WO1999032286A9

WO1999032286A9 - Integral food tray

Info

Publication number: WO1999032286A9
Application number: PCT/US1998/027177
Authority: WO
Inventors: Victor Day; Francis H Sheehan; George Zhang
Original assignee: Moore Co; Victor Day; Francis H Sheehan; George Zhang
Priority date: 1997-12-19
Filing date: 1998-12-17
Publication date: 1999-09-23
Also published as: AU2088899A; WO1999032286A1

Abstract

The present invention is directed to a receptacle (16) for containing food products which tend to exude liquids, which includes a structural support layer (10) and a liquid absorbing layer (12) laminated to the support layer (10). The present invention is also directed to a method for producing a receptacle (16) for containing food products which tend to exude liquids, and to a method for absorbing fluid exuded from a food product by placing the food product within the food receptacle (16) of the invention.

Description

INTEGRAL FOOD TRAY

FIELD OF THE INVENTION

The present invention is directed to a tray intended for packaging and

displaying poultry, fish, meat, and other foods which tend to exude fluids after packaging.

More particularly, the invention is directed to a tray or other container including a moisture

absorbing food contact layer and a second layer for providing structural integrity and a

moisture barrier. The present invention is also directed to methods for making and using

such a tray.

BACKGROUND OF THE INVENTION

Conventionally, foods such as fresh poultry, fish, meat, and other foods which

tend to exude fluids after packaging, are packaged for refrigerated display by employing a

tray to receive the food. Generally, a transparent or translucent plastic film is wrapped and

sealed around the food placed on the tray itself and the tray to provide a finished, sealed

package. The tray provides structural integrity and acts as a reservoir for fluids. Ideally, the

tray also serves as a moisture barrier.

One type of tray is generally constructed from compressed wood pulp.

However, the structural integrity of this type of tray is diminished by the absorption of fluids

from the product placed on the tray. Another type of tray is made from a non-absorbent

material which can retain its structural integrity upon exposure to fluids and moisture.

Suitable non-absorbent materials include thermoplastic materials, such as polyethylene,

polypropylene, polystyrene, and polyvinyl chloride. Although trays made from thermoplastic materials as described above have several advantages in terms of cost, weight, aesthetics,

durability, and other characteristics, the inability of these materials to absorb moisture often

results in the accumulation of fluid exuded from the food product placed on the tray. The tray

with the food product is customarily wrapped and optionally heat sealed with a transparent,

flexible thermoplastic film so that the finished product may be displayed in a refrigerated

display case in such a manner that the consumer may view the food product directly through

the packaging. Accordingly, the accumulation of fluids in the tray surrounding the food

product is undesirable because it results in an unsightly, unappetizing and therefore

unappealing packaged product. Furthermore, and more importantly, although the package is

sealed with a flexible transparent film the accumulated fluid may leak from the package. In

addition, accumulated fluids may promote the growth of bacteria.

One approach to solving this problem has been to provide an absorbent pad

between the upper surface of the non-absorbent tray and the food product. In theory, the pad

will absorb the fluids exuded from the food product preventing the accumulation of free

fluids within the package. Another proposed solution to the problem has been to provide a

separate reservoir within the tray such that fluids exuded by the food product are drained

away from contact with the product, generally by providing a retaining surface above the

bottom wall of the tray. The retaining surface includes drain holes extending therethrough

such that fluid drains from the product retaining surface and is retained above the lower wall

of the tray. Examples of food trays are shown in U.S. Patents 3,575,287, 4,275,811,

4,321,997, 4,410,578, 4,929,480 and 4,949,897. The disclosure of each of the foregoing U.S.

patents is hereby incorporated by reference. The use of absorbent pads for the absorption of fluids from the food product

suffers from the disadvantage that the two component food tray must be assembled before the

food is placed in the tray, resulting in increased labor costs. Further, after the pad is saturated

with moisture it tends to stick to the food product and must be physically separated from the

food product by the consumer after the package is opened. Because the pad is saturated with

fluids exuded by the food product, this is a generally unappealing exercise.

The use of a separate fluid reservoir to separate and retain exuded fluids

suffers from other disadvantages. The construction of the food tray is complex, requiring at

least two layers separated by a free space to serve as the reservoir. Further, it is difficult to

keep the fluid within the reservoir when the package is upset from a level orientation.

