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Title:
MODIFIED ATMOSPHERE PACKAGING GAS, METHOD FOR NON-THERMAL PLASMA TREATMENT OF ARTICLE, AND ARTICLE OF MANUFACTURE FOR USE THEREIN
Document Type and Number:
WIPO Patent Application WO/2011/137359
Kind Code:
A1
Abstract:
A foodstuff or medical device is subjected to a treatment with non-thermal plasma and ozone generated from a modified atmosphere packaging gas comprising a mixture of CO2 and O2, wherein a vol/vol ratio of O2 and CO2 ranges from 9:1 to 1.5:1.

Inventors:
RASANAYAGAM VASUHI (US)
SUNDARAM MEENAKSHI (US)
Application Number:
PCT/US2011/034595
Publication Date:
November 03, 2011
Filing Date:
April 29, 2011
Export Citation:
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Assignee:
AIR LIQUIDE (FR)
RASANAYAGAM VASUHI (US)
SUNDARAM MEENAKSHI (US)
International Classes:
A23L1/00; C01B32/50; A23L3/3418; A23L3/3445; A23L13/00; A61L2/00; A61L2/03; B65D51/16; B65D81/20
Domestic Patent References:
WO2004016118A12004-02-26
Foreign References:
FR2595583A11987-09-18
CA2489738A12006-03-07
US20030091705A12003-05-15
US20110014330A12011-01-20
Other References:
PAUL A. KLOCKOW, KEVIN M. KEENER: "Safety and quality assessment of packaged spinach treated with a novel ozone-generation system", LILVT FOOD SCIENCE AND TECHNOLOGY, vol. 42, no. 6, July 2009 (2009-07-01), pages 1047 - 1053
OKAZAKI ET AL., J. PHYS. D: APPL. PHYS., vol. 26, 1993, pages 889 - 892
ROTH ET AL., J. PHYS. D: APPL. PHYS., vol. 38, 2005, pages 555 - 567
CERNAK ET AL., EUR. PHYS. J. APPL. PHYS., vol. 47 2, 2009, pages 22806
Attorney, Agent or Firm:
CRONIN, Christopher J. et al. (LLC2700 Post Oak Blvd.,Suite 180, Houston Texas, US)
Download PDF:
Claims:
What is claimed is:

1 . A modified atmosphere packaging gas, comprising a mixture of C02 and O2, wherein a vol/vol ratio of 02 and C02 ranges from 9:1 to 1 .5:1 .

2. The modified atmosphere packaging gas of claim 1 , wherein the modified atmosphere comprises a mixture of 10-70% of a non-N2 inert gas and 90-30% of the C02 and 02 mixture. 3. The modified atmosphere packaging gas of claim 1 , wherein the modified atmosphere essentially consists of 10-70% of a non-N2 inert gas and 90-30% of the C02 and 02 mixture.

4. The modified atmosphere packaging gas of claim 1 , wherein the non-N2 inert gas is Ar.

5. The modified atmosphere packaging gas of claim 1 , wherein the non-N2 inert gas is Xe. 6. An article of manufacture, comprising a sealed package containing an object and the modified atmosphere packaging gas of claim 1 , wherein the object is a foodstuff or a medical device.

7. The article of manufacture of claim 6, wherein the article is a foodstuff.

8. The modified atmosphere packaging gas of claim 7, wherein the foodstuff is poultry or non-cured pork. 9. The article of manufacture of claim 7, wherein the foodstuff is fish.

10. The article of manufacture of claim 6, wherein the article is a medical device.

11 . The article of manufacture of claim 10, wherein the medical device is selected from the group consisting of non-metallic surgical instruments, endoscopy kits, metallic surgical instruments, non-metallic surgical implants, and metallic surgical implants.

12. A method of providing a non-thermal plasma and ozone treatment to an article, comprising the steps of:

subjecting the modified atmosphere packaging gas of claim 1 to eiectrical field conditions sufficient for generating a non-thermal plasma and ozone therefrom; and

placing an article in an ambient atmosphere comprising the generated non-thermal plasma and ozone.

13. The method of claim 12, wherein the non-thermal plasma is generated by applying a high voltage potential to electrodes on opposite sides of the article contained within a sealed package or container made of a dielectric material.

14. The method of claim 12, wherein:

the article and ambient atmosphere are contained within a package or container; and

the non-thermal plasma and ozone are generated remotely from the package or container and are allowed to flow to an interior of the package or container.

