Carbon dioxide atmosphere modifiers for packaging

Details Carbon dioxide atmosphere modifiers for packaging Carbon dioxide atmosphere modifiers for packaging

2001-04-09

2003-07-15

Alexander, Reginald L. (Department: 1761)

Food or edible material: processes, compositions, and products

Packaged or wrapped product

Package containing separate noncoated or laminated interior...

C426S316000, C426S398000, C426S418000

Reexamination Certificate

active

06592919

ABSTRACT:

TECHNICAL FIELD
This invention relates to methods and apparatus used in packaging. More particularly, the principles of the present invention relate to the packaging of food products such as meat using atmosphere modifiers.
Reference to the packaging of meat should not be seen to be limited as the principles of the present invention may be equally applied to the packaging of other food products.
BACKGROUND ART
The export and domestic consumption of meat, such as beef, lamb, chicken and other meats, provides a significant source of revenue for many countries. It is therefore important that this product arrives at its destination having the highest possible quality. It therefore follows that packaging methods used to contain the meat in transit must be of high quality in order to keep the meat in a desired state.
There are however problems with the current methods and apparatus used to package meat.
A natural process that must be mitigated or avoided, is oxidation. This occurs by oxygen coming in contact with the meat during storage and transit, causing oxidation.
In general, consumers perceive that meat coloured red is fresh, and therefore preferable to discoloured meat. However, storage under conditions where oxygen is present results in gradual browning of the meat. While in many cases the product is still acceptable for consumption, consumers are deterred by the brownish appearance of the meat which they associate with a spoiled product.
In cases where long-term storage of meat is necessary, the presence of oxygen can result in spoilage of the meat in addition to the browning of the meat.
One method of avoiding oxygen spoilage, is vacuum packaging the meat in an oxygen impermeable barrier film. The problems associated with this are that the meat, under a low or nil oxygen modified atmosphere or a vacuum atmosphere, tends to develop a purple colouration which consumers find unacceptable.
High oxygen/CO
2
modified atmosphere systems are successfully used for retail cuts of red meat, but the storage life is relatively low due to loss of colour.
A well known packaging system known as low oxygen/CO
2
packaging is in current use however has been mainly directed to non-retail ready markets.
The shelf life of CO
2
packaged meat is longer than for vacuum packed meat. The meat stored under CO
2
will rebloom on exposure to oxygen, giving the red colouration which consumers associate with freshness.
The display life of CO
2
packaged meat, in the oxygenated state appears to be longer than that of vacuum packed meat. This may be attributed to the low oxygen concentration throughout the product lifetime.
The use of low oxygen/high CO
2
packaging is well known, as is the use of oxygen absorbing compositions with meat products.
CO
2
will be absorbed in significant quantities by the meat within the first 48 hours of exposure. This absorption causes the internal pressure of the package to be reduced, unless there is a sufficient excess of CO
2
to saturate the meat, and a suitable mechanism by which the volume of the package may contract.
Therefore if the meat is placed on a conventional sized tray, evacuated, gas flushed with CO
2
and then sealed under a barrier film, severe distortion will occur as the CO
2
is absorbed and the internal pressure of the system is reduced. This is because the volume of the rigid tray cannot contract in a controlled manner like that of a bag, and because insufficient CO
2
is present to compensate for that which is absorbed by the meat.
This effect may be reduced if a high package volume in relation to the volume of the product is achieved. However this is undesirable to consumers and results in excessive packaging and waste.
One solution to the above problems has been to provide a sachet of a substance that absorbs oxygen and releases CO
2
in response to humidity. The sachet may be placed between one gas permeable layer immediately surrounding the meat, and a second gas impermeable layer.
In some embodiments, the sachet is placed over a hole in the permeable layer. This allows activation by in-pack humidity. The holes also allows rapid equilibration of gases. This embodiment thus produces a modified atmosphere package whereby distortion, excess oxygen and their associated negative effects is reduced.
Although this process has been successful, there have been problems associated with it.
Due to a number of steps that must be undertaken to implement the system for packaging the meat, the packaging process is complicated and expensive. For example, the process must be made accurate enough so that the sachet containing the regulating chemicals is placed over the hole in the permeable layer. An absorbing layer must also be placed in the package between the meat and the bottom of the package in order to absorb the fluids that may exude from the meat. The supermarkets place a pricing or use by date label over the hole once the sachet is removed, to avoid leakage and prevent contamination.
Other methods of atmosphere modification are desiccant sachets, sulfur dioxide emitters and devices for liberating chlorine dioxide.
These, combined with oxygen absorbers, and combined oxygen absorber/CO
2
generators form part of the technology known as active packaging.
Sachets that contain a CO
2
liberating chemical substance may be used in active packaging. This sachet may be made from a micro-porous, non-permeable membrane that allows transfer of humidity, but does not allow the transfer of liquid through the membrane.
There is also a need to transfer humidity from the pack to the sachet in order to initiate the atmosphere regulating chemicals. European Patent EP0128795 describes oxygen or CO
2
generators housed in sub-compartments of packages. The chemicals react on contacting the drip from the meat. No microporous films are used.
French Patent 2 621 015, describes CO
2
releasing chemicals, which are distributed in a fibrous structure. The hydro-phobicity of the fibres prevents the chemicals from leaching into the food.
European Patent EP0 468 880 A1, describes oxygen absorbers and/or CO
2
generators housed in liquid impermeable vapour permeable packets. The packets have two compartments housing the reactive components linked by a weak seal. Rupture of the weak seal causes the two components to react, thus modifying the package atmosphere.
All of the above documents describe devices that suffer the problem of requiring moisture vapour to activate the compounds, wherein the vapour is not drawn around or local to the sachet to sufficiently activate the compounds in the sachet.
What is needed then is a system of modifying the atmosphere of a closed package, by a
process that is uncomplicated and does not necessitate the steps previously used.
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 device for maintaining or modifying the atmosphere in a package, the device including:
at least two containing layers,
a moisture activated chemical substance contained by the containing layers,
and at least one absorbent layer attached to at least one of the containing layers.
The present invention also relates to a method of packaging characterised by the step of placing into a package a device as described immediately above.
The absorbent layer may be any device capable of retaining and/or absorbing and/or transferring liquid or humidity.
The absorbent layer may be any suitable material, but preferably of food-grade quality.
The absorbent layer may contain a cellulosic absorbent such as paper or wood pulp or viscose fibers, superabsorbent polymers and the like and is preferably heat sealed to the adjoining layer.
Preferably the absorbent layer is of a thickness and type to absorb all of the fluid released by the product.
A preferred feature of the present inventi

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