This invention relates to novel designs of tray lids and tray bases for modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, this invention relates to novel designs of landscaped lids and corresponding tray bases which enable cooling air to be circulated in single or multiple directions through stacked lid and tray combinations that contain fresh fruits, vegetables and cut flowers in a modified atmosphere environment.
The quality attributes of fresh fruits, vegetables and cut flowers should be maintained as much as possible for as long as possible to ensure consumer acceptability. Quality deterioration of horticultural produce such as fresh fruits, vegetables and flowers comes about through inherent plant tissue enzyme reactions including respiration, ripening and senescence. Deterioration also occurs through microbial growth and water loss from the tissue. A method of inhibiting the deteriorative enzyme reactions, and the growth of yeasts, molds and bacteria in fresh produce involves the reduction of the produce temperature to between 1° and 12° C., and the creation of low O2/high CO2 modified atmosphere (MA) around the produce. Another quality reducing factor is that water in fruits and vegetables can be lost readily under low relative humidity conditions thereby causing dehydration, skin wrinkling, wilting and reduction in crispness and firmness of the fruits, vegetables and flowers. The rate of water loss from such fresh produce can be restricted by storing the produce in closed package systems consisting of walls with low moisture permeability.
Corrugated paperboard boxes and cartons are used commercially for the storage and transport of fresh horticultural commodities. Advantages of corrugated paperboard boxes and cartons include relatively low cost per unit volume, low thermal energy conductivity, impact absorption which prevents bruising of commodities and ease of disposal at the receiving end of the shipping route. One type of globally used corrugated paperboard box is known as a Eurotray. It has a standard horizontal dimension of 40 cm width and 60 cm length which is compatible for storage in stacks on pallets in ISO conforming containers.
Conventional corrugated paperboard has a very high gas and moisture permeability and as such is unsuitable for modified atmosphere packaging of horticultural produce. The fresh produce industry incorporates the use of stackable corrugated fiberboard cartons or returnable plastic crates of various sizes and shapes to accommodate a wide array of fresh fruits and vegetables for transportation to market. In general, there are two broad categories of stackable fiberboard cartons used in the produce industry, namely open style cartons which incorporate apertures such as hand-holds and concavities for refrigerated air circulation and closed style cartons which do not include the apertures and concavities but incorporate selective gas permeable membranes to limit gas exchange between the interior headspace of the sealed cartons and ambient atmosphere.
Open style cartons are advantageous because they allow for direct field packing of the harvested produce in the cartons, followed by refrigeration and shipment to market. The simple packaging and cooling of the produce provides significant time, labor and cost savings. A main disadvantage of this type of packaging is that the free movement of oxygen around the harvested produce maintains produce respiration rates and thus reduces the amount of time the produce can be stored and/or transported without quality deterioration. To offset some of these deleterious effects, produce is conventionally harvested earlier in the growing season while the produce is still green. This is before optimal nutritional values and desirable tastes have developed in the produce, thus reducing the quality of the produce delivered to market. Another disadvantage of the open style packaging is the minimal protection afforded to ambient temperature fluctuations frequently encountered during transportation to market.
Closed style cartons, known also as modified atmosphere packaging (MAP), have an advantage because the produce can be harvested when ripe. Such packaging of fruits, vegetables and flowers involves:
During storage, the fruits, vegetables and flowers respire and convert O2 from the headspace to CO2 with the result that the O2 content in the headspace decreases while the CO2 content increases. The respiring fruits, vegetables or flowers generate heat which offsets refrigeration. An objective in the design of an effective package system for MAP of fresh produce is to regulate the influx of O2 into the package and the efflux of CO2 from the package headspace. In this way, it is possible to achieve and maintain a desirable low O2, high CO2 modified equilibrium atmosphere and controlled temperature in the headspace around the stored produce for optimum retention of the fresh quality attributes and for the reduction of microbial growth while the fruits, vegetables and flowers are being shipped from source to destination, and storage at the destination.
