WO2005002990A2

WO2005002990A2 - Packaging for foodstuff, comprising a displaceable bottom

Info

Publication number: WO2005002990A2
Application number: PCT/NL2004/000497
Authority: WO
Inventors: Antonius Aloyisius Michael Maria Reinders
Original assignee: Sallcoll B.V.
Priority date: 2003-07-08
Filing date: 2004-07-08
Publication date: 2005-01-13
Also published as: NL1026618A1; WO2005002990A3; NL1026618C2

Abstract

The invention relates to a packaging for foodstuffs, comprising: a plastic receptacle (1) having on its top side a mouth opening and on its underside a bottom with an upright body (3) connecting thereto; which mouth opening is bounded by a mouth rim (4) which, after filling of the receptacle with foodstuff, can co-act in hermetically sealing manner with a lid; a displaceable part which forms part of the bottom and acts as displacer, and optionally a filling with a gas serving as protective atmosphere. The packaging has the feature that at least a substantial part to a size of at least 40% of the projected area of the bottom has little bending stiffness and is embodied as a plastic foil (5) connected sealingly and without any tensile stress to the rest of the receptacle.

Description

PACKAGING FOR FOODSTUFF, COMPRISING A DISPLACEABLE BOTTOM

The invention relates to a packaging for foodstuff to be offered for sale, comprising: a plastic receptacle having on its upper side a mouth opening and on its underside a bottom with an upright body connecting thereto; which mouth opening is bounded by a mouth rim which, after filling of the receptacle with foodstuff and optionally a chosen gas or gas mixture, can co-act in hermetically sealing manner with a lid, for instance a foil connected by sealing to the mouth rim; a displaceable part which forms part of the bottom and acts as displacer, and which is connected to the peripheral part of the bottom; and optionally a filling with a gas serving as protective atmosphere, for instance a mixture of C0₂ and N₂ or C0₂ and 0₂. Such a packaging is known from US-A-3 426 939. The packaging known from this American patent comprises a round central bottom part which is connected to the rest of the bottom via a coupling edge with a generally truncated cone shape. The bottom can have a round, oval or generally rectangular form. A drawback of the known packaging is that the displacement of said bottom part has only a relatively small influence on the effective volume of the container. Referred to as an example of application is the placing of foodstuff in heated state in a packaging and subsequent closure of the packaging. The packaging with its content then cools, whereby an underpressure is created in the packaging. The consequence hereof is that the ambient air, in particular the oxygen present therein, is given the opportunity after a time, depending on the type of packaging, to penetrate into the foodstuff. This shortens the possible shelf life, i.e. the time between the production phase and the moment of consumption of the foodstuff. In the known art the receptacle and the lid must moreover be able to withstand the pressure difference between the pressure of the outside air and the considerably lower pressure in the filled packaging. It is an object of the invention, among others, to provide a packaging for foodstuffs which is embodied such that relatively low mechanical demands are made of the receptacle as well as the lid which can be used after filling to hermetically seal the container, and that the packaging can be manufactured inexpensively. A further object of the invention is to provide a packaging which is embodied such that the shelf life can be prolonged substantially, even without the use of possible preservatives. Use can however be made of a protective atmosphere, for instance nitrogen gas, carbon dioxide or other gases or gas mixtures. In respect of the above, the invention provides a packaging of the stated type, which has the feature that at least a substantial part to a size of at least 40% of the projected area of