PACKAGE FOR PRESERVING RESPIRING PRODUCE AND METHOD

Abstract

A package for preserving respiring produce contained in the package, in particular vegetables, fruit, herbs, spices and/or flowers, and an associated method are provided. The package defines a package volume for containing a portion of the produce and a package atmosphere, and comprises a packaging material, in particular a polymer film (1A), provided with at least one perforation (3) enabling gas exchange with the atmosphere surrounding the package (1) to form the package into a Controlled Atmosphere Package (CAP). The packaging material has a Water Vapour Transmission Rate (WVTR), a carbon dioxide transmission rate (CO.sub.2TR) and an oxygen transmission rate (O.sub.2TR), wherein the WVTR of the packaging material is in a range of 50-1200 ml/(m.sup.2.Math.24 hrs), the CO.sub.2TR of the packaging material is larger than 1000 ml/(m.sup.2.Math.24 hrs), and a ratio β=CO.sub.2TR/O.sub.2TR of the packaging material is larger than 4.

Claims

1. A package for preserving respiring produce contained in the package, the package comprising a packaging material, provided with at least one perforation enabling gas exchange with the atmosphere surrounding the package to form the package into a controlled atmosphere package, and the package defining a package volume for containing a portion of the produce and a package atmosphere, and wherein the packaging material has a water vapor transmission rate in a range of 100-1200 ml/(m.sup.2.Math.24 hrs), a carbon dioxide transmission rate larger than 1000 ml/(m.sup.2.Math.24 hrs), and a ratio β=carbon dioxide transmission rate/oxygen transmission rate larger than 4.

2. The package according to claim 1, wherein the water vapor transmission rate of the packaging material is in a range of 100-1000 ml/(m.sup.2.Math.24 hrs).

3. The package according to claim 1, wherein the water vapor transmission rate of the packaging material is in a range of 700-1100 ml/(m.sup.2.Math.24 hrs).

4. The package according to claim 1, wherein the carbon dioxide transmission rate of the packaging material is in a range of 1000-12000 ml/(m.sup.2.Math.24 hrs).

5. The package according to claim 1, wherein the oxygen transmission rate of the packaging material is in a range of 500-4000 ml/(m.sup.2.Math.24 hrs).

6. The package according to claim 1, wherein the ratio β=carbon dioxide transmission rate/oxygen transmission rate of the packaging material is in a range of 4-20.

7. The package according to claim 1, wherein the packaging material is a polymer film having a thickness in a range of 10-200 micrometers.

8. The package according to claim 1, wherein the at least one perforation is at least one microperforation having an open area of below 1 square millimeter.

9. The package according to claim 1, wherein the packaging material is biodegradable.

10. The package according to claim 1, wherein the packaging material is a polymer film, the polymer being manufactured from natural produce and/or by substantially biological processes.

11. The package according to claim 1, containing at least one portion of respiring produce.

12. A method of manufacturing a package for preserving respiring produce, comprising steps of: providing a portion of a packaging material; providing a portion of the produce; forming, from the portion of packaging material and the portion of the produce, a closed package defining a package volume and containing in the package volume the portion of produce and a package atmosphere; wherein the method further comprises providing one or more perforations in the packaging material to determine a predetermined transmission rate of the package for at least one atmosphere component and forming the package into a controlled atmosphere package; and wherein the packaging material has a water vapor transmission rate in a range of 100-1200 ml/(m.sup.2.Math.24 hrs), a carbon dioxide transmission rate larger than 1000 ml/(m.sup.2.Math.24 hrs), and a ratio β=carbon transmission rate/oxygen transmission rate of larger than 4.

13. The package according to claim 7, wherein the polymer film has a thickness in a range of 20-100 micrometers.

14. The package according to claim 1, wherein the ratio of the carbon dioxide transmission rate to the oxygen transmission rate is in a range 4-10.

15. The package according to claim 1, wherein the water vapor transmission rate is in a range of 400-600 ml/(m.sup.2.Math.24 hrs).

16. The package according to claim 1, wherein the carbon dioxide transmission rate is in a range of 5000-8500 ml/(m.sup.2.Math.24 hrs).

17. The package according to claim 1, wherein the oxygen transmission rate is in a range of 1000-2500 ml/(m.sup.2.Math.24 hrs).

18. The package according to claim 1, wherein the area of the at least one microperforation is about 0.25 square millimeter.

