INDICATING PACKAGE

Abstract

A package of oxygen sensitive product (10) has a body (5) a lid (15). The lid (15) includes a membrane (17), which incorporates ink (16), adapted to react to the presence or absence of a particular gas or mixture of gases in the headspace (25) of the package. The ink (16) is protected from the external environment by a barrier material (50, 51, 52), but is in fluid communication with the headspace (25). The barrier material (50, 51, 52) is chosen such that a user of the package may detect the reaction of the ink (16) through the barrier material.

Description

TECHNICAL FIELD

The present invention relates to a package for holding products, which are sensitive to oxygen. In particular, the package incorporates ink, which shows whether the inside of the package has been exposed to air and hence oxygen, by a colour change or response to an external stimulus.

BACKGROUND ART

Where a package contains a product, which is sensitive to oxygen, the package healspace (the space within the package not filled by the product) is conventionally flushed with inert gas (for example a mixture of carbon dioxide and nitrogen) to remove the air and oxygen component thereof, prior to sealing the package. By removing the air from the headspace, deterioration of the product is minimised

Indicating inks, which exhibit a colour change in the presence of certain gases, also form part of the state of the art. For example

• Patent Citation 0001: US 2003199095 2003-10-23.

describes a material, which changes colour in the presence of a certain concentration of carbon dioxide and

• Patent Citation 0002: US 2004258562 2004-12-23.

23.12.2004 relates to a similar oxygen indicator, which changes colour in the presence of oxygen.

DISCLOSURE OF INVENTION

The present invention makes use of such inks in a package for products, which are sensitive to oxygen. Accordingly, the invention provides a package for an oxygen sensitive product having a body and a lid,

wherein the lid includes a gas bather material arranged facing the external environment, which may be opened by a user to gain access to the inside of the package. The invention is characterised in that the lid includes an ink, adapted to indicate the presence or absence of a particular gas or mixture of gases by a visible colour change or by using a measuring device. The ink is protected from the external environment by the barrier material, but is in fluid communication with the inside of the package and any change of the ink is visible to or measurable by a user of the package through the barrier material.

The package includes ink sensitive to the gases present in the headspace of the sealed package and visible to or measurable by a user of the package. The ink responds to specified changes to the composition of the headspace gases by either colour change or some other means. Thus, leaks and the resultant ingress of air (oxygen) may be detected. The bather material blocks the ink from exposure to the gases present in the surroundings thereby preserving the ink's state until it reacts to changes in the composition of gases within the headspace. The barrier material is sufficiently translucent or transparent that a user of the package may observe the colour or measure the response of the ink through the barrier material.

According to the invention, the ink is separated from the product and headspace gases, to avoid cross-contamination. This is of particular concern when packaging food products because of food contact issues. Such food contact issues are of particular concern when packaging food intended to be consumed by infants, for example milk powder. Such physical separation between the ink and the product must be made from a material, which is permeable to gas, thus enabling the ink to accurately respond to the headspace gases.

The conventional method for packaging products that are sensitive to oxygen includes flushing the headspace gases from the package with an inert mixture, for example carbon dioxide and nitrogen. In an embodiment of the invention, the inventors have exploited this process by incorporating ink into the package, which is sensitive to carbon dioxide. After flushing and sealing, the headspace gases within the package are abundant in carbon dioxide and the ink will thus turn the appropriate colour to indicate the presence of carbon dioxide. If the package leaks, the carbon dioxide present in the headspace will escape, to be replaced by air from the surroundings. Once the level of carbon dioxide reduces below a threshold level, the ink will change colour. This indicates to a user of the package that the seal has been compromised and the product has come into contact with air and may thereby have degraded.

As the user of the package may be unfamiliar with the colour change expected from the ink, a colour comparison portion on the outside of the package is preferably to provided. This allows a user of the package to easily identify whether or not the contents of the package has been exposed to air (oxygen) and may have thereby degraded.

In an alternative embodiment, ink that is sensitive to oxygen is used. This requires the headspace gases to be substantially free of oxygen. As existing oxygen inks are very sensitive, a scavenger is incorporated into the package to “scrub” the headspace of any oxygen remaining after the package is flushed and sealed. Existing oxygen sensitive inks have to be activated in some way (for example, by exposure to UV light) once the package is sealed and any remaining oxygen has been scrubbed from the headspace by the scavenger. Such sensitive inks and the additional process steps required to activate the inks may be relatively expensive and cost may be a prohibitive factor in certain applications. Although production of the package is more complex, the package thus produced is much more sensitive to the ingress of air (oxygen).

