[0001] The present invention relates to a new and improved structure for absorbing liquids
from food products. More particularly, the invention relates to an absorbent pad for
meat and poultry products.
[0002] Over the years, the methods of marketing and selling food products have changed dramatically,
especially with perishable products such as meat, poultry, fish, and vegetables. A
long-standing tradition has been to display such products in bulk form, thereby allowing
the purchaser to individually select the item or items to be purchased. This was particularly
true with respect to meat and poultry products which were most commonly sold by a
butcher from display cases. Today, many of these products arrive at the grocery store
prepackaged. Such packaging, especially with respect to meat and poultry, involves
the use of a semi-rigid tray to contain the product and a plastic overwrap to seal
the product within the tray to maintain the freshness of the contents for a finite
period.
[0003] Such products as meat and poultry naturally contain liquids/juices and occasionally
added water which with time will drain from the product. When such products were sold
at butcher counters, these liquids would drain to the bottom of the display case.
However, when the same products are packaged within relatively air- and liquid-tight
packages, these liquids end up collecting within the tray and subsequently leaking
during transportation and handling. Market analysis has revealed that the consumer
finds such liquid-containing packages to be less than desirable. Consequently, many
such packages today employ an absorbent material in the bottom of the tray to absorb
the liquids as they are released from the food product.
[0004] One commonly used material for such purposes is tissue and/or wood pulp fluff which
is usually encased within a material such as plastic film or tissue paper. Many other
designs have also been developed to be used generally with food packaging. Other designs
have been specifically developed to act in concert with a particular package design.
[0005] A liquid absorbing and concealing device which includes both a liquid absorbing bag
and a tray is disclosed in DuPuiS, U.S. Patent No. 3,156,402. The liquid absorbing
bag is composed of two superposed sheets of material which are sealed by heat welding
or adhesive around their marginal edges. The sheets may be formed from material such
as waxed paper, cellophane, polyethylene, or other thermoplastic or thermosetting
plastic materials. Each of the sheets contain a series of openings or holes to permit
fluid to enter the bag from either the top or the bottom by the use of gravity and
capillary action.
[0006] In a reverse application, United States Patent No. 3,940,062 to Rainey discloses
a moisture pad for use in hydration of consumable vegetables which have been sealed
in plastic and refrigerated. The pad includes a water containing reservoir element
which is encased in a sheath of moisture-proof film with openings for escape of the
moisture from the reservoir. The pad consists of a sponge or other absorbent or porous
pad which is saturated with water to act as the water reservoir. The hydrated sponge
is then located within a flexible water-impervious envelope which is sealed or otherwise
closed about its periphery. The envelope is then provided with openings to allow for
the escape of moisture from the absorbent sponge within.
[0007] Another liquid-absorbing device, in this case a liquid-absorbing sectional pack,
is disclosed in U.S. Patent No. 4,124,116 to McCabe, Jr. The pack is formed from upper
and lower contiguous filter sheets which are bonded to each other at the outermost
contiguous edges thereof to form an enclosure. The enclosure itself is divided into
a plurality of sectional compartments which are isolated from each other by dissolving
barrier sheets which consist essentially of a water-soluble carboxymethylcellulose
compound. Each of the sectional compartments contain a predetermined quantity of absorbent
granules and the barrier sheets function to dissolve when the granules have absorbed
a pre-determined amount of moisture so as to provide for increased space in which
to contain the moist granules.
[0008] A receptacle for moisture-exuding food products is described in U.S. Patent No. 4,321,997
and U.S. Patent No. 4,410,578 both to Miller. A receptacle is provided for containing
and displaying food products which tend to exude juices or liquids which comprises
a supporting member such as a tray or bag, and an absorbent pad associated therewith.