19. The package according to claim 1, wherein the polymer film has a thickness in a range of 20-100 micrometers, the water vapor transmission rate is in a range of 400-600 ml/(m.sup.2.Math.24 hrs), the carbon dioxide transmission rate is in a range of 5000-8500 ml/(m.sup.2.Math.24 hrs) and the oxygen transmission rate is in a range of 1000-2500 ml/(m.sup.2.Math.24 hrs).

20. The method according to claim 12, wherein the polymer film has a thickness in a range of 20-100 micrometers, the water vapor transmission rate is in a range of 400-600 ml/(m.sup.2.Math.24 hrs), the carbon dioxide transmission rate is in a range of 5000-8500 ml/(m.sup.2.Math.24 hrs) and the oxygen transmission rate is in a range of 1000-2500 ml/(m.sup.2.Math.24 hrs).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The above-described aspects will hereafter be more explained with further details and benefits with reference to the drawing showing an exemplary embodiment.

[0063] FIG. 1 schematically shows an embodiment of an apparatus and indicates at least part of an embodiment of a method;

[0064] FIG. 2 is a graph showing the results of Table II.

DETAILED DESCRIPTION OF EMBODIMENTS

[0065] It is noted that the drawings are schematic, not necessarily to scale and that details that are not required for understanding the present invention may have been omitted. The terms “upward”, “downward”, “below”, “above”, and the like relate to the embodiments as oriented in the drawings, unless otherwise specified. Further, elements that are at least substantially identical or that perform an at least substantially identical function are denoted by the same numeral, where helpful individualized with alphabetic suffixes.

[0066] Further, unless otherwise specified, terms like “detachable” and “removably connected” are intended to mean that respective parts may be disconnected essentially without damage or destruction of either part, e.g. excluding structures in which the parts are integral (e.g. welded or molded as one piece), but including structures in which parts are attached by or as mated connectors, fasteners, releasable self-fastening features, etc. The verb “to facilitate” is intended to mean “to make easier and/or less complicated”, rather than “to enable”.

[0067] FIG. 1. shows schematically an apparatus 1 for manufacturing modified atmosphere packages 3. The apparatus 1 comprises a package forming device 5 for forming, from portions of packaging material 7 and portions of produce 9, modified atmosphere packages 3 each defining a package volume V and containing in the package volume V a portion of produce 9 and a modified atmosphere. Here, the packaging material is supplied as a web of a packaging film 11 on a roll 13 for forming packaging portions, e.g. bags or tray lids, but other forms and types of packaging material are also possible; e.g. two or more types of packaging material may be provided, such as trays and sealing film (not shown). In FIG. 1 the produce is provided as separate portions 9 by a produce transporter 14, but other ways of providing the produce as, or into, portions 9 may be used. Here, the apparatus 1 is configured to form and fill the packages 3 and also to close and separate them.

[0068] The apparatus 1 comprises an optional supply of different atmosphere modification gases to provide the package as a MAP. E.g. CO.sub.2 and N.sub.2, here in the form of gas bottles 21, 23. The apparatus 1 here comprises an optional supply of pressurized air in the form of a compressor 22. The oxygen for ozone formation may be provided from a separate tank 24 as shown. The atmosphere modification gas(es) may be supplied pressurized so that they may be transported by flowing under their own pressure so that one or more propellers are not needed; however, these may be provided.

[0069] Here, the device 25 comprises a manifold 27 connected by a gas supply conduit 31 to the package forming device 5. The manifold 27 and an optional feedback sensor signal line 33 are connected to a controller 29.

[0070] As indicated in FIG. 1, the apparatus 1 further comprises a perforator, here a (possibly pulsed) laser 35 providing a (pulsed) laser beam 36, configured to provide the film 11 with microperforations. The apparatus 1 further comprises a camera 37 for imaging the microperforations and/or other control processes. The laser 35 and the camera 37 are operably connected with a perforation controller 39 for operational control, quality control and/or feedback control of the laser 35. The controller 39 may be programmable for determining one or more of the number, size and positions of the microperforations.

[0071] Further, not shown in any detail, the apparatus 1 may comprise a detector 41 and a calculator 43 configured to determine, e.g. by measuring and calculating on the basis of measurement results, one or more respiration properties, e.g. an O2 consumption and/or CO.sub.2-production of the produce to be packaged and, based on that/those, determining one or more of a composition of the target modified atmosphere, a composition of the modifying atmosphere, a number and/or size of one or more microperforations (to be) made in the packaging material of the package(s).

