BAcKGRouND ART T One of the conditions which drastically affects the storage life of a foodstuff is the level of oxygen within the package. Oxygen amount and levels should be as low as possible and whilst various factors determine that oxygen cannot be eliminated entirely the lowest levels within a package are desirable.

In a conventional modified atmosphere packaging apparatus a chamber is evacuated and then flushed when a desired gas mixture is introduced into the chamber. The flushing (return gas) process causes movement and mixing of both the incoming gases and the residual gases left in the chamber (at the end of the evacuation stage).

The evacuation process is designed to reduce the amount and/or level of oxygen within a completed package and the flushing process is designed to enhance the storage life and/or presentability of a packaged product.

Conventional gas flush packaging apparatus include a main chamber that can be evacuated and flushed with another gas.

The gas flush chamber is commonly made of two parts. The upper and lower parts are usually separated by the lid film that will be used to seal the tray.

A tray or other receptacle containing a food-stuff is placed within the chamber. At this point, the gas in the chamber will be largely atmospheric.

The chamber is sealed. The chamber is then evacuated to as great an extent as possible, through ports in the chamber connected to a vacuum source.

Next, the chamber is flushed with the desired gas, which is usually carbon dioxide. The atmosphere now is largely carbon dioxide. The tray is then sealed, with the high carbon dioxide concentration surrounding the food-stuff.

A sealing device, which is commonly a heat seal plate is situated in the top chamber, and is brought down onto the contact point between the tray and the lid film, to seal the lid film to the tray.

The tray is then removed from the chamber, and the process repeated.

The term"head space"is used to refer to the internal space between the product in the tray, and the lid used to seal the tray. The lid is usually a plastic film.

As is outlined above, it is important to remove as much of the oxygen as possible before sealing the lid to the tray. This is because microbial bacteria within the food-stuff are responsive to oxygen, and have an increased chance of thriving, and multiplying with increased available oxygen. The microbes spoil the food-stuff, or render it unappealing to a consumer.

The entry points of the replacement gas in typical gas flush apparatus

cause the non-evacuated gas molecules to gather within the headspace or randomly spread throughout the chamber. When the tray lid is sealed onto the tray some of the non-evacuated gas molecules, which includes oxygen, are sealed within the pack which is undesirable.

An object of the present invention is to utilise the return of gases into the chamber of a gas flushing apparatus to minimise the level of oxygen in the completed package.

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 providing a modified atmosphere to a package, characterised by the steps of : (i) placing a package in a chamber, the package having a head space, and (ii) evacuating the chamber of gas, and (iii) introducing a replacement gas into the chamber by directing the replacement gas into the head space of the package, and (iv) sealing the package to contain the replacement gas.

According to another aspect of the present invention, there is provided an apparatus for providing a modified atmosphere to a package, the apparatus including

a chamber capable of being evacuated of gas, and the chamber capable of holding a package with a headspace, at least one gas port into the chamber, the apparatus characterised in that the gas port is configured so as to direct gas directly into the head space of the package.

Reference to a headspace may be made with reference to the space between the contents of the package and the means used to seal the package.

In preferred embodiments, the chamber may include two parts.

Reference to the two parts may be made with reference to an upper and a lower part. This should not be seen to be limiting, as the orientation of the parts may vary according to the application of the present invention.

Preferably, the upper part of the chamber may include a sealing means arranged to seal the package.

Reference to gas ports may be made with reference to conduits used to remove gas from the chamber, and/or to reintroduce gas to the chamber.

In preferred embodiments, the gas ports may be located within the walls of the chamber.

Reference to the ports being located in the chamber wall should not be seen to be limiting in any way. Other port configurations may be employed within the scope of the present invention.

For example there may be a separate inlet tube or conduit into the chamber forming the ports.

The ports may preferably be connected to a gas and/or vacuum source, via a conduit.

Preferably, the gas port may be located on one side of the chamber.

In other embodiments the ports may be arranged in the walls of the chamber, and co-ordinated to inject gas at predetermined intervals.

Preferably the ports may include a cavity that directs replacement gas flow directly into the headspace.

Other embodiments may include a nozzle or directing vane attached to the port to assist in directing gas into the headspace.

Preferably, the cross-section of the ports may be rectangular. This should not be seen to be limiting in any way, as the cross-section may be circular, oval, hexagonal, pentagonal, or some other polygonal shape.

In preferred embodiments, the upper surface of the directing cavity of the port may form part of, or be located adjacent, the chamber wall.

In other preferred embodiments, the upper surface of the directing cavity of the port may be part of the upper part of the chamber.

Reference to a package may be made with reference to any package that may require gas flushing such as a container, a tray, a bag and so forth.

Reference to a package may now be made with reference to a tray

containing a foodstuff.

Preferably, a plastic film may be located between the two chamber parts to seal the package, and isolate the chamber parts when the replacement gas is introduced to the chamber.

