WO1997011009A1

WO1997011009A1 - Extended shelf-life package for fruits and vegetables and the like

Info

Publication number: WO1997011009A1
Application number: PCT/US1995/012075
Authority: WO
Inventors: Carol Ann Blaney; William Francis Cartwright
Original assignee: Kimberly-Clark Worldwide, Inc.
Priority date: 1995-09-22
Filing date: 1995-09-22
Publication date: 1997-03-27
Also published as: AU1854897A

Abstract

Disclosed is a fruit or vegetable storage container (10) which significantly increases the amount of time that fruits, vegetables or the like can be stored under refrigerated conditions before spoilage occurs. The container (10) includes a bag (14) formed from a thermoplastic material and a moisture controlling device (20) which is formed, at least in part, from a cellulosic material and which is located within the bag (14).

Description

EXTENDED SHELF-LIFE PACKAGE FOR FRUITS AND VEGETABLES AND THE LIKE

FIELD OF THE INVENTION

The field of the present invention is directed to devices for increasing the time a fruit or vegetable can be transported, displayed and/or stored desirably, but not necessarily, under refrigerated conditions while still being edible.

BACKGROUND OF THE INVENTION

Fruits and vegetables continue to respire after they are harvested. Respiration is the oxidative breakdown of sugars, starches, and organic acids to simpler molecules including, but not limited to, carbon dioxide and water, with an energy release in the form of heat and metabolic energy. The ratio of carbon dioxide produced to oxygen consumed during respiration is normally about 0.7 to 1.3. The rate and ratio of production of these gases during respiration can be affected by altering certain of the characteristics of the atmosphere which surrounds the fruit or vegetable. For example, temperature and gaseous composition (eg. oxygen, carbon dioxide, water, and ethylene concentrations) are known to affect these rates and ratios.

It is known that most produce (fruits and vegetables) are typically tolerant of carbon dioxide levels up to about 5-10 percent, and tolerant of oxygen levels of as little as about 1-5 percent. However, once these limits are passed, fruits and vegetables can incur physiological damage, with increases in anaerobic respiration and the development of off flavors due to accumulation of such chemical compounds as ethanol and acetaldehyde. The tolerance of fruit and vegetables to carbon dioxide, oxygen, and other gases (eg. ethylene) is known to be dependent upon the temperature at which the fruit or vegetable has been and is being maintained, the physiological condition of the fruit or vegetable, the maturity of the fruit or vegetable, and the manner, physically, in which the fruit or vegetable has been previously treated.

Past packaging systems have attempted to optimize the atmospheric composition surrounding the food in an attempt to minimize respiration and maximize shelf life. For example, an ideal film used to package fruits or vegetables would allow more carbon dioxide to exit than oxygen to enter, since there is about a one-to-one correspondence between moles of oxygen consumed to moles of carbon dioxide produced, coupled with the intolerance of most fruits and vegetables to carbon dioxide levels greater than about 5-10 percent as discussed above. Typically, the carbon dioxide permeability of such an ideal film should be somewhere in the range of 3 to 5 times greater than the oxygen permeability. Low-density polyethylene and polyvinyl chloride films, commonly used in food packaging, possess this property. Those skilled in the art have also utilized oxygen, carbon dioxide, and ethylene sorbents in food packaging systems as an attempt to modify the atmosphere surrounding the fruit or vegetable. But, as is well known, these materials do not address the problems associated with incorrect humidity control. That is, desiccation, condensation or wilting.

It is known that one of the major atmospheric variables affecting shelf-life is relative humidity. If the relative humidity is too low, transpirational damage occurs. This results in a loss of turgidity, eg. wilting, which leads to desiccation, increased respiration, and, ultimately, an unmarketable and inedible product. If the relative humidity is high, moisture can condense on the produce (fruit and vegetables) . This yields conditions favorable for microbial growth due to the presence of free water which encourages the growth of bacteria and fungi, resulting in spoilage of the fruit or vegetable. Condensation on the film package surface may also effect the packaging gas permeability, leading to production of an unfavorable surrounding atmosphere, as well as unsightly water droplets which act as loci for bacterial/fungal proliferation.

With some existing film fruit and vegetable packages, which can maintain an adequate relative humidity inside the packaging system, moisture condensation is a significant problem. Those skilled in the art have attempted to overcome this problem by inclusion of desiccant moisture absorbents in the packaging system in an attempt to lower the relative humidity. Unfortunately, these systems frequently lower the relative humidity excessively, leading to wilting. Anti-fog films are available that prevent visible condensation on the film, but condensation on the product can still occur. Because this leads to an environment conducive to the growth of bacteria and fungi, anti-fog films are not totally satisfactory.

Those of skill in the meat packaging industry have incorporated absorbent trays inside packaging materials. However, these absorbents have only been designed to pick up moisture at or near the lower region of the meat by direct physical contact. Such a system would do nothing to remove water from other areas of the packaged product. That is, near the top of the fruit or vegetable. Accordingly, they would not be satisfactory.

Nishino et al. in U.S. Patent No. 4,061,785 disclose a product which incorporates an anti-fungal or anti-bacterial pesticide within the packaging material to inhibit rotting. Although this system may be scientifically effective in some cases, the public concern about the use of pesticides in such proximity with edible foods makes this option unacceptable. In fact, the long-term effects of such a product are essentially unknown.

