EP3022128A1 - A system for preparing a food product, a package and a method for packaging food products - Google Patents

A system for preparing a food product, a package and a method for packaging food products

Info

Publication number
EP3022128A1
EP3022128A1 EP14818272.8A EP14818272A EP3022128A1 EP 3022128 A1 EP3022128 A1 EP 3022128A1 EP 14818272 A EP14818272 A EP 14818272A EP 3022128 A1 EP3022128 A1 EP 3022128A1
Authority
EP
European Patent Office
Prior art keywords
package
opening
cover film
food product
overpressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP14818272.8A
Other languages
German (de)
French (fr)
Other versions
EP3022128A4 (en
Inventor
Henrik JACOBSON
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Micvac AB
Original Assignee
Micvac AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Micvac AB filed Critical Micvac AB
Publication of EP3022128A1 publication Critical patent/EP3022128A1/en
Publication of EP3022128A4 publication Critical patent/EP3022128A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
    • B65D81/34—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents for packaging foodstuffs or other articles intended to be cooked or heated within the package
    • B65D81/3446—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents for packaging foodstuffs or other articles intended to be cooked or heated within the package specially adapted to be heated by microwaves
    • B65D81/3453—Rigid containers, e.g. trays, bottles, boxes, cups
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/10—General methods of cooking foods, e.g. by roasting or frying
    • A23L5/17—General methods of cooking foods, e.g. by roasting or frying in a gaseous atmosphere with forced air or gas circulation, in vacuum or under pressure
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/30—Physical treatment, e.g. electrical or magnetic means, wave energy or irradiation
    • A23L5/34—Physical treatment, e.g. electrical or magnetic means, wave energy or irradiation using microwaves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D2205/00—Venting means
    • B65D2205/02—Venting holes