EXAMPLE 1

[0072] Transmission rate tests were performed on polymer film of 25 micrometre thickness made by extrusion from a blend of copolymers derived from potato starch, without plasticisers; the source materials were in accordance with EU Directive 2002/72/EG. The material was sold as a food-contact safe and biodegradable film material conform EN 13432 and ASTM D6400. The single-layer film was thermally weldable facilitating forming the packages as foil wraps, bags, seal trays, etc. Several samples were tested. All test samples were unperforated and intact.

[0073] The Water Vapour Transmission Rate (WVTR) of the film was determined in accordance with ISO 2528 (gravimetric method) at a test temperature of 38° C. and a relative humidity of 90% rH. Three individual measurements were performed. The test results were 1037 g/(m.sup.2.Math.24 hrs), 1111 g/(m.sup.2.Math.24 hrs) and, respectively, 1071 g/(m.sup.2.Math.24 hrs), i.e. on average WVTR=1073 g/(m.sup.2.Math.24 hrs) with a standard deviation of 37 g/(m.sup.2.Math.24 hrs). Compared to other films, this is a high WVTR.

[0074] The Oxygen Transmission Rate (O.sub.2TR) of the film was determined in accordance with ASTM D3985 2556 (coulometric method) at a test temperature of 23° C. Three individual measurements were performed. The test results were 1609 ml/(m.sup.2.Math.24 hrs), 1602 ml/(m.sup.2.Math.24 hrs) and, respectively, 1595 ml/(m.sup.2.Math.24 hrs), i.e. on average O.sub.2TR=1602 ml/(m.sup.2.Math.24 hrs) with a standard deviation of 7 ml/(m.sup.2.Math.24 hrs).

[0075] The Carbon Dioxide Transmission Rate (CO.sub.2TR) of the film was determined in accordance with ISO 2556 (manometric method) at a test temperature of 23° C. Three individual measurements were performed. The test results were 7675 ml/(m.sup.2.Math.24 hrs), 8195 ml/(m.sup.2.Math.24 hrs) and, respectively 8235 ml/(m.sup.2.Math.24 hrs), i.e. on average CO.sub.2TR=8035 ml/(m.sup.2.Math.24 hrs) with a standard deviation of 312 ml/(m.sup.2.Math.24 hrs).

[0076] The O.sub.2TR of the film is therefore about 20% of the CO.sub.2TR, or in other words, the ratio β=CO.sub.2TR/O.sub.2TR is about 5.0. Compared to other films, this is a high value.

[0077] Similarly, a film of 80 micrometers thickness of the material still has a WVTR of about 120 g/(m.sup.2.Math.24 hrs) and an O.sub.2TR of about 750 ml/(m.sup.2.Math.24 hrs) and a CO.sub.2TR of about 3750 ml/(m.sup.2.Math.24 hrs) at a ratio β of 5.

COMPARATIVE EXAMPLES

[0078] A series of test packages were made. In these tests, various types of respiring produce were provided and packaged, using the apparatus and method described above, in different polymer foils as packaging material. Each package was formed as a CAP package by providing the respective packaging material with one or more microperforations of controlled size, together providing an open area of the microperforations determined to provide an optimized transmission rate of the package as whole for oxygen. The respective open area of each package was determined by measuring a respiration rate of the produce to be packed and taking into account the packaged amount of produce, the amount of packaging material, the volume of the produce in the package, the package volume (the two volumina enabling to determine the head space of the package). The CAP packages for each type produce were, after manufacturing, stored under refrigerated and controlled conditions. Shelf life, on the basis of produce quality, was determined by a test panel composed of appropriately trained and experienced persons.

[0079] The tested materials are listed below in Table 1. The test results are listed in Table 2 and graphically presented in FIG. 2.