U.S. Patent No. 4,961,632, discloses the use of an absorbent material laminated to a film to maintain a dry environment inside a bag utilized for the storage of electronic equipment and dry food-stuffs. Unfortunately, this product does not address the problem of storing fruits and vegetables and the need to maintain a high humidity inside the bag while eliminating the occurrence of condensation drops on the contents of the bag. While unnecessary in the electronics area, also not addressed is the need (by the produce consumer) for the consumer to see inside the bag for quick identification of the viability of its contents.

In summary, none of the above mentioned methods or products have adequately addressed the combination of needs required by an acceptable produce storage container. That is, the need to maintain high humidity conditions in the range of from about 80 percent to less than about 100 percent relative humidity (to prevent wilting) while, at the same time, eliminating the presence of condensation beads or drops of water on the fruit or vegetable so as not to promote microbial decay.

OBJECTS OF THE INVENTION

Accordingly, it is a general object of the present invention to provide a produce storage container capable of preserving fruits, vegetables and the like that is environmentally benign (pesticide-free) , inexpensive, convenient, simple to use, and which provides a significantly longer shelf-life to fruits, vegetables and the like which are stored in such a system.

It is another object of the present invention to provide a method for producing such a produce storage container.

These and other objects and the broad scope of applicability of the present invention will become apparent to those of skill in the art from the details given hereinafter. However, it should be understood that the detailed description of the presently preferred embodiments of the present invention is given only by way of illustration because various changes and modifications well within the spirit and scope of the invention will become apparent to those of skill in the art in view of this detailed description. SUMMARY OF THE INVENTION

In response to the foregoing problems and difficulties encountered by those in the art, a new and improved produce storage container is provided which significantly increases the amount of time that produce or the like can be typically stored under refrigerated conditions before spoilage occurs. Of course, the produce storage container may be used to store other items which would benefit from storage in the controlled relative humidity environment disclosed below. In this regard the term "produce" is used herein to generally designate any such item. Generally speaking, the container is made up of at least two elements or parts.

The first element or part of the container is, e.g., a bag. The bag may, for example, be formed from a thermoplastic material. Alternatively, the bag may be formed from cellose acetate. The thermoplastic material, in some embodiments, may be one or more polyolefins or another thermoplastic material such as polyvinyl chloride. The thermoplastic polyolefin may be selected from the group including one or more polyethylenes, polypropylenes and polybutylenes. In some embodiments, the polyethylene is a linear low density polyethylene. The interior of the bag forms a relative humidity maintaining compartment. The bag is also provided with a mouth which is adapted to be selectively opened and retainingly closed so that produce can be placed in or removed from the relative humidity maintaining compartment. As is well known to those of skill in the art, the mouth of the bag can be provided with any conventional mechanism for maintaining it in a closed configuration. Examples of such configurations include, for example, Dow Chemical Co. ZIPLOC® brand closing mechanisms, VELCRO® brand closing mechanisms, a strip of adhesive, or a deformable wire which can be wrapped around the mouth of the bag when it is in a gathered and closed configuration. Alternative configurations or designs well known to those of skill in the art are, of course, possible. In order to increase the time that produce can be stored, the bag is formed from a material which substantially prohibits the passage of gaseous oxygen into the compartment when the mouth is closed. As used herein the term "substantially prohibits the passage of gaseous oxygen" refers to a material which has an oxygen permeability in the range of from about 0.05 to about 500 [cubic centimeters (at standard temperature and pressure) X millimeters per square centimeter per second per centimeter of mercury] X 10¹⁰. Such a material typically also generally prohibits the passage of microbes into the compartment. In some embodiments the bag may be formed from a material which is transparent so that the condition of the contents can be visually ascertained without opening the container. The second element or part of the container is a moisture controlling device which is located within the compartment. When produce is placed in the relative humidity maintaining compartment and the mouth of the bag is closed, the relative humidity within the compartment will rise to high levels as the produce transpires or gives off moisture. The moisture controlling device serves to wick condensed and/or pooled liquid away form the produce while still allowing the relative humidity within the compartment to remain in the range of from at least about 80 percent to less than 100 percent. This action retards, if not eliminates, an environment which is conducive to the growth of bacteria or other harmful organisms because they tend to flourish in such pooled and/or condensed water ("free water").

In some embodiments the bag is formed from a material which is more permeable to gaseous carbon dioxide than to gaseous oxygen. In particular, the material would generally allow passage of gaseous carbon dioxide out of the compartment when the mouth of the bag is closed.

In some embodiments the moisture controlling device may be formed, in whole or part, from cellulose. The cellulose so utilized may be one or more of several different types. For example, the cellulose may be in the form of cellulose sheet, tissue, paper towel, paper, bacterially produced cellulose, wood pulp, wood fluff pulp, cotton, cotton liners, rayon (reconstituted cellulose) .

In other embodiments the moisture controlling device may be formed from a matrix of a thermoplastic web and hydrophilic cellulosic particles. As used herein the term "particles" is intended to include fibers and groups of fibers. The web may be formed from one or more materials including woven webs and nonwoven webs such as meltblown webs, spunbonded webs and apertured films. The matrix may include a meltblown web and hydrophilic cellulosic particles, a spunbonded web and hydrophilic cellulosic particles or a bonded carded web. Where the matrix is a spunbonded web and hydrophilic cellulosic particles, the matrix may be hydroentangled to produce a spunlaced matrix.