Definitions

  • the present invention relates to a system for preparing a food product, a package for food products and a method for packaging food products.
  • the one-way valve is a separate component attached to the cover film and which, at a certain combination of parameters in the form of heat and pressure, opens and closes the package respectively.
  • the one-way valve is associated with several problems in that it makes the package more expensive and complicated, and further it is also sensitive to variations in processing parameters. A certain amount of packages with a one-way valve suffers from valve failure, which results in that the packaged food product must be discarded. Further, the one-way valve is sensitive for choice of material in, for example, the cover film, whereby heating of the cooked and packaged food product in a later stage is limited to microwave heating.
  • An object of the present invention is to provide a system for preparing a food product, a package and a method for simple and inexpensive packaging of food products.
  • a further object is to reduce the abovementioned shortcomings with a oneway valve of food product packages.
  • the invention therefore relates to a system for preparing a food product comprising a microwave source for heating a food product, and a package for the food product.
  • the package comprises a tray and a cover film comprising an opening for venting of gas at overpressure that is produced when cooking a food product contained in the package during supply of microwaves at a power P.
  • the opening has an opening area A adapted so that the ratio between the opening area A and the supplied power P is in the range of 0,005 and 0,06 mm 2 /W, preferably between 0,01 and 0,03 mm 2 /W, and more preferably between 0,015 and 0,025 mm 2 /W.
  • the opening thus has a sufficiently large opening area A so that it allows a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure. Further, the opening area A is sufficiently small to maintain an overpressure in the package during a time period after the supply of microwave energy has ceased, which time period allows the package to be sealed in a subsequent processing step.
  • the opening area A may be adapted such that the time period is greater than 2 seconds, preferably more than 5 seconds, or more than 10 seconds. Thereby the time period is sufficiently long to allow the package to be sealed in a subsequent processing step.
  • the opening may be formed with a smooth edge to minimize points of fracture, which could entail that the package breaks due to overpressure during cooking.
  • the opening may be circular. Thereby the edge of the opening is smooth essentially without points of fracture.
  • a circular opening is also strong since it provides a large opening area for a minimized perimeter of the edge.
  • the opening may be formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped. Thereby material in the cover film is moved radially outward relative to the extension of the tool and strengthens the edge around the opening. No material is removed from the cover film when using this technology.
  • Another advantage with this technology is that openings may be formed in the cover film in a later processing step, when the cover film already is sealed to the tray. Since no material is removed from the cover film, there is no risk that material from the cover film is brought into the packaged food product.
  • the opening may be formed in the cover film by perforation of the cover film by means of laser cutting, punching or melting. Since these technologies entail a removal of material from the cover film (evaporation when laser cutting, mechanical removal when punching, and removal when melting), openings should be pre-formed in the cover film with these technologies, before it is sealed to the tray. Laser cutting has the advantage of very precisely being able to define the form and shape of the opening.
  • the microwave power may be in the range 200-800 W, preferably 300-600 W, more preferably 400-500W.
  • the opening area A may be between 3-8 mm 2 .
  • the plastic film may comprise a ductile material, preferably polyamide. Thereby it is achieved a mechanical stability in the cover film, to withstand the overpressure that occurs during cooking.
  • the plastic film may also comprise a barrier material, such as polypropylene and/or polyamide, which works as barrier material for diffusion of oxygen into the food product.
  • the plastic film may further comprise a material which is suitable for being attached to the tray by heating or welding. Examples of such materials may be polypropylene or polyethylene, depending on the material used in the tray.
  • the package may further comprise an adhesive label intended for sealing the opening and which comprises a barrier material.
  • an adhesive label intended for sealing the opening and which comprises a barrier material.
  • the number of openings in the cover film may be several, which jointly form the opening area A so that they allow a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure. Thereby it is achieved a further strengthening of the opening, since forces that arise around the edges of the opening during the influence of the overpressure in the package are distributed over a larger edge length for a given opening area.
  • Each opening is preferably formed with a smooth edge, such as circular openings.
  • a package is achieved, which is cooked during supply of microwave power where the risk of the package breaking during cooking is small, and where the package, when cooking is completed, in an easy way and during a sufficiently long time period may be sealed in a separate subsequent processing step.
