BE1020270A3 - IMPROVED PROCESS FOR POULTRY POULTRY. - Google Patents

Abstract

The subject of the invention is an improved method of packaging fresh poultry, ready to cook under a protective atmosphere, making it possible to increase the shelf life of poultry.

Description

The invention relates to a method for packaging fresh poultry ready to cook to increase their life.

For the purposes of the present invention, the term "fresh poultry ready to cook" means a whole naked poultry. These birds are usually wrapped in a food film and kept cool at a temperature of 0 ° C to + 4 ° C before consumption.

Traditionally, the food film used to package fresh, ready-to-cook poultry is a stretchable polyvinyl chloride film. The shelf life for a fresh poultry ready to cook and packaged is typically about ten days. For a fresh chicken ready to cook, it is for example generally eleven days.

This may seem rather long. But if we consider that ready-to-cook poultry are generally marketed in supermarkets, this period is rather short, because during these few days the poultry must be transported to the shelves of supermarkets and then it also takes a certain time to sell the poultry once she is in the ray. The time left to sell the poultry is usually 6 days, which is quite short, and sometimes the poultry is not sold in time. As a result, the management of a ready-to-cook poultry department is difficult and there are losses (also known as "breakages") when the poultry could not be sold before the end of their cut-off date. consumption.

The French patent application FR 08 52262, which the applicant company owns, describes a process for packaging fresh poultry ready to cook which makes it possible to increase the lifespan of these poultry by several days. This process comprises: a step of forming a tube made of a heat-shrinkable and gas-barrier food film; - A step of introducing a fresh poultry ready to cook in this tube; a step of sweeping the tube with CO2 alone or mixed with O2 and / or N2; a step of sealing a first end of the tube; a step of sealing a second end of the tube; and a step of retraction of the food film around the poultry at a temperature of between 160 and 200 ° C.

However, the finished product obtained by this process has a pleated appearance a few days after packaging. This phenomenon increases throughout the life of the product. Thus, despite the extended life time through this process, consumers are unlikely to buy the product because of its unattractive visual appearance.

The Applicant Company has indeed observed that the protective atmosphere of poultry in a hermetically sealed barrier film package always generates a pocket known as "ballooned".

In particular, it has been found that the excess of gas still contained in the packaging before it passes through the retraction tunnel expands and comes into opposition with the film when it retracts. As a result, the film is limited in its shrinkage by the gas under slight pressure. During the hours following packing, poultry absorbs gases, including CO2. This absorption then results in a kind of natural evacuation, because the rapid kinetics of CO2 absorption and the use of a gas barrier film do not compensate for the "natural evacuation". by the arrival of another gas, for example the surrounding atmosphere.

As a result, the surplus film, limited during its retraction, generates folds during the "natural evacuation", thus damaging the final appearance of the product in the linear.

The Applicant Company has also shown that the best indicator of the vacuum is the level of CO2 inside the packaging and that the latter decreases sharply during the first 48 hours after packaging. For an initial mixture of gases comprising, for example, 80% by volume of CO 2, the CO 2 content thus increases to about 37% by volume after 48 hours. This CO2 content continues to decline throughout the lifetime but stabilizes at around 27% by volume after about 18 days.

The Applicant Company has thus been able to demonstrate that the C02 level and the pleated appearance are correlated.

In view of these disadvantages, the applicant company has developed a new packaging process, subject of the French patent application FR 10 50197, which reduces the formation of folds after conditioning while maintaining the increase in the duration of the final product obtained with the method described above, said method comprising: - a step of introducing a fresh poultry ready to bake in a tube or bag in a heat-shrinkable food film forming a gas barrier; a step of creating a protective atmosphere inside the tube or the bag; a step of sealing a first end of the tube or of the open end of the bag; when using a tube, a step of sealing a second end of the tube; and a first step of retraction of the food film around the poultry at a temperature of between 150 and 190 ° C .; characterized in that it comprises, after the first step of retraction, a step of storing the packaged poultry for a period of 6 to 18 hours, followed by a second additional step of retraction of the food film around the poultry, this second retraction step being carried out at a temperature ranging from 165 to 180 ° C.

