The present invention relates to improvements in fresh meat packaging, and in

particular, to an improved retail case-ready packaging and a method of packaging fresh

meat in a substantially oxygen-free atmosphere, whereby the packaging provides for a

prolonged shelf life of the packaged meat products so that the meat will bloom to a

desired red color when the packaging is opened.

BACKGROUND OF THE INVENTION

In accordance with known case-ready fresh meat packaging techniques, fresh meat

products are processed from primais into various cuts at the meat processing plant where

they are then packaged prior to shipment to the retail market. The packaging step

typically includes placing the cuts within a styrofoam tray which is overwrapped with a

non-barrier clear plastic film. The overwrapped trays are then placed within a vacuum

packed and gas-flushed barrier bag. The above described packaging technique is typically

done in the normal nitrogen-oxygen atmosphere o the meat packing facility. Such

packaging typically only has a shelf life of between ten to fifteen days. This relatively

short shelf life is due. in large part, to the prolonged exposure of the meat to the residual

oxygen that is present in the packaging.

Prolonged exposure of fresh meat to oxygen is known to cause bacterial decay and

discoloration of the meat. Also, conventional fresh meat packaging is very sensitive to

temperature variations, thus requiring careful handling of the packaged meat products

during transport to the retail display case.

In the case of red meat, in paπicular. prolonged exposure to oxygen causes the

conversion of myoglobin meat pigmentation to the grey or brown metmyoglobin. which

is generally unacceptable for the average retail customer. However, a controlled exposure

of the meat product to oxygen is necessary in order to oxygenate the meat pigment to

bright red oxymyglobin. This creates the desired red "bloom" of the meat which the

average retail customer associates with freshness and wholesomeness.

It is known in the art to package fresh meat in a modified atmosphere environment

whereby the packaging is flushed with a preservation-enhancing gas mixture, typically

containing a bacterial inhibitor such as carbon dioxide. In the case where styrofoam

packing trays are used, however, residual oxygen is trapped inside the porous openings of the styrofoam tray material and eventually diffuses out over time, thereby causing

premature discoloration and bacterial decay of the meat.

U.S. Patent Nos. 4.685.274 and 5.522.53. both issued to Anthony J. M. Garwood.

disclose a packaging system for fresh meat which utilizes a specially constructed retail

case-ready tray for prolonging the shelf life of the fresh meat product. Garwood teaches

that the tray may be constructed of a gas barrier plastic material. The packaging system

of Garwood further includes a laminated web of gas permeable clear flexible plastic wrap

material which seals the meat within the tray and a lid which forms a domed enclosure over the laminated web. In use. the packaging is evacuated of normal atmosphere and is

flushed with a gas mixture of carbon dioxide and nitrogen to preserve the contents.

When the dome is pulled off. oxygen is allowed to contact the meat and the product

blooms.

Under ideal storage conditions ( ie.. where storage temperature is maintained

between 29°F and 32 °F). the Garwood packaging system is able to achieve a shelf life in

a range of about twenty to forty days. The maximum shelf life for the Garwood

packaging system, however, is determined by the maximum amount of carbon dioxide

that can be practicably stored within the domed enclosure, which is typically only 60-70%

b> volume of the total gas mixture Nitrogen, or some other like inert gas. must be used

as a filler, otherwise the packaging will implode as the meat absorbs the carbon dioxide

within the limited volume domed enclosure

Another drawback of the Garwood packaging system is that the addition of the

special lid for forming the domed enclosure increases the overall cost of the packaging

over conventional plastic overwrapped trays For many retailers, the benefit of the

increased shelf life does not outweigh the additional cost incurred b\ the packaging A

less expensiv e packaging which also atfords increased shelf life would be desirable

Further, it would be desirable to be able extend the shelf life of the packaged meat

beyond the present maximum shelf life of about twenty to forty day s, and preferabh , up

to a maximum shelf life of sixty or even ninety days

SUMMARY OF THE INVENTION

It is therefore a principal object of the present invention to provide an inexpensive

retail case-ready packaging for perishable products, such as fresh meat, which provides a

maximum shelf life that is considerably greater than that which is presently attainable by

the fresh meat packagmgs of the prior art.

Broadly stated, the present invention, to be described in greater detail below, is

directed to a method of packaging fresh meat for retail case-ready display in a

substantially oxygen-free atmosphere The packaging method of the present invention

provides a prolonged shelf life for the packaged meat products in a range of from about

forty to about ninetv days, after which the meat still blooms up to a desired fiery red

color upon exposure ofthe packaged meat product to oxygen

In accordance with one aspect of the invention. a plastic overwτapped packing tray

is provided for receiving a cut of meat. In use. the overwrapped tray is received within a

barrier outer bag which is first evacuated of normal atmosphere and is then flushed with a

preservation-enhancing gas. after which it is then sealed. The overwrapped tray is

"ventilated" with strategically placed perforations which allow the preservation-enhancing

gas to penetrate all enclosed regions of the ventilated overwrapped tray without clogging

due to run off juices from the meat or shifting o the meat inside the tray during transpoπ.