  • the sealing of the opening may occur during a time period of more than 2 seconds, preferably more than 5 seconds, or more than 10 seconds after the supply of microwave power has ceased and while an overpressure is being maintained in the package during this time window. Thereby the time period is sufficiently long to allow that the package is sealed in a subsequent processing step.
  • the sealing of the opening may occur during a time period in the range of 2- 60 seconds, preferably 5-30 seconds, more preferably 10-20 seconds after the supply of microwave energy has ceased and while an overpressure is maintained in the package during this time window.
  • the opening may be formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped, in such a way that the opening gets a smooth edge. Thereby it is achieved an opening with a smooth edge which minimizes breaking points, which could mean that the package breaks due to overpressure during cooking.
  • the opening may be formed by perforation of the cover film after a food product is packaged in the tray and the cover film is sealed to the tray. Thereby the packaged and non-cooked food product is kept sealed until the perforation step.
  • Fig. 1 shows a cross section of a package for food products, at a number of steps (a)-(f) of a method for packaging of food products according to one embodiment of the invention.
  • Fig. 2 shows one (a) and several (b) openings in the cover film.
  • Fig. 3 shows a method according to one embodiment of the invention.
  • Fig. 4 shows a diagram of time t to sealing for different opening areas A.
  • Fig. 1 shows a cross section of a package for food products, at a number of method steps (a)-(f).
  • Fig. 1 a shows a package 101 comprising a tray 103 with a food product 102 to be packaged and cooked.
  • the tray is made in a material that withstands microwave heating and that has a low permeability to oxygen, for example polypropylene.
  • the package further comprises a cover film 104 of a material that withstands microwave heating.
  • the cover film comprises several layers of different materials, such as a polyamide layer which brings mechanical stability and a barrier function, i.e. a low permeability of oxygen, and a layer, such as polypropylene, for heat welding to the tray.
  • the cover film comprises an opening 105, which is located centrally on the cover film relative to the tray. According to the embodiment shown in Fig. 1 a, the opening is formed in the cover film before sealing to the tray. If the cover film is provided on a roll, openings may be pre-formed in the cover film on the roll.
  • the openings may be formed in the cover film in a perforation step which is performed before the cover film is sealed to the tray.
  • the opening area A may be formed by a single opening 205 in the cover film 204 (Fig. 2a), or by several sub-openings 215 in the cover film 204 (Fig. 2b).
  • the sub-openings 215 thus jointly and together form the opening area A.
  • the cover film is sealed to the tray at a joint 106 around the edge of the tray. This may be done for example by applying heat or by welding, such as ultrasonic welding. In the tray there is thereby formed a space 107 which contains said food product and a certain amount of gas (air). The gas in the space 107 may be vented through the opening 105 in the cover film.
  • the food product in the package is heated by supply of microwaves 108.
  • a typical microwave power is 400-500W.
  • the whole absorbed microwave power generates water vapor in the space 107 that holds gas.
  • the pressure in this space increases, and the gas is vented out through the opening 105.
  • the opening has a sufficiently large opening area A and is formed with a smooth edge so that it allows a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure. Thereby it is avoided that the cover film breaks up due to tension in the film, and that the sealing between cover film and tray is maintained.
  • the sealing takes place while there is still an overpressure in the package.
  • the opening 105 is sealed, Fig. 1 e, with an adhesive label 1 10 in order to seal the space 107 in the package.
  • the adhesive label comprises a layer with barrier properties such as polypropylene, for limiting transportation of oxygen from the surroundings into the space 107 and the food product 102 in the package.
  • Fig. 4 shows a graph of measured time period (seconds) to sealing for a package, for different opening areas A (mm 2 ).
  • the package was cooked at a microwave power of 440 W.
  • the ratio between the opening area and supplied power is 0,009 mm 2 /W.
  • a time period of 24 s is reached before the package should be sealed.
  • the ratio between the opening area and supplied power is 0,012 mm 2 /W. At this opening area, a time period of 16 s is reached before the package should be sealed.
  • the ratio between the opening area and supplied power is 0,014 mm 2 /W. At this opening area, a time period of 14 s is reached before the package should be sealed.
  • the ratio between opening area and supplied effect is 0,005 mm 2 /W, and at an opening area of 10 mm 2 the ratio is 0,023 mm 2 /W.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Food Science & Technology (AREA)
  • Health & Medical Sciences (AREA)
  • Nutrition Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Polymers & Plastics (AREA)
  • Mechanical Engineering (AREA)
  • Package Specialized In Special Use (AREA)