However, this method has the disadvantage of imposing, on the one hand, the storage of poultry for 6 to 18 hours and, on the other hand, a second step of retraction of the film after storage. Although the product obtained by this process has a very clearly improved visual appearance compared to the process comprising a single retraction step, the costs generated by the storage and the second step of retraction of the film make this process too expensive and therefore the products obtained. less profitable.

In order to solve the technical problem mentioned above, and in order to avoid having to carry out a second retraction step after a few hours of storage, a solution could have been to modify the composition of the protective atmosphere so as to reduce the amount of CO2 that can be absorbed by poultry. However, CO2 has a bacteriostatic effect and allows a better preservation of poultry. When the CO2 content is lowered, for example in favor of nitrogen, the life of the poultry is reduced.

It therefore remains desirable to have a method to maintain the attractive appearance and shelf life of the final product obtained with the method described above, but without generating extra production costs.

However, the Applicant Company, after extensive research and many trials, has had the merit of developing a process for packing fresh poultry ready to cook, including: i. a step of introducing a fresh poultry ready to cook in a tube or bag in a heat-shrinkable food film and forming a gas barrier; ii. a step of creating a protective atmosphere inside the tube or bag; iii. a step of sealing a first end of the tube or the open end of the bag; iv. when using a tube, a step of sealing a second end of the tube; and V. a step of shrinking the food film around the poultry at a temperature between 130 and 200 ° C; characterized in that it comprises a step of evacuation of residual gas by applying a mechanical pressure on the poultry thus introduced into the tube or the bag of heat-shrinkable food film before performing step iv of sealing the second end of the film tube, or simultaneously with it, this application of a mechanical pressure being effected by means of a block of foam having a density of between 15 and 20 kg / m3.

Thanks to this process, without producing additional production costs, a final product having a good shelf life and whose visual appearance, especially at the end of its service life, is significantly improved compared to that of the product obtained by the process described in the French patent application FR 08 52262.

The process according to the invention is implemented for the packaging of fresh poultry, ready to cook.

Indeed, the phenomenon of pleating of the film observed after poultry packaging by the process described in the French patent application FR 08 52262 is mainly observed for fresh poultry, ready to cook, which absorb the CO 2 of the modified atmosphere.

However, the method of the present invention can also be used for the packaging of cooked poultry when the complete evacuation of the residual gas is desired. This may include the use of one and the same packaging line for fresh, ready-to-cook poultry and whole cooked poultry.

Lifetime

For the purposes of the present invention, the term "shelf life" means the period between the date of slaughter of the product and the date when the product is no longer consumable, either for bacteriological reasons or for organoleptic reasons.

This lifetime is determined according to a microbiological validation protocol defined according to standard NF 01-003. The test consists of a search and counting of different germs. These measures take place on the day of slaughter, the day of the end of presumed life and 2 days after the date of end of life presumed for farm poultry. These measurements are made on two different productions with 5 samples. These measurements are made under the temperature conditions of 0 to + 4 ° C. The germs sought under these conditions in the case of fresh poultry ready to cook are indicator germs such as Pseudomonas, Escherichia coli, Staphylococci coagulase + and Salmonella (research on neck skin). Other germs are sought at the end of the life of the product, such as lactic flora for products packaged in a protective atmosphere, always in storage conditions of 0 to + 4 ° C. The service life under these conditions thus corresponds to the number of days between the slaughter and the moment when the limit of contamination is reached for at least one of the desired germs. The reference value is 1 * 104 cfu / g for E-coli, 5 * 103 cfu / g for coagulase staphylococci + and 5 * 107 cfu / g for lactic flora. The product is no longer consumable as soon as there are (1) 3 out of 5 samples with values between the reference value and 10 times the reference value for at least one of the desired seeds or (2) a sample for which value for a seed is greater than 10 times the respective reference value.

