Patent Publication Number: US-6221411-B1

Title: Meat packaging apparatus and method

Description:
FIELD OF THE INVENTION 
     The invention generally relates to the packaging of meat products in a controlled environment. More specifically the invention relates to an apparatus and method of packaging meat products in a first modified atmosphere environment for shipping to prolong shelf life and in a second atmospheric environment for display. 
     BACKGROUND OF THE INVENTION 
     Fresh meat products are typically processed to various cuts, at a meat processing facility, and then packaged in atmospheric conditions and shipped directly to the supermarket or retail market. Typically, the meat is packaged at the retail market in the Styrofoam trays which are overwrapped with a clear plastic film. Attempts have also been made to package the individual meat products at the processing facility in overwrapped Styrofoam trays, which are then placed within a vacuum-packed barrier bag. The shelf life of such packaging method is relatively short, which is primarily due to the prolonged exposure of the meat product to the residual oxygen present in the packaging. The prolonged exposure to oxygen also causes bacterial decay and discoloration of the meat product. 
     Particularly in red meat, the prolonged exposure to oxygen causes the conversion of myoglobin meat pigmentation to the grey or brown metmyoglobin, which is unacceptable to the customer. A controlled exposure to oxygen is necessary to oxygenate the meat pigment to a bright red color which, in general, retail customers associate with freshness. 
     To prevent discoloration and extend the shelf life of meat products, modified atmosphere packaging technologies are used. For example, U.S. Pat. Nos. 5,667,827 and 5,711,978 to Breen et al., disclose a package and method for packaging fresh meat in a substantially oxygen-free atmosphere, which includes a tray that is ventilated with holes and slits and sized to receive a piece of meat. A clear plastic wrapping material covers the tray. A number of these trays are then placed within an outer barrier bag which is evacuated and flushed with carbon dioxide and then sealed. The outer barrier bag is removed when the meat trays are ready for retail case-ready display. 
     One problem with this system is that it requires use of a perforated tray which may allow bacteria to enter the meat product while displayed. In addition, the packaging process requires the cumbersome grouping and packaging of a number of trays in an outer barrier bag, which then must be evacuated and flushed. 
     It would be desirable to have a package and process that would avoid the above problems and provide a package which would extend the storage life of meat products. In addition, it would be desirable to have an easy and efficient method for sealing a modified atmosphere tray. Moreover, it would be desirable to have a safe and efficient means of changing the atmosphere within the tray for retail display of the meat product. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention provides a meat packaging apparatus comprising a tray containing a modified atmosphere and meat product, film sealed to the tray and including an opening formed therein, and a two-piece label attached to the film and covering the opening. The two-piece label includes a first layer removably attached to a second layer. An inner side of the second layer is secured to a portion of the film surrounding the opening. The second layer is made of a highly oxygen permeable material to allow oxygen to enter the tray when the first layer is removed. The first layer may be made of a material substantially impermeable to oxygen. Preferably, the tray includes a flange portion and the film is heat-sealed to the flange portion. The modified atmosphere may preferably comprise a blend of CO 2  and Nitrogen. Preferably, the inner side of the second layer is secured to the film with adhesive. Preferably, the first layer of the label may be made of a barrier-type plastic. Preferably, the second layer of the label may be made of a highly oxygen permeable material including, for example, paper. The second layer may further include a patterned barrier varnish to prevent wicking of oxygen. Preferably, the first layer of the label includes a raised portion to allow a user to grasp the raised portion and pull off the first layer. 
     Another aspect of the invention provides a method of preparing a meat product apparatus for retail presentation. A tray containing a modified atmosphere and meat product is provided. A film is sealed to the tray. The film includes an opening formed therein. A two-piece label is attached to the film and covers the opening. The two-piece label includes a first layer removably attached to a second layer. An inner side of the second layer is secured to a portion of the film surrounding the opening. The second layer is made of a highly oxygen permeable material. The first layer of the two-piece label is then removed. Oxygen flows through the highly oxygen permeable material of the second layer into the tray. This allows the meat product within the tray to achieve a bright red pigmentation. Prior to removing the first layer of the label the tray may be stored for an extended period of time, which may, for example, be about 14 days. 
