MODIFIED ATMOSPHERE PACKAGE

Abstract: A modified atmosphere package for storing oxygen sensitive goods which contains a gas impermeable tray (12) with flanges (14) around its perimeter of said tray and fitted with a first one-way valve (22) on the bottom of said tray. The package also includes a gas impermeable film (18) fitted with a second one-way valve (20); the film is positioned over and adjacent to the flanges of the tray, and the film is heat sealed to such flanges to form the package. During use, a modified atmosphere is flowed from the first one-way valve through the package, thereby forcing oxygen out of the second one-way valve.

Description: Description Modified Atmosphere Package Technical Field A modified atmosphere package for storing oxygen sensitive goods. Background Art In United States patent 5,698,250., a "modified atmospheric package" was claimed. This package contained "...an oxygen scavenger activated with an activating agent...." According to the patentees, the oxygen scavenger is necessary because "Low-level oxygen systems relying upon evacuation techniques to diminish oxygen levels suffer from several disadvantages.... the evacuation techniques render it difficult to remove any oxygen within a previously wrapped package such as an overwrapped meat tray....The trapped oxygen raises the residual oxygen level in the package and can also cause billowing and subsequent damage to the package during evacuation" (see lines 3-15 of column 2 of this patent). United States patent 5,698,250 is typical of prior art references in which an oxygen scavenging package is used with a modified atmospheric package. This oxygen scavenging package often contains elemental iron, and it is preferably injected with a dilute solution of acetic acid to catalyze the oxidation reaction of iron. The use of this oxygen scavenger is expensive; and it presents a risk of contamination of the meat disposed in the package by either the elemental iron, ferrous oxide, ferric oxide, acetic acid, and/or reaction products thereof. It would be desirable to produce a "modified atmosphere package" which did not require the presence of an expensive and potentially dangerous oxygen scavenger to prevent spoilage of the meat packed therein. Unfortunately, when the system of United States patent 5,698,250 is used without the oxygen scavenger, the oxygen levels within the system are high enough to cause the meat to irreversibly brown, thereby rendering the meat unsaleable. It is an object of this invention to provide a flexible, low cost apparatus for establishing a variety of modified atmospheric conditions within a package containing a food or non-food product. Disclosure of the invention In accordance with this invention, there is provided a modified atmosphere package for storing oxygen sensitive goods, comprising: a gas impermeable tray including flanges around the perimeter of said tray and fitted with a first one-way valve on the bottom of said tray to introduce a modified atmosphere within said package, and a gas permeable film fitted with a second one-way valve, said film positioned over and adjacent to said flanges of said tray, said film is heat sealed to said flanges of said try forming said package whereby said modified atmosphere flows from said first one-way valve through said package forcing the oxygen out of said second one-way valve to create a modified atmosphere within said package. Brief Description of the Drawings The present invention will be more fully understood by reference to the following detailed description thereof, when read in conjunction with the attached drawings, whereiin like reference numerals refer to like elements, and wherein: Figure 1 is a graph showing the relationship between oxygen concentration and protein degradation on fresh meat; Figure 2 is a sectional view of one preferred package of the invention; Figure 3 illustrates a process of replacing the atmosphere within the package of Figure 2; Figures 4 and 5 are sectional views of other preferred packages of the invention; and Figures 6 and 7 illustrates processes for manufacturing the packages depicted in Figures 2, 3, 4, and 5. Best Mode for Carrying Out the Invention Figure 1 illustrates the relationship of oxygen pressure to the pigment color and state in red meat products. Reference may be had, e.g., the a book by Hedrick et al. entitled "Principles of Meat Science/' Third Edition (Kendall/Hunt Publishing Company, 1994). Figure 2 is a sectional view of one preferred package of the invention. Referring to Figure 2, it will be seen that barrier film tray package 10 includes a gas impermeable tray 12 to contain oxygen sensitive food or non-food goods. A gas impermeable film or lid 18 is positioned over the goods and the tray 12. The tray 12 incorporates a first one-way valve 22 on the bottom of the tray 12, and the film 18 incorporates a second one-way valve 20 on the top of the film 18. In this two valve configuration, a modified atmosphere can be introduced into the package through the first one-way valve 22 on the bottom of the tray 12, and the oxygenated atmosphere in allowed to escape through the second one-way valve 20 in the top of the film 18. The surfaces of the flanges 14 of the tray 12 and