The shelf life is also determined by end-of-life organoleptic criteria to identify visual or olfactory impairment of the product.

The increase of the service life by the packaging method according to the invention is compared with the processes for packaging fresh poultry to be cooked that does not include a step of sweeping the food film tube with CO2 alone. or mixed with O2 and / or N2.

Poultry

The term "poultry" in the sense of the present invention, chicken, guinea fowl, cockerel, turkey, duck, capon, wild game such as quail and pheasant, and lagomorphs such as rabbit. The preferred poultry are chicken, turkey and rabbit and especially chicken.

Introduction of poultry into a film tube

The first step of the poultry packing method according to the invention comprises the introduction of ready-to-cook fresh poultry into a heat-shrinkable and gas barrier tube or bag.

The heat shrinkable and gas barrier food film used in the process of the invention may advantageously be a complex of polyolefin (polyethylene), polyolefin barrier (Ethylene Vinyl Alcohol) and polyolefin anti-fog (polyethylene).

Such a film is in particular sold by Sealed Air under the name "BDF® film", for example under the reference Cryovac BDF® 750 or Cryovac BDF® 8050.

The ready-to-cook fresh poultry is advantageously deposited on a support, such as an expanded polystyrene tray, before being introduced into the food film tube. It is then introduced with this support into said tube. It is however possible to introduce the poultry alone in the tube, without support. It is also possible to introduce the poultry into the tube with any type of food carrier, such as cardboard, a rigid plastic tray, an expanded polystyrene tray, etc.

Stage of creation of a protective atmosphere

After the step of introducing the poultry into a tube or bag of heat-shrinkable food film, the method according to the invention comprises a step of creating a protective atmosphere inside the tube or bag.

The term "protective atmosphere" in the sense of the present invention, any gas or gas mixture that improves the life of the packaged poultry. Such a gas or gas mixture is also called a "protective gas" or "protective gas mixture".

In general, the oxygen content of the protective atmosphere is between 0 and 30% of O 2, preferably between 0.01 and 10%, more preferably between 0.05 and 5%, and more preferably between between 0.01 and 3% of O2.

Indeed, oxygen tends to favor the bacteriological development of poultry, thus limiting its life.

The creation of the protective atmosphere can be carried out by sweeping the tube or the bag with the protective gas or the mixture of protective gases or, in particular when using a bag, by suction of the ambient atmosphere followed by an injection of the protective atmosphere.

In one embodiment of the invention, the gas used may be CO 2 alone. It is thus possible to increase the life at a temperature of 0 to +4 ° C of a fresh poultry ready to cook for three to seven days. The shelf life at a temperature of 0 to +4 ° C of a fresh chicken ready to cook is thus at least 13 days, preferably 14 to 18 days, and more preferably 15 to 16 days.

In another embodiment, a mixture of CO2, N2 and O2 can be used. This mixture advantageously comprises from 10 to 50% by volume of CO2, from 10 to 20% by volume of N2, and from 30 to 80% by volume of O2.

Very good results have been obtained when using a mixture of CO 2 and N 2. According to a preferred embodiment, this mixture comprises from 50 to 90% by volume of CO 2 and from 50 to 10% by volume of N 2, preferably from 60 to 90% by volume of CO 2 and from 40 to 10% by volume of N2, and even more preferably about 80% by volume of CO2 and about 20% by volume of N2 or about 70% by volume of CO2 and about 30% by volume of N2.

The service life at a temperature of 0 to +4 ° C of fresh poultry ready for cooking is thus increased by at least three to seven days. The shelf life at a temperature of 0 to +4 ° C. of a fresh chicken ready to cook is thus at least 13 days, preferably 14 to 18 days, and more preferably 15 to 16 days according to the method. of the invention.

The best results, both in terms of the lifetime of the final product and in terms of its visual appearance (color in particular) at the end of its service life, were obtained with a mixture of approximately 70% by volume of CO2 and about 30% by volume of N2.

