AU4485299A - Improvements to methods of testing - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: SEALED AIR (NZ) LIMITED Actual Inventor: Peter Catcheside Address for Service: MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: "IMPROVEMENTS TO METHODS OF TESTING" The following statement is a full description of this invention, including the best method of performing it known to us.

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Adelaide, South Australia, Australia Invention title: "IMPROVEMENTS TO METHODS OF TESTING" The following statement is a full description of this invention, including the best method of performing it known to us.

IMPROVEMENTS TO METHODS OF TESTING TECHNICAL FIELD This invention relates to improvements to testing.

More specifically, the present invention relates to improvements to methods for checking modified atmosphere packaging.

BACKGROUND ART Modified atmosphere packaging (MAP) is used extensively in the packaging of food products.

MAP is used extensively in the packaging of meat. In particular, modified 10 atmospheres with high concentrations of carbon dioxide are used in the process of packaging red meat such as beef or lamb. The high carbon dioxide concentration provides extended shelf life of the meat during transit and storage.

Such meat products are also commonly packaged in opaque metallised laminate plastic bags and pouches. The terms "bag" and "pouch" are to be used interchangeably. This metallised material provides a near impermeable barrier to the escape of the carbon dioxide modified atmosphere.

The meat is usually placed in a metallised bag, which is then gas flushed and sealed, and then placed in a box, with a liner separating the metallised plastic bag from the box walls.

Alternatively, the meat may be placed in a metallised bag, placed in a box with a liner separating the metallised plastic bag from the box walls, the metallised plastic bag then gas flushed and sealed.

Sometimes, the bag seal may not be formed to a sufficient standard, or the bag may rupture. This may cause the carbon dioxide to escape through the rupture, and simultaneously may allow oxygen to enter the bag atmosphere.

This can result in a spoiling of the meat or at least rendering the meat unsuitable for sale.

Other modes of MAP packaging such as lidded trays, such as that disclosed in US 5,686,126, may also be used.

Various methods of checking have been used in the past.

Some involve randomly selecting boxes of meat, and opening the liner and examining *o the contents of the bags. However this can be unsatisfactory, because of the opaque 10 nature of the metallised plastic bag. It is not possible to clearly determine the condition of the meat in the plastic bag through the opaque plastic.

Consequently it is hard to determine using this method if a leak has developed.

Another method has been the "snap back" test, where the bag may be pinched and **pulled to observe whether there is a snap back towards the meat by the plastic bag, which would indicate the absence of a leak. This is not an accurate method as it only detects large holes, and is labour intensive and time consuming.

The above methods can also not identify where in the production process/supply chain, the breaches of the modified atmosphere are occurring which can be of vital importance.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description, which is given by way of example only.

DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided a method of checking the integrity of MAP packages, characterised by the steps of placing a gas indicator between the MAP packages and a liner, observing the gas indicator to determine the presence or non-presence of a leakage gas.

The MAP packages may include any materials, or modes of packaging used to achieve a modified atmosphere package. The material may be any barrier material and for example, may be metallised, clear, opaque or coloured.

For example, the packaging may include bags, parcels, package trays and other types of 10 packaging used in modified atmosphere packaging technology. These may include TRIFRESH TM and thermoform packs, CO 2 modified atmosphere packs and barrier liners.

In preferred embodiments, the packaging used may be a MAP bag.

An example of other packaging types that may be used in accordance with the present invention without departing from its scope, is disclosed in US Patent No. 5,686,126.

Preferably, the product packaged by the MAP bags may be meat.

Reference to the product being packaged in the MAP bag being meat should not be seen to be limiting in any way, as other products such as vegetables, fruit and other organic produce or other product (for example medical equipment) may be packaged by the MAP bags while still deriving the same advantages of the present invention.

In some embodiments, the bag used may be manufactured from a plastic film.

Reference to the bag being manufactured from a plastic film should not be seen to be limiting in any way as other materials may be used to construct the bag, such as foil, laminated structures and so forth.

In further preferred embodiments, the plastic film may be an opaque metallised film.

Such films may include those manufactured by "Saehan". These may include a grade such as MP542.

