Non-invasive method of determining oxygen concentration in a sealed package

• US 20070212789A1
• Filed: 03/13/2006
• Published: 09/13/2007
• Est. Priority Date: 03/13/2006
• Status: Active Grant

• Current Assignee: Cryovac Incorporated (Sealed Air)
• Original Assignee: Cryovac Incorporated (Sealed Air)
• Inventors: Barmore, Charles, Havens, Marvin
• Granted Patent: US 7,749,768 B2
• Time in Patent Office: Days
• US Class Current: 436/138
• CPC Class Codes: G01M 3/226 for containers, e.g. radiators
• CPC Class Codes: G01M 3/38 by using light G01M3/02 takes precedence
• CPC Class Codes: G01N 2021/6432 Quenching
• CPC Class Codes: G01N 2021/6478 Special lenses
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held
• CPC Class Codes: G01N 2201/1211 for temperature
• CPC Class Codes: G01N 31/225 for oxygen, e.g. including dissolved oxygen
• CPC Class Codes: G01N 31/229 for investigating time/temperature history
• CPC Class Codes: G01N 33/12 Meat; fish
• CPC Class Codes: Y10T 436/20 Oxygen containing
• CPC Class Codes: Y10T 436/209163 Dissolved or trace oxygen or oxygen content of a sealed environment

Abstract

The invention is a method of measuring oxygen concentration in a package having an oxygen sensitive product disposed therein. The method includes exposing a luminescent compound that is disposed in an interior of the package to light having a wavelength that is absorbed by the luminescent compound so that the luminescent compound is promoted into an excited state. When the exposure of the light is terminated, the excited luminescent compound emits light that is detectable by a detector positioned outside of the package. The intensity of the emitted light is inversely proportional to the oxygen concentration and is used in conjunction with mathematical function that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature to calculate the oxygen concentration. The method may be used to verify and track the oxygen concentration of a package as it moves through a distribution system.

Claims

1. A method of verifying the oxygen concentration of a sealed package comprising:

providing a sealed package defining an interior and having a luminescent compound provided in the interior of the sealed package the luminescent compound having a luminescent emission that is sensitive to quenching by oxygen;

exposing the luminescent compound to light having a wavelength that is absorbed by the luminescent compound so that the luminescent compound is promoted into an excited state;

terminating the exposure of the luminescent compound when the luminescent compound achieves a steady state between excitation and luminescence;

measuring luminescent intensity over a period of time to produce an exponential decay curve;

calculating the coefficient of the decay curve to determine tau;

measuring a temperature that is indicative of the temperature of the luminescent compound;

determining the oxygen concentration within the sealed package using a mathematical function that that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature; and

comparing the measured oxygen concentration to a predetermined minimum or maximum to verify that the measured oxygen concentration is within acceptable limits.

2. A method according to claim 1, wherein the step of calculating the oxygen concentration within the sealed package further comprises applying the equation:

[O₂]=(A_Ta(T)²+B_Ta(T)+C_Ta)(tau)²+(A_Tb(T)²+B_Tb(T)+C_Tb)(tau)+(A_Tc(T)²+B_Tc(T)+C_Tc)

wherein;

T is the measured temperature;

tau is the coefficient of the exponential decay curve; and

A_Ta, B_Ta, C_Ta, A_Tb, B_Tb, C_Tb, A_Tc, B_Tc, and C_Tc are previously determined coefficients for the luminescent compound that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature.

3. A method according to claim 1, wherein the coefficient of the decay curve is calculated by calculating the area under the decay curve.

4. A method according to claim 1, wherein the sealed package includes an oxygen sensitive product disposed therein.

5. A method according to claim 1, wherein a meat product is disposed in the interior of the sealed package.

6. A method according to claim 1, wherein the sealed package comprises a low oxygen atmosphere.

7. A method according to claim 6, wherein the low oxygen atmosphere comprises nitrogen, carbon monoxide, carbon dioxide, argon, or a combination thereof and substantially no oxygen.

8. A method according to claim 6, wherein the sealed package comprises a vacuum package or a modified atmosphere package.

9. A method according to claim 1, wherein the sealed package includes a representation of a unique identification number and further comprises the step of inputting the representation of the unique identification code into a data system.

10. A method according to claim 9, further comprising the step of associating the calculated oxygen concentration with the unique identification number in the data system.

11. A method according to claim 10, wherein the representation of the unique identification code is a machine readable code and the step of inputting the unique identification code comprises scanning the machine readable representation of the unique identification code with a data entry device.

12. A method according to claim 1, further comprising imparting a representation of a unique identification code to the sealed package and wherein the unique identification code is associated with information that is unique to the sealed package in a data system.

13. A method according to claim 1, wherein the step of measuring a temperature further comprises contacting an outer surface of the sealed package with a temperature sensor that is thermally isolated from the surrounding environment.

14. A method according to claim 1, wherein the luminescent compound is in the form of a label.

15. A method according to claim 1, wherein the luminescent compound comprises a metal porphyrin.

26. A method of tracking the oxygen concentration within a sealed package according to claim 6, wherein the package comprises:

a support member having an interior space for disposing a food product therein; and

the barrier layer attached to said support member and sealably enclosing a food product in said interior space.