The absorbent pad comprises a mat of liquid-absorbent material such a wood fluff,
an upper liquid-impermeable plastic sheet overlying the absorbent mat, and a bottom
plastic sheet underlying the absorbent mat. At least one of the sheets is perforated,
and rigid spacer means is disposed between the two sheets to maintain their separation
under a compressive load such that the ability of the pad to absorb liquids is unimpaired
when the pad is subjected to compressive loading from the food product resting thereon
or the like. In this construction, it is preferred that only the bottom sheet be perforated
such that when a food product is positioned upon the upper sheet of the absorbent
pad, any exuded liquids will flow around the pad and enter the mat by capillary action
through the perforated openings in the bottom sheet so as to hold the liquids out
of contact with the food product to minimize contamination of the product and maintain
its appearance and improve its shelf life.
[0009] A receptacle and absorbent pad for containing and displaying food products which
tend to exude juices or liquids are disclosed in U.S. Patent Nos. 4,275,811 and 4,382,507
both to Miller. The pad comprises a mat of liquid absorbent material, an upper liquid
impermeable sheet overlying the absorbent mat and a perforated bottom sheet underlying
the absorbent mat. When a food product is positioned upon the upper sheet of the absorbent
pad, the exuded liquids flow around the pad and enter the mat by capillary action
through the perforated openings of the bottom sheet and the liquids are held out of
contact with the food product by the impermeable upper sheet. In preferred embodiments
the absorbent mat is composed of a relatively thick layer of wood fluff and a relatively
thin layer of tissue-like paper wadding which may be interconnected by embossing.
In addition, various additives may be added to increase liquid absorbency.
[0010] Another absorbent pad for use with packaged meats is disclosed in U.S. Patent No.
4,451,377 to Elves, et al. The absorbent pad is made from a nonwoven fabric material
such as viscose rayon, superabsorbent viscose rayon, or polyvinyl alcohol. One side
of the pad has a layer of binder material to provide a surface with reduced absorbency
as compared to the remainder of the pad with the remainder of the pad being free of
binder. In addition, the pad may have apertures formed therein to allow fluid to pass
through the binder layer and into the remainder of the nonwoven material. The fibers
of the nonwoven material are entangled by needle punching or preferably by the use
of high-pressure water jets. The web is then dried and after drying a binder is applied
to the one surface of the pad.
[0011] A food tray for supporting, containing, and displaying food products which tend to
exude or purge juices or liquids is disclosed in U.S. Patent No. 4,576,278 to Laiewski.
The tray has a false bottom which leads to an exudate reservoir. The false bottom
is made from a perforated liquid-impermeable thermoplastic film such as polyethylene.
[0012] The primary function of each of the above-described devices is to absorb the fluids
which are exuded from packaged food products. Leaky packages are among the foremost
complaints received by food store operators. Their use in such products, therefore,
adds to the cost of the overall product. As a result, a major driving force in the
development of such products is to provide an absorbent structure which provides ample
absorbency while employing cost-efficient components. Furthermore, such designs should
yield products with good wet strength, resilience and fluid retention characteristics.
Products such as tissue tend to break apart when wetted. Such materials also readily
release their absorbed fluids when placed under a compressive load. This most notably
happens when packages are stacked one upon the other.
[0013] It is therefore, an object of the present invention to provide an absorbent structure
for collecting and retaining fluids released from foods which provides good containment
of exuded fluids and which does not readily release such fluids when under compression
or break apart when wet. This object is solved by the absorbent structures as described
in the independent claims. Further advantageous features of the absorbent structures
of the invention are evident from the dependent claims.
[0014] The present invention also provides an absorbent structure which while having the
capability of absorbing fluids does not aggressively extract the fluids from the food
product.
[0015] The present invention relates to a new and improved structure for absorbing liquids
from food products and in particular meat and poultry. The absorbent structure comprises
a top sheet of fluid permeable material such as a nonwoven spunbonded or meltblown
material. Alternatively the top sheet may be constructed of a fluid impermeable material
such as plastic with at least one perforation therein to allow fluid passage therethrough.