15. The method of claim 14, wherein: the non-thermal plasma and ozone are generated by passing the modified atmosphere packaging gas of claim 1 through a dielectric tube; and a high voltage potential is applied to electrodes disposed on opposite sides of the dielectric tube.

16. The method of claim 14, wherein:

the article is a foodstuff;

the package or container is integrated with a food packaging machine; and

the non-thermal plasma and ozone are allowed to flow to an interior of the package or container after a vacuum is applied to an interior of the package or container.

17. The method of claim 14, wherein the non-thermal plasma and ozone are produced continuously and are temporarily stored in a buffer tank prior to flowing to an interior of the container or package.

18. The method of claim 12, wherein the non-thermal plasma and ozone are generated at atmospheric pressure and room temperature.

19. The method of claim 2, wherein the non-thermal plasma is generated via dielectric barrier discharge.

20. The method of claim 12, wherein the non-thermal plasma is generated via corona discharge.

21 . The method of claim 12, wherein the non-thermal plasma is generated via capacitive discharge.

Description:
MODIFIED ATMOSPHERE PACKAGING GAS, METHOD FOR NONTHERMAL PLASMA TREATMENT OF ARTICLE, AND ARTICLE OF

MANUFACTURE FOR USE THEREIN Cross-Reference to Related Applications

None.

Background

Ozone is a known antimicrobial agent which approved by the U.S. Food & Drug Administration for direct food application, it is generally generated onsite by the corona discharge method using oxygen or air as a feed gas. Several attempts have been made to use ozone as part of a modified atmosphere to reduce the microbial population in packaged food. However, it was found that the amount of ozone needed to sufficiently reduce the microbial population, often had a negative effect upon the quality of the food, such as a bad odor or flavor. Ozone is also a reactive by-product from the plasma ionization of oxygen. Recently, Purdue University developed a method to generate plasma inside a sealed package containing food. Paul A. Kiockow, Kevin M. Keener, "Safety and quality assessment of packaged spinach treated with a novel ozone-generation system", LWT Food Science and Technology, Vol 42, Issue 6, July 2009, pp 1047-1053. The technology can be adopted to generate ozone from air or oxygen inside the package.

One of the current limitations of using air or oxygen in non-thermal plasma/ozone treatment is the process time, in some instances, the process time is greater than 3 minutes, when a more industrially practical process time is probably less than 30 seconds. A limitation of using pure oxygen in nonthermal plasma/ozone treatment is the deleterious impact the ozone can have upon the flavor or aroma of a foodstuff. Thus, there is a need for an improved method and system that can achieve a shorter process time.

Summary

There is provided a modified atmosphere packaging gas, comprising a mixture of C0 2 and 0 2 , wherein a vol/voi ratio of 0 2 and C0 2 ranges from 9:1 to 1.5:1 .

There is atso provided an article of manufacture, comprising a sealed package containing an object and the above modified atmosphere packaging gas, wherein the object is a foodstuff or a medical device.

There is also provided a method of providing a non-thermal plasma and ozone treatment to an article that includes the following steps. The above modified atmosphere packaging gas is subjected to electrical field conditions sufficient for generating a non-thermai plasma and ozone therefrom. An article is placed in an ambient atmosphere of the generated non-thermal plasma and ozone. The modified atmosphere packaging gas, article or manufacture, and method may include one or more of the following aspects:

the modified atmosphere comprises a mixture of 10-70% of a non~N 2 inert gas and 90-30% of the C0 2 and 0 2 mixture.

the modified atmosphere essentially consists of 10-70% of a non-N 2 inert gas and 90-30% of the C0 2 and 0 2 mixture.

the non-N 2 inert gas is Ar.

the non-N 2 inert gas is Xe.

the article is a foodstuff.

the foodstuff is poultry or non-cured pork.

the foodstuff is fish.

the article is a medical device. the medical device is selected from the group consisting of wherein the medical device is selected from the group consisting of non-metaliic surgical instruments, endoscopy kits, metallic surgical instruments, non-metallic surgical implants, and metallic surgical implants.

the non-thermal piasma is generated via dielectric barrier discharge the non-thermal plasma is generated via corona discharge,

the non-thermal plasma is generated via capacitive discharge.

the non-thermal plasma is generated by applying a high voltage potential to electrodes on opposite sides of the article contained within a sealed package or container made of a dielectric material.

the article and ambient atmosphere are contained within a package or container and the non-thermal plasma and ozone are generated remotely from the package or container and are allowed to flow to an interior of the package or container.

the non-thermal plasma and ozone are generated by passing the modified atmosphere packaging gas of claim 1 through a dielectric tube and a high voltage potential is applied to electrodes disposed on opposite sides of the dielectric tube.