the edges of the film 18 are heat sealed to prevent gases from escaping the interior of the package 10. The gas escaping the second one-way valve 20 in the film 18 can be monitored to determine when the appropriate modified atmosphere levels have been reached within the package 10. With this two valve configuration, the need for solid carbon dioxide and/or an oxygen absorber is not required. The two valve configuration allows for changing the gas within the package 10 or repair of a damaged lid, tray, or heat seal if the damage is discovered before the meat has been exposed to oxygen for an extended period of time. The damaged lid, tray, or seal can be repaired and a modified atmosphere reintroduced through the first one-way valve 22 in the bottom of tray 12. The package 10 can also be used in microwaveable applications, since the pressure within the package 10 is self- venting. Unlike existing food packages, the top of the package 10 does not have to be peeled back or the contents removed from the package or holes punched in the film. The package 10 can be placed directly into the microwave oven. As pressure builds inside the package 10, the one-way valve 24 on the top of the tray 12 will vent, allowing the gas to escape. The tray 12 can be constructed of a thermoformable mono layer structure of polyester (such as amorphous poly[ethylene terephthalate]), or polyvinyl chloride. The total thickness of the material prior to thermo forming is from about 0.010 to about 0.030 inches. The tray 12 can be made of gas permeable or substantially gas impermeable materials. In one embodiment, the tray material is dense enough to prevent seepage of liquid. One may utilize absorbent trays, such as those supplied by Vitembal (France) or Linpak (US/Europe). Alternatively, one may use other means, such as an absorbent pad, for absorbing liquids exuded from meat. The tray may consist essentially of polyolefms (such as polypropylene/polyvinylidene chloride/polypropylene, with ties layers between the polypropylene and the polyvinylidene chloride), high density polyethylene, polyvinylidene chloride/high density polyethylene with tie layers between the high density polyethylene and the polyvinylidene chloride, and the like. The tray may be constructed of a plastic foam (open celled or closed celled), such as polystyrene, polypropylene, polyvinyl chloride, and polyester; and it may include a substantially gas impermeable plastic layer laminated thereto or any combination of plastic, paper, glass, aluminum or coatings, coextrusions or laminations of such materials such that the combination contemplated provides a barrier to oxygen permeation equal to or less than 0.55 cc-mil per 100 square inches per day in ambient atmosphere at one atmosphere pressure. In one embodiment, the laminated barrier layer is manufactured from a co-extruded LLDPE/polyvinylidene chloride/LLDPE structure with tie layers between the LLDPE and polyvinylidene layers and with a thickness of from about 0.003 to about 0.006 inches. Alternatively, the tray may be constructed of a polyamide (such as nylon), a coextruded nylon/ENOH structure laminated to a LLDPE or LLDPE/LPDE heat sealable layer with tie layers between the nylon and EVOH layers, said structure being commercially available from Allied Specialty Films in the United States. Figure 3 illustrates a process which may be used to replace the atmosphere within package 10. A modified atmosphere is introduced into the package 10 through the first oneway valve. The modified atmosphere is preferably more dense than oxygen. This fact, combined with the pressure in which the modified atmosphere enters the package 10, forces the oxygen up and out though the second one way valve 20 in the film 18. If desired, the escaping gas through the second one-way valve 20 can be monitored to determine if the concentration of oxygen has reached the necessary level within the package 10. Figure 4 illustrates a second embodiment of barrier film tray package 10, which includes a first web in the form of a gas impermeable tray 12 which includes flanges 14, solid carbon dioxide 16, goods such as red meat or other oxygen sensitive product disposed within the tray 12, and a second web 18 in the form of a gas impermeable film material onto which has been fitted a one-way valve 20 (such as the one-way valve produced by Plitek LLC of Des Plaines, Illinois). The amount of solid carbon dioxide 16 used in the tray 12 varies depending upon the type of goods disposed within the tray 12 and the size of the 12. In any event, there must be a sufficient quantity of carbon dioxide 16 to force oxygen within the package 10 through the one-way valve 20 to leave a substantially 100 percent carbon dioxide within the package 10. As the solid carbon dioxide sublimes, it accumulates in the barrier film/tray package 10, thereby increasing the pressure within the package 10, causing the less dense oxygen to gravitate towards the one-way valve 20 and forcing it through valve 20. One-way valve 20 is sle-adjusting, allowing the atmosphere within the package 10 to remain substantially 100 percent carbon dioxide. One may tolerate small amounts of oxygen (less than 500 parts per million) when the goods are red meat. One may