In other embodiments, the film may be a clear plastic film.

Such films may include those manufactured by the applicant, which are well known in the art.

In preferred embodiments, the gas to be detected may be the gas or gas mixture used in the MAP bags.

Reference to the gas being detected as that in the MAP bags should not be seen to be limiting.

The principles of the present invention may apply with equal advantage, to the detection of gasses derived from the product being packaged, the ambient atmosphere surrounding the package and so forth.

Preferably the modified atmosphere may have a high concentration of carbon dioxide.

There may also be a mix of oxygen and carbon dioxide.

Other gases such as nitrogen may be included in that modified atmosphere.

The modified atmosphere may be a mix of gases mixed to preserve food as well known in the art.

Reference to the checking of the integrity of the MAP bags may be made with reference to whether the barrier between the MAP bags atmosphere and the ambient atmosphere has been breached in any way.

This may be by way of a tear, hole, failed seal, faulty or inferior MAP bag material and so forth.

Reference to a liner may be made with reference to a particular method of packing MAP bags whereby the packaged goods are placed in a container, with a liner between the package(s) and the container wall.

Reference to a liner shall be made with reference to a plastic liner although this should not be seen to be limiting as liners manufactured from other materials such as paper, cellulose, rubber and so forth, may be used.

Reference to the container may be made with reference to any container used to 10 transport or store a packaged item.

For example this may include plastic containers, barrels, boxes, crates, bags, and so forth.

In preferred embodiments, the container may be a cardboard box.

*Reference to the container as a cardboard box should not be seen to be limiting in any way, as the principles of the present invention may be applied to the use of containers other than cardboard boxes, including those mentioned in the above examples.

In other preferred embodiments, the container may be a shipping container.

Reference to a gas indicator may be made with reference to any device that produces an observable response to the presence of a particular gas.

For example the gas indicator may be chemical, electronic, organic and so forth.

Any gas level change may be detected using a gas analyser by physically placing a gas sensor into the package and noting the reading on the gas analyser attached to the sensor.

This may be a device such as a "Portamap manufactured by Sistech Instruments.

In preferred embodiments however the indicator may be a chemical indicator.

Reference to a chemical indicator should not be seen to be limiting as the principles of the present invention may be applied using indicators of other types, including those mentioned in the above examples.

In preferred embodiments, the gas being detected may be carbon dioxide. In alternate embodiments other gas levels may be detected, for example the amount of oxygen may be detected which may be useful in itself or as an indication that the balance of gases may be upset as a consequence of a leak.

10 Preferably, the indicator may be a chemical indicator used to detect carbon dioxide.

The indicator may be able to detect the presence or non-presence of carbon dioxide.

The nature of the chemical indication may preferably be visual.

For example the indicator may change colour, or become opaque or transparent. In other applications, the intensity of the indicator colour may change.

Preferred indicators which can be used with the present invention for the detection of carbon dioxide may be a salt of an indicator anion and a lipophilic organic quaternary cation.

Suitable indicator anions may be azo dyes (including alpha napthol orange), nitrophenol dyes (including M-nitrophenol and P-nitrophenol), phothalein dyes (including alpha-naphtholphthalein and o-cresol phthalein), sulphonephthalein dyes (including M-crysol purple, crysol red, thymol blue and alphanaphtholsulphonephthalein), triphenylmethane dyes (including rosolic acid) and indophenol dyes (including indophenol and l-naphthol-2-suphonic acid indophenol).

Examples of suitable quaternary cations are: Ammonium cation (including benzyltrimethyl ammonium, trioctylemethyl ammonium, triceprylmethyl ammonium, tetrabutyl ammonium, tetrapexyl ammonium, and tetraoctyl ammonium) and phosphonium cation (including tetrapenyl phosphonium, trioctyl phosphonium and hexadecyl tributyl phosphonium).

A preferred quaternary cation is tetrabutyl ammonium.

In preferred embodiments, the indicator may be configured as a portion of material with a self-adhesive on one side of the material, and the indicating substance printed on the same side as the self-adhesive side.