The bottom sheet is constructed of a fluid impermeable material. An absorbent inner
core of pulp coform material is positioned between and joined to the top and bottom
sheets. The pulp coform material contains between 50 and 90 percent by weight wood
pulp fluff (based upon the weight of the absorbent core) and between 10 and 50 percent
by weight synthetic fibers. Included within the absorbent core there may be placed
superabsorbent material such as carboxymethylcellulose.
[0016] In a preferred embodiment of the present invention the top and bottom sheets are
sealed about their periphery to create a fluid collection pouch with an inner chamber
to house a stratified absorbent core. The stratified absorbent core includes a first
layer of pulp coform material adjacent the top of the pouch and a second layer adjacent
the bottom of the pouch. The first layer is substantially devoid of superabsorbent
material and the second layer contains a superabsorbent such as carboxymethylcellulose
in a weight percent add on of from 5 to 100 percent based upon the total weight of
the absorbent inner core.
[0017] Other objects and advantages of the present invention will become more readily apparent
upon a further review of the following specification and drawings.
Figure 1 is a perspective view of an absorbent structure for collecting and retaining
fluids released from foods according to the present invention.
Figure 2 is a perspective view with a partial cutaway of another absorbent structure
for collecting and retaining fluids released from foods according to the present invention.
Figure 3 is a cross-sectional view of an absorbent structure for collecting and retaining
fluids released from foods according to the present invention.
Figure 4 is a graph showing the water absorbency of the inner core material of the
present invention alone and in combination with varying amounts of superabsorbent
material.
[0018] The present invention relates to an absorbent pad for collecting and retaining fluids
from foods, most notably meat and poultry. Much of the meat and poultry sold in stores
today is prepacked in styrofoam trays and wrapped with transparent polymeric film.
It has now become common practice to place an absorbent material within the package
to absorb the fluids that are released from the food product. Due to space and cooling
constraints, these packages are often stacked one upon the other, thereby multiplying
the compressive load upon each of the packages, their contents and the absorbent pads.
In addition, the packages when stacked are rarely in a completely horizontal plane.
As a result, the juices absorbed by the pad will commonly be compressed, at least
partially, back out of the pad and pool in the lowest point of the package. Consequently,
there is still a high probability that the package will leak.
[0019] Referring to Figure 1 there is shown an absorbent structure 10 for collecting and
retaining fluids released from foods. The structure 10 has an outer cover including
a fluid permeable top sheet 12 and bottom sheet 14 of fluid impermeable material such
as polyethylene film. Positioned between and joined to the top and bottom layer 12
and 14 is a fluid absorbent inner core 16 which is joined to the outer layers 12 and
14 by suitable means such as adhesives or embossments. To permit the exuded fluids
from the food to enter the absorbent structure 10, there is provided at least one
perforation 18 in the top sheet 12 which may take the form, for example, of a hole,
slit, or capillary funnel. In the embodiment shown in Figure 1 the top sheet 12 is
supplied with a plurality of perforations 18 to facilitate transfer of fluid into
the absorbent core 16. Alternatively, the top sheet 12 may be formed from a fibrous
nonwoven material such as a spunbond or meltblown which will allow the passage of
fluids to the absorbent core 16.