produce an atmosphere of 100 percent of carbon dioxide with the use of the device of this invention and, preferably, oxygen absorbers. Alternatively, or additionally, a vacuum can also be applied to the one-way valve to accomplish quicker evacuation of the oxygen from the package 10. The one-way valves can be adjusted to allow the pressure within the package to be greater than one atmosphere. With a pressure greater than one atmosphere, the food and nonfood goods can be naturally protected due to the formation of a "cushion" provided by the atmosphere within the package. Figure 5 illustrates a third embodiment of package 10, which is similar to the package 10 depicted in Figure 4 with the exception that the one-way valve 20 is palced on the tray 12 instead of the film 18. Figure 6 illustrates a preferred process to manufacture the package described in Figures 2 and 3. An empty tray 12, with a one-way valve 22, proceeds down a conveyor line or a similar piece of equipment. A good or goods, such as meat, is then disposed within the tray 12. Next, a barrier film 18 fitted with a one-way valve 20 is sealed to the flanges 14 of the tray. Next, a modified atmosphere gas source is connected to the bottom of the tray and a vacuum is applied to the one-way valve 20 to accomplish the evacuation of the oxygen from the package. Next, the package 10 is weighed and labeled and placed in a suitable packaging device, such as a cardboard carton. Figure 7 illustrates a process used to manufacture the package of Figures 4 and 5 in which an empty tray proceeds down a conveyor line (or other similar equipment), a good or goods (such as meat) is disposed within the tray 12, a suitable quantity of carbon dioxide 16 is then placed into the tray 12, a barrier film 18 fitted with a one-way valve 20 is sealed to the flanges of the tray, the barrier film/tray package 10 is then sent to a holding area to allow carbon dioxide to sublime and to force oxygen from the barrier film/tray package 10 (or a vacuum can be applied to the one-way valve 20 to accomplish the evacuation of the oxygen more rapidly), and the package 10 is weighed and labeled and placed in a suitable packaging device, such as a cardboard carton. Upon arrival at its destination, the barrier film/tray package 10 is removed from the cardboard packaging and is exposed to the oxygen rich ambient atmosphere by adding an air source to the first one-way valve 22 and pressing on the film 18 near the second one-way valve 20 to replace the modified atmosphere with oxygenated air at the retail store, thus causing the meat to "bloom" or assume a red color. The atmosphere can also be replaced by other means to allow the passage of oxygen into the package 10, such as removing the second one-way valve 20. The following examples illustrate the claimed invention but are not to be deemed limitative thereof. Unless otherwise specified, all parts are by weight, and all temperatures are in degrees Centigrade. Example 1 A 3-%70% carbon dioxide/nitrogen gas mixture containing 0.004% oxygen, at various flow rates, was used to flush a one-liter polystyrene foam barrier tray having dimensions of 5.5" x 7.5". The inside volue of the tray was measured by weighing the amount of water needed to fill the tray, and it was found to be one liter. The inside bottom of the tray was fitted with a 7.5" x 1.75" Plitek valve. A barrier film obtained from Koch Inc. of St. Louis, Missouri was heat sealed to the flange of the barrier tray. Thereafter, the barrier film was fitted on its outside surfaces with the same size valve as used in the tray bottom. The oxygen content inside the tray (as a function of time to reach 500 parts per million) was measured using a Model 9900 oxygen analyzer, purchased from Topac Instrumentation of Higham, Mass. At gas flow rates of 4.7, 9.4, 18.8, 21J, 23.5, and 28J liters per minute, respectively, the time it took to reach 500 parts per million of oxygen witin the tray, as measured in seconds/cubic centimeter of container volume, was 0J02, 0.067, 0.032, 0.024, 0.018, and 0.017 seconds per cubic centimeter. It can be seen that the time to reach 500 parts per million approached a constant value as the flow rate of gas increased. This was attributable to the limited size of the Plitek valve used in this experiment. Shorter times to reach 500 parts per million can be obtained by using diffeent valve sizes. This data can be used to estimate the production rates to be expected for a given tray size (volume). Thus, e.g., an empty one-liter tray will have 300 cubic centimeters of free volume when meat is packed in the tray. The time required to reduce the oxygen level to 500 parts per million at a gas flow rate of 28J liters/minute = 0.017 seconds/ cubic centimeter x 300 cubic centimeters; and its is equal to 5J seconds. This is equivalent to a production rate of 12 containers per minute. It is to be understood that the aforementioned description is illustrative only and that changes can be made in the apparatus, in the ingredients and their proportions, and in the sequence of combinations and process steps, as well as in other aspects of the invention discussed herein, without departing from the scope of the invention as defined in the following claims.