the article is a foodstuff; the package or container is integrated with a food packaging machine; and the non-thermal plasma and ozone are allowed to flow to an interior of the package or container after a vacuum is applied to an interior of the package or container.

the non-thermal plasma and ozone are produced continuously and are temporarily stored in a buffer tank prior to flowing to an interior of the container or package.

the non-thermal plasma and ozone are generated at atmospheric pressure and room temperature.

the modified atmosphere packaging gas has the below proportions of CO2, 0 2 , and non-N 2 inert or mixture of non~N 2 inert gases: parts parts % vol/vol C0 2 /0 2 % vol/vol non-N 2 inert

C0 2 ** 0 2 ** * mixture gas *

1.0-1.5 9.0-8.5 100 0

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1.5 9.0-8.5 90-85 10-15

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1.5 9.0-8.5 85-80 15-20

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1.5 9.0-8.5 80-75 20-25

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1.5 9.0-8.5 75-70 25-30

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5 2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1 .0-1 .5 9.0-8.5 70-65 30-35

1 .5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1 .0-1 .5 9.0-8.5 65-60 35-40

1 .5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1 .5 9.0-8.5 60-55 40-45

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1 .5 9.0-8.5 55-50 45-50

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1 .5 9.0-8.5 50-45 50-55

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5 .5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1 .0-1 .5 9.0-8.5 45-40 55-60

1 .5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1.0-1.5 9.0-8.5 40-35 60-65

1.5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

1 .0-1 .5 9.0-8.5 35-30 65-70

1 .5-2.0 8.5-8.0

2.0-2.5 8.0-7.5

2.5-3.0 7.5-7.0

3.0-3.5 7.0-6.5

3.5-4.0 6.5-6.0

* or mixture of non-N 2 inert gases

* * relative to 0 2

* ** relative to C0 2

Brief Description of the Drawings

For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein: The FIGURE is a graph of generated ozone concentration versus oxygen concentration in the modified atmosphere for a variety of binary gas mixtures.

Description of Preferred Embodiments

A foodstuff or medical device may be treated with ozone and a nonthermal plasma generated from a modified atmosphere in order to reduce pathogens present thereupon. In the case of foodstuffs, the treatment may also be used to extend the shelf-life of the foodstuff. In the case of medical devices, the treatment may be performed to a degree such that the medical device is considered sterilized.

The modified atmosphere may be a binary gas mixture containing 1 -4 parts C0 2 and 9-6 parts 0 2 . The modified atmosphere may also be a ternary gas mixture containing 10-70 vol/vol % of a non~N 2 inert gas and 90-30 vol/vol % of a gas mixture of 1-4 parts CO 2 and 9-6 parts 0 2 . The non-N 2 inert gas may be a quantum gas such as He or a noble gas such as Ar or Xe or a mixture of any two or more of He, Ar, and Xe. Particular combinations of C0 2 , 0 2 , and optional non-N 2 inert gases are listed above.

Three well known techniques are used for generating non-thermal plasmas: dielectric barrier discharge (DBD) type, corona discharge type, or capacitive discharge type. The selection of the non-thermal plasma

generation technique for a given application will depend upon a number of design considerations such as size, geometry, cost, energy usage, etc.

In a first way, DBD-generated non-thermal plasma can be produced by placing the processing gas in a chamber made of a dieiectric material. On the sides of the chamber opposite the processing gas are disposed two

electrodes against which a low power, AC or DC high voitage is applied. The dielectric material insulates the electrode thereby limiting current densities to below the threshold at which an arc is created between the electrodes.

Alternatively, the container of meat or seafood may be made of a dielectric material and serve as the chamber made of a dielectric material. In this alternative case, both of the electrodes may be kept separate from the container or one of the electrodes may be adhered to an outer surface of the container. n a second way, DBD-generated non-thermal plasma can be produced by placing the processing gas in a chamber which also includes a dielectric- coated electrode. A kHz range power is applied to two electrodes outside the container that are capacitively coupled to the dielectric-coated electrode inside the container in order to drive a DBD at the surface of the dielectric- coated electrode inside the container. The dielectric materia! coating insulates the inner electrode thereby limiting current densities to below the threshold at which an arc is created between the electrodes. Alternatively, the container of meat or seafood may be made of a dielectric material and serve as the chamber made of a dielectric material.