The hydrophilic cellulosic particles utilized in the matrix may be selected from one or more of the group including cellulose sheet particles, tissue particles, paper towel particles, paper particles, bacterially produced cellulose particles, wood pulp particles, wood fluff pulp particles, cotton, cotton linters, rayon particles (reconstituted cellulose) . As was stated earlier the term "particles" is intended to include all forms of cellulosic material and, in particular, fibrous forms and non-fibrous forms such as particulate cellulosic materials available under the trade designation AVICEL®.

As was previously stated, the moisture controlling device is capable, in the presence of produce or the like (fruits, vegetables etc.) , of wicking pooled and/or condensed water away from the contents of the compartment while allowing the humidity within the compartment, when the mouth is closed, to be maintained within the range of from at least about 80 percent to less than 100 percent. More particularly, within the range of from at least about 80 percent to less than about 95 percent. Even more particularly, within the range of from at least about 85 percent to less than about 95 percent. Yet even more particularly, within the range of from at least about 85 percent to less than about 90 percent.

The amount of hydrophilic cellulosic material necessary to wick the pooled and/or condensed water away from the contents of the compartment while still achieving the desired relative humidity ranges within the compartment will vary with the size of the container, the type of fruit and/or vegetable(s) the container is designed to store and the quality (freshness or physical condition) of the fruit and/or vegetables(s) actually stored. Additionally, this will also vary depending upon the type of hydrophilic cellulosic material utilized. Another factor is that, since the cellulosic material is conformable, it may also be employed directly to blot any free moisture present on the produce arising from a washing step prior to storage. However, generally speaking, at least about one (l) gram of hydrophilic cellulosic material should be present in the moisture controlling device per 300 grams of produce to be contained in the container. More particularly, at least about two (2) grams of hydrophilic cellulosic material should be present in the moisture controlling device per 300 grams of produce to be contained in the container. Even more particularly, at least about four (4) grams should be present in the moisture controlling device per 300 grams of produce to be contained in the container. In other embodiments the moisture controlling device may be formed from first and second juxtaposed and joined layers with the first layer being the matrix of a thermoplastic web and hydrophilic cellulosic particles and the second layer being a spunbonded web. In this embodiment the second layer, the spunbonded web, acts as an isolating agent so that the matrix which wicks and retains wicked water, retains the wicked water substantially out of physical contact with the fruit or vegetable(s) . This lessens the likelihood of bacteria or other harmful organisms coming in contact with the fruit or vegetable(s) as a result of their growth in pooled water on the surface of the fruit or vegetable(s) . Further, it also lessens the likelihood of the rapid growth of bacteria in such pooled water sites on the produce.

In some embodiments the bag may be formed from a transparent material so as to allow visual inspection of the contents of the container.

In some embodiments, the moisture controlling device may define one or more apertures adapted to provide an enhanced view of produce contained within the container to a consumer who wishes to inspect the contents of the container without opening the container. Alternatively, indicator devices may be incorporated into the device to visually or otherwise indicate the status of the items contained within the container.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front perspective view of one embodiment of a produce storage container in accordance with the present invention.

Fig. 2 is a cross-sectional view of a produce storage container including a one-layered moisture controlling device.

Fig. 3 is a cross-sectional view of a produce storage container including a two-layered moisture controlling device.

Fig. 4 is a cross-sectional view of a produce storage container including a moisture controlling device formed from a matrix of a thermoplastic web and hydrophilic cellulosic particles.

Fig 5. is a front perspective view of another embodiment of a produce storage container where the moisture controlling device defines one or more apertures. Fig. 6 is a schematic illustration of a method for forming the produce storage container of the present invention.

Fig. 7 illustrates yet another embodiment of the present invention.

DETAILED DESCRIPTION Turning now to the Figures where like reference numerals represent like structure and, in particular, to FIG. 1 which is a front perspective view of one embodiment of a produce storage container 10 made in accordance with the teachings of the present invention. The produce storage container 10 desirably has a relative humidity maintaining compartment 12 which is configured to receive produce or, for that matter, any article which would benefit from storage in a controlled humidity environment. Generally speaking, the container 10 is made up of at least two components.