Thus, it is an object of the present invention to provide a food product tray

which is capable of absorbing fluid exuded from a food product placed within the tray, yet

does not require either the use of a separate pad or a complex separate fluid reservoir. It is

yet another object of the present invention to provide a food tray which is inexpensive, easy

to manufacture, and requires no extra labor in packaging or unwrapping the food product.

SUMMARY OF THE INVENTION

In a first aspect, the present invention is directed to a receptacle for containing

food products which tend to exude liquids. The receptacle includes a laminate which consists

of a structural support layer and a liquid absorbing layer laminated to the support layer. The

laminate may be formed into any suitable shape to form a receptacle for food.

In another aspect, the present invention is directed to a method for producing a

receptacle for containing food products which tend to exude liquids, comprising the steps of providing a structural support layer with a top surface and a bottom surface, where the

structural support layer is made from a thermoplastic material, providing an absorbing layer

with a top surface and a bottom surface, and attaching the bottom surface of the absorbing

layer to the top surface of the structural support layer to form a laminate.

In a third aspect, the invention is directed to a method for absorbing fluid

exuded from a food product placed within a food receptacle, comprising the steps of

providing a food receptacle which includes a structural support layer made of a thermoplastic

material having a top surface and a bottom surface, and a liquid absorbing layer with a top

surface and a bottom surface, where the bottom surface of the liquid absorbing layer is

laminated to the top surface of the support layer, and placing a food product which tends to

exude liquids above the top surface of said absorbing layer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of one embodiment of a laminate of the

present invention.

FIG. 2 is a cross-sectional view of a second embodiment of a laminate of the

present invention.

FIG. 3 is a cross-sectional view of a food tray constructed from the laminate of

the present invention.

FIG. 4 is a cross-sectional view of a third embodiment of the present

invention.

FIG. 5 is a enlarged, cross-sectional view of a perforated cover sheet. DETAILED DESCRIPTION OF THE INVENTION

All patents, patent applications, and publications referred to herein are

incorporated by reference in their entirety. In case of a conflict in terminology, the present

disclosure controls.

The present invention relates to a receptacle or food tray constructed from a

laminate material including at least two layers. With reference to Fig. 1, a cross-sectional

view of a preferred laminate according to the present invention is shown. Fluid absorbing

layer 12 rests upon structural layer 10. A wicking layer 14 is applied to the upper surface of

fluid absorbing layer 12.

Structural layer 10 serves to form and maintain the desired shape of the tray,

provide structural integrity and support for the food product provided on the tray and provide

a moisture barrier to prevent fluid from leaking or penetrating in or out of the tray. Layer 10

may be made from any suitable thermoplastic material such as polyethylene, polypropylene,

PAPER, polystyrene, or polyvinyl chloride cellular materials. Layer 10 is preferably made

from polystyrene foam obtained from either expanded polystyrene or sheet molding.

Fluid absorbing layer 12 rests upon the upper surface of layer 10. Layer 12

may be constructed of a flexible polyurethane foam, natural or synthetic hydrophilic open-

cell cellular materials (such as natural rubber foam treated with a wetting agent or foams

made from acrylics or ethylene vinyl acetate). Although absorbing layer 12 will generally be

somewhat compressible and will compress where the food product is placed upon it, the layer

must nonetheless be capable of absorbing fluid exuded from the food product placed on the

tray. In addition, absorbing layer 12 must be compatible with structural layer 10 such that the

two layers may be laminated. If desired, the lamination surface of either layer 10 or 12 may be treated to enhance lamination, by for example flame treatment or corona discharge

treatment. If a more rigid foam is employed as the absorbing layer 12, then the structural

layer 10 need not provide as much support.