the bottom has relatively little bending stiffness and is embodied as a plastic foil connected sealingly to the rest of the receptacle. Said bottom part can consist of a material other than that of the receptacle. Because a longer shelf life can be realized with the invention, the invention also provides the possibility of an increased commercial potential. In respect of transport of the packagings with the invention, a greater delivery radius can for instance be realized, which can substantially increase the market potential according to the invention. A specific embodiment has the feature that the receptacle is manufactured by thermoforming or vacuum- forming, for instance from a laminate. Such an embodiment is relatively inexpensive and allows manufacture with relatively small wall thicknesses. To the extent that a well-defined wall thickness is desired, a variant can have the special feature that the container is manufactured by injection moulding. In a particular embodiment the packaging has the feature that the receptacle consists substantially of foam material. There are different methods of manufacturing a receptacle from foam material, for instance injection moulding with a foaming plastic. Recommended however is an embodiment wherein the receptacle is formed from a strip of foam material. This embodiment can have the special feature that the strip of foam material is manufactured by extrusion and optional sizing. For the purpose of an additional mechanical strength and/or to obtain a good sealing for a gas component present in the packaging, the packaging can have the special feature that by a laminating operation following the extrusion there is arranged on at least one side a foil layer, for instance an oxygen-barrier foil. It will be apparent that the foil layer can also be arranged on both sides. In another embodiment the packaging has the feature that the strip of foam material is not fully foamed and that by supplying heat to the mould cavity of a mould an additional foaming occurs, whereby a desired, for instance uniform wall thickness can be obtained. The advantage of this embodiment can be based on the fact that within certain limits any desired wall thickness can be realized, and that the wall thickness can for instance be the same all over. This is not possible when forming takes place from a strip of fully foamed foam material. This may give the user of such a simple receptacle the impression that the receptacle is of lesser quality. An example of foodstuffs for filling the packages according to the invention are potatoes, in particular peeled potatoes, and fish. Potatoes and fish have the property of absorbing gas. During the filling process a protective atmosphere is introduced into the container, consisting for instance of a mixture of carbon dioxide and nitrogen. Due to said absorption an underpressure is gradually created after hermetic closure of the container. In this embodiment the foil compensates the resulting pressure difference substantially by moving from an outward displaced position to a more inward displaced position. The packaging according to the invention thus continues to substantially retain its nominal shape under the given varying conditions. A specific embodiment of the packaging according to the invention has the special feature that the packaging is intended for potatoes and/or fish or products based thereon, that the gas mixture contains C0₂ and N₂ and that the ratio of these gas components amounts to 70:30, preferably 80:20 and still more preferably 90:10. When a ratio of 70:30 is used more gas is present in the packaging according to the invention than in the prior art packaging. When another gas composition is used, such as 80:20, not only is there physically more gas available in the packaging but there is also physically more C0₂ present which can provide the preservative action. The prediction that a ratio in the order of 90:10 would provide a still further improvement in the shelf life has also been proven experimentally.