The first component of the container 10 is a bag 14. The bag 14 may, for example, be formed from any solvent cast, air blown, or cast film which may be amorphous or semi- crystalline. This includes, without limitation, polyethylenes, polypropylenes, polyvinyl chloride, polyvinylidene chloride, cellulose acetate, polystyrene, nylon-6, polyester, polycarbonate, ethylcellulose, methylcellulose, polyvinyl alcohol, polyvinyl fluoride, cellulose triacetate, polychlorotrifluoroethylene and vinylchloride acetate. Many of these materials are thermoplastic and, as a group, thermoplastic materials are generally acceptable for use in the present invention. The thermoplastic material, in some embodiments, may be one or more polyolefins, blends of polyolefins, and blends including olefin comonomeric polymers. In particular, the thermoplastic polyolefin may be one or more polyethylenes, polypropylenes and/or polybutylenes and blends of any of these. If the bag 14 is formed from a thermoplastic polyethylene material, the polyethylene may be a linear low density polyethylene. It is the interior of the bag 14 that forms the relative humidity maintaining compartment 12. The bag 14 is also provided with a mouth 16 which is configured to be selectively opened and retainingly closed so that produce (not shown) can be placed in or removed from the compartment 12. The mouth 16 can be provided with any conventional mechanism 18 for maintaining it in a closed configuration when such is desired while still being able to access the compartment 12 through the mouth 16. Such configurations are well known to those of skill in the art and include, for example, Dow Chemical Co. ZIPLOC® brand closing mechanisms, VELCRO® brand closing mechanisms, an adhesive flap or a deformable wire which can be wrapped around the mouth 16 of the bag 14 when it is in a gathered and closed configuration. In order to increase the time that produce can be stored, the bag 14 is desirably formed from a material which substantially prohibits the passage of gaseous oxygen and microbes into the compartment when the mouth is closed. In some embodiments, the bag 14 may be formed from a material which is transparent so that the condition of the contents of the compartment 12 can be ascertained by an individual without the necessity of opening the container 10. Those of skill in the art will readily recognize that bags 14 of this type are readily available from a wide variety of sources. For example, such bags can be obtained from most grocery stores under the trade designation, for example, Dow Chemical Co. ZIPLOC® brand storage bags.

In some embodiments the bag 14 may be formed from a material which is more permeable to gaseous carbon dioxide than to gaseous oxygen. In particular, the material would generally allow passage of gaseous carbon dioxide out of the compartment 12 when the mouth 16 of the bag 14 is closed.

The second component of the container 10 is a moisture controlling device 20 which is located within the compartment 12. When produce is placed in the compartment 12 and the mouth 16 of the bag is closed, the device 20 allows the humidity within the compartment 12 to be maintained at a high level. That is, the device allows the relative humidity to be maintained within the closed compartment 12 in the range of from at least about 80 percent to less than 100 percent for an extended period of time. The device 20 also is capable of wicking condensed water vapor (liquid water) off of and away from the surface of any produce with which the device 20 comes into contact. In this regard the device 20 acts to retard, if not eliminate, an environment conducive to the growth of bacteria or other harmful organisms. In some embodiments, the moisture controlling device 20 may be formed from a one layered structure 22 as is illustrated in cross-section in FIG. 2. Alternatively, the device 20 may be multi-layered 22, 24 as is illustrated in cross-section in FIG. 3. In either case, at least one of the layers 22 may desirably be formed, in whole or part, from cellulose. The cellulose so utilized may be one or more of several different types. For example, the cellulose may be in the form of cellulose sheet, tissue, paper towel, paper, bacterially produced cellulose, wood pulp, wood fluff pulp, cotton, cotton liners, rayon (reconstituted cellulose) . Those of skill in the art will readily recognize that cellulosic sheets etc. of these types are readily available from a wide variety of sources. For example, such sheets can be obtained from the Kimberly-Clark Corporation under the trade designation HI-DRI® paper towels.

In some embodiments, the layer 22 of the moisture controlling device 20 which is desirably formed, in whole or part, from cellulose, may be formed from a matrix 26 of a thermoplastic web 28 and hydrophilic cellulosic particles 30. Such a matrix 26 is illustrated in cross-section in Fig. 4. The web 28 may be formed from one or more materials including meltblown webs, spunbonded webs and apertured films. The matrix 26 may include a meltblown web and hydrophilic cellulosic particles, a spunbonded web and hydrophilic cellulosic particles or a bonded carded web. Where the components 28, 30 of the matrix 26 are a spunbonded web and hydrophilic cellulosic particles, the matrix 26 may be hydroentangled to produce a spunlaced matrix. Those of skill in the art will readily recognize that these materials are readily available from a wide variety of sources. For example, such meltblown, spunbonded and coformed materials can be obtained from the Kimberly-Clark Corporation.

The hydrophilic cellulosic particles 30 utilized in the matrix may be selected from one or more of the group including cellulose sheet particles, tissue particles, paper towel particles, paper particles, bacterially produced cellulose particles, wood pulp particles, wood fluff pulp particles, cotton, cotton linters, rayon particles (reconstituted cellulose) .

As was previously stated, the moisture controlling device 20 is capable, in the presence of produce (fruits, vegetables etc.), of allowing the relative humidity to be maintained within the compartment 12 when the mouth 16 is closed at a high level while still being capable of wicking pooled and/or condensed liquid water off of and away from the surface of the contents of the container 10. For example, the device 20 is capable of allowing the relative humidity to be maintained within the range of from at least about 80 percent to less than 100 percent. More particularly, within the range of from at least about 80 percent to less than about 95 percent. Even more particularly, within the range of from at least about 85 percent to less than about 95 percent. Yet even more particularly, within the range of from at least about 85 percent to less than about 90 percent.