Two types of DBD-generated non-therma! plasmas are the filamentary discharge type and the diffuse discharge type. A filamentary non-thermal plasma refers to the visual plasma structure which exhibits many brief (for example, <100 ns) and narrow (for example, about 200 pm) current filaments or streamers. Filamentary discharges produce a relatively low density of active species where most of the atoms and radicals are produced inside the narrow filaments and are rapidly lost to recombination. Researchers at

Purdue University have developed a relatively simple technique for producing fiiamentary-type non-thermal plasma, in a diffuse discharge, no filamentary structure is observed. Diffuse discharges have been shown to deliver a relatively more homogeneous and efficient surface treatment than filamentary DBD. One example of diffuse discharge includes Atmospheric Pressure Glow (APG). Okazaki et al., J. Phys. D: Appl. Phys. 26 (1993) 889-892. Another type includes One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). Roth et al., J. Phys. D: Appl. Phys. 38 (2005) 555-567. Yet another type includes Diffuse Coplanar Surface Barrier Discharge (DCSBD). Cernak et al., Eur. Phys. J. Appl. Phys. 47 2 (2009) 22806.

Many different corona discharge devices are commercially available. Typically, the corona discharge device is an ozone generator which is operated under conditions to suppress the production of ozone. In other words and as described above, unacceptable levels of 0 2 in the processing gases are avoided.

Capacitively coupled non-thermal plasma is generated from two closely spaced electrodes one of which is connected to a radio-frequency RF power supply and the other of which is grounded. The processing gas is of course disposed between the electrodes.

The amount of ozone and non-thermal plasma generated from the modified atmosphere gas is related to the electron density in the plasma, the dielectric properties of the container (if the non-thermal plasma is directly generated within the container), the amount of O 2 and CO2 in the processing gas, and the processing time in which the modified atmosphere gas is subjected to the non-thermal plasma generating electric field. Thus, for low plasma electron densities and/or brief processing times, it may be desirable to utilize a modified atmosphere gas having a relative high level of O 2 and CO 2 .

While, a non-limited list of suitable materials for the container include polymers (for example, in bag or rigid container form) and glass container, basically any container exhibiting dielectric properties may be used.

The temperature and pressure of the modified atmosphere gas (except the electron temperature) before generation of the non-thermal plasma typically are around 20-25 °C and 1.0-1 .2 atm. During non-thermal plasma generation, the temperature rise of the gas (except for the electron

temperature) is due to energy released and the residence time of the gas in the plasma. The temperature rise of a gas in conventional non-thermal plasma generation techniques are commonly less than 200 °C. For food processing applications, the temperature rise should be less than 50 °C.

The generation time is defined as the time needed to ionize the gas mixture to generate the desired amount of stable reactive molecules (in this case it is 0 3 and CO). The O 2 /CO 2 gas mixture reduces plasma generation time considerably for a given plasma set-up. The generation time is related to the amount of O 3 desired, the amount of O 2 and CO 2 present in the

processing gas that is subjected to the non-thermal plasma, the plasma electron density, and the presence of plasma-initiating gases such as noble gases. Under certain conditions, the generation time might serve as a bottleneck to an overall process of filling containers with the foodstuff or medical device and the modified atmosphere gas (or ozone and non-thermal plasma generated from the modified atmosphere gas), and sealing the containers. In such a case, the generation time may be decreased by maintaining the plasma electron density at a relatively higher level and/or by including a noble gas in the modified atmosphere gas. Typically, the processing time is no more than 5 minutes. More typically, it is no more than 1 minute. We have found that the selectivity of Ar or Xe is better than N 2 in terms of increasing the ozone concentration. Ar & Xe not only increase the concentration of ozone, but helps to increase the electrode gap by enhancing the creation of the non-thermal plasma. The method of using gas molecules to increase the ozone concentration, decreases the plasma ionization time and thus makes the technology easier to scale-up. The ozone and non-thermai plasma may be generated either within the container of foodstuff or medical dev ice it may be generated remote from the container where the container is subsequently filled with the generated ozone and non-thermai plasma.

In the first case, the container is filled with the modified atmosphere gas and the foodstuff or medical device. The container may be sealed before application of the electric field and generation of the non-thermai plasma inside it. At expiration of the desired processing time, application of the electric field is discontinued and the container is sealed if not already done.

For best results, before filling the container with the modified atmosphere gas it is first subjected to a vacuum to remove some of the oxygen present either in the atmosphere inside the container or within the foodstuff or medical device (in the case of medical devices having porous portions).