Abstract

The invention relates to a system and package for food products which comprises a tray and a cover film which comprises an opening for venting of gas at overpressure that arises when cooking a food product contained in the package during supply of microwaves at a power P, wherein the opening has an opening area A adapted such that the ratio between the opening area and the supplied effect is in the range of 0,005 and 0,06mm2/W, preferably between 0,01 and 0,03 mm2/W, more preferably between 0,015 and 0,025 mm2/W, so that the opening has a sufficiently large opening area A that it allows a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure, and so that the opening area A is sufficiently small to maintain an overpressure in the package during a time period after the supply of microwave power has ceased, which time period allows the package to be sealed in a subsequent processing step. Further there is described a method for packaging of food products.

Description

A SYSTEM FOR PREPARING A FOOD PRODUCT, A PACKAGE AND A METHOD FOR PACKAGING FOOD PRODUCTS
Technical field
[0001 ] The present invention relates to a system for preparing a food product, a package for food products and a method for packaging food products.
Background
[0002] It is previously known from SE 51 1353 to boil and vacuum pack mussels with shells and other food products by using microwave heating. The packaging of what is to be stored is done in a somewhat flexible plastic package which is sealed. On top of the package there is a venting hole, which releases steam when boiling but is immediately closed when microwave heating ceases, wherein negative pressure is formed in the package when the steam is condensed. Thus a vacuum packed pasteurized product is obtained in a single step.
[0003] Furthermore, there is previously described the design of a vent in the form of a one-way valve, see SE 520355, SE 519320 and SE 521684. The one-way valve is a separate component attached to the cover film and which, at a certain combination of parameters in the form of heat and pressure, opens and closes the package respectively. The one-way valve is associated with several problems in that it makes the package more expensive and complicated, and further it is also sensitive to variations in processing parameters. A certain amount of packages with a one-way valve suffers from valve failure, which results in that the packaged food product must be discarded. Further, the one-way valve is sensitive for choice of material in, for example, the cover film, whereby heating of the cooked and packaged food product in a later stage is limited to microwave heating.
[0004] Thus there is a need for a simpler and improved package and packaging method. Summary of the invention
[0005] An object of the present invention is to provide a system for preparing a food product, a package and a method for simple and inexpensive packaging of food products.
[0006] A further object is to reduce the abovementioned shortcomings with a oneway valve of food product packages.
[0007] The invention therefore relates to a system for preparing a food product comprising a microwave source for heating a food product, and a package for the food product. The package comprises a tray and a cover film comprising an opening for venting of gas at overpressure that is produced when cooking a food product contained in the package during supply of microwaves at a power P. The opening has an opening area A adapted so that the ratio between the opening area A and the supplied power P is in the range of 0,005 and 0,06 mm2/W, preferably between 0,01 and 0,03 mm2/W, and more preferably between 0,015 and 0,025 mm2/W. The opening thus has a sufficiently large opening area A so that it allows a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure. Further, the opening area A is sufficiently small to maintain an overpressure in the package during a time period after the supply of microwave energy has ceased, which time period allows the package to be sealed in a subsequent processing step.
[0008] Thereby there is obtained a package that may be cooked during supply of microwave power wherein the risk of the package breaking during cooking is small, and wherein the package, when cooking has been completed, in an easy way and during a sufficiently long time period, may be sealed in a separate subsequent processing step.
[0009] The opening area A may be adapted such that the time period is greater than 2 seconds, preferably more than 5 seconds, or more than 10 seconds. Thereby the time period is sufficiently long to allow the package to be sealed in a subsequent processing step.
[0010] The opening may be formed with a smooth edge to minimize points of fracture, which could entail that the package breaks due to overpressure during cooking. The opening may be circular. Thereby the edge of the opening is smooth essentially without points of fracture. A circular opening is also strong since it provides a large opening area for a minimized perimeter of the edge.
[001 1 ] The opening may be formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped. Thereby material in the cover film is moved radially outward relative to the extension of the tool and strengthens the edge around the opening. No material is removed from the cover film when using this technology. Another advantage with this technology is that openings may be formed in the cover film in a later processing step, when the cover film already is sealed to the tray. Since no material is removed from the cover film, there is no risk that material from the cover film is brought into the packaged food product.
[0012] The opening may be formed in the cover film by perforation of the cover film by means of laser cutting, punching or melting. Since these technologies entail a removal of material from the cover film (evaporation when laser cutting, mechanical removal when punching, and removal when melting), openings should be pre-formed in the cover film with these technologies, before it is sealed to the tray. Laser cutting has the advantage of very precisely being able to define the form and shape of the opening.
[0013] The microwave power may be in the range 200-800 W, preferably 300-600 W, more preferably 400-500W. The opening area A may be between 3-8 mm2. Thereby a range is obtained, where the risk of the package breaking during cooking is small, and where the package, when cooking is completed, in an easy way and during a sufficiently long time period, may be sealed in a separate subsequent processing step.