By way of illustration:

C0₂ :N₂= 70 30 best before 7 days 80 20 best before 9 days 90 10 best before 12 days

Many receptacles available on the market at the moment are not able to withstand the underpressure created in the packaging. The structure according to the invention is however capable of doing this. Another composition of the protective atmosphere is a mixture of C0₂ and 0₂, optionally supplemented with the inert N₂, whereby less problems are encountered from a "pseudo-vacuum", this as used in the meat industry. A usual ratio of these gas components CO₂.N₂ is 50:50. The dosing of oxygen is used here so as to not allow discolouration of the meat. It is known that addition of additional C0₂ increases the shelf life. It is conceivable however that this will cause some discolouration. Following the above reasoning in respect of C0₂ and N₂, it could be supposed that without changing the gas composition more C0₂ is present in the packaging according to the invention for preservative purposes. If this extra C0₂ is absorbed, there then remains relatively more 0₂ to prevent discolouration. This means that the gas composition can be adjusted in the sense of increasing the relative amount of C0₂ without there having to be any fear of discolouration. In respect of the foregoing, the invention also provides a packaging which has the feature that the packaging is intended for meat or products based thereon, that the gas mixture contains C0₂ and 0₂ and that the ratio of these components is chosen to achieve an optimum in respect of discolouration of the packed foodstuff and the shelf life. When a foil is used as deformable part of the bottom according to the teaching of the invention, there results an additional advantage. In meat packages an absorbent cloth is often used to absorb meat juices. In the packaging according to the invention of the described type this is not necessary, since the juice leaving the meat can collect in the "moat" all around, i.e. the peripheral part of the bottom. An annular absorbent cloth can optionally be laid therein. As already discussed above, particular attention has been paid in the invention to fresh products such as potatoes and meat. Fish should also be included herein. In such packages there is generally a receptacle with only one compartment. In another type of product, namely ready-to-eat meals, there is a plurality of compartments in one receptacle. Finally, the invention relates to a packaging intended for frozen goods, for instance ice cream or deep-frozen products, wherein the protective atmosphere is absent and wherein after removal of the lid the frozen product can be released from the receptacle by pressing the displaceable part inward. In the case that the receptacle is manufactured by thermoforming, vacuum-forming or injection moulding, the packaging can have the special feature that the receptacle is manufactured by placing a foil in the mould cavity of a mould and, through raised temperature and pressure, adhering this foil sealingly to the rest of the receptacle to be formed by the mould, wherein prior to closing of the mould and forming of the receptacle the foil has greater dimensions than its projected area after forming of the receptacle, whereafter the receptacle with a bottom part consisting of the foil is removed, optionally after cooling, from the opened mould. The packaging according to the invention can for instance have the special feature that the receptacle consists of PP. In an alternative, the packaging has the feature that the foil comprises a layer of PP or PET. It is noted that it is of course essential that the foil is connected to the receptacle in properly adhering, sealing manner. This preferably takes place by means of fusing. It will be apparent that in the case of a temperature increase it must be ensured that the thin foil, which can have a thickness of 10 - 100 μm, does not degenerate or lose its integrity. If such a risk exists, use can optionally be made of an intermediate adhesive layer, whereby the temperature increase can remain limited during production. In yet another embodiment, the packaging has the special feature that the foil comprises a laminate with a layer of PP and a layer of PET. In the case where a very good oxygen barrier is desired, the above specified laminate can be provided with an intermediate layer of EVOH. In yet another embodiment, the packaging can have the special feature that the receptacle consists of expanded PS and that the foil is fused thereto in the mould. As an alternative, the packaging can have the special feature that the receptacle consists of expanded polystyrene and that the foil is adhered thereto by means of an adhesive layer. Finally, the invention relates to a receptacle which has yet to be filled and closed with a lid, which receptacle has the special feature that it is manufactured from plastic and has a bottom part, of which at least a substantial part has relatively little bending stiffness and is embodied as a plastic foil. The invention will now be elucidated with reference to the annexed drawings. Herein: Fig. 1 shows a cross-section through a receptacle according to the invention; and Fig. 2 shows a schematic cross-section through a mould for manufacturing a receptacle according to the invention. Fig. 1 shows a receptacle, comprising a receptacle 1, comprising a bottom edge 2, an upright body 3 which connects thereto and to which connects a flat peripheral mouth rim 4. With this mouth rim 4 a sealing foil acting as lid can be arranged after filling of the receptacle. Sealingly connected to the bottom edge is a bottom foil

5 which, as drawn, has larger dimensions than its projected area such that the foil provides an additional space whereby it can move inward and outward, so that the volume of the sealed packaging is thus variable. Fig. 2 shows a mould 6, consisting of a first mould part 7 and a second mould part 8, which in closed position together bound a mould cavity, the shape of which corresponds to that of the receptacle of Fig. 1. Mould part 8 can be displaced as according to arrow 9 toward and away from mould part 7. Prior to closing of the mould a plastic foil 10 is laid on the bottom of the mould cavity, whereafter the mould can be closed by downward displacement of mould part 8. In this exemplary embodiment, injection of heated and thus plasticized plastic takes place via two injection channels 11, 12 such that only the edges of the clamped foil are embedded by the injected plastic. After injection there is a cooling period, whereafter the mould can be opened and the receptacle with the foil bottom can be ejected by means of ejectors (not shown) . The injected thermoplastic plastic material can for instance be polypropylene. After the modelling in mould

6 and the moulding of receptacle 1, the polypropylene is hard, while the foil is flexible and has little bending stiffness . The foil can also consist of PP, of PET, of a laminate of PP and PET, optionally with an intermediate layer of EVOH. Alternatively, the receptacle can also be modelled by vacuum-forming or thermoforming on the basis of EPS. In such an embodiment the receptacle is also relatively stiff, while the foil has little bending stiffness and can accommodate a variable volume.