In the second case, the foodstuff or medical device is placed within the unsealed container. Those skilled in the art will recognize that medical devices made of materials that are disruptive of non-thermal plasma generation may not be satisfactorily treated in this manner. Outside the container, an electric field is applied to the modified atmosphere gas in a chamber under conditions sufficient to generate the non-thermal plasma. This may be performed either in batch or continuous mode. In batch mode, once the processing time has expired, application of the electric field is

discontinued and the resultant ozone and non-thermal plasma are conveyed directly to the container for fiiling thereof. In continuous mode, an electric field is applied to a stream of the processing gas. The ozone and non-thermal plasma exiting the electric field flows directly into an interior of the container with the foodstuff or medical device. The stream of ozone and non-thermai plasma may be diverted to different container interiors with the use of an appropriately designed gas manifold such as a modified atmosphere packaging machine. Regardless of whether a batch or continuous mode is elected, a vacuum may be applied to the container interior to remove an amount of oxygen in the foodstuff or medical device and enhance the fiow of the ozone and non-therma! plasma into the container. The application of vacuum could be performed while the container is in a food packaging machine. A suitable system for performing this is described in US

201 10014330 A1 filed on December 3 , 2009. Optionally, the ozone and non-thermal plasma may be blended with an inert gas subsequent to the nonthermal plasma generation in order to provide the composition of the modified atmosphere desired in the container with the foodstuff or medical device.

When the article to be treated with ozone is a foodstuff, the modified atmosphere is especially applicable to pale or white foods such as poultry, uncured pork, or white-fleshed fish. When the article to be treated with ozone is a medical device, the modified atmosphere is especially applicable to non- oxygen sensitive products needing sterilization.

This is because ozone treatment can sometimes bleach color. The gas mixture containing O 2 , CO 2 (either C0 2 /0 2 mixture or as 3-gas mixture with noble gas) can be subjected to plasma ionization to treat food products such as white meat (chicken, turkey), other non-oxygen sensitive products (e.g. white fish) or medical devices, consumer products ( disposable pipettes, containers etc) that needs sterilization

Without being bound by any particular theory, it is believed that the CO generated from the CO2 present in the modified gas atmosphere moderates the sometimes deleterious effect of ozone upon flavors and aromas in the foodstuff to be treated. Thus, a desired ozone level for reduction of pathogens can be generated without the often-associated undesirable flavors and aromas.

For sterilization of medical devices or other consumer products, the ozone concentration need not be limited to 1 %. Rather, the ozone

concentration is instead driven by the particular type of pathogen of concern as well as the residual ozone concentration that is tolerable in the container or package when open by a user.

Examples

Non-thermal p!asmas were generated within plastic bags for different binary gas mixtures containing varying levels of C0 2 and 0 2 and different binary gas mixtures containing varying levels of N 2 and 0 2 . Each bag (1 gallon Ziploc brand bags) was filled with 4.5 liters of the gas mixture being tested. The filled bag was placed between two electrodes separated by a gap of 10 mm. The electrodes were formed from coils of wire wound around a dielectric base to provide a treatment area of 51 cm 2 (8.5 cm by 6 cm). A voltage potential of about 12 kV was applied to the electrodes with a DC voltage generator operated at 55 watts. In each case, a non-thermal plasma was generated for 5 minutes. At the expiration of the plasma generation period, a gas sample was withdrawn from the bag and immediately analyzed with an ozone analyzer as well as by FTIR.

The FIG shows the amount of ozone generated within the bags versus the oxygen content for both types of binary gas mixtures. As clearly shown by the FIG, the inclusion of C0 2 in the gas atmosphere greatly increases the amount of ozone generated.

Performance of the invention yields significant advantages. In the case where it is desirable to package the foodstuff or medical device with relatively lower oxygen content, a desired ozone level is still possible by including C0 2 in the modified atmosphere. Inclusion of a noble or quantum gas (selected as the non-N2 inert gas) such as Ar, Kr (noble gases), or He (quantum gas) within the modified atmosphere enhances plasma generation such that the electrodes may be separated by a much greater inter-electrode distance or gap. Thus, thicker containers or packages may be inserted between the electrodes that might not otherwise fit when the modified atmosphere does not contain such a gas. Additionally, inclusion of such a gas also enhances ozone generation. Thus, when the noble or quantum gas is included to allow greater separation between the electrodes, the amount of ozone being generated should not be deieteriously impacted.

Preferred processes and apparatus for practicing the present invention have been described. It will be understood and readily apparent to the skilled artisan that many changes and modifications may be made to the above- described embodiments without departing from the spirit and the scope of the present invention. The foregoing is illustrative only and that other

embodiments of the integrated processes and apparatus may be employed without departing from the true scope of the invention defined in the following claims.