TABLE-US-00001 TABLE 1 Specifications of packaging materials used in the tests of Table 2. Comp 1 Comp 2 Comp 3 Example Material LDPE Polyamide Flexfresh Copolymers Thickness [micrometer] 25 30 30 25 WVTR [ml/(m.sup.2 .Math. 24 5 60 180 1000 hrs)] O.sub.2TR [ml/(m.sup.2 .Math. 24 2000 20 1500 1600 hrs)] CO.sub.2TR [ml/(m.sup.2 .Math. 24 8000 60 4500 8000 hrs)] beta = CO2TR/O2TR 4, 0 3, 0 3, 0 5, 0

TABLE-US-00002 TABLE 2 Shelf life under optimum storage conditions of oxygen-optimized microperforated CAP packages with the packaging materials of Table 1 for various types of respiring produce, in days. Comp 1 Comp 2 Comp 3 Example Asparagus 12 22 28 35 Avocado 14 — 48 65 Bell Peppers 12 24 26 30 Blueberry 14 45 50 55 Broccoli 14 28 35 40 Brussels sprouts 14 20 25 35 Celeriac 7 — 55 68 Cherries 10 40 50 60 Chinese cabbage 14 38 48 62 Coriander 5 14 17 20 Cucumber 5 18 20 26 Dill 5 14 15 18 Eggplant 5 18 21 25 Grapes 21 27 40 50 Green beans 0 12 16 20 Hot pepper 7 18 20 25 Iceberg lettuce 7 20 25 32 Leeks 7 18 20 28 Mango 0 — 42 50 Papaya 10 16 20 25 Pomegranate 10 22 28 40 Stawberry 5  8 12 15 Sweet pointed pepper 7 — 21 25

[0080] From these results the following becomes apparent:

[0081] The material of comparative example Comp 1 was LDPE, this is a standard fresh produce packaging material. Although LDPE has a combination of an average O.sub.2TR, a high CO.sub.2TR, and a high ratio β=CO.sub.2TR/O.sub.2TR of about 4.0, it has a very low WVTR. As a result, CAP packages of LDPE wherein the total open area of the microperforations is optimized with respect to the oxygen transmission rate of the package as a whole, provide a high relative humidity in the package atmosphere.

[0082] It is noted that to reduce the relative humidity in an LDPE-based package, additional and/or larger perforations could be made to increase the open area but this would degrade or destroy the oxygen control. Also or alternatively, hygroscopic and/or otherwise water-consuming materials could be added but this would increase costs and could not be allowable for reasons of hygiene and/or food safety. In the presented test series, no such measures going beyond mere packaging the produce in a perforated film as an oxygen-optimized CAP package were taken.

[0083] The material of comparative example Comp 2 was polyamide, which is another standard fresh produce packaging material. Although polyamide has a significantly higher WVTR than LDPE, it is a barrier material with very low O.sub.2TR and CO.sub.2TR, yet the value of its ratio β=CO.sub.2TR/O.sub.2TR of about 3.0 is average. As a result of the low O.sub.2TR, CAP packages of polyamide require a very large open area of the microperforations (i.e. high number of perforations and/or large open area per perforation) to optimize the total open area with respect to the oxygen transmission rate of the package as a whole. Thus, the ratio of the transmission rates of the package as a whole of CO.sub.2 and 0.sub.2, and therewith the flow ratio of CO.sub.2:O.sub.2 through the package is about 1 and the equilibrium concentration of carbon dioxide in the package atmosphere tends to be high. Due to the large open area of the microperforations, in spite of the low WVTR of the packaging material, the transmission rate for water vapour of the package as a whole is increased to provide a low relative humidity in the package atmosphere. The combined effect is an extended shelf life over LDPE-based CAP packages.

[0084] The material of comparative example Comp 3 was a state of the art packaging material sold by the company Uflex Limited under the brand name Flexfresh™ film. The material provides a significant improvement over LDPE and polyamide. It exhibits a comparably significantly higher WVTR, a moderate O.sub.2TR but above average values of CO.sub.2TR and of the ratio β. As a result, CAP packages of this material require comparably less open area of the microperforations to optimize the total open area with respect to the oxygen transmission rate of the package as a whole, while providing a larger transmission for water vapour and CO.sub.2. The resultant packages provide a longer shelf life than those with LDPE and polyamide.

[0085] In CAP packages according to the presently provided insights, wherein the packaging material was that of Example 1, the packaging material has a combination of a very high WVTR, a moderate O.sub.2TR and a high value of the ratio β=CO.sub.2TR/O.sub.2TR of about 5.0. Thus, in such CAP packages, the open area of the microperforations can be optimized for oxygen while the transmission rate for water and CO.sub.2 of the package as a whole is very high. From the test results it will be evident that the shelf life of such CAP packages is significantly extended for all tested species of produce compared to the other packages.

[0086] The disclosure is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims. For instance elements and aspects discussed in relation to a particular embodiment may be suitably combined with those of any other embodiment.