It has been found that the device 20 is capable of allowing the relative humidity within the compartment 12 to remain within these desired ranges because of the attributes of cellulose fibers in that they: (1) rapidly wick and absorb standing water which contacts them but; (2) only weakly absorb surrounding water vapor. This later point, stated another way, means that cellulosic materials generally have a much higher relative humidity equilibrium point, for a given moisture loading, than other types of absorbents. That is, cellulosic materials will more readily transpire wicked water in the form of water vapor than, for example, superabsorbent materials and, in particular, inorganic desiccants which do not readily release moisture in the form of water vapor. This higher relative humidity equilibrium point allows the container 10 of the present invention to maintain high relative humidity for an extended time when the mouth 16 of the bag 14 is closed. In contrast, if a superabsorbent material was utilized as the particulate material 30 for the moisture controlling device 20, the superabsorbent material would readily wick and absorb the standing liquid water with which it came in contact. However, the superabsorbent material also more strongly holds water vapor and, accordingly, would act as a desiccant within the closed confines of the compartment 12. This action would greatly hasten the wilting of produce or the like contained within the compartment 12. Put yet another way, it can be stated that, in contrast to superabsorbent materials and inorganic desiccants, the present invention, because of the higher relative humidity equilibrium point of cellulosic materials, creates a system which is interactive with the moisture humidity in the environment of the closed compartment 12 in that, when the compartment 12 is opened and thereafter closed, the moisture controlling device 20 readily responds to the concomitant lowering of the relative humidity within the compartment 12 by interactively giving off water vapor to re- establish the desired high relative humidity range of at least about 80% to 100%.

Those of skill in the art will, upon reflection on the present specification, readily recognize that the amount of hydrophilic cellulosic material necessary to allow maintenance of the desired relative humidity ranges and also properly wick moisture away from the produce will vary with the size of the compartment 12 and the type of fruit and/or vegetable(s) the container 10 is designed to store. Additionally, the amount of hydrophilic cellulosic material necessary to rapidly wick moisture while achieving the desired relative humidity ranges will also vary depending upon the type of hydrophilic cellulosic material utilized. However, generally speaking, at least about one (1) gram of hydrophilic cellulosic material should be present in the moisture controlling device 20 per 300 grams of produce to be contained in the container 10. More particularly, at least about two (2) grams of hydrophilic cellulosic material should be present in the moisture controlling device 20 per 300 grams of produce to be contained in the container 10. Even more particularly, at least about four (4) grams should be present in the moisture controlling device 20 per 300 grams of produce to be contained in the container 10. An additional factor affecting the function of the present invention, at least as regards to the capability of the device 20 to readily wick pooled water off of produce contained within the compartment 12, is the degree of contact between the exterior surface of the contents of the container 10 and the surface of the device 20. Naturally, the greater the degree of surface-to-surface contact between these two surfaces, the greater the likelihood that the device 20 will be able to rapidly wick pooled water from off of the surface of the stored contents. Accordingly, it is generally desired that the moisture controlling device 20 be sized to cover at least about 20% of the surface of the compartment 12. For example, the moisture controlling device 20 may be sized to cover at least about 30% of the surface of the compartment 12. More particularly, the moisture controlling device 20 may be sized to cover at least about 40% of the surface of the compartment 12. Even more particularly, the moisture controlling device 20 may be sized to cover at least about 50% of the surface of the compartment 12. That is, at least about 75% of the surface of the compartment 12 may be covered by the device 20. In some embodiment, at least as much as 90% of the surface of the compartment 12 may be covered by the moisture controlling device 20.

As earlier stated, in some embodiments, (See FIG. 3.) the moisture controlling device 20 may be formed from first 22 and second 24 juxtaposed and joined layers with the first layer 22 being the matrix 26 of a thermoplastic web 28 and hydrophilic cellulosic particles 30 and the second layer 24 being a spunbonded web. In this embodiment the second layer 24, the spunbonded web, acts as an isolating agent so that the matrix 26 which retains wicked water, retains the wicked water substantially out of physical contact with the fruit or vegetable(s) . This lessens the likelihood of large concentrations of bacteria or other harmful micro-organisms coming in contact with the fruit or vegetable(s) because it lessens the chance that the contents of the container 10 will be subjected to excessive wetness. It is well known that excessive wetness can promote microbial growth and thus decay. It is envisioned that the present invention may be utilized in quite large embodiments which may, for example, line the interior of a transportation system such as a truck or rail car. In such situation, the bag 14 would not have to be transparent. Additionally, in such large applications, it may be necessary, in order to achieve optimum results, for the device 20 to be made up of more than one sheet with the contents of the bag 14 and the sheets of the device 20 being alternated so that pooled/condensed water located in the interior of the large bag can be rapidly wicked into the device 20. Naturally, in such a large application, the device 20 could, as stated above, be separate sheets or, alternatively, one large sheet that is, in serpentine fashion, folded back and forth to effect sandwiching of the contents.

In some embodiments, where consumer inspection of the produce is desired, the bag 14 may be formed from a transparent material so as to allow visual inspection of the contents of the container 12. Alternatively, as will be discussed more thoroughly below, the device 20 can be configured to allow greater ease of viewing the contents.

FIG. 5 illustrates yet another embodiment of the present invention where the moisture controlling device 20 is configured to define one or more apertures 32 adapted to provide an enhanced view of produce contained within the container 10.