The gas injection flow rate during the step of scanning with CO2 alone or mixed with ΓO 2 and / or N 2 is advantageously at least 100 l / min, preferably at least 120 l / min. and more preferably about 150 l / min.

Sealing and retraction steps

Once the poultry in the film tube or in the bag, the tube sealing steps are implemented using techniques well known to those skilled in the art. The sealing may, for example, be carried out by welding means, such as a welding bar or ultrasounds.

The sealing of the tube makes it possible to obtain a hermetically sealed package.

After the sealing step, a step of retraction of the food film around the poultry is carried out at a temperature sufficient to allow the film to shrink around the poultry, and especially between 130 and 200 ° C., preferably between 140 and 200 ° C. 180 ° C, and even more preferably between 150 and 165 ° C.

Those skilled in the art will adjust the temperature of the retraction step according to the nature of the heat-shrinkable gas barrier film used for packing poultry.

During the step of retracting the food film around the poultry, the ambient air, including the controlled atmosphere inside the food film tube is heated to these temperatures, causing the shrinkage of the food film around the poultry.

The shrinkage temperature is chosen by those skilled in the art according to the nature of the heat-shrinkable film used. If the properties of the film allow, retraction at lower temperatures can be envisaged as long as the food film is, after retraction, well stretched around the poultry.

Once the film thus stretched around the poultry, it is advantageous to apply a cold air blade to better freeze the film in its position. The temperature of the cold air is advantageously between 4 and 10 ° G.

Residual gas evacuation step

The packaging method according to the invention furthermore comprises a step of evacuation of residual gases after the step of sweeping the tube with CO2 alone or mixed with 02 and / or N2. Thus, the amount of residual gas around the bird is greatly reduced.

This is particularly advantageous because the retraction of the food film around the poultry is all the better as the amount of gas around the poultry is low. This step of evacuation of the gas thus makes it possible to obtain a packaged product having a smooth appearance throughout the life of the poultry, without a second step of retraction of the film being necessary.

The residual gas evacuation step is performed by applying a mechanical pressure on the poultry thus introduced into the film tube before performing step iv of sealing the second end of the film tube, or simultaneously with it.

It should be noted that such a step of evacuating residual gases by pressing the poultry in the film tube before the step of sealing the second end of the film tube has already been envisaged in the processes of the art. prior. However, it is merit of the applicant to have discovered, after many tests, that by applying a mechanical pressure on the poultry using a foam having a density and / or a particular shape, the elimination of the gas could be improved so that the amount of residual gas around the poultry after sealing the second end is decreased, thus facilitating the retraction of the food film around the poultry. The packaged poultry then has very little gas that can be absorbed during its storage, which considerably limits the formation of folds on the package.

It is in particular of the merit of the applicant to have demonstrated that the density of the foam block, and / or the shape of the borrowed hole in the block of foam are critical to optimize the evacuation of residual gas.

The pressing is carried out using a block of foam having a density of between 15 and 20 kg / m3.

In particular, the foam may have a density of between 16 and 19 kg / m 3, preferably between 16 and 18 kg / m 3 and more preferably about 17 kg / m 3.

The foam block can be made of any type of material having the desired density. The material is in particular an easily compressible material, flexible and low hardness.

The elongation (longitudinal and transverse) of the material can be up to 120%, and is preferably of the order of 110%.

In particular, the material may have a tensile strength (longitudinal and transverse) of between 50 and 100 KPa, preferably between 60 and 80 KPa and more preferably between 65 and 75 KPa.

The material may also have a compressive strength at 25% of between 0.5 and 5 KPa, preferably between 1 and 4 KPa and more preferably between 1 and 3 KPa.

The material may, moreover, have a compressive strength at 50% of between 0.5 and 5 KPa, preferably between 1 and 4 KPa and more preferably between 2 and 4 KPa.

In particular, the material used for the foam block according to the invention may have the property of absorbing water.

According to a preferred embodiment, the foam is a polymer foam, such as a latex foam, a polyether foam or a polyurethane foam, and more preferably a polyurethane foam such as for example those marketed by the company Plastiform's under the reference PU - Ether density 17 kg / m3 white.

The block of foam may be in various forms, for example any volume of round section, oval, square or rectangular.

When the method is used for packaging a fresh chicken ready for cooking, the foam block may, whatever its shape, be part of a rectangular parallelepiped having a length of between 20 and 40 cm, preferably between 25 and 35 cm and more preferably from 26 to 33 cm; a width between 15 and 35 cm, preferably between 20 and 30 cm and more preferably from 23 to 28 cm; a height of between 5 and 25 cm, preferably between 10 and 20 cm and more preferably between 12 and 16 cm.

According to a particularly preferred embodiment, the block of foam is dug in part of its height of a shape corresponding to the upper part of the poultry to be packaged, said upper part including the thighs and the keel bone, said dug being thus adapted to conform to the shape of the upper part of the poultry on which it is pressed so as to evacuate the maximum residual gas around the poultry before the step iv of sealing the second end of the film tube, or simultaneously with Ci it.

Second optional retraction step

In some rare cases, during the hours following packing, poultry can absorb some of the CO2. The excess film, however considerably limited by the pressing and retracting steps, can then generate folds that affect the final appearance of the product in the linear.

In this case, a second step of retraction of the food film around the poultry, after storage of the packaged poultry for a period of 6 to 18 hours, may be considered.

Such an even more optimized method is more expensive because of the second retraction step. To be profitable, it is preferably used for the packaging of high-end products.

The inventors have found that within six hours, the adsorption of CO2 is not yet sufficiently advanced. So there is still a surplus of gas that keeps the film smooth and tense. Beyond eighteen hours, the highly advanced adsorption of CO2 establishes a vacuum set too high to implement a second retraction step at a temperature of 160 to 180 ° C.

It is therefore preferable to store the poultry between 5 and 18h, preferably between 6 and 12 h.

The second retraction step eliminates wrinkles that may have formed during storage and thus obtain a true smoothing of the film around the poultry.

In a particular embodiment, the second retraction step, when performed, is carried out at a temperature of between 165 and 175 ° C, preferably at a temperature of about 170 ° C. Thus, we obtain an optimal pleat smoothing.

It has been found that most of the film folds that form during the storage step are on top of the packaged poultry. During the second step of retraction, it is therefore advantageous to direct hot air, heated to the temperatures indicated above, first on the top of the poultry and then on the sides to further improve the smoothing effect.

As indicated above, the ambient air, including the controlled atmosphere inside the food film tube, is heated to a temperature between 160 and 180 ° C, preferably between 165 and 175 ° C, and more more preferably at about 170 ° C during the second step of retraction of the food film around the poultry. Under these conditions, the food film retracts again and tends around the poultry. Once the film thus stretched around the poultry is advantageously applied a cold air blade to better freeze the film in its final position. The temperature of the cold air is advantageously between 4 and 10 ° C.

Used Machines

The steps of introduction of the poultry, creation of a protective atmosphere inside a film tube, sealing steps of the ends of the tube, and pressing of the poultry carried out as part of the process according to the invention. The invention may, for example, be implemented using a horizontal bagging machine. Such baggers are well known to those skilled in the art and marketed for example by ULMA under the name Pacific.

The retraction step of the film around the poultry is implemented, for example, by means of a shrink tunnel such as the one sold under the reference CJ61 by Sealed Air Cryovac.

In particular, the method according to the invention can therefore preferably be implemented using a ULMA horizontal bagger marketed under the name Pacific, supplemented by a shrink tunnel such as that marketed under the reference GJ61 by Sealed Air Cryovac.

The details and embodiments described in connection with the general description of the invention, of course also apply to the two variants described above. The invention will now be illustrated by the following nonlimiting examples.

Figure 1 is a top view of the hollow foam block used in the pressing step of the method according to the invention.

Figure 2 is a bottom view of the foam block of Figure 1.