The above embodiment of the indicator may be adhered to the inside of the liner, .9 10 which means the indicator may be observed through the opaque or clear film or container in which the MAP packages are placed.

In further embodiments, the indicator may be placed in the space between the liner and the MAP bags.

In preferred embodiments however, the indicator may be placed on the MAP bags.

15 In other preferred embodiments, the gas indicator may be disposed within the container, but outside of the MAP bags, for detecting the presence or non-presence of a 9 gas.

This placement may preferably be semi-permanent. The semi-permanent attachment may be by way of adhesive or sealant or some other adhesive means.

The observing of the gas indicator may be a visual observation in preferred embodiments.

However if an electronic device is used, then the observation may be performed electronically and remote from the MAP bags for example, spectroscopically.

In preferred embodiments, the carbon dioxide indicator may be calibrated to react to carbon dioxide concentrations of This has a number of advantages. Carbon dioxide in the air is normally about 0.03%.

The concentration in MAP bags using modified atmosphere technology may be 100% carbon dioxide concentration. The selection of the 1.0% threshold is to ensure that the carbon dioxide level detected by the indicator is a level well above atmospheric or ambient fluctuations.

Furthermore, the threshold concentration needs to be low with respect to the concentration inside the MAP bags, so as to be able to detect a small leak.

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10 Preferably, the sensitivity of the indicator may be adjusted to be best suited to the length of time taken from the packaging stage to the consumer, and to the method of go•• packaging.

9 The applicants envisage two methods of placing the MAP packaging into the container with the liner between the container wall and the bags.

For example, the product may be placed in the bags, which may then be placed in the container with the liner between the container wall and the bags. The bags may then be gas flushed and sealed. This may be referred to as packaging system 1.

Packaging system 2 may involve placing the product in the bag, gas flushing and sealing the bag. The bag may then be placed in the container with the liner between the container wall and the bags.

Packaging system 1 can allow carbon dioxide to be present between the MAP bags and the liner, and between the liner and the cartons.

When packaging system 1 is used, then a higher indicator threshold may be chosen.

This is because if the carbon dioxide gas takes a number of days to dissipate from the cavities within the container, particularly if fluked board is used, and the space between the container and the liner, and more particularly the space between the liner and the MAP bags, the indicator sensitivity may be selected to operate above the initial carbon dioxide levels.

This is so that the indicator does not change status as a result of the higher than usual ambient carbon dioxide concentration resulting from the packaging process, which may be mistaken for a breached barrier.

Preferably, if the second method of packaging is employed, the sensitivity threshold may be lower. This is because the second method prohibits carbon dioxide from reaching the space outside the MAP bag. A high sensitivity indicator having a lower indicator threshold) may therefore be used to detect leaks within hours of the completed packaging operation. This is because in the second method, it would be •unusual to have higher carbon dioxide levels than that normally found in atmosphere present in the container.

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In some further embodiments, the liner may be a gas barrier liner.

•Normal liners are commonly permeable to gases and can allow leakage gases to escape over time. The leakage gas concentration in the liner space can fall to below the detector threshold level.

If there is small rupture in the MAP bag, the escaping carbon dioxide may permeate through the permeable liner at a rate which does not permit the carbon dioxide level to reach the critical level for detection, such that the gas indicator no longer validly indicates a breach.

The advantage of using a gas barrier liner is that the carbon dioxide that has escaped from the MAP packaging will be held approximate to the indicator, which will give a valid indication of the integrity of the MAP packaging.

The gas barrier liner may be manufactured from many gas barrier materials, such as those employing layers of nylon, ethylene vinyl alcohol, polyvinylidinedichloride and coated or oriented films.

In some preferred embodiments, the indicator may include a plurality of indicators.

The indicators may be configured with different carbon dioxide detection thresholds.

The level of carbon dioxide detected may provide information that may help identify the reason for the leak.

The present invention has a number of advantages. By this visual checking method, 90 10 leakers, the term used to describe MAP bags whose integrity has been breached, can be .9.o detected early. This means that bad products are less likely to reach the consumer, which benefits the consumer. The distributor and packager also gain an advantage in 9 that their reputation for supplying a good product is preserved and improved.