[0014] The opening may be provided at a central portion of the cover film.
Thereby it is achieved that the opening, at normal orientation of the package, during cooking of a food product contained in the package, due to the
overpressure in the package forms a highest point of the package, why mainly gas flows out of the opening.
[0015] The plastic film may comprise a ductile material, preferably polyamide. Thereby it is achieved a mechanical stability in the cover film, to withstand the overpressure that occurs during cooking. The plastic film may also comprise a barrier material, such as polypropylene and/or polyamide, which works as barrier material for diffusion of oxygen into the food product. The plastic film may further comprise a material which is suitable for being attached to the tray by heating or welding. Examples of such materials may be polypropylene or polyethylene, depending on the material used in the tray.
[0016] The package may further comprise an adhesive label intended for sealing the opening and which comprises a barrier material. Thereby the opening can, in an easy way, be sealed in a subsequent processing step, and at the same time seal the packaged food product so that the risk of diffusion of oxygen into the food product is reduced.
[0017] The number of openings in the cover film may be several, which jointly form the opening area A so that they allow a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure. Thereby it is achieved a further strengthening of the opening, since forces that arise around the edges of the opening during the influence of the overpressure in the package are distributed over a larger edge length for a given opening area. Each opening is preferably formed with a smooth edge, such as circular openings. [0018] The invention further relates to a method for packaging of food products comprising the steps of,
- providing a package for food products according to any previous claim
- packaging the food product in the tray,
- sealing the cover film to the tray,
- supplying microwave power to the package to cook said food product,
- ceasing with supply of microwave power, and
- in a processing step after the cessation of the supply of microwave power, while an overpressure is maintained in the package, sealing the opening to seal the package.
[0019] As described earlier, by using the method a package is achieved, which is cooked during supply of microwave power where the risk of the package breaking during cooking is small, and where the package, when cooking is completed, in an easy way and during a sufficiently long time period may be sealed in a separate subsequent processing step.
[0020] The sealing of the opening may occur during a time period of more than 2 seconds, preferably more than 5 seconds, or more than 10 seconds after the supply of microwave power has ceased and while an overpressure is being maintained in the package during this time window. Thereby the time period is sufficiently long to allow that the package is sealed in a subsequent processing step. The sealing of the opening may occur during a time period in the range of 2- 60 seconds, preferably 5-30 seconds, more preferably 10-20 seconds after the supply of microwave energy has ceased and while an overpressure is maintained in the package during this time window.
[0021 ] The opening may be formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped, in such a way that the opening gets a smooth edge. Thereby it is achieved an opening with a smooth edge which minimizes breaking points, which could mean that the package breaks due to overpressure during cooking. [0022] The opening may be formed by perforation of the cover film after a food product is packaged in the tray and the cover film is sealed to the tray. Thereby the packaged and non-cooked food product is kept sealed until the perforation step.
[0023] The opening may be formed in the cover film by perforation of the cover film by means of laser cutting, punching or melting. The opening may be formed by perforation of the cover film before the cover film is sealed to the tray. Thereby perforated cover film may be supplied to the package on a roll, or cover film may be perforated in a separate processing step before sealing of the package.
Short description of the drawings
[0024] The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Fig. 1 shows a cross section of a package for food products, at a number of steps (a)-(f) of a method for packaging of food products according to one embodiment of the invention.
Fig. 2 shows one (a) and several (b) openings in the cover film.
Fig. 3 shows a method according to one embodiment of the invention.
Fig. 4 shows a diagram of time t to sealing for different opening areas A.
Detailed description
[0025] In the following there is a detailed description of various embodiments.
[0026] Fig. 1 shows a cross section of a package for food products, at a number of method steps (a)-(f). Fig. 1 a shows a package 101 comprising a tray 103 with a food product 102 to be packaged and cooked. The tray is made in a material that withstands microwave heating and that has a low permeability to oxygen, for example polypropylene. The package further comprises a cover film 104 of a material that withstands microwave heating. Typically, the cover film comprises several layers of different materials, such as a polyamide layer which brings mechanical stability and a barrier function, i.e. a low permeability of oxygen, and a layer, such as polypropylene, for heat welding to the tray.
[0027] The cover film comprises an opening 105, which is located centrally on the cover film relative to the tray. According to the embodiment shown in Fig. 1 a, the opening is formed in the cover film before sealing to the tray. If the cover film is provided on a roll, openings may be pre-formed in the cover film on the roll.
Alternately, the openings may be formed in the cover film in a perforation step which is performed before the cover film is sealed to the tray.
[0028] With reference to Fig. 2 the opening area A may be formed by a single opening 205 in the cover film 204 (Fig. 2a), or by several sub-openings 215 in the cover film 204 (Fig. 2b). The sub-openings 215 thus jointly and together form the opening area A.