Low levels of O2 and elevated levels of CO2 in the headspace around a horticultural commodity reduce the respiration and ripening rates, and the growth of spoilage organisms (spoilogens) of the commodity. Unsuitable modified atmospheres around fresh produce in a package system can induce physiological damage, inhibit wound healing, enhance senescence and cause formation of off-flavor components in the produce. Oxygen levels of less than 1% vol. bring about anaerobic respiration and off-flavor development, whereas CO2 levels of about 10% vol. or higher inhibit microbial growth. CO2 levels greater than 20% vol. over an extended period may cause tissue damage to CO2-sensitive fresh produce.
Package systems for MAP must be designed and constructed with specific packaging materials to meet the following requirements:
The gas and moisture permeabilities of the package components of MA package systems are critical parameters. The technology of plastic polymeric films has advanced to such an extent that a specific gas permeability requirement can be met with a single plastic film or a multi-layer film combination, with or without vent pinholes.
In 1960, Eaves (J. Hort. Sci. 37:110, 1960) reported the effectiveness of gas-permeable, flexible polymeric barrier film as a package system for extending the life of fresh commodities. Tomkins (J. Appl. Bacteriol. 25:290, 1962) used polymeric film-covered trays as package systems to determine their effectiveness in establishing equilibrium MA around apples. Prior art on the use of bags made from polymeric plastic, gas permeable film such as polyethylene and polyvinylchloride, for prolonging of shelf-life of stored fruits and vegetables, is exemplified by U.S. Pat. No. 3,450,542, Badran, U.S. Pat. No. 3,450,544, Badran et al., and U.S. Pat. No. 3,798,333, Cummin. A more complex package system has been described by Rumberger (U.S. Pat. No. 3,630,759) in that an inner plastic pouch containing the produce is enveloped by an outer pouch containing an atmosphere of less than 15% O2. Both pouches are to be constructed from gas-permeable films.
U.S. Pat. No. 5,575,418, issued 19 Nov. 1996, Wu et al., relates to novel package systems for refrigerated modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, the patent discloses the design, construction, closure, sealing and use of gas-permeable corrugated paperboard package systems for prolonging the storage life of fresh fruits, vegetables and cut flowers under modified atmosphere in the headspaces of the closed package system. The corrugated gas permeable paperboard comprises: (a) a first layer of kraft paper; (b) a layer of polymer having a gas permeability which permits gas to be transmitted through the polymeric film at prescribed levels; (c) a second layer of kraft paper, said first and second layers of kraft paper sandwiching the polymer between them; (d) a corrugated fluting; and (e) a third layer of kraft paper affixed to the corrugated fluting.
U.S. Pat. No. 5,609,293, issued 11 Mar. 1997, Wu et al., relates to the design, construction and use of lined or coated corrugated paperboard package systems (e.g. boxes, cartons) for prolonging the storage life of fresh fruits and vegetables under modified atmospheres (MA) in the headspaces of the closed package systems. The plastic-paperboard construction comprises a first layer of polymeric film, a second layer of kraft paper adjacent the first layer, a kraft paper corrugated flute adjacent the second layer and a fourth layer of kraft paper adjacent the flute.
U.S. Pat. No. 6,050,412, issued 18 Apr. 2000, Clough, et al., relates to a novel method and apparatus for packaging and shipping horticultural products including cut flowers. In particular, the patent discloses a novel method of and packaging for packaging cut flowers in a modified atmosphere package to prolong shelf life in shipping the packaged flowers to the destination, and then at the destination, opening the package and rehydrating the cut flowers in the package by saturating the stems of the flowers with water.
Patent Cooperation Treaty application Serial No. PCT/CA2006/001404, 25 Aug. 2006, discloses novel Eurotray compatible package systems for refrigerated modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, the application relates to the design, construction, closure, sealing and use of gas-permeable paperboard package systems and shipping trays for prolonging the storage life of fresh fruits, vegetables and cut flowers under modified atmosphere in the headspaces of the closed package system. A gas permeable paperboard comprising: (a) a first layer of kraft paper; (b) a layer of polymer having a gas permeability which permits gas to be transmitted through the polymeric film at prescribed levels; (c) a second layer of kraft paper, said first and second layers of kraft paper sandwiching the polymer between them.