The absorbing layer may optionally include a super absorbent polymer (SAP)

material, and/or a biocide material. "SAP" refers to one or more hydrocolloid materials

capable of absorbing many times their own weight of aqueous fluid. These materials are

generally water soluble or water swellable polymers, prepared by polymerization of suitable

monomers, leading to the formation of homopolymers, or copolymers. The polymers are

typically reacted with a crosslinking agents during and/or after polymerization to form

crosslinked polymers, which confers a degree of water insolubility to otherwise water soluble

polymers, while retaining susceptibility of the polymer to swelling in water and water-

containing fluids. Typically, the superabsorbent polymers are salts of poly (acrylic acid) or

acrylic acid copolymers. Additional superabsorbents include hydrophilic polymer grafts onto

starch or cellulose backbones, crosslinked carboxylated celluloses, and the salts of maleic

anhydride copolymers.

Absorbing layer 12 is preferably a polyurethane foam made by in-situ

polymerization. Polyether or polyester polyols of functionality 2-7 and having a molecular

weight range of between 500 - 7000, are mixed with silicone surfactants and water as well as

catalysts. An example of a suitable polyether polyol is PolyG8334 available from Olin

Chemicals. An example of a suitable polyester polyol is Fomrez 50 available from Witco

Chemicals. A suitable silicone surfactant is Dabco 5043 from Air Products and a suitable

catalyst is Dabco 33-LV, also from Air Products. The polyol mixture is then reacted with a

polyisocyanate such as diisocyanatophenyl methane (MDI) or toluene diisocyanate (TDI) employing a mixer at between 1000 and 5000 rpm. The resultant polyurethane foam may

then be cast to form sheet material. The polyurethane foam thus formed may be cast alone or

onto preformed structural layer 10, thereby directly laminating the absorbing layer 12 onto

structural layer 10.

Absorbing layer 12 may include from 0 to 10 % by weight SAP and/or from 0

to 1 % by weight of a biocide. It is preferred that layer 12 have a thickness suitable for

commercial application, e.g., from about 1/16" to 1/4". The absorbing layer will preferably

absorb water in an amount of from about 10 to 30 times the weight of the layer.

Finally, absorbing layer 12 may optionally be covered with food contact

membrane 14. Membrane 14 serves to wick moisture away from the food product and into

the absorbing layer 12. Preferably, membrane 14 is made from a polyethylene film. The film

is punched to provide perforations to allow fluid to pass downward from the food contact

surface into the absorbing layer 12. One preferred polyethylene film has a basis weight of 23

grams/m². However, with reference to Fig. 5, the perforations are formed such that the upper

diameter 18 of a given perforation, facing food contact surface 16, is larger than the lower

diameter 20. For this reason, absorbed fluid is less likely to migrate, through capillary action

or otherwise, from absorbing layer 12 to the food contact surface of membrane 14. This

feature has the added benefit of minimizing the migration of biocide or SAP from absorbing

layer 12 to the food contact surface 16. At the same time, because membrane 14 is preferably

made from a hydrophobic material such a polyethylene, it does not actively draw fluid from

the food product as might occur if the food product directly contacted absorbing layer 12.

In the embodiment shown in Fig. 4, the laminate of the present invention

includes structural layer 10 directly laminated to absorbing layer 12. In the embodiment of Fig. 1, structural layer 10 is directly laminated to absorbing layer 12, and membrane 14 is

provided on absorbing layer 12. In the embodiment of Fig. 2 structural layer 10 is laminated

to absorbing layer 12 by adhesive 11, and membrane 14 is provided on absorbing layer 12

Adhesive 11 may be any adhesive compatible with the two layers, and acceptable for use in a

food packaging environment. Examples of such adhesives include ethylene vinyl acetate

(EVA); acrylics, urethanes, polyamides, polyesters, polyamides, etc. An example of a

suitable EVA adhesive is Airflex 460, available from Air Products.

The finished laminate should be constructed from materials compatible with

commercial and residential microwaves and freezers.

Construction of the laminate of the present invention may be accomplished in

several ways. The absorbing material 12 may be formed, for example by casting to the

desired gauge using standard foaming equipment. The foam may be cast directly onto the

structural layer 10 or cast separately for lamination to structural layer 10 in a separate step.

After the laminate has been constructed, a tray may be shaped by

thermoforming, vacuum forming, stamping, or other techniques known in the art.

Membrane 14 may be adhered to the upper surface of absorbing layer 12 by

thermobonding, ultrasonic welding of the membrane to the lip 24 of tray 22. The membrane

may be adhered to absorbing layer 12 or structural layer 10. In a preferred embodiment,

membrane 14 is secured to the tray only at lip 24 and the membrane thus "floats" on the

surface of the absorbing material 12 in the body of the tray.