EXAMPLES

EXAMPLE 1 (according to the prior art)

A whole, naked, flanged chicken is packaged using a Pacific model Ulma Packaging horizontal bagger according to the following procedure: 1. Manual unloading of a polystyrene tray on a conveyor belt; 2. Manual deposit of a whole naked chicken flanged in the tray; 3. Transfer via the conveyor belt of the tray and chicken; 4. Formation of a film tube around the conveyor belt by unwinding a heat shrinkable food film and forming a gas barrier (Cryovac BDF 750 sold by Cryovac) in a single coil from above around the shaper; 5. Release of the adjoining part of the film, under the conveyor belt, into a rotating jaw which seals the film longitudinally; 6. Enter the chicken into its tray in the film tube created in the previous step; 7. Sweeping of the tube with a mixture of 70% CO2 and 30% N2 at a flow rate of 150 l / min by a cane; 8. Sealing the tube at its end out of the bagger with a second accompanying jaw; 9. Transfer the chicken into its tray at the bottom of this tube.

10. Evacuation of the residual gas by a foam presser which is integral with the second jaw, and which presses the chicken in the closed tube at one end to drive the residual gas; 11. Sealing the second end of the tube and then cutting the film to create an airtight pocket; 12. Transfer of this pocket into a retraction tunnel; 13. Retraction of the film under the action of hot air (between 155 and 160 ° C) retracts during about 2 meters of the tunnel, the film is thus stretched around the chicken; 14. At the exit of the retraction tunnel, a cold air blade froze the film in its final position.

The foam used in step 10 of the process has a density of about 25 kg / m3 and is in the form of a rectangular block having the following dimensions: height: about 14 cm length: about 30 cm width: about 25 cm.

The foam block is, in particular, not dug in part of its height of a shape corresponding to the upper part of the poultry to be packaged.

The packaged chicken is stored at a temperature of 0 to +4 ° C and a humidity of ambient air of 90%.

EXAMPLE 2 (according to the invention)

A whole, naked, flanged chicken is packaged using a Pacific model Ulma Packaging horizontal bagger according to the following procedure: 1. Manual unloading of a polystyrene tray on a conveyor belt; 2. Manual deposit of a whole naked chicken flanged in the tray; 3. Transfer via the conveyor belt of the tray and chicken; 4. Formation of a film tube around the conveyor belt by unwinding a heat shrinkable food film and forming a gas barrier (Cryovac BDF 750 sold by Cryovac) in a single coil from above around the shaper; 5. Release of the contiguous part of the film, under the conveyor belt, into a rotating jaw which seals the film longitudinally; 6. Enter the chicken into its tray in the film tube created in the previous step; 7. Sweeping the tube with 70% CO2 and 30% N? at a rate of 150 l / min by a cane; 8. Sealing of the tube at its end out of the Tensacheuse by a second accompanying jaw; 9. Transfer the chicken into its tray at the bottom of this tube.

10. Evacuation of the residual gas by a foam presser which is integral with the second jaw, and which presses the chicken in the closed tube at one end to drive the residual gas; 11. Sealing the second end of the tube and then cutting the film to create an airtight pocket; 12. Transfer of this pocket into a retraction tunnel; 13. Retraction of the film under the action of hot air (between 155 and 160 ° C) retracts during about 2 meters of the tunnel, the film is thus stretched around the chicken; 14. At the exit of the retraction tunnel, a cold air blade froze the film in its final position.

The foam used in step 10 of the process is marketed by Plastiform's under the reference PU-Ether density 17 kg / m3 white and is in the form of a rectangular block having the following dimensions: height: about 14 cm length : about 30 cm width: about 25 cm.

The block of foam has been dug in part of its height of a shape corresponding to the upper part of the poultry to be packaged, in order to match the shape of the upper part of the poultry on which it is pressed.

The packaged chicken is stored at a temperature of 0 to +4 ° C and a humidity of ambient air of 90%.

The appearance of the packaging obtained in Examples 1 and 2 was compared after 18 hours of storage.