Claims: I claim: 1. A modified atmosphere package for storing oxygen sensitive goods, comprising: a gas impermeable tray including flanges around the perimeter of said tray and fitted with a first one-way valve on the bottom of said tray to introduce a modified atmosphere within said package; and a gas impermeable film fitted with a second one-way valve, said film positioned over and adjacent to said flanges of said tray, said film is heat sealed to said flanges of said tray forming said package, whereby said modified atmosphere flows from said first one-way valve through said package forcing the oxygen out of said second one-way valve to create a modified atmosphere within said package. 2. The package as recited in claim 1, wherein a sensor is placed within the path of oxygen forced from said second valve to provide for the measurement of the atmosphere within said package. 3. A modified atmosphere package for microwaving food products, comprising: a gas impermeable tray including flanges around the perimeter of said tray and fitted with a first one-way valve on the bottom of said tray to introduce a modified atmosphere within said package; a gas impermeable film fitted with a second one-way valve, said film positioned over and adjacent to said flanges of said tray, said film is heat sealed to said flanges of said tray forming said package, whereby said package is placed in a microwave oven and as heat and pressure build within said package, air escapes from said second one-way valve to provide for the integrity of said package and to facilitate the heating of the food product. 4. A modified atmosphere package for storing oxygen sensitive goods, comprising: a gas impermeable tray including flanges around the perimeter of said tray; solid carbon dioxide disposed within said tray; and a gas impermeable film fitted with a one-way valve, said film positioned over and adjacent to said flanges of said tray, whereby said film is heat sealed to said flanges of said tray to provide for the sublimation of said carbon dioxide within said package which forces the removal of oxygen from within said package through said one-way valve. 5. The package as recited in claim 3, wherein an oxygen absorber is disposed within said package to facilitate quicker removal of oxygen from said package. 6. The package as recited in claim 3, wherein a vacuum is applied to said one-way valve to facilitate rapid removal of oxygen from said package. 7. A modified atmosphere package for storing oxygen sensitive goods, comprising: a gas impermeable tray including flanges around the perimeter of said tray and fitted with a one-way valve to allow removal of oxygen within said package; solid carbon dioxide disposed within said tray; a gas impermeable film positioned over and adjacent to said flanges of said tray, whereby said film is heat sealed to said flanges of said tray, whereby the sublimation of said carbon dioxide forces the removal of oxygen from within said package through said one-way valve. 8. The package as recited in claim 6, wherein an oxygen absorber is disposed within said package to facilitate quicker removal of oxygen from said package. 9. The package as recited in claim 6, wherein a vacuum is applied to said one-way valve to facilitate rapid removal of oxygen from said package. 10. A method for manufacturing a modified atmosphere package for storing oxygen sensitive goods, comprising: placing an empty gas impermeable tray fitted with a first one-way valve on the bottom of said tray on a moving conveyor line; disposing an oxygen sensitive good within said tray; disposing a gas impermeable film fitted with a second one-way valve above said tray and in contact with the flanges around the perimeter of said tray; heat sealing said film to said flanges; connecting a modified atmosphere gas source to said one-way valve on said tray and connecting a vacuum to said second one-way valve to provide for removal of oxygen from within said package; weighing and labeling said package; and placing said package in a shipping carton. 11. A method for manufacturing a modified atmosphere package for storing oxygen sensitive goods, comprising: (a) placing an empty gas impermeable tray on a moving conveyor line, (b) disposing an oxygen sensitive good within said tray, (c) placing solid carbon dioxide within said tray, (d) disposing a gas impermeable film fitted with a one-way valve above said tray andin contact with the flanges around the perimeter of said tray, (e) heat sealing said film to said flanges, (f) sending said package to a holding area to allow time for oxygen depletion within said package, (g) weighing and labeling said package, and (h) placing said package in a shipping carton.

Applicants: COLOMBO EDWARD ARMANDO, COLOMBO, EDWARD, ARMANDO
Application year: 1999
Main classification: B65D81
IPC codes: B65D77, B65D81