None of the foregoing cited references discloses a stackable lid and tray system which incorporates modified atmosphere technology, allows single or dual angular direction cooling and ventilation of stacked and/or palletized packages or facilitates visual inspection of the package contents without opening the sealed package.
There is a need for a closed stackable lid and tray package system which incorporates modified atmosphere technology, allows harvesting and packaging of produce in either the field or in a centralized facility, allows single or dual direction of cooling and ventilation of stacked and/or palletized packages to offset produce respiration, allows visual inspection of the packaged produce at any point following packaging and provides the ability to refrigerate the fresh produce during transit.
U.S. Pat. No. 6,880,748,B2, Machado, discloses a modified atmosphere packaging system and method which allows field and/or centralized facility packing of fresh produce and refrigerated air to circulate throughout a palletized stack of cartons. The packaging includes a transparent lid with raised stacking supports at the four corners. The lid is sealingly attached to a corrugated fiberboard carton with a gas permeable membrane. The transparent lid allows for inspection of perishable produce contained therein without breaching an established modified atmosphere. A problem with this system is that when the cartons are stacked on one another, unless care is taken to ensure that the upper carton is squarely mounted on the lower carton, the lower corners of the upper carton can miss the corner supports and drop into the grooves in the lid on the lower carton. Another shortcoming is that the total surface area of the raised supports at the four corners of the carton is not large and load bearing capability is minimized.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.
The invention is directed to a gas-permeable modified atmosphere package combination comprising a lid constructed of a polymer, the lid in one embodiment having on the top surface thereof at the mid-regions of each side a plurality of raised load supports and in between grooves; and a base with a hollow interior constructed of corrugated kraft paper polymer and having a configuration at the top edges which conforms with the interior profile of the lid; the grooves enabling air to be circulated over the lid when one package combination is stacked on another.
The top surface of the lid can have around its periphery at least one raised load support in the mid-region of each end and at least one raised load support in the mid-region of each side, and a depressed area between the raised end and side load supports. The top surface of the lid can have around its periphery at least two raised load supports in the mid-region of each end and at least three raised side supports in the mid-region of each of the two sides of the lid, and a depressed area between the raised end and side load supports. The top surface of the lid can have around its periphery at least two raised load supports in the mid-region of each end and at least four raised side supports in the mid-region of each of the two sides of the lid, and a depressed area between the raised end and side load supports.
The corners of the top surface of the lid can have diagonal grooves therein. The grooves at the sides of the lid can be disposed laterally while the grooves at the ends of the lid can be disposed longitudinally. The grooves of the surface of the lid can have an “X” type pattern. The lid and the base can be 60 cm in length and 40 cm in width.
The base can comprise a first outer layer of kraft paper, a first intermediate layer of corrugated kraft paper, a second intermediate layer of polymer and a second outer layer of kraft paper. The polymer in the base can be selected from the group consisting of ethylene vinylacetate (EVA), ethylbutyl acetate (EBA), a crosslinked ionomer resin, cast polyester (PET), a polyamide and polycarbonate (PC). The polymer can be low density polyethylene or high density polyethylene, or a copolymer of low density polyethylene and ethylenebutylacetate.
The gas permeability of the polymer of the base can be between about 50 and 100,000 cc3/m2 24 hr. 1 atm.
The invention is also directed to a lid for a gas-permeable modified atmosphere package comprising a top surface which can be rectangular or square, said surface including a plurality of raised load supports and in between grooves arranged around its periphery, the grooves enabling air to be circulated over the lid when one package is stacked on another.
Each end of the lid can have in the mid-region thereof at least one raised load support and each side of the lid can have in the mid-region thereof at least one raised load support and a depressed area can exist between the raised end and side load supports. Each end of the lid can have in the mid-region thereof at least two raised load supports and each side of the lid can have in the mid-region thereof at least three raised side supports. Each end of the lid can have in the mid-region thereof at least three raised load supports and each side of the lid can have in the mid-region thereof at least four raised side supports.