[0029] The opening 205 or each opening 215 is formed with a circular and smooth edge, i.e. without clear breaking points. According to one embodiment, each opening is formed by perforation of the cover film with a sharp and smooth tool with an extension, such as a sharp and smooth needle. Thereby material in the cover film is moved radially outward relative to the extension of the tool and strengthens the edge around the opening. No material is removed from the cover film with this technology. Another advantage with this technology is that openings may be formed in the cover film in a later processing step, when the cover film is already sealed to the tray. Since no material is removed from the cover film, no material from the cover film risks being brought into the packaged food product.
[0030] According to other embodiments, the opening 205 or openings 215 are pre-formed in the cover film before it is sealed to the tray, by perforation of the cover film by means of laser cutting, punching or melting with a heated tool. Since all of these technologies entail a removal of material from the cover film (evaporation when laser cutting, mechanical removal when punching, and removal when melting), they are not suited for openings being able to be formed in the cover film at a later processing step, when the cover film is already sealed to the tray. Laser cutting has the advantage of very precisely being able to define the form and shape of the opening.
[0031 ] With reference to Fig. 1 b, the cover film is sealed to the tray at a joint 106 around the edge of the tray. This may be done for example by applying heat or by welding, such as ultrasonic welding. In the tray there is thereby formed a space 107 which contains said food product and a certain amount of gas (air). The gas in the space 107 may be vented through the opening 105 in the cover film.
[0032] In the next step according to Fig. 1 c, the food product in the package is heated by supply of microwaves 108. For a serving of food, a typical microwave power is 400-500W. When the whole volume of food product has reached boiling point, the whole absorbed microwave power generates water vapor in the space 107 that holds gas. The pressure in this space increases, and the gas is vented out through the opening 105. The opening has a sufficiently large opening area A and is formed with a smooth edge so that it allows a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure. Thereby it is avoided that the cover film breaks up due to tension in the film, and that the sealing between cover film and tray is maintained.
[0033] The supply of microwaves is ceased when the cooking of the food product is completed. In the next step according to Fig. 1 d, a time period 109 is then achieved where an overpressure is maintained in the space 107. This time period arises due to the opening area A being sufficiently small to maintain said overpressure. Thus the time period allows the package to be sealed in a
subsequent processing step during a time period of more than 2 seconds, and up to 30 seconds, after the supply of microwaves has ceased. The sealing takes place while there is still an overpressure in the package. [0034] After this time period, the opening 105 is sealed, Fig. 1 e, with an adhesive label 1 10 in order to seal the space 107 in the package. The adhesive label comprises a layer with barrier properties such as polypropylene, for limiting transportation of oxygen from the surroundings into the space 107 and the food product 102 in the package.
[0035] While the contents of the package (food product and water vapor) cools off, the water vapor condenses and the contained volume in the package shrinks, Fig. 1f, so that the space contains no or only a small amount of gas. Thereby there is obtained a hygienic packaging of the food product.
[0036] According to Fig.3 , the corresponding method 300 is shown, for packaging of a food product which comprises the steps of supplying 301 a package for food products according to what has been described above, packaging 302 the food product in the tray, sealing 303 the cover film to the tray, supplying 304 microwave power to the package to cook said food product, ceasing 305 with the supply of microwave power, and in a processing step 306 after the cessation of supply of microwave power, while an overpressure is maintained in the package, sealing said at least one opening in order to seal the package.
[0037] Fig. 4 shows a graph of measured time period (seconds) to sealing for a package, for different opening areas A (mm2). The package was cooked at a microwave power of 440 W. At an opening area of 3,9 mm2, the ratio between the opening area and supplied power is 0,009 mm2/W. At this opening area, a time period of 24 s is reached before the package should be sealed.
[0038] At an opening area of 4,7 mm2, the ratio between the opening area and supplied power is 0,01 1 mm2/W. At this opening area, a time period of 19 s is reached before the package should be sealed.
[0039] At an opening area of 5,5 mm2, the ratio between the opening area and supplied power is 0,012 mm2/W. At this opening area, a time period of 16 s is reached before the package should be sealed. [0040] At an opening area of 6,3 mm2, the ratio between the opening area and supplied power is 0,014 mm2/W. At this opening area, a time period of 14 s is reached before the package should be sealed.
[0041 ] At an opening area of 7, 1 mm2, the ratio between the opening area and supplied power is 0,016 mm2/W. At this opening area, a time period of 1 1 s is reached before the package should be sealed.
[0042] Correspondingly, at an opening area of 2 mm2 and a microwave power of 440 W, the ratio between opening area and supplied effect is 0,005 mm2/W, and at an opening area of 10 mm2 the ratio is 0,023 mm2/W.
[0043] Further attempts show that an average opening area per supplied power of 0,012 mm2/W reaches a highest pressure in the package of 13 kPa, an average opening area per supplied power of 0,019 mm2/W reaches a highest pressure in the package of 5 kPa, and that an average opening area per supplied power of 0,026 mm2/W reaches a highest pressure in the package of 2,5 kPa.
The highest pressure in the package of 13 kPa is reached at:
Supplied
power Area A A/P
P mm2 mm2/W
300 2,8 0,0094
440 5,4 0,0122
600 8,2 0,0137
The highest pressure in the package of 5 kPa is reached at:
Supplied
power Area A A/P
P mm2 mm2/W
300 5,9 0,020
440 8,5 0,019
600 1 1 ,3 0,019 The highest pressure in the package of 2,5 kPa is reached at:
Supplied
power Area A A/P
P mm2 mm2/W
300 7,67 0,025
440 1 1 ,9 0,027
600 15,0 0,025
[0044] It should be understood that the invention is not limited to the herein described embodiments, which are disclosed as examples and thus do not limit the scope of protection, which is defined by the following patent claims.

