, said container being made of a first foil suitable for contact with food, which is arranged to face the food, said first foil including at least one layer comprising at least 70% polyethylene terephthalate of which at least 15 percent is in crystalline state (CPETT) and having a thickness of at least 200 μm, and where the container part of the package is made by a method including a step of shaping the foil by thermoforming,

5 - a closure part made from a second foil including at least two layers, where at least one barrier layer is made of a material selected from a group comprising aluminium, aluminium oxide (AIOx), aluminium alloy, ethyl vinyl alcohol (EVOH), modified polyester with improved barrier properties, polyvinylidene chloride (PVDC), polyamide (PA) and silicium oxide (SiOx), and at least one base layer suitable for contact with 10 food and preferably comprising at least 90% polyethylene terephthalate (PEET), said base layer being arranged to face the food, and where the closure part is arranged to close and seal the receiving opening of the container part, and where at least part of the closure part is removable from the container part by peeling.

15 25. Method of preserving food in a package, said method comprising:

placing the food in a thermoformed container part comprising a food receiving opening, said container being made of a first foil suitable for contact with food, which is arranged to face the food, said first foil including at least one layer comprising at least 20 70% polyethylene terephthalate of which at least 15 percent is in crystalline state (CPET) and having a thickness of at least 200 μm,

- closing and sealing the receiving opening of the container part with a peelable closure part to form a closed package, said closure part being made from a second foil including at least two layers, where at least one first layer is a barrier layer made of a

25 material selected from a group comprising aluminium, aluminium oxide (AIOx), aluminium alloy, ethyl vinyl alcohol (EVOH), modified polyester with improved barrier properties, polyvinylidene chloride (PVDC), polyamide (PA) and silicium oxide (SiOx), and at least one second layer is a base layer suitable for contact with food and preferably made of polyethylene terephthalate, said second layer being arranged to

30 face the food, and

- heat treating the package including the food to a temperature above 70 degrees Celsius, preferably above 100 degrees Celsius.

26. Method of preserving food in a package according to claim 25, wherein the package is 35 in an embodiment according to any of claims 1-24.

27. Use of a package according to any of claims 1-24 to preserve food for storage in ambient temperatures above 5 degrees Celsius and below 25 degrees Celcius.