The container 10 may be sold in a prefabricated form as an integral unit or the bag 14 and the device 20 may be sold separately. For example, the device 20 could be sold in a rolled sheet form which could be regularly perforated so that various sizes of sheet could be removed from the roll. Thus, a consumer would form the device 20 by tearing off a portion from a roll of such sheet material. Thereafter, the consumer would wrap the produce in the device 20 to the extent necessary and insert the wrapped produce into a bag 14 and close the mouth 16 of the bag 14 for subsequent storage of the produce. FIG. 6 is a schematic illustration of a method for forming the container 10 of the present invention. Supply roll 34a, 34b supply the material from which the bag 14 is manufactured. Supply rolls 36a, 36b supply the material from which the device 20 is formed. Layers from each of the rolls are juxtaposed with the layers 36a, 36b being sandwiched between the layers 34a, 34b by a pair of nip rollers 38. Thereafter, a conventional sealing/perforating bar 40 forms the seal which creates the bottom of each bag 14 and also perforates the layers in the cross-machine direction so that individual bags 14 can be separated as desired. Also, conventional side sealing devices 42 seal the for layers together along their machine direction periphery to unify the side edges of the bags 14. Lastly, the still unified roll of bags 14 is wound up on storage roll 44.

FIG. 7 illustrates yet another embodiment of the present invention. In this embodiment of the container 10 , the moisture controlling device 20 is, itself, in the form of a bag 46. The mouth 48 of the bag 46 may desirably be provided with a closing mechanism equivalent to the mechanism 18 of the bag 14. Alternatively, the mouth 48 of the bag 46 may be provided with a conventional elastic periphery 50 so that the mouth 48 of the bag 46 can be stretched open to receive produce but will then retract back into snug contact with the contents (not shown) of the bag 46. As is pictured in FIG. 7, in this embodiment it is desirable for the bag 46 to define view ports 32 so that the condition of the contents of the bag 46 can readily be viewed without the need for opening it. Once an item to be stored is placed within the bag 46, the bag 46 is then placed within the bag 14 and the mouth 16 of the bag 14 is closed using the mechanism 18.

The invention will now be discussed with regard to specific examples which will aid those of skill in the art in a full and complete understanding thereof. EXA PLE 3-

An experiment was conducted on a group of romaine lettuce heads of substantially the same form and appearance. Each head of lettuce weighed approximately 7 ounces. Because the heads of lettuce were obtained from the same batch at the same source, it is assumed that they all were (1) harvested at about the same time; and (2) subjected to substantially the same treatment. Seven of the heads of lettuce were selected to evaluate seven different packaging systems.

The first head of lettuce was placed in a 10.5 inch by 12 inch polyethylene bag having a ZIPLOC® brand closure. The bag was then sealed using the provided integral ZIPLOC® brand closure.

The second head of lettuce was placed in a polyethylene bag identical to the bag into which the first head of lettuce was placed. Also placed inside of the bag was a two layer composite sheet. The sheet was approximately eight inches by sixteen inches in size. The first layer of the sheet was coformed and the second layer was spunbonded polypropylene treated for wettability with Triton X102® brand surfactant, a food-grade surfactant, which can be obtained from the Rohm and Haas Chemical Company of Philadelphia, Pennsylvania. Triton X102® brand surfactant is known by those of skill in the art to be an octylphenoxypolyethoxyethanol. The treatment with Triton X102® brand surfactant consisted of applying about 0.016 weight percent of the Triton X102® brand surfactant to the first layer of the sheet, and about 0.08, weight percent, to the second layer of the sheet. The coformed layer was approximately 70%, by weight, processed wood pulp and 30%, by weight, meltblown polypropylene. The basis weight of the sheet was about 225 grams per square meter (gsm) . The basis weight of the coformed layer was about 190 gsm. The basis weight of the spunbonded layer was about 35 gsm. In this experiment, the sheet was sized so that it would cover about 58% of the surface of the interior of the bag. That is, about 58% of the surface of the compartment.

The third head of lettuce was placed in a polyethylene bag identical to the bag used for the first head of lettuce. Also placed in the bag was a 2-ply pulp tissue sheet which was 11 inches by 9 inches in size. The pulp tissue sheet weighed about 8.5 grams. The pulp tissue sheet was wrapped around the head of lettuce in a manner substantially identical to the sheet wrapped around the second head of lettuce. That is, so that it would cover about 58% of the surface of the interior of the bag. That is, about 58% of the surface of the compartment.

The fourth head of lettuce was placed in a polyethylene bag identical to the bags used for the first three heads of lettuce. Before the fourth head of lettuce was placed inside its bag, it was placed inside of a HUGGIES® brand UltraTrim for Him Step 4 superabsorbing diaper containing polyacrylate superabsorbing polymer. In like manner to the second and third heads of lettuce, the diaper was wrapped around the fourth head of lettuce so that it would cover about 58% of the surface of the interior of the bag. That is, about 58% of the surface of the compartment.

The fifth head of lettuce was placed in a polyethylene bag identical to the bags used for the first four heads of lettuce with the exception that the bag was perforated about every centimeter with holes having an approximate diameter of from about 0.5 to about 1 millimeters. The function of the holes was to allow passage of gases and vapor into and out of the bag.

The sixth head of lettuce was placed in a polyethylene bag identical to the apertured bag into which the fifth head of lettuce was placed. Also placed inside of the bag was a two layer composite sheet substantially identical to the sheet utilized for the second head of lettuce. The two layer composite sheet was wrapped about the sixth head of lettuce in a manner substantially identical to the wraps of the second, third and fourth heads. That is, so that it would cover about 58% of the surface of the interior of the bag. That is, about 58% of the surface of the compartment.