[0020] The design of the absorbent core 16 of the present invention provides both good absorbency
and structural integrity to resist the release of fluids when the core material 16
is placed under compression. To accomplish this, the absorbent core material 16 is
comprised of a pulp coform material which is made from a mixture of wood pulp fluff
and extruded thermoplastic synthetic fibers. One way to make this material is referred
to as the pulp coform process which is disclosed in United States Patent No. 4,100,324
to Anderson, et al, which is commonly assigned to the Kimberly-Clark Corporation and
incorporated herein by reference. To provide the necessary degree of wet resilience
and absorbency the pulp coform material contains between 50 and 90 percent by weight
of wood pulp fluff and between 10 and 50 percent by weight of synthetic fibers based
upon the total weight of the wood pulp fluff and synthetic fibers. The wood pulp acts
as the absorbent while the synthetic fibers, which are disposed throughout the wood
pulp, make the composite more resilient both when wet and dry. The wood pulp fluff
is 100 percent softwood pulp, or softwood pulp containing up to 30 percent hardwood
fiber. Softwood pulp fibers generally exhibit fiber diameters in the range of 35 µm
to 45 µm and lengths of 3 mm to 5 mm. After processing into coformed structures the
fiber length is reduced and averages approximately 2 mm. Hardwood fibers exhibit fiber
diameters from about 14 µm to 32 µm with lengths in the range of approximately 1 mm
to 2 mm. The synthetic fibers are most typically made from extrudable meltblown thermoplastic
materials such as polypropylene or polyethylene fibers with an average fiber diameter
of up to 10 µm and more preferably in the range of 2 to 6 µm. These fibers are discontinuous
and as a result have a length generally in excess of the staple fiber wood pulp fluff
material. Densities for the pulp coform material used in the present invention range
from about 0.03 g/cm³ to about 0.20 g/cm³ with various absorbencies when tested using
deionized water as the absorbing fluid. (See the absorbency graph of Figure 4).
[0021] To further enhance the capacity of the absorbent core 16, a superabsorbent material
20 may be added to the pulp coform material of the core 16. One method of adding such
material is disclosed in United States Patent No. 4,604,313 which is assigned to the
Kimberly-Clark Corporation and incorporated herein by reference. Any number of superabsorbents
may be used with the absorbent structure 10, however, because the absorbent structure
10 is used in conjunction with food, the superabsorbent should be cleared by the United
States Food and Drug Agency or any other relevant authority. One such preferred superabsorbent
is carboxymethylcellulose (CMC) such as is sold by the Aqualon Company of Wilmington,
Delaware under the designation A-250. The superabsorbent may be added to the pulp
coform material in powder or other form either during the formation of the coform
material or thereafter. The measure of the increase in fluid absorbency in the absorbent
core 16 is dependent upon the amount of superabsorbent 18 added to the pulp coform
material. Preferably the superabsorbent 20 is added to the absorbent core 16 in a
weight percent add on of from 5 to 100 percent based upon the total weight of the
absorbent core material 16.
[0022] In use, the absorbent structure 10 is placed between the food product (not shown)
and the tray or other packaging material (not shown) with the perforated top sheet
12 in contact with the food product. As juices, etc., are released from the food product,
they pass through the perforations 18 or the nonwoven material of the top sheet 12
and are collected and retained within the absorbent core 16. Unlike simple wood pulp
fluff, the pulp coform material of the present invention is more resistant to compression
when wet due to the use of the synthetic fibers. As a result, the absorbent structure
10 is less likely to release its fluids when compressed, especially if a superabsorbent
20 is being used.
[0023] A more self-contained and preferred embodiment 30 of the present invention is shown
in Figures 2 and 3 of the drawings. As with the embodiment of Figure 1, the absorbent
structure 30 has a top sheet 32 and a bottom sheet 34 of the same materials as previously
mentioned and an absorbent core 36 of pulp coform material. One or more perforations
38 are present in the top sheet 32 if it is not made from a nonwoven material and
a superabsorbent 40 as previously discussed may be used within the pulp coform material.
[0024] Unlike the embodiment shown in Figure 1, the top and bottom sheets 32 and 34 are
sealed about their periphery 35 by adhesive, heat or other means. As shown in Figure
2, the absorbent structure 30 may be made of two separate sheets 32 and 34 which are
sealed about their entire periphery 35. Alternatively, as shown in cross-section in
Figure 3, the top and bottom sheets 32 and 34 may be formed from a single sheet of
material which is folded over on itself, thus only requiring sealing on three sides.
Also note that the absorbent structures 10 and 30 are not limited to square or rectangular
shapes and may be designed in any other shape to suit the particular application.