Claims

1. Packaging for foodstuffs to be offered for sale, comprising: a plastic receptacle having on its upper side a mouth opening and on its underside a bottom with an upright body connecting thereto; which mouth opening is bounded by a mouth rim which, after filling of the receptacle with foodstuff and optionally a chosen gas or gas mixture, can co-act in hermetically sealing manner with a lid, for instance a foil connected by sealing to the mouth rim; a displaceable part which forms part of the bottom and acts as displacer, and which is connected to the peripheral part of the bottom; and optionally a filling with a gas serving as protective atmosphere, for instance a mixture of C0₂ and N₂ or C0₂ and 0₂; characterized in that at least a substantial part to a size of at least 40% of the projected area of the bottom has relatively little bending stiffness and is embodied as a plastic foil connected sealingly and without any tensile stress to the rest of the receptacle.

2. Packaging as claimed in claim 1, characterized in that the receptacle is manufactured by thermoforming or vacuum-forming, for instance from a laminate.

3. Packaging as claimed in claim 1, characterized in that the receptacle is manufactured by injection moulding.

4. Packaging as claimed in claim 1, characterized in that the receptacle consists substantially of foam material .

5. Packaging as claimed in claim 4, characterized in that the receptacle is formed from a strip of foam material.

6. Packaging as claimed in claim 5, characterized in that the strip of foam material is manufactured by extrusion and optional sizing.

7. Packaging as claimed in claim 6, characterized in that by a laminating operation following the extrusion there is arranged on at least one side a foil layer, for instance an oxygen-barrier foil.

8. Packaging as claimed in claim 5, characterized in that the strip of foam material is not fully foamed and that by supplying heat to the mould cavity of a mould an additional foaming occurs, whereby a desired, for instance uniform wall thickness can be obtained.

9. Packaging as claimed in claim 1, characterized in that the packaging is intended for potatoes and/or fish or products based thereon, that the gas mixture contains C0₂ and N₂ and that the ratio of these gas components amounts to 70:30, preferably 80:20 and still more preferably 90:10.

10. Packaging as claimed in claim 1, characterized in that the packaging is intended for meat or products based thereon, that the gas mixture contains C0₂ and 0₂ and that the ratio of these components is chosen to achieve an optimum in respect of discolouration of the packed foodstuff and the shelf life.

11. Packaging as claimed in claim 1, characterized in that the packaging is intended for frozen goods, for instance ice cream or deep-frozen products, wherein the protective atmosphere is absent and wherein after removal of the lid the frozen product can be released from the receptacle by pressing the displaceable part inward.

12. Packaging as claimed in claim 2 or 3, characterized in that the receptacle is manufactured by placing a foil in the mould cavity of a mould and, through raised temperature and pressure, adhering this foil sealingly to the rest of the receptacle to be formed by the mould, wherein prior to closing of the mould and forming of the receptacle the foil has greater dimensions than its projected area after forming of the receptacle, whereafter the receptacle with a bottom part consisting of the foil is removed, optionally after cooling, from the opened mould.

13. Packaging as claimed in claim 1, characterized in that the receptacle consists of PP.

14. Packaging as claimed in claim 1, characterized in that the foil comprises a layer of PP or PET.

15. Packaging as claimed in claim 1, characterized in that the foil comprises a laminate with a layer of PP and a layer of PET.

16. Packaging as claimed in claim 15, characterized by an intermediate layer of EVOH.

17. Packaging as claimed in claim 2, characterized in that the receptacle consists of expanded PS and that the foil is fused thereto in the mould.

18. Packaging as claimed in claim 2, characterized in that the receptacle consists of expanded PS and that the foil is adhered thereto by means of an adhesive layer.

19. Packaging as claimed in any of the foregoing claims, characterized in that the bottom part consists of a material other than that of the receptacle.

20. Receptacle intended and adapted to form part of a packaging as claimed in any of the foregoing claims, which receptacle is manufactured from plastic and has a bottom part, of which at least a substantial part has relatively little bending stiffness and is embodied as a plastic foil.