The seventh head of lettuce was placed on top of a piece of the two layer composite sheet which was used to wrap the second and sixth heads of lettuce. The two layer composite sheet was approximately eight inches by eight inches in size. Thus, the seventh head of lettuce was essentially unprotected and unwrapped.

All seven heads of romaine lettuce were stored at approximately 50% relative humidity (RH) and 40 degrees Centigrade (C).

After only a few days, the seventh, unprotected, head of lettuce had wilted.

After one week, both the fifth head of lettuce, which had been stored in the perforated bag, and the sixth head of lettuce, which had been stored in the perforated bag along with a two layer composite sheet, showed obvious signs of wilting and rotting.

Between the first and second week, the first head of lettuce, which had been stored in the polyethylene bag, demonstrated signs of rotting. Also, between the first and second week of storage, the fourth head of lettuce, which had been stored in the polyethylene bag and wrapped with a superabsorbent diaper, demonstrated signs of wilting. At the end of this experiment, after 6 weeks: (1) the first head of lettuce was significantly and thoroughly rotted; (2) the fourth head of lettuce was moderately wilted; and (3) the fifth, sixth and seventh heads of lettuce were all severely wilted and rotted. By comparison, at the conclusion of this experiment, after 6 weeks, the second and third heads of lettuce were both still fresh, crisp, and edible, and showed no signs of wilting or rotting.

EXAMP E 2

A similar experiment was run as above with mung bean sprouts divided into batches which were equal in form and weighed approximately 5 ounces each. Because the mung bean sprouts were obtained from the same batch at the same source, it is assumed that they all (1) represented an equivalent stage of growth; and (2) were subjected to substantially the same treatment.

A batch of mung bean sprouts was placed into each of the six packaging systems and wrapped as described in Example l.

A seventh batch of mung bean sprouts was left unprotected on a two layer composite sheet as described with regard to the seventh head of lettuce in Example 1.

At the end of one week, (1) the first batch of mung sprouts was affected by rot and wilting to a moderate extent; (2) the fourth batch of mung sprouts was slightly effected by rot; (3) the fifth and sixth batches of mung sprouts were thoroughly rotted and very dark brown in color; and (4) the seventh batch of mung sprouts was unacceptably desiccated.

By comparison, the second and third batches of mung sprouts were both fresh and crisp with no visual evidence of rot.

EXAMPLE 3

A similar experiment was run as in Example 2 with strawberries divided into batches which were equal in form and weighed approximately 4 ounces each. Because the strawberries were obtained from the same batch at the same source, it is assumed that they all were (l) harvested at about the same time; and (2) subjected to substantially the same treatment. A batch of the strawberries was placed into each of the six packaging systems and wrapped as described in Example 1. A seventh batch of the strawberries was left unprotected on a two layer composite sheet as described with regard to the seventh head of lettuce in Example 1. At the end of one week, (1) over half of the strawberries in the first batch were wet, mushy and inedible; (2) the strawberries in the fourth batch were almost completely firm and fresh; (3) the strawberries in both the fifth and sixth batches were thoroughly mushy; and (4) the strawberries in the seventh batch were dripping wet, mushy, and thoroughly softened, with white mold.

By comparison, over 75%, by volume, of the second and third batches of strawberries were still fresh and firm with the remainder showing some signs of softening.

EXAMPLE 4

The procedures of Example 3 were repeated with the exception that the strawberries were observed for three weeks.

After three weeks, (1) the strawberries in batches one, two and three were still firm but showed signs of mold in about ten percent of the strawberries; (2) the strawberries in the fourth batch were more damaged with about fifty percent of them rotting; (3) the strawberries in the fifth and sixth batches were completely covered with a layer of green-grey mold with no signs of the red strawberry showing through; and the strawberries in the seventh batch were severely dried out with about twenty percent of the surface covered with a white mold.

It is to be understood that variations and modifications of the present invention may be made without departing from the scope of the invention. It is also to be understood that the scope of the present invention is not to be interpreted as limited to the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the foregoing disclosure.

Claims

WHAT IS CLAIMED IS:

1. A produce storage container defining a relative humidity maintaining compartment, the container comprising: a bag defining: the relative humidity maintaining compartment; and a mouth which is adapted to be selectively opened and retainingly closed whereby produce can be placed in or removed from the compartment; and wherein the bag is adapted to substantially prohibit the passage of gaseous oxygen into the compartment when the mouth is closed; and a moisture controlling device located within the compartment and adapted, when produce is placed in the compartment and the mouth closed, to: maintain a relative humidity within the compartment of from at least about 80 percent to less than 100 percent; and wick water away from the produce.

2. The produce storage container of claim 1, wherein the bag is further adapted to allow passage of gaseous carbon dioxide out of the compartment when the mouth is closed.

3. The produce storage container of claim 1, wherein the bag is formed from at least one material selected from the group consisting of thermoplastic materials and solvent cast materials.

4. The produce storage container of claim 3, wherein the thermoplastic material is selected from the group consisting of one or more polyolefins.

5. The produce storage container of claim 1, wherein the moisture controlling device comprises cellulose.

6. The produce storage container of claim 5, wherein the cellulose is selected from the group consisting of cellulose sheet, tissue, paper towel, paper, wood pulp, fluff pulp, cotton, cotton linters, rayon and bacterially produced cellulose.