     A further aspect of the invention provides for a method of packaging a tray with meat product. Trays containing meat product positioned on an intermittent conveyer are provided. A gassing rail positioned along the conveyer is also provided. A punch station and a label application station are positioned along a film infeed path and upstream of a sealing station. The trays are moved intermittently along the conveyer toward the sealing station. Controlled environment gas is flowed through the gassing rail and into the trays. An opening is punched in the film as it passes through the punch station. A two-piece label is then applied over the opening in the label application station. The portion of the film including the label covered opening is sealed to the tray to retain a modified atmosphere within the tray. Preferably, the film is dispensed in timed sequence with the intermittent conveyer. 
     The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing a preferred embodiment of a process for packaging fresh meat in accordance with the invention; 
     FIG. 2 is a perspective view of a preferred embodiment of a meat packaging apparatus made in accordance with the invention; 
     FIG. 3 is a perspective view of the embodiment of FIG. 2 showing a top layer of a two-piece label being peeled off to allow airflow into the package; 
     FIG. 4 is a top view of a preferred embodiment of a two-piece label made in accordance with the invention; and 
     FIG. 5 is a bottom view of the embodiment of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a meat packaging system is generally shown as  10 . The system generally includes a conveyer  12 , which carries open top trays  14  filled with meat product  16  in the direction indicated by arrow  18 . Plastic film  20  passes through punch station  22  where an opening  23  is cut through the film  20 . A patterned adhesive-backed two-piece label  24  is then applied over the opening  23  at the label application station  26 . The label  24  preferably includes a top layer  25  and bottom layer  27 . The film  20  is then sealed to a flange portion  32  of the tray  14  in the sealing station  28 . 
     As shown in FIG. 1, the open trays  14  and meat products  16  are preferably exposed to controlled environment gas or modified atmosphere gas using gassing rails  30 . Preferred embodiments of the gassing rail  30  are disclosed in, for example, U.S. application Ser. Nos. 08/643,821 and 08/816,389, the entire disclosures of which are incorporated herein by reference. A preferred conveyer  12 , which is preferably an intermittent conveyer, and sealing system are disclosed in, for example, U.S. application Ser. No. 08/886,963, the entire disclosure of which is incorporated herein by reference. Preferably, the meat product  16  is exposed to a controlled environment gas from the gassing rails  30  to reduce the residual oxygen to preferably less than 1 percent. For red meat, a preferred controlled environment gas may be a CO 2  and Nitrogen blend. Various CO 2  and Nitrogen blends may be used ranging from, for example, 40-60% CO 2  and 60-40% Nitrogen. In one preferred embodiment, for ground beef, a 50% CO 2  and 50% Nitrogen blend is used. Once sealed, the trays  14  may have an extended shelf life under refrigeration. Ground beef, for example, may be stored 14 days prior to retail display. Other lower pH products and/or salted products, including, for example, sausage may be stored, for about one month prior to removing the top layer  25 . Generally, once the top layer  25  is removed the meat product has a display life of 3 days. 
     Although the punch station  22  and label station  26  are shown in a horizontal alignment in FIG. 1, these stations may be preferably vertically oriented and/or combined into a single station. In addition, the label application station  26  may further include a heat-sealer, which is designed to heat-seal the bottom layer  27  of the label  24  to the film  20 . The heat-sealer may also be a stand alone station. If heat-sealed, the bottom side of the bottom layer  27  would not need adhesive. Preferably, the punch station  22  may be any conventional metal die punch. The punch  22  may be used to perforate or form a single opening in the film. If perforated, a greater film area and larger-sized label may be necessary to achieve adequate flow of oxygen into the tray once the top layer  25  of the label  24  is removed. The label application station  26  may include any conventional blown-on style label applicator, for example, as provided by Label-Aire of California. Alternatively, a tamping style label applicator with brush wipe may be used. As shown in FIG. 1, a nip roller  33  may preferably provide sufficient force to assure that the label  24  is securely attached to the film  20 . The roller  33  also aids in removing any air bubbles trapped between the label  24  and film  20 . 