Another alternative embodiment of the invention also uses ink that is sensitive to oxygen, but in this case the oxygen concentration is measured by fluorescent emission from the ink The measurable response of the ink is dependent upon the concentration of oxygen within the headspace. Stimulating the ink using a device external to the package triggers the fluorescence response. Although this approach requires an external device to determine the oxygen concentration, a quantitative value of oxygen concentration is obtained and the necessity of scavenging residual oxygen from the headspace is no longer required.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 shows a side view of a food can used in both the prior art and the invention;

FIG. 2 shows a side section through a can according to the invention having a peelable membrane and ink, which changes colour in response to carbon dioxide;

FIG. 3 shows a side section through a can according to another embodiment of the invention having a peelable membrane, ink (which changes colour in response to oxygen in the headspace) and a scavenger material;

FIG. 4 shows a plan view of an unseamed lid suitable for use in the package shown in FIG. 3;

FIG. 5 illustrates the structure of a membrane suitable for use in the package shown in FIG. 2;

FIG. 6 illustrates the structure of a membrane suitable for use in the package shown in FIG. 3.

FIG. 1 illustrates a metal container conventionally used for packaging foodstuffs such as dried milk powder. This package includes a can body 5

made from a flat sheet of metal, which is formed into a cylinder. The two adjacent edges of the metal sheet are then seamed together to form a cylindrical body 5, having a side seam 6 and two open ends. A lid 15 closes one end of the cylindrical body 5 and the resulting hollow package is filled with a product 10, through the remaining open end. Where the product 10 is sensitive to oxygen (a constituent of air) an end 30 is loosely crimped to the open end after filling with the foodstuff 10. At this stage, the package remains unsealed and the headspace 25 above the surface of the foodstuff 10 is filled with air from the surroundings. The package is then flushed with a mixture of carbon dioxide and nitrogen and the end 30 is sealed on to the can body 5 using a conventional double seaming process. The headspace 25 is now filled with the carbon dioxide and nitrogen mixture, to preserve the oxygen sensitive foodstuff.

Considering a container for dried milk powder, the lid 15 conventionally takes the form of a metal ring 19 and a membrane 17 that seals the orifice in the centre of the ring (as shown in FIGS. 2, 3 and 4). The metal ring 19 is joined to the can body 5 by means of a double seam 20 and a user gains access to the dried milk powder 10 by peeling back the foil or membrane 17.

FIG. 2 illustrates a metal container according to one embodiment of the invention. The package is similar to that discussed above, but the membrane 17 includes an Ink 16, which is sensitive to carbon dioxide. The membrane 17 has a barrier layer, which protects the ink 16 from gases in the surroundings, but allows gases from the headspace 25 to contact the ink 16. The membrane 17 is sufficiently transparent or translucent to allow a user of the package to observe the colour change exhibited by the ink 16 through the membrane 17. The can body 5 is filled with a foodstuff 10 using a conventional process, such as that described above. The end 30 is then crimped onto the open end of the can body 5 but the package remains unsealed and still contains air from the surroundings. The ink adopts a first colour (bright purple, for example) to indicate that the package contains air. Once the package has been flushed with a mixture of carbon dioxide and nitrogen, the package contains the carbon dioxide and nitrogen mixture, and the ink 16 responds to the carbon dioxide sealed within the container and adopts a different colour (yellow or salmon pink, for example).

If this container leaks, carbon dioxide will escape from the headspace to be replaced by air from the surroundings. Once the level of carbon dioxide reduces to a threshold level, the ink will return to its first colour, indicating that the package has been compromised. Thus, in this example, the ink undergoes a reversible colour change depending upon whether or not the headspace contains a defined level of carbon dioxide.

A package according to an alternative embodiment is illustrated in FIGS. 3 and 4. The ink 16 used in this package is sensitive to oxygen. This requires package to be substantially free of oxygen, before the ink 16 is “activated”. This may be achieved by a combination of the flushing process described above with the addition of an oxygen scavenger 18, chosen to scrub the gases remaining in the sealed container of any remaining oxygen. Once the oxygen level is below a threshold value (determined by the ink), the oxygen sensitive ink may be “activated” by means of UV light. Once the container is sealed and the ink “activated”, an undesirable level of air (oxygen) leaking into the container will trigger a colour change in the ink.

In a preferred example, a Palladium-group metal dispersed on a fibrous polymeric support provides the scavenger 18. The inventors chose a palladium type scavenger, because it enables the package to be produced and filled in a dry environment and is easy to handle. The palladium type scavenger 18 works via a catalytic process and requires the headspace 25 to be flushed with a modified atmosphere, which includes hydrogen. The hydrogen combines with any residual oxygen in the headspace gases to form water. If the gases used to flush the headspace 25 are a mixture of hydrogen and nitrogen, a mixture with less that 5.7% hydrogen is classified as non-flammable according to ISO 10156. Hydrogen can be used as a “modified atmosphere gas” for packaging because it appears on the positive list of food additives under number E949 (directive 2001/5/EC).