The grooves at the sides of the lid can be disposed laterally while the grooves at the ends of the lid can be disposed longitudinally. The top surface of the lid can have diagonally disposed grooves at each of the four corners of the lid. The lid can be formed of transparent polymer.
The lid can have a planar top surface and can be formed of a transparent material. The top surface of the lid can be quadrilateral such as square or rectangular and the transparent material can be a transparent polymer. The lid can be deployed on a hollow base constructed of paperboard.
The lid can be formed of transparent polymer, can have a top surface with a square configuration and a plurality of raised load supports and in between grooves positioned around its periphery. The raised supports can be located at the mid-regions or the corners of the top sides of the lid.
In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.
Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.
Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
To deal with the long distance and the time required for continental and overseas shipment of MAP preserved fruits, vegetables and flowers, we have invented a unique family of lids having an uneven top surface comprising a series of raised load bearing areas around the circumference of the lid and grooves between the raised areas and a central depressed area. In one aspect, the invention includes a family of corresponding congruent tray base designs. Together the lid and tray base can be used for the shipment of fresh fruit such as grapes, peaches, nectarines and the like, vegetables such as sweet peppers, spinach, lettuce, tomatoes and the like, and fresh flowers in a modified atmosphere environment.
In one preferred version of the lid and tray base, the lid and tray base can measure 60 cm by 40 cm to conform with Eurotray standards. The modified Eurotray, according to the invention, has a top lid surface incorporating a plurality of raised supports around the circumference and a plurality of in between grooves. The grooves enable cooling air to circulate between Eurotrays when such trays are stacked on a pallet and stored in a refrigerator or shipped in an ISO conforming container. The cool air circulated through the stacked Eurotrays helps to offset heat generated by the respiring vegetables, fruit or flowers packaged in the Eurotrays. The top surfaces of the raised areas can be roughened or have a friction creating pattern thereon to enhance grip between trays when stacked.
A common request from customers of packaged fruits, vegetables and flowers is a capability of viewing the packaged product without opening the package. The lid of the subject invention is preferably formed of a transparent polymer.
Since the packaged product is refrigerated and since moisture is present in the interior of the package from respiration of the packaged fruit, vegetables or flowers, the interior of the lid typically collects condensation. The raised supports and grooved lid can, if desired, be molded from a polymer which contains an anti-fog agent. Alternatively, a moisture resistant agent can be applied to the interior surface of the lid.
A common problem with conventional modified atmosphere packaged fruit, vegetables or flowers is that they are packaged in corrugated paperboard containers which inherently provide insulation, which retains heat. If the fruit or vegetable product in the package is warm, time is required to cool the packaged fruit, vegetables or cut flowers to acceptable modified atmosphere refrigeration levels. A transparent lid is useful because it is reasonably heat conductive and transmits respiration heat from the packaged produce to the atmosphere, whereas conventional corrugated linerboard packaging inhibits heat transmission. The grooved surface of the lid enables cooling air to be circulated through stacked trays and thereby cool the produce quickly to refrigeration temperatures, and subsequently to maintain the produce in a cool condition.
Specific embodiments of the invention will now be discussed in association with the drawings.
The modified lid and tray base are preferably sized to standardized shipping container specifications (ISO specifications), namely 40 cm width×60 cm length. The grooves in lid 2 of
Storage life of fresh fruits and vegetables is dependent on storage temperature, gas composition around the produce and degree of physical abuse leading to bruises, abrasions and cuts. Storage and transportation of fruits and vegetables is facilitated by the packing of the produce in suitable package systems which provide features such as prolonging storage life, reducing physical abuse and lowering the rate of water loss of produce.
Corrugated paperboard boxes and cartons are used commercially for the storage and transportation of fresh fruits and vegetables for the following reasons:
Corrugated paperboard has very high O2 and CO2 permeabilities, so this material by itself is generally unsuitable for the construction of MA package systems. However, in the MAP lid and base package according to the invention, the base can be formed of a paperboard construction with an intermediate gas permeable film as disclosed in U.S. Pat. Nos. 5,574,418 and 5,609,293. By utilizing a gas-permeable polymer in the paperboard construction, the lid can be customized to provide a gas barrier or specific gas and moisture permeabilities.