Claims

Claims
1 A system for preparing a food product comprising
a microwave source for cooking a food product with microwaves at a power P, and a package for the food product which comprises a tray and a cover film comprising an opening for venting an overpressure of gas which is produced when cooking the food product, wherein the opening has an opening area A configured such that the ratio between the opening area A and the supplied microwave power P is in the range of 0,005 and 0,06 mm2/W, preferably between 0,01 and 0,03 mm2/W, more preferably between 0,015 and 0,025 mm2/W.
2 The system according to claim 1 wherein the opening of the package is formed with a smooth edge.
3 The system according to claim 2 wherein the opening of the package is circular.
4 The system according to any of claims 1 -3, wherein the opening of the package is formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped.
5 The system according to any of claims 1 -4, wherein the opening of the package is formed in the cover film by perforation of the cover film by means of laser cutting, punching or melting.
6 The system according to any of the previous claims wherein the
microwave power P is in the range of 200-800 W, preferably 300-600 W, more preferably 400-500 W, and wherein the opening area A is between 3-8 mm2.
7 The system according to any of the previous claims wherein the opening of the package is provided at a central portion of the cover film.
8 The system according to any of the previous claims wherein the cover film comprises a ductile material, preferably polyamide. 9 The system according to any of the previous claims, further comprising an adhesive label adapted to seal the opening of the package and which comprises a barrier material.
10 The system according to any of the previous claims wherein the number of openings in the cover film is several, which jointly form the opening area A such that they allow a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure.
1 1 A package for packaging a food product by microwave cooking at a power P, which comprises a tray and a cover film comprising an opening for venting an overpressure of gas which is produced when cooking the food product under supply of microwaves at a power P, wherein the opening has an opening area A configured such that the ratio between the opening area A and the supplied power P is in the range of 0,005 and 0,06 mm2/W, preferably between 0,01 and 0,03 mm2/W, more preferably between 0,015 and 0,025 mm2/W.
12 The package according to claim 1 1 wherein the opening is formed with a smooth edge.
13 The package according to claim 12 wherein the opening is circular.
14 The package according to any one of claims 1 1 -13, wherein the opening is formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped.
15 The package according to any one of claims 1 1 -13, wherein the opening is formed in the cover film by perforation of the cover film by means of laser cutting, punching or melting.
16 The package according to any one of claims 1 1 -15 wherein the opening area A is between 3-8 mm2. 17 The package according to any one of claims 1 1 -16 wherein the opening is provided at a central portion of the cover film.
18 The package according to any one of claims 1 1 -17 wherein the cover film comprises a ductile material, preferably polyamide.
19 The package according to any one of claims 1 1 -18, further comprising an adhesive label adapted to seal the opening and which comprises a barrier material.
20 The package according to any one of claims 1 1 -19 wherein the number of openings in the cover film is several, which jointly form the opening area A such that they allow a sufficient flow of gas during cooking to avoid that the package breaks due to overpressure.
21 A method for packaging of food products comprising the steps of,
- supplying a package for food products according to any of the previous claims,
- packaging the food product in the tray,
- sealing the cover film to the tray,
- supplying microwaves with the power P to the package to cook said food product,
- ceasing with the supply of microwave power, and
- in a processing step after the cessation of supply of microwave power, while an overpressure is maintained in the package, sealing the opening in order to seal the package.
22 The method according to claim 21 wherein the sealing of the opening occurs during a time period more than 2 seconds, preferably more than 5 seconds, or more than 10 seconds after the supply of microwave power has ceased and while an overpressure is maintained in the package during this time period.
23 The method according to claim 21 wherein the sealing of the opening occurs during a time period in the range of 2-60 seconds, preferably 5-30 seconds, more preferably 10-20 seconds after the supply of microwave power has ceased, while an overpressure is maintained in the package during this time period.
24 The method according to any one of claims 21 -23 wherein the microwave power is in the range of 200-800 W, preferably 300-600 W, more preferably 400- 500 W, and wherein the opening area A is between 3-8 mm2.
25 The method according to any one of claims 21 -24, wherein the opening is formed in the cover film by perforation of the cover film with a sharp and smooth tool, preferably needle-shaped, in such a way that the opening has a smooth edge.
26 The method according to claim 25, wherein the opening is formed by perforation of the cover film after the food product is packaged in the tray and the cover film is sealed to the tray.
27 The method according to any of claims 21 -24, wherein the opening is formed in the cover film by perforation of the cover film by means of laser cutting, punching or melting.
28 The method according to claim 25 or 27 wherein the opening is formed by perforation of the cover film before the cover film is sealed to the tray.
EP14818272.8A 2013-06-28 2014-06-27 A system for preparing a food product, a package and a method for packaging food products Withdrawn EP3022128A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1350794A SE1350794A1 (en) 2013-06-28 2013-06-28 Food packaging and method of packaging food
PCT/SE2014/050805 WO2014209218A1 (en) 2013-06-28 2014-06-27 A system for preparing a food product, a package and a method for packaging food products