In this way. the preservation-enhancing gas is effectively absorbed by the packaged meat

product.

Once the packaged meat product arrives at the retailer, the individually

overwτapped trays are removed from their barrier outer bags to allow oxygen to enter

through the perforations of the ventilated overwrapped tray. The oxygen contact with the

meat causes it to bloom up so that the pigmentation of the meat changes to a desired

bright red color.

In accordance with an advantageous aspect of the invention. the placement of the

perforations in the ventilated overwrapped tray are not readily visible to the casual

observer. Also, the top web of plastic wrap which overlies the meat product is not pierced

so that the retailer does not need to worry about lining up the ventilated overwrapped

trays in the retail display case in any paπicular way so that the product does not dry out or

look as though it has been tampered with.

Also, since the top web of the ventilated overwrapped tray is not pierced, the

workers at the meat packing plant do not have to be conscious of leaving a void space

beneath the top web so that the meat product does not inhibit the vacuum and gas flushing

steps.

Methods and apparatus which incorporate the features described above and which

are effective to function as described above constitute specific objects of this invention

Other and fuπher obiects of the present invention will be apparent from the

following description and claims and are illustrated in the accompanying drawings, which

by way of illustration, show preferred embodiments of the present invention and the

principles thereof and what are now considered to be the best modes contemplated for

applying these principles Other embodiments of the invention embodying the same or

equivalent principles may be used and structural changes may be made as desired by

those skilled in the aπ without depaπmg from the present invention and the purview of

the appended claims

BRIEF DESCRIPTION OF THE DRAWING VIEWS

Fig. 1 is an isometric perspective view of a v entilated overwrapped packing tray in accordance with the present invention

Fig. 2 is a side elevation iew of a ventilated overwrapped packing tray in

accordance with another embodiment of the present invention

Fig. 3 is cross-section v iew of the ventilated overwrapped packing tray taken

along the line and in the direction of arrows 3-3 of Fig. 1

Fig. 4 is an enlarged fragmentary view of a corner region of the ventilated

overwrapped packing tray shown encircled by arrows 4-4 of Fig. 3

Fig. δ is an isometric perspective view showing multiple units of ventilated

overwrapped packing trays arranged in stacked fashion within a sealed outer barrier bag

Fig. 6 is a cross-section view taken along the line and in the direction of arrows 6-

6 of Fig. 5

Fig. 7 is a block diagram illustrating the steps of the packaging methodology of

the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An improved fresh meat packaging constructed in accordance with one

embodiment of the present invention is designated generally by reference numeral 10 in

Fig. 1.

The packaging 10 includes a packing tray 12 which is sized for receiving a piece

of fresh meat of predetermined cut (not shown ). The tray 12 is preferably made from a

material which is impermeable to or does not retain residual oxygen. Preferred materials

of construction for the tray 12 would include. but not be limited to. sturdy thermo¬

formable plastics such as polyvinyl and polystyrene.

The tray 12 includes side and end walls which are preferably flared upwardly and

outwardly. An outwardly protruding continuous perimeter lip 14 is formed along the side

and end walls of the tray 12. The tray 12 is provided with perforations, preferably in the

form of a plurality of holes 16 that are disposed, spaced an. in upper poπions of the side

and end walls of the tray. As is seen in the embodiment of Fig. 1. four holes 16 are

provided in the tray 12. one hole for each of the four corners of the tray 12.

The placement of the holes 16 is selected to be sufficiently high along the walls to

permit gas exchange through the walls of the tray without the possibility of clogging due

to run off juices from the meat or shifting of the meat within the tray 12. To this end. one

design scheme that may be employed for the formation and location of the holes 16 is

shown in Figs. 3 and 4. In this example, the corners regions of the tray 12 are formed

with an upper recessed step poπion in which the holes 16 are punched or otherwise

formed

Fig. 2 shows a side elev ation iew of an embodiment similar to that shown in Fig.

1. except that the perforations in the tray 12 of Fig. 2 are in the form of several holes 16'

disposed at spaced intervals and just under the perimeter lip 14 along each of the four

5 walls of the tray 1

In both ofthe embodiments shown in Figs. 1 and 2. the tray 12 is overwrapped

ith a web of clear non-barrier film or plastic wrapping material 18 The plastic

wrapping material 18. in combination with the outwardly protruding perimeter lip 14 of

the trav 12. define two enclosed regions, including a first enclosed region 20 formed bv

o the enclosure of the hollow inteπor of the tray 12 by the overlying top web poπion 18a

of the plastic wrapping material 18 (see eg Fig. 1 ). and a second generally annular-

shaped enclosed region 22 formed by the outer perimeter overwrap poπion 18b ofthe

plastic wrapping material which extends from the outwardly projected perimeter lip 14 to

the bottom of the tray 12 (see eg Fig. 2)

s A number of perforations, preferablv in the form of v eπical slits 24 . are provided

in the perimeter overwrap poπion 18b of the plastic wrapping material 18 The slits 24.