     As shown in FIGS. 1 and 2, the tray  14  is preferably made from a material, which is substantially impermeable to or does not retain residual oxygen. The tray  14  may, for example, be made of thermo-formable plastic, including, but not limited to, polypropylene, polyvinyl chloride, polystyrene, polyester and any other barrier multi-layer laminations. The tray  14  includes a flange  32  which provides a sealing surface for film  20 . The film  20  is preferably heat-sealed and cut in sealing station  20 . 
     The two-piece adhesive-backed label  24  includes first or top layer  25 , which is preferably substantially impermeable to oxygen, and a second or bottom layer  27 , which is highly permeable to oxygen. Alternatively, the top and bottom layers may be substantially impermeable only in combination and in an unpeeled state. For example, the top and bottom layers may both be made of semi-permeable materials, but when used in combination provide a substantially impermeable label. Both layers preferably include pressure sensitive material, which may be stamped, marked, printed upon or otherwise inscribed with words or other symbols. The top layer  25  may include operating instructions, for example, “Remove for Retail Presentation” on its outer side. The bottom layer  27  may include a marking for the grade of meat, for example, “USDA Prime.” The bottom layer  27  may additionally include the name of the retail store, a bar code, weight, price/lb., price and safe handling instructions. The top layer  25  preferably may include a raised portion and/or corner  29 , which may include a portion or corner which does not contain adhesive to allow a user to easily grasp and peel the top layer  25  from the bottom layer  27 . A light adhesive applied around the inner side of the top layer  25  and outer side of the bottom layer  27  may be sufficient to hold the top layer  25  in place during transportation and prolonged storage of the tray, and also allow the top layer  25  to be easily removed for store display. The top layer  25  may preferably be made of EVOH (ethyl vinyl alcohol) co-extrusion with a peelable adhesive coating on its bottom side. Alternatively, the top layer  25  may be made of other highly oxygen impermeable materials, including, Nylon, and other PVDC (poly vinyl dichloride) coated structures. The bottom layer  27  may preferably be made of a highly oxygen permeable material, which will allow sufficient oxygen into the tray to change the pigmentation of the meat to bright red, but prevent bacteria from contaminating the meat. Preferably, the bottom layer  27  may be highly permeable to oxygen and selectively impermeable to CO 2 . The bottom layer  27  preferably includes an adhesive at least around the perimeter of the inner side of the bottom layer  27  to secure the label  24  to the film  20 . The adhesive is preferably sufficiently strong to hold the bottom layer  27  in place during transportation and prolonged storage, and when the top layer  25  is peeled away. 
     The size of opening  23  may vary depending on, for example, the size of the tray and type and weight of the meat. For standard cut meats or ground beef contained in standard 6.75×8.75 inch trays, a 1⅛ inch diameter opening would be sufficient to allow a steady flow of oxygen into the tray. A 1.5×1.5 inch label would be sufficient to cover the opening and provide sufficient surface area to adhere to the surface of the film  20  surrounding the opening  23 . Although a rectangular or square-shaped label  24  is shown, various shapes and sizes of labels may alternatively be used. 
     Referring to FIGS. 4 and 5, a preferred embodiment of the label  24  is shown for use with a 6.75×8.75 inch tray filled, for example, with ground beef. As shown in FIG. 5, the bottom side  51  of the bottom layer  27  includes a patterned hot melt adhesive  52 , for example, having a thickness of 1 mil. The adhesive  52  covers all of bottom side  51  except for the area  53 , which aligns with opening  23 . The label  24  in the embodiment shown in FIGS. 4 and 5, may have, for example, the following dimensions: A=3 inches, B=1⅛ inches, C=½ inch, D=2⅝ inches, E=1⅛ inches, F=½ inch, and G=½ inch. As shown in FIG. 4, the top side of the bottom layer  27  may preferably include various printed fields including type and/or grade of meat  55 , safe handling instructions  56 , bar code  57 , net weight  58 , price/lb.  59 , total price  60  and retail name  61 . These fields may be printed on the bottom layer  27  prior to application on the film  20 , which will reduce the retail operator&#39;s handling costs in preparing the tray for case display. In the embodiment of FIGS. 4 and 5, the bottom layer  27  preferably has an absolute filtration rating of 0.2 microns, which will restrict bacteria from penetrating into the sealed tray. The top layer  25  may preferably be a die-cut barrier label film, which includes a patterned adhesive  63  on its backside, except for the circular area  62  (shown in phantom) which aligns with opening  23 . Approximately, 1 mil of adhesive  63  may be used. The bottom layer  27  may, for example, be paper with a 0.2 micron weave which may include a patterned barrier varnish applied to an upper surface except in area  53 . The patterned barrier varnish aids in increasing the impermeability of the label and in preventing wicking of oxygen into the tray. The bottom layer  27  may further preferably include a patterned ink receptive varnish to receive various print colors applied by, for example, an ink jet printer. On the backside of the bottom layer  27 , the patterned adhesive  52  of, for example, 1 micron secures the label  24  to the lid stock barrier film  20 . The bottom side  51  of the bottom layer  27  may be covered with a silicone-coated paper liner. This liner is removed prior to application of the label  24  on the film  20 . This label design allows the area of the bottom layer  27 , which communicates with opening  23 , to be free of any varnish or adhesive to allow oxygen to quickly enter the tray once the top layer  25  of the label  24  is removed. 