In a preferred embodiment, a semi-rigid hydrophilic polyurethane foam is

laminated to a polystyrene structural layer. In another embodiment, a laminate may be constructed according to the

present invention for use in conjunction with an existing food tray or receptacle. Such a

laminate is cut to a desired shape to fit within the food receiving area of the tray. In this

embodiment support layer 10 does not have to provide as much support as it does when the

laminate is use to form the tray itself. Accordingly layer 10 may be of a thin moisture barrier

film such as polyethylene. Alternatively, layer 10 may be eliminated entirely.

Claims

WHAT IS CLAIMED IS:

1. A receptacle for containing food products which tend to exude liquids,

comprising a laminate, said laminate comprising a structural support layer having a top

surface and a bottom surface, and a liquid absorbing layer with a top surface and a bottom

surface, wherein said bottom surface of said liquid absorbing layer is laminated to said top

surface of said support layer.

2. The receptacle of claim 1 wherein said laminate further comprises a

hydrophobic membrane disposed above said top surface of said absorbing layer, wherein said

hydrophobic membrane includes perforations, said perforations having an upper and a lower

diameter.

3. The receptacle of claim 1 wherein said support layer is a thermoplastic

material selected from the group consisting of polystyrene, polyethylene, polypropylene, and

polyvinyl chloride cellular materials.

4. The receptacle of claim 1 wherein said absorbing layer is polyurethane

foam.

5. The receptacle of claim 4, wherein said absorbing layer further

comprises a superabsorbent polymer.

6. The receptacle of claim 4, wherein said absorbing layer further

comprises a biocide.

7. The receptacle of claim 5, wherein said superabsorbent polymer

comprises from 0 to 10 weight percent of said absorbing layer.

8. The receptacle of claim 7, wherein said biocide comprises from 0 to 1

weight percent of said absorbing layer.

9. The receptacle of claim 2, wherein said hydrophobic membrane is

polyethylene.

10. The receptacle of claim 9, wherein said upper diameter of said

perforations of said hydrophobic membrane is larger than said lower diameter of said

perforations.

11. The receptacle of claim 2, wherein said bottom surface of said

hydrophobic membrane is attached to said top surface of said absorbent layer.

12. The receptacle of claim 2, wherein said receptacle comprises a lip, and

wherein said hydrophobic membrane is attached only to said lip, wherein said bottom surface

of said hydrophobic membrane is disposed upon, but is not attached to, said upper surface of

said absorbing layer.

13. A method for producing a receptacle for containing food products

which tend to exude liquids, comprising the steps of:

providing a structural support layer with a top surface and a bottom surface,

wherein said structural support layer is comprised of a thermoplastic material;

providing an absorbing layer with a top surface and a bottom surface; and

attaching said bottom surface of said absorbing layer to said top surface of said

structural support layer to form a laminate.

14. The method of claim 13, further comprising providing a food contact

membrane with a top surface and a bottom surface and attaching said bottom surface of said

food contact membrane with said top surface of said absorbing layer.

15. The method of claim 13 wherein said absorbing layer is a polyurethane

foam produced by reacting one or more members selected from the group consisting of

polyether polyols and polyester polyols with a polyisocyanate.

16. The method of claim 15 wherein said polyisocyanate is selected from

the group consisting of diisocyanatophenyl methane or toluene diisocyanate.

17. A method for absorbing fluid exuded from a food product placed

within a food receptacle, comprising the steps of:

providing a food receptacle which comprises a structural support layer having

a top surface and a bottom surface, wherein said structural support layer comprises a

thermoplastic material, and a liquid absorbing layer with a top surface and a bottom surface,

wherein said bottom surface of said liquid absorbing layer is laminated to said top surface of

said support layer; and

placing a food product which is disposed to exude liquids above the top

surface of said absorbing layer.

18. The method of claim 17, wherein said food receptacle further

comprises a food contact membrane with a top surface and a bottom surface, wherein said

bottom surface of said food contact membrane is disposed above said top surface of said

absorbing layer, and wherein said food product is disposed upon said food contact membrane.