7. The produce storage container of claim 5, wherein the humidity maintaining device consists essentially of cellulose.

8. The produce storage container of claim 1, wherein the moisture controlling device is a bag.

9. The produce storage container of claim 8, wherein the bag defines view ports.

10. A produce storage container defining a relative humidity maintaining compartment, the container comprising: a bag formed from a thermoplastic polyolefin, the bag defining: the relative humidity maintaining compartment; and a mouth which is adapted to be selectively opened and retainingly closed whereby produce can be placed in or removed from the compartment; and wherein the bag is adapted to substantially prohibit the passage of gaseous oxygen into the compartment when the mouth is closed; and a moisture controlling device comprising matrix of a thermoplastic web and hydrophilic cellulosic particles, the device being located within the compartment and adapted, when produce is placed in the compartment and the mouth closed, to: maintain a relative humidity within the compartment of from at least about 80 percent to less than 100 percent; and wick water away from the produce.

11. The produce storage container of claim 10, wherein the bag is further adapted to allow passage of gaseous carbon dioxide out of the compartment when the mouth is closed.

12. The produce storage container of claim 10, wherein the thermoplastic polyolefin is selected from the group consisting of polyethylenes, polypropylenes and polybutylenes.

13. The produce storage container of claim 12, wherein the polyethylene is a linear low density polyethylene.

14. The produce storage container of claim 10, wherein the thermoplastic web is selected from the group consisting of meltblown webs, spunbonded webs and apertured films.

15. The produce storage container of claim 10, wherein the moisture controlling device is formed from one or more materials selected from the group consisting of coformed materials, bonded carded web materials and spunbonded materials.

16. The produce storage container of claim 15, wherein the spunbonded material is spunlaced.

17. The produce storage container of claim 10, wherein hydrophilic cellulosic particles are selected from one or more of the group consisting of cotton, cotton linters, rayon, wood pulp and bacterially produced cellulose.

18. The produce storage container of claim 10, wherein the moisture controlling device is adapted to maintain the humidity within the compartment in the range of from at least about 80 percent to less than 95 percent.

19. The produce storage container of claim 10, wherein the moisture controlling device is adapted to maintain the humidity within the compartment in the range of from at least about 85 percent to less than 95 percent.

20. The produce storage container of claim 10, wherein the moisture controlling device is adapted to maintain the humidity within the compartment in the range of from at least about 85 percent to less than 90 percent.

21. The produce storage container of claim 10, wherein the moisture controlling device is a bag.

22. The produce storage container of claim 21, wherein the bag defines view ports.

23. A produce storage container defining a relative humidity maintaining compartment, the container comprising: a bag formed from a thermoplastic polyolefin, the bag defining: the relative humidity maintaining compartment; and a mouth which is adapted to be selectively opened and retainingly closed whereby produce can be placed in or removed from the compartment; and wherein the bag is adapted to substantially prohibit the passage of gaseous oxygen into the compartment when the mouth is closed; and a moisture controlling device comprising first and second juxtaposed and joined layers with the first layer comprising a matrix of a thermoplastic web and hydrophilic cellulosic particles and the second layer comprising a spunbonded web; the device being located within the compartment and adapted, when produce is placed in the compartment and the mouth closed, to: maintain a relative humidity within the compartment of from at least about 80 percent to less than 100 percent; wick water away from the produce; and maintain wicked water out of contact of the produce.

24. The produce storage container of claim 23, wherein the bag is further adapted to allow passage of gaseous carbon dioxide out of the compartment when the mouth is closed.

25. The produce storage container of claim 23, wherein the thermoplastic polyolefin is selected from the group consisting of polyethylenes, polypropylenes and polybutylenes.

26. The produce storage container of claim 25, wherein the polyethylene is a linear low density polyethylene.

27. The produce storage container of claim 23, wherein the thermoplastic web is selected from the group consisting of meltblown webs, spunbonded webs and apertured films.

28. The produce storage container of claim 23, wherein the moisture controlling device is formed from one or more materials selected from the group consisting of coformed materials, bonded carded web materials and spunbonded materials.

29. The produce storage container of claim 28, wherein the spunbonded material is spunlaced.

30. The produce storage container of claim 23, wherein hydrophilic cellulosic particles are selected from one or more of the group consisting of cotton, cotton linters, rayon, wood pulp and bacterially produced cellulose.

31. The produce storage container of claim 23, wherein the moisture controlling device is adapted to maintain the humidity within the compartment in the range of from at least about 80 percent to less than 95 percent.

32. The produce storage container of claim 23, wherein the moisture controlling device is adapted to maintain the humidity within the compartment in the range of from at least about 85 percent to less than 95 percent.

33. The produce storage container of claim 23, wherein the moisture controlling device is adapted to maintain the humidity within the compartment in the range of from at least about 85 percent to less than 90 percent.

34. The produce storage container of claim 23, wherein the bag is formed from a transparent material.

35. The produce storage container of claim 23, wherein the moisture controlling device defines apertures adapted to provide an enhanced view of produce contained within the container.

36. The produce storage container of claim 23, wherein the moisture controlling device is a bag.

37. The produce storage container of claim 36, wherein the bag defines view ports.