If a stage in the MAP bags process is causing the loss of integrity of the MAP bags, 15 then this may be identified by continual checking of the products. By process of elimination, the trouble spots can be identified and eliminated.

999999 The present invention has other applications in addition to the transport of produce such as meat. Medical supplies that are kept in modified atmospheres may be checked for breaches in their MAP bags by using the appropriate indicator.

Items such as vegetables and fresh salads may be kept fresh and spoilt ones discarded, upon detecting using the present invention.

BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the following description, which is given by way of example only and with reference to the accompanying drawings in which: Figure I shows a view of a typical MAP bag arrangement to which the present invention may be applied.

BEST MODES FOR CARRYING OUT THE INVENTION With reference to Figure 1 there is shown an arrangement used in the method of checking the integrity of a MAP bag in a total package shown by general arrow 1. A gas-impermeable bag 2, containing the product in a modified atmosphere, is placed in a container 3. The gas-impermeable bag 2 may be constructed from EVOH extruded 1 films, or laminates with PVDC gas barriers, or any other film used as a oxygen barrier such as a metallised plastic.

o A liner 4 is positioned between the metallised plastic bag 2 and the container 3. In some embodiments, the liner may be 30 microns of polyethylene.

*A gas level indicator 5 is placed between the liner 4 and the bag 2.

S- The determined threshold of the indicator 5 allows any breaches of the integrity of the MAP bags to be detected by detecting the escaping modified atmosphere gas.

Preferably, this will be carbon dioxide.

The total package may be checked at interim periods between the packing phase and up to and including the point at which the meat is removed from the MAP bag.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims.

Claims (13)

1. 2. A method as claimed in claim 1 wherein the integrity of the MAP package o refers to whether the barrier between the atmosphere of MAP package and the SS. ambient atmosphere has been breached.
2. 3. A method as claimed in either claim 1 or claim 2 wherein the method of packing MAP packages includes the placing of the packages in a container with Sa liner between the packages and container walls.
3. 4. A method as claimed in any one of claims 1 to 3 wherein the gas indicator is a gas analyser. S5. A method as claimed in any one of claims 1 to 3 wherein the gas indicator is a S chemical indicator.
4. 6. A method as claimed in any one of claims 1 to 5 wherein the gas being detected is carbon dioxide.
5. 7. A method as claimed in any one of claims 1 to 6 wherein the nature of indication is visual.
6. 8. A method as claimed in any one of claims 1 to 3 or 5 to 7 wherein the indicator is a portion of material with a self-adhesive on one side and an indicating substance printed on the same side as the self-adhesive side.
7. 9. A method as claimed in any one of claims 1 to 8 characterised by the further step of placing the indicator in a space between a liner and the MAP package. A method as claimed in any one of claims 1 to 3 or 5 to 9 wherein the placement of the indicator is semi-permanent.
8. 11. A method as claimed in any one of claims 1 to 10 wherein the gas indicator is calibrated to react to carbon dioxide concentrations of about 1%.
9. 12. A method as claimed in any one of claims 1 to 11 characterised by the steps of 9 placing product into MAP packages, oo placing the MAP packages in a container with a liner positioned between the container wall and the packages, and 9.. gas flushing the MAP packages, and t I. sealing the MAP packages. S* 13. A method as claimed in any one of claims 1 to 12 characterised by the steps of placing product in a MAP package, gas flushing and sealing the MAP package, and 99 9c placing the MAP package in a container with a liner between the container wall and the MAP package.
10. 14. A method as claimed in any one of claims I to 13 wherein the liner is a gas barrier liner. A method as claimed in any one of claims I to 14 wherein the indicator includes a plurality of indicators complete with different thresholds.
11. 16. An indicator for use with the method as claimed in any one of claims I to
12. 17. A method substantially as herein described with reference to and as illustrated by the accompanying drawings.
13. 18. An indicator substantially as herein described with reference to and as illustrated by the accompanying drawings. Dated this 31st day of August 1999 SEALED AIR (NZ) LIMITED by its Patent Attorneys MADDERNS