[0025] An important additional feature of the embodiment shown in Figures 2 and 3 is the
stratified absorbent core 36. In this embodiment the absorbent core 36 is comprised
of a first layer 36a adjacent the top sheet 32 and a second layer 36b adjacent the
bottom sheet 34. Both the first layer 36a and the second layer 36b are formed from
the same pulp coform material as described with respect to the embodiment of Figure
1. Again, the pulp coform material should contain between 50 and 90 percent by weight
wood pulp fluff and between 10 and 50 percent by weight synthetic fibers. If desired,
the layers 36a and 36b may have the same or different ratios of wood pulp fluff and
synthetic fibers.
[0026] In the embodiment of Figures 2 and 3, the super-absorbent 40, most preferably carboxymethylcellulose,
is only present in the second layer 36b. As a result, it is desirable to have a higher
synthetic fiber concentration in the second layer 36b to provide greater interstitial
spacing to prevent gel blocking as the second layer 36b and superabsorbent 40 absorb
fluids. Again the superabsorbent concentration should be from 5 to 100 percent by
weight based upon the combined weight of the wood pulp fluff and synthetic fibers.
[0027] By splitting the absorbent core 36 into two layers 36a and 36b and placing the superabsorbent
in the second layer 36b, two distinct advantages are achieved. First, the superabsorbent
material 40 is located away and separated from the fluid permeable top sheet 32. As
a result, there is less likelihood that the superabsorbent 40 will filter through
the perforations 38 in the top sheet 32 and come in contact with the food product.
Secondly, whenever a superabsorbent is used in an absorbent material, it increases
the capillary action or "drawing power" of the absorbent. With food products, this
can result in a premature dehydration of the food product. By distancing the superabsorbent
from the food product, this drawing power is reducing while still allowing the enhanced
utilization of the fluid retentive properties of the superabsorbent.
[0028] Lastly, the absorbent structure 30 of Figures 2 and 3 may be provided with a fluid
reservoir area 42 within the absorbent structure 30 between the absorbent core 36
and the sealed periphery 35. In so doing, the absorbent structure 30 is provided with
a contained fluid run-off area for temporary storage of the fluids when the structure
30 is under severe compression or when the structure 30 has received more fluid than
the absorbent core 36 can hold. As a result, the absorbent structure of the present
invention can more readily receive and contain fluids received from the food product
stored within the food package (not shown). Furthermore, by providing a self-contained
system with perforations directly in contact with the food product, there is less
likelihood of pooling of fluids within the food tray and ultimate leakage from the
container.
EXAMPLES
[0029] Representative absorbencies were evaluated for different basis weight pulp coform
inner core materials both with and without the use of superabsorbent. Absorbencies
for each of the pulp coform materials were evaluated using the following procedure:
1. A 4 inch (10.2 cm) by 6 inch (15.2 cm) sample of the pulp coform material was weighed
and then immersed in a deionized water bath for 20 minutes.
2. The sample was removed from the bath by lifting with a glass rod placed in the
middle of the sample so as to drape the sample over the rod.
3. The rod with the sample draped over it was then suspended to allow any free water
not bound in the superabsorbent or coform material to flow from the sample for a period
of one minute.
4. The sample was then placed on a balance and the wet weight was recorded.
5. The water absorbency was calculated by subtracting the dry weight from the wetted
weight of the sample and plotted in Figure 4.
Example Ia:
[0030] A pulp coform sample devoid of carboxymethylcellulose was subjected to the test procedure
outlined above. The sample had a basis weight of 75 g/m² with 80 percent by weight
pulp and 20 percent by weight polypropylene fiber. Sample thickness was 1.02 mm and
the bulk density was 0.073 g/cm³. As plotted in Figure 4, water absorbency was 1.05
g/6.45 cm² surface area.
Example Ib:
[0031] 5.0 g/m² of carboxymethylcellulose was added to a sample of material identical to
Example Ia. Water absorbency was 1.98 g/6.45 cm² as shown in Figure 4.
Example Ic:
[0032] 10.0 g/m² of carboxymethylcellulose was added to a sample of material identical to
Example Ia. Water absorbency was 2.51 g/6.45 cm² as shown in Figure 4.