     Tests were run using the following: a 6¾×8¾ multi-layer barrier tray, one pound of ground beef, a 50/50 CO 2  and Nitrogen blend of controlled environment gas, and barrier lid stock heat-sealed to the tray. The label  24 , shown in FIGS. 4 and 5 was used. In this test, the sealed tray initially contained 0.25% oxygen. Over a period of 14 days, the oxygen within the tray slowly increased to a level of 0.5%. Once the top layer  25  was removed on day 15, the oxygen content rose in a short time period of about 15 minutes to 18.5% and reached 20.9% within a few hours. This rapid inflow of oxygen is beneficial to retail store operators to allow the meat to properly bloom within about an hour of removing the top layer  25 . Selective permeability of the label  24  to CO 2  may aid in maintaining a partial bacterial static CO 2  atmosphere within the tray. 
     In operation, the freshly cut meat product  16  may be placed into trays  14  moving along conveyer  12 . Soaker pads may also be placed in the trays  14  prior to placing in the meat  16 . The soaker pads absorb excess juices from the meat which may occur during periods of prolonged storage. The trays  14  and meat product  16  are then exposed to controlled environment gas from gassing rails  30  as the trays  14  are indexed forward to the sealing station  28 . A combination of vacuum and controlled environment gassing may alternatively be used. While the trays  14  are indexed toward the sealing station  28 , the film  20  is dispensed to allow opening  23  to be cut out at the punch station  22  and label  24  to be applied at the label application station  26 . For example, the punch station  22  may be positioned two tray pitches from the sealing station  28 , and the label application station  26  may be positioned one container pitch from the sealing station  28 . Alternatively, the punch station  22  and label application station  26  may be combined into one station, where the opening  23  is punched and the label  24  is applied simultaneously or immediately after the opening  23  is punched. For this alternative embodiment, the punch/label station may be positioned, for example, one pitch away from the sealing station. 
     At the sealing station  28  the portion of the film  20  which includes the label covered opening  23  is positioned over the tray  14  to allow communication of the opening  23  with the atmosphere within the tray  14 . Preferably, the film  20  is dispensed with dispensing system rollers  40 , which may be programmed along with the intermittent conveyer  12  in timed sequence with a programmable logic controller. The film  20  is then preferably heat-sealed to the flange  32 , and cut outside and along the perimeter of the flange  32 . This set-up provides an efficient packaging operation, while allowing flexibility to quickly adjust the punch station  22  to provide openings or cuts of various sizes and configurations. This system also allows a user to quickly replace the labels  24  to match the size and/or configuration of the openings  23 . Moreover, labels with standardized markings including, for example, meat grades, may be quickly inserted to match each different grade of meat being packaged. 
     Referring to FIGS. 2 and 3, the sealed tray or meat packaging apparatus  50  may then be shipped to its retail destination where the first or top layer  25  may be removed from the bottom layer  27 . Oxygen then flows through the semi-permeable membrane of the second or bottom layer  27  to allow the meat to bloom to an appealing red color. The size of the opening  23  and the high oxygen permeability of the bottom layer  27  allow a sufficient amount of oxygen to enter the tray to achieve the desired red color, without overexposing the meat product  16  to the outside environment and its many contaminants including bacteria. 
     While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.