In some cases, it may be advisable to have the lid formed of a gas permeable polymer. The gas permeable polymeric lid can be formed from homopolymers or copolymers produced as a monolayer or coextruded layers with specific formulation and caliper selected to produce the required oxygen (O2) and carbon dioxide (CO2) permeabilities. The polymers are usually selected from the polyolefin family, typically Low Density Polyethylene (LDPE), linear low density polyethylene (LLDPE), medium and high density polyethylene (MDPE and HDPE), polypropylene (PP). However, other polymers such as ethylenevinylacetate (EVA), ethyl butyl acetate (EBA), ionomer resins (cross-linked), cast polyester (PET), nylon (polyamide) and polycarbonate (PC) may also be considered.
A further unique embodiment of this invention is the ability of the base and lid to maintain internal equilibrium under varying gas compositions in the headspace. The gas permeability of the base and lid prevents a vacuum condition developing which can occur in conventional MAP systems if the packaged produce begins to absorb carbon dioxide. If such conditions were to develop in the permeable base and lid, the controlled influx of gases through the gas permeable polymer film in the base will not allow a deleterious vacuum to develop in the interior headspace of the lid and base.
For specific product applications, the rate of gas exchange within the base and lid combination may be achieved by controlled film porosity of the gas permeable intermediate polymer film layer. Porosity may also be achieved by piercing predetermined holes through the polymer containing inner liner either at the corrugating stage, die cutting operation, box forming stage, or in the completed box. Hole size, either single or multiple, may vary depending on the required gas exchange rate but typical hole diameters would be in the range of 0.25 to 2.00 mm. Hole positions on the base or lid will vary depending on the optimum location for each packaged product and the gas flow dynamics within the base and lid combination. Once the produce is packaged in the base and lid combination, the lid, if desired, can be sealed to the base by tape or some other sealing mechanism.
The oxygen (O2) and carbon dioxide (CO2) gas exchange rates through the lid and base of the invention should preferably be within the range 50-100,000 cc3/m2 24 hr. 1 atm.
It has also been found that the following additional factors must be critically controlled if consistent polymer characteristics are to be achieved:
The base, preferably of Eurotray dimensions, may be constructed of multiple layers of kraft paper, or of a plastic film membrane sandwiched between two sheets of kraft paper to form a tri-layer complex. The film membrane may be a gas-permeable plastic film or a plastic coating applied to one of the sheets of kraft paper, and then sealed between the two adjoining sheets. The membrane can be bonded to both of the kraft paper sheets when the plastic is in semi-molten state and the two paper sheets are pressed together.
When 25 g/m2 low density polyethylene was used, and extrusion laminated on 40 g/m2 and 125 g/m2 MG kraft, the O2 and CO2 permeabilities were 1300 and 2200 cc/m2 24 hr. 1 atm. respectively. When a 35 g/m2 coating of 17% EBA and LDPE was extrusion laminated, the O2 and CO2 permeabilities were 2300 and 4700 cc/m2 24 hr. 1 atm. respectively.
Studies have been carried out on fruits and vegetables packaged in sealed polymeric, plastic film bags in a corrugated paperboard box (Prince, 1989). However, several disadvantages of using a bag-in-a box are evident:
A benefit of injecting gas into an hermetically sealed MA box is that it is possible to include a trace gas, typically helium or sulphur hexafluoride as a leak detection method. Provided the MA box is relying on gas permeability and not porosity, it is possible to sense gas escape through cracks, unwanted pinholes or faulty glue seals.
Upon the insertion of a gas nozzle into the inlet aperture and upon the flow of the pressurized gas mixture through the headspace of the package system, plugs with vent pinholes or styrofoam plugs can be used for produce with high respiration rates and gas-impermeable plastic plugs may be used for low respiration rate produce.
While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
Number | Date | Country | Kind |
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PCT/CA2007/001056 | Jun 2007 | CA | national |