Example Id:
[0033] 15.0 g/m² of carboxymethylcellulose was added to a sample of material identical to
Example Ia. Water absorbency was 3.17 g/6.45 cm² as shown in Figure 4.
Example IIa:
[0034] A pulp coform sample again devoid of carboxymethylcellulose was subjected to the
test procedure outlined above. The sample had a basis weight of 200 g/m² with 80 percent
by weight pulp and 20 percent by weight polypropylene fiber. Sample thickness was
4.04 mm and the bulk density was 0.050 g/cm³. As plotted in Figure 4, water absorbency
was 2.93 g/6.45 cm² surface area.
Example IIb:
[0035] 5.0 g/m² of carboxymethylcellulose was added to a sample of material identical to
Example IIa. Water absorbency was 4.47 g/6.45 cm² as shown in Figure 4.
Example IIc:
[0036] 10.0 g/m² carboxymethylcellulose was added to a sample of material identical to Example
IIa. Water absorbency was 4.54 g/6.45 cm² as shown in Figure 4.
Example IId:
[0037] 15.0 g/m² of carboxymethylcellulose was added to a sample of material identical to
Example IIa. Water absorbency was 5.20 g/6.45 cm² as shown in Figure 4.
[0038] As can be seen from the foregoing data, the absorbency of pulp coform material can
be increased by the addition of a superabsorbent material. In comparing the absorbency
of Example Id and IIa it can be seen that a thinner superabsorbent containing pulp
coform material can be used in place of a thicker non-superabsorbent containing pulp
coform material. As a result, a thinner product with equal absorbency can be achieved
if so desired.
[0039] Having thus described the invention in detail, it should be appreciated that various
modifications and changes can be made in the present invention without departing from
the spirit and scope of the following claims.
1. An absorbent structure (10) for collecting and retaining fluids released from foods
comprising:
a fluid permeable top sheet (12),
a fluid impermeable bottom sheet (14), and
an absorbent inner core (16) of pulp coform material positioned between and joined
to said top (12) and bottom (14) sheets, said absorbent inner core (16) containing
between 50 and 90 percent by weight wood pulp fluff and between 10 and 50 percent
by weight synthetic fibers based upon the combined weight of said wood pulp fluff
and said synthetic fibers.
2. The absorbent structure of claim 1 wherein said absorbent inner core (16) further
includes a superabsorbent material (20).
3. The absorbent structure of claim 2 wherein said superabsorbent (20) is carboxymethylcellulose
and is present in said absorbent inner core (16) in an amount equal to from 5 to 100
percent by weight of the combined weight of said wood pulp fluff and said synthetic
fibers.
4. An absorbent structure (30) for collecting and retaining fluids released from foods
comprising:
a fluid collection pouch having a fluid permeable top sheet (32), a fluid impermeable
bottom sheet (34) defining a chamber therein, and
an absorbent inner core (36) of pulp coform material within said chamber containing
50 to 90 percent by weight wood pulp fluff and 10 to 50 percent by weight synthetic
fibers based upon the combined weight of said wood pulp fluff and said synthetic fibers,
said absorbent inner core (36) being divided into a first layer (36a) adjacent said
top sheet (32) of said pouch and a second layer (36b) adjacent said bottom sheet (34)
of said pouch, said first layer (36a) being substantially devoid of a superabsorbent
material and said second layer (36b) containing a superabsorbent (40) in a weight
percent add on of from 5 to 100 percent based upon the combined weight of said wood
pulp fluff and said synthetic fibers.
5. The absorbent structure of claim 4 wherein said superabsorbent (40) in said second
layer (36b) is carboxymethylcellulose.
6. The absorbent structure of claim 4 or 5 wherein said fluid collection pouch and
said absorbent inner core (36) define a fluid reservoir area (42) between said absorbent
inner core (36) and said sealed periphery (35) for additional storage of said fluids.