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EP3022128A1 true EP3022128A1 (en) 2016-05-25
EP3022128A4 EP3022128A4 (en) 2017-01-18

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Publication number Priority date Publication date Assignee Title
PL424485A1 (en) * 2018-02-02 2019-08-12 Grzegorz Stopa Package for cooking food products
EP4371415A1 (en) * 2022-11-21 2024-05-22 MicVac AB Method and system for preparing a food product

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3133193B2 (en) * 1993-05-21 2001-02-05 株式会社デューシステム Pressure regulating valve, automatic cooking package having the pressure regulating valve, and food and beverage packaged with the automatic cooking package
SE511353C2 (en) * 1998-06-23 1999-09-20 Joel Haamer Method and apparatus for boiling and vacuum packing of microwaves with microwaves
US6844534B2 (en) * 1998-06-23 2005-01-18 Micvac Ab Process for microwave cooking and vacuum packing of food
EP0967160B1 (en) * 1998-06-24 2003-04-23 Alcan Technology & Management AG Sealing membrane with a pressure relief valve
WO2002066336A1 (en) * 2001-02-16 2002-08-29 Vanda Janka Method for heat treatment and preservation under controlled gas pressure
SE521684C2 (en) * 2001-04-30 2003-11-25 Micvac Ab Resealable one-way valve for food packaging
SE0203420L (en) * 2002-11-20 2003-09-16 Micvac Ab Packaging and method of pasteurization and vacuum packaging of food
NL1029353C2 (en) * 2005-06-28 2007-01-02 Greencore Convenience Foods Li Method and device for subjecting a food product to a heat treatment.

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SE1350794A1 (en) 2014-12-29
WO2014209218A1 (en) 2014-12-31

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