16. A method of tracking the oxygen concentration within a sealed package, the method comprising:

providing a substantially oxygen-impermeable package having an interior space and an outer barrier layer configured to enclose a food product therein, and said barrier layer having an inner surface and a luminescent compound attached thereto;

exposing the luminescent compound to light that promotes the luminescent compound into an excited state;

measuring a luminescent emission of the excited luminescent compound as it relaxes from the excited state;

measuring a temperature that is indicative of the temperature of the luminescent compound with a temperature sensor that is in contact with an outer surface of the barrier layer;

determining the oxygen concentration within the sealed package using a mathematical function that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature;

comparing the measured oxygen concentration to a predetermined minimum or maximum value to verify that the measured oxygen concentration is within acceptable limits;

applying a representation of an identification code to an exterior surface of the package; and

associating the measured oxygen concentration with the identification code in a data system so that the measured oxygen concentration is recallable by inputting the representation of the identification code into the data system.

17. A method of tracking the oxygen concentration within a sealed package according to claim 16, further comprising the subsequent steps of:

inputting the representation of the identification code into a data system to recall information associated with the identification code, the recalled information including the previously measured oxygen concentration;

taking a second measurement of the oxygen concentration within the sealed package;

comparing the second measured oxygen concentration to the predetermined minimum or maximum to verify that the second measured oxygen concentration is within acceptable limits; and

associating the second measured oxygen concentration with the identification code in the data system so that the second measured oxygen concentration is recallable by inputting the representation of the identification code into the data system.

18. A method of tracking the oxygen concentration within a sealed package according to claim 17, wherein the recalled information includes the predetermined minimum or maximum oxygen concentration for the package.

19. A method of tracking the oxygen concentration within a sealed package according to claim 17, wherein an exterior surface of the sealed package includes a label attached thereto, the label including the predetermined minimum or maximum oxygen concentration for the package.

20. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein the representation of an identification code is an RFID tag, and wherein the method further comprises writing the measured oxygen concentration to the RFID tag so that the measured oxygen concentration is recallable by reading the RFID tag.

21. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein the step of taking the second oxygen concentration measurement further comprises:

exposing the luminescent compound to light that promotes the luminescent compound into an excited state;

measuring a luminescent emission of the excited luminescent compound as it relaxes from the excited state;

measuring the temperature of the sealed package with a temperature sensor that is in contact with an outer surface of the sealed package; and

determining the oxygen concentration within the sealed package using a mathematical function that that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature.

22. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein the identification code is unique to the package.

23. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein a red meat product is disposed in the interior of said package.

24. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein the package has a modified atmosphere comprising about 30 vol. % carbon dioxide, from about 0.1 to 5 vol. % carbon monoxide, and a balance nitrogen.

25. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein the barrier layer has an oxygen transmission rate no greater than 10 cc at STP/m²/24 hr/atm.

27. A method of tracking the oxygen concentration within a sealed package according to claim 17, wherein the step of taking a second measurement of the oxygen concentration is preceded by one or more of storing, shipping, or displaying the sealed package.

28. A method of tracking the oxygen concentration within a sealed package according to claim 16, wherein the step of packaging a food product further comprises the steps of

placing a raw meat product in an interior of a barrier support member;

evacuating the atmosphere from said interior;

flushing said interior with a mixture of gases to provide a low oxygen atmosphere; and

attaching a substantially oxygen impermeable lidstock to the support member to enclose the meat product therein, the lidstock including a luminescent compound disposed thereon.

29. A method of tracking the oxygen concentration within a sealed package according to claim 16, further comprising at least one of the following steps:

disposing of the sealed package if the measured oxygen concentration exceeds the predetermined minimum or maximum value;

accepting the sealed package if the measured oxygen concentration exceeds the predetermined minimum or maximum value;

returning the sealed package if the measured oxygen concentration exceeds the predetermined minimum or maximum value;

or selling the sealed package if the measured oxygen concentration exceeds the predetermined minimum or maximum value at a discounted price.

30. A method of evaluating the likelihood of spoilage in a sealed atmosphere package comprising:

packaging a perishable food product in a package having an outer barrier layer configured to enclose a food product in an interior space having a low oxygen environment, and said barrier layer having an inner surface and a luminescent compound attached thereto;

measuring the oxygen concentration within the interior of the package at least once to determine if the interior space of said sealed package has been exposed to an oxygen concentration above a predetermined threshold that increases the likelihood of spoilage in the food product, wherein the step of measuring the oxygen comprises;

exposing the luminescent compound to light that promotes the luminescent compound into an excited state;

measuring a luminescent emission of the excited luminescent compound as it relaxes from the excited state;

measuring a temperature that is indicative of the temperature of the luminescent compound with the temperature sensor that is in contact with an outer surface of the barrier layer; and

determining the oxygen concentration within the sealed package using a mathematical function that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature.

31. A method according to claim 30, further comprising associating the measured oxygen concentration with an identification code in a data system.

32. A method according to claim 30, wherein the step of measuring the oxygen concentration is preceded by one or more of storing, shipping, or displaying the package.