The packaging obtained with the method of Example 1 is much more pleated than that of Example 2, the appearance of which is close to the packaging obtained immediately after shrinkage, before storage.

Claims (11)

A method of packaging fresh ready-to-cook poultry, comprising: i. a step of introducing a fresh poultry ready to cook in a tube or bag in a heat-shrinkable food film and forming a gas barrier; ii. a step of creating a protective atmosphere inside the tube or bag; iii. a step of sealing a first end of the tube or the open end of the bag; iv. when using a tube, a step of sealing a second end of the tube; and V. a step of shrinking the food film around the poultry at a temperature between 130 and 200 ° C; characterized in that it comprises a step of evacuation of residual gas by applying a mechanical pressure on the poultry thus introduced into the tube or the bag of heat-shrinkable food film before performing step iv of sealing the second end of the film tube, or simultaneously with it, this application of a mechanical pressure being effected by means of a block of foam having a density of between 15 and 20 kg / m3. 2. The packaging method according to claim 1, characterized in that the foam has a density of between 16 and 19 kg / m3, preferably between 16 and 18 kg / m3 and more preferably a density of about 17 kg / m3. . 3. The method of packaging according to one of claims 1 or 2, characterized in that the foam is a polymer foam, preferably a polyurethane foam. 4. Packaging method according to one of claims 1 to 3, characterized in that the foam block is dug in part of its height of a shape corresponding to the upper part of the poultry to be packaged, said upper part comprising in particular the thighs and the keel bone, said hollow foam thus being adapted to conform to the shape of the upper part of the poultry on which it is pressed so as to evacuate the maximum residual gas around the poultry before the step iv of sealing the second end of the film tube. 5. Packaging method according to one of claims 1 to 4, characterized in that the step of retraction of the food film around the poultry is carried out at a temperature between 140 and 180 ° C, preferably between 150 and 165 ° C. 6. Packaging method according to any one of claims 1 to 5, characterized in that the protective atmosphere consists of a mixture of CO2 and N2. 7. Packaging method according to any one of claims 1 to 6, characterized in that the mixture of CO 2 and N 2 comprises from 50 to 90% by volume of CO 2 and from 50 to 10% by volume of N 2, preferably 50 to 80% by volume of CO 2 and 50 to 20% by volume of N 2, and more preferably about 80% by volume of CO 2 and about 20% by volume of N 2 or about 70% by volume of CO 2 and about 30% by volume of N2. 8. Packaging method according to any one of claims 1 to 7, characterized in that the scanning of the tube with CO 2 alone or mixed with 02 and / or N2 is carried out at a gas flow rate of minus 100 l / min, preferably at least 120 l / min, and still more preferably about 150 l / min. 9. A method of packaging according to any one of claims 1 to 8, characterized in that the poultry is selected from chicken, turkey, duck, rabbit, capon, guinea fowl, pheasant and quail. 10. The method of packaging according to any one of claims 1 to 9, characterized in that the poultry is a whole fresh poultry ready to cook. 11. A method of packaging fresh, ready-to-cook poultry, comprising i. a step of forming a tube in a heat shrinkable food film and forming a gas barrier; ii. a step of introducing a fresh poultry ready to cook in this tube; iii. a step of creating a protective atmosphere inside the tube; iv. a step of sealing a first end of the tube; v. a step of sealing a second end of the tube; vi. a first step of retraction of the food film around the poultry at a temperature between 130 and 200 ° C; vii. a storage step of the packaged poultry for a period of 6 to 18 hours, and viii. a second step of retraction of the food film around the poultry, this second retraction step being carried out at a temperature ranging from 165 to 180 ° C, characterized in that it comprises a step of evacuation of residual gas by application of a mechanical pressure on the poultry thus introduced into the film tube before carrying out the step v of sealing the second end of the film tube, or simultaneously with it, this application of a mechanical pressure being carried out by means of a block of foam having a density of between 15 and 20 kg / m3.