In preferred embodiments the package may be sealed by heat sealing a plastic film to the package. However, this should not be seen to be limiting as other methods of sealing the package such as crimping, adhesives, and so forth may be used.

In preferred embodiments, the sealing means in the chamber may be a heat seal plate that in use heat seals the plastic film to the package.

In some embodiments, the upper surface of the directing cavity of the port may be formed by the plastic film.

Preferably, when the chamber is flushed with the replacement gas, the two chamber parts will be pressurised substantially equally.

Preferably, the chamber will be pressurised to atmospheric pressure by the introduction of the replacement gas.

Reference to a replacement gas may be made with reference to any gas that may be needed to modify the atmosphere of the package appropriate for storage of the contents of the package, for example this may include carbon dioxide, oxygen, nitrogen and so forth.

Preferably the replacement gas may be carbon dioxide.

BRIEF DESCRIPTION OF DRAWINGS Aspects of the present invention will become apparent from the

ensuing description and is given by way of example only and reference to the accompanying drawings in which, (a) Figures 1 to 5 show illustrative steps of the apparatus, and method in accordance with the prior art, and (b) Figure 6 shows an illustrative version of the apparatus and method in accordance with the present invention.

(c) Figure 7 is a perspective view of Figure 6 showing the port configuration.

(c) Figure 8A and 8B show embodiments of the gas ports.

BEST MODES FOR CARRYING OUT THE INVENTION With respect to figures 1 to 5 of the drawings a typical chamber indicated by arrow 1 includes two parts a lid 2 and a base 3. Gas ports 4 and 5 are communicable with the interiors of the chamber 1. Film sealing means 6 is provided within the chamber 1. In a conventional apparatus the gas ports 4,5 are used for evacuation and flushing. A headspace region 1A is created within the region beneath film 7 and above a tray 8 containing a foodstuff item 9, the tray in this instance resting on a support 10 within the base 3.

In a conventional apparatus gas ports 4,5 are connected to a common valve (not shown) or can be connected to separate valves and during the process the sealing means 6, commonly in the form of a seal plate and pressure bellows, is accommodated within the lid 2.

Prior to evacuation (figure 2) the chamber contains atmospheric gas.

This gas is illustrated symbolically in figures 2 through to 6 by the

segmentally shaded circles.

During evacuation (figure 3) molecules of gas are removed to a typical level of 0.1% atmosphere pressure. All air is not removed and a small percentage approximately 0.1% of the original volume remains.

After evacuation (figure 4) there are a reduced number of original gas molecules and the gas ports 4 and 5 are closed off.

Conventionally, when gas re-entry of the cycle is initiated through ports 4,5 to introduce a replacement gas, (figure 5) the balance of air in the chamber moves to the headspace 1A.

Where a film 7 separates lid 2 and base 3 a pressure balance is created by introducing a gas into the space above the film whilst re-entry gas illustrated symbolically in fig 5 by the fully shaded circles enters the bottom chamber. The residual original air is substantially concentrated within the headspace of the tray. It is undesirable to have the molecules concentrated in this space. This is because when the film 7 is secured to the tray 8, a greater proportion of residual air molecules may be sealed within the tray.

These air molecules, which include oxygen, deteriorate the desired modified atmosphere, and may lead to discoloration of the foodstuff, or the promotion of bacteria, which may cause the foodstuff to spoil.

The present invention in Figure 6 proposes a modification to the existing apparatus by the configuration of gas ports in the base 3 adjacent the headspace so that the replacement gas flows directly into the headspace. The applicants have found that the introduction of the replacement gas in this way significantly reduces the concentration of

the residual molecules that are sealed in the tray. Most of the residual molecules are pushed to the point furthest from the gas ports.

It is important that the gas that is used to re-pressurise the lid 2 of the chamber 1 is pressurised to the same degree as in the base 3, to prevent bulging or sagging of the film 7.

One form of the gas port is illustrated by figures 7 and 8A and 8B.

Chamber 1 is similar to that previously described except that in or associated with one wall of the base 3 gas ports 13 are provided. One or more ports 13 may be provided each connected to a conduit 11 further connected to a common replacement gas or vacuum source 12. The foodstuff 9 is not shown in Figure 7.

In Figure 8B, the port 13 may be formed by providing a rebate in the upper surface of the wall surrounding each port 13 such that when the lid 2 is closed on the base a directing cavity is created which directs the replacement gas at the headspace during gas flushing.

The preferred configuration of the port 13 is shown in Figure 8A and is to form the directing cavity of the port 13 within the base wall, so that the upper extremity of the directing cavity will be the chamber base 3 wall, without the rebate described above.

The ports 13 may be used to evacuate the chamber 1 or a separate arrangement may be provided for this purpose.

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 thereof as defined in the appended claims.