The sealing membrane 17 may be provided as a laminate. For example, a laminate film suitable for detecting the levels of carbon dioxide in the headspace is illustrated in FIG. 5. This film may include an upper, barrier layer comprising a layer of PET 50 and a thin layer of Aluminium Oxide 51. The next layer or a portion thereof includes the ink 16. The barrier layer 50, 51, 52 stops the surrounding air from coming into contact with the ink 16, whilst allowing a user to observe the colour of the ink. The inventors have discovered that many adhesives 60 react unfavourably with the ink 16 and therefore, the ink 16 is protected from the adhesive 60 by a layer of PVB 56. Finally the layer adjacent to the headspace 25 (inside of the container) is provided by a layer of material 55, which is permeable to the headspace gases (Polypropylene, for example). Polypropylene has the additional advantage that it acts as a heat-sealing layer for heat-sealing the membrane 17 to the metal ring 19.

In order for a user of the package to more clearly interpret the colour change of the ink, one or more comparison colours may be provided on the membrane 17 to indicate the colour of the relevant inks when the package is sealed and/or when the package has been compromised.

FIG. 6 illustrates a laminate membrane incorporating oxygen sensitive ink 16 and a scavenger 18. An oxygen scavenging system may be used to prevent the development of mould or oil oxidation and prevent rancidity and staling. Examples of products for which such packaging may be useful includes foodstuffs, particularly those with high water and/or oil content; tea, tobacco, grain or leather; electronic products and drinks, such as wine, beers, fruit juices and soft drinks

The preceding examples have been described in relation to a package having a cylindrical body 5 and two open ends sealed by a lid 15 and end 30—a so called “3-piece” can. However, it will be apparent to those skilled in the art that the body 5 may take the form of a shaped can and the can body 5 requires only one end, the lid, the other end being formed integrally with the side wall of the body—a so called “2-piece” can.

Claims

1. A package for an oxygen sensitive product comprising:

a body that is impervious to gases,

a lid sealed to the body incorporating a gas barrier material and arranged between the external environment and the body to form a gas sealed chamber for the product, and

an ink adapted to react to the presence or absence of a particular gas or mixture of gases, the ink is protected from the external environment by the barrier material, the product is protected from the ink by a gas permeable material allowing fluid communication with the inside of the package, whereby

the reaction of the ink is capable of detection by a user of the package through the barrier material.

2. A package according to claim 1, wherein the reaction of the ink is measured through the barrier material using an external device.

3. A package according to claim 1, wherein the reaction of the ink is a color change, which is visible though the barrier material.

4. A package according to claim 3, wherein the lid further includes a reference color against which the color of the ink may be compared.

5. A package according to claim 1, further including a filling aperture and a gas impermeable end (30) for sealing the filling aperture.

6. A package of oxygen sensitive product comprising:

a body and a lid sealed to the body to encapsulate the product and a headspace therein,

the lid including a gas barrier material arranged between the external environment and the body, and

an ink adapted to react to the presence or absence of a particular gas or mixture of gases in the headspace, the ink is protected from the external environment by the barrier material and the inside of the package is protected from the ink 16 by a gas permeable material allowing fluid communication with the headspace.

7. A package of oxygen sensitive product according to claim 6, wherein

the lid includes a gas permeable material arranged between the ink and the headspace.

8. A package of oxygen sensitive product according to claim 6, wherein the lid has a laminate structure, which includes a layer of barrier material, a layer incorporating the ink and a layer of gas permeable material.

9. A process for packaging an oxygen sensitive product comprising the steps of,

securing a lid comprising an ink to a hollow body,

filling the body with an oxygen sensitive product to define a headspace above the free surface of the product,

flushing the headspace with a gas or mixture of gases, which cause the ink to adopt a first state so long as the headspace contains the gas or mixture of gases at a predetermined level.

10. A process for packaging an oxygen sensitive product according to claim 9, wherein the ink reacts in response to the level of carbon dioxide in the head space.

11. A process for packaging an oxygen sensitive product according to claim 9 wherein the ink reacts in response to the presence of a defined level of oxygen in the headspace and the lid further includes an oxygen scavenger,

flushing the headspace with a gas or mixture of gases after filling with a product to substantially remove air from the headspace any remaining oxygen being removed by the scavenger, and

activating the ink so that it responds to a defined level of oxygen in the headspace.

12. A process for packaging an oxygen sensitive product according to claim 11, wherein the scavenger is a palladium catalyst and the headspace is flushed with a mixture of gases containing hydrogen, which reacts with any oxygen remaining in the headspace to form water.

13. A process for packaging an oxygen sensitive product according to claim 11, where the oxygen sensitive ink is activated by exposure to UV light.