in combination with the holes 16. 16' in the tray 12. allow for gas communication

between the first and second enclosed regions 20 and 22. respectively . and the outside

ambient atmosphere The prov lsion of the holes in the trays and the slits in the film

o mateπal provide an overwrapped tray or packaging that is said to be "ventilated"

Referring now to the block diagram of Fig. 7. the method steps involved in

packaging fresh meat using the ventilated overwrapped tray of the present inv ention will

now be described The packaging method of the present invention is directed to

packaging the fresh meat product in a substantially pure carbon dioxide env ironment.

vvherein the meat is allowed to age for a sufficient minimum length of time so that

formation of lactic acid bacteria in the meat is allowed to flourish Λs has been noted in

the scientific literature, the high concentration of lactobacillus (lactic acid bacteria) in

meat is believed to reverse brown pigment change in the meat and also is believed to

5 contribute to a fiery red bloom of the meat Lactobactena do grow in a substantially pure

CO environment, even at temperatures as low as 29' F and the enzymes secreted bring on

an enhanced red color over time We have also found that the desired aging period

necessary to achieve a desired bright red bloom to be in the range of anywhere from a

minimum of 4-5 day s to about two weeks The aging period selected depends on the

i o color sensitiv ity of the cut poπion of the meat For example, shoulder cuts are more color

sensitive than tender nb cuts and thus require more aging time to ensure a desired fiery red bloom.

In accordance with the packaging method of the present invention, the meat

product is prepared into the selected cuts at step 30 The cuts are then placed within the

15 tray s 12 at step 32 Preferably , the tra s 12 hav e alreadv been perforated to include the

holes 16 or 16' prior to step 32 The tray s 12 are then overwrapped with the clear film or

plastic wrapping material 18 at step 34 At step 36. the overwrap poπions 18b of the

plastic wrapping material 18 are perforated to form the slits 24

Referring now to Figs. 5-6. a number of the individual packagings or entilated

20 overwrapped tray s 10 are placed in stacked fashion w ithin an outer barrier bag 26 The

outer barrier bag is composed o a material which is essentially imper ious to oxygen

The outer barrier bag 26 is evacuated of normal atmosphere at step 40 and is then flushed

with a preservation-enhancing gas comprising substantially pure carbon dioxide at step

42 The outer barrier bac 26 is then sealed

The slits 24 in combination with the holes 16 or 16' ensure that residual oxygen is

removed from the first and second enclosed regions 20 and 22. respectively , of the

ventilated overwrapped trays 10 duπng the evacuation or vacuum step 40 Also, the slits

24 and holes 16 or 16' ensure that carbon dioxide gas is allowed to effectively contact the

s packaged meat product so that it may be absorbed thereby in order to preserve and age the

meat product.

Platter paper (not shown) or like buffering means may be placed between

successive ones of the stacked ventilated overwrapped trays 10 and also between the

upper disposed ventilated overwrapped trays 1 and the inner surface of the outer barrier

o bag 26 When used in this fashion, the platter paper advantageously protects against

unsightly tears or punctures in the plastic wrapping material of the ventilated

overwrapped trays 10 and also protects against punctures in the barrier outer bag which

can sometimes result from the abrading action of protruding bones in the packaged meat

products during handling and transpoπ.

s As an additional measure to ensure against the presence of residual oxygen from

prematurely spoiling the packaged meat products, desiccants or oxygen scav engers may

be placed in the outer barrier bag prior to sealing.

Also, soaker pads may be placed within the trays 10 prior to placing the meat

therein, in order to absorb the excess run off juices from the meat which may occur during

o periods of prolonged storage

We have consistently found that measurements of the oxygen content within the

outer bamer bag 26 just after sealing to be very low. typically falling within a range of

between 30-50 ppm. Also, immediately after sealing the outer bamer bag 26.

measurements of the oxvαen content within the first enclosed region of the v entilated

overwrapped tray ( ie.. the air space immediately surrounding the packaged meat product )

are consistently found to be under 250 ppm. After a period of two to three minutes from

the time that the barrier outer bag is sealed, the oxygen levels in both the greater volume

of the outer barrier bag 26 and inside the ventilated overwrapped trays 10 stabilizes to a

maximum equilibrium of about 250 ppm. after which the oxygen levels drop off

significantly upon absoφtion by the meat.

The internal volume of the outer banier bag 26 is preferably large enough to

ensure an ample supply of carbon dioxide gas for preserving the packaged meat products

without the outer banier bag 26 being sucked inwardly any appreciable amount which

could cause physical damage to the appearance of the ventilated overwrapped trays 10

contained therein. In other words, a sufficient additional volume of the carbon dioxide

gas is provided within the surrounding interior volume of the barrier outer bag 26 so that

the packaging does not distoπ or implode as the meat absorbs the carbon dioxide gas.

We have found that meat products packaged in accordance with the above

described method to have a shelf life of up to ninety days and still bloom up to a desired

fiery red color when removed from the outer barrier bag.

While we have illustrated and described the preferred embodiments of our

invention. it is to be understood that these are capable of variation and modification, and

we therefore do not wish to be limited to the precise details set foπh. but desire to avail

ourselves of such changes and alterations as fall within the purview of the following

claims.

What is claimed is: