CA2072996C - Package for perishable food and horticultural products - Google Patents

Abstract

An improved package is described for use in packaging a wide variety of products, and in particular perishable food and horticultural products. The products are placed within a container of the type which establishes a modified atmosphere environment therein and is cooled, as by placing the container in contact with a cooling element partially surrounding the container. The cooling element may hold liquid which is evaporated to enhance the cool-ing. The container and cooling collar may be subjected to vacuum cooling. The container may include a mechanism to enhance the bulk gas transfer rate during the application of the vacuum while still maintaining the desired atmosphere within the container. The container atmosphere may be precharged with gas of a desired composition, In addition, fumigants may also be included therein.
The package is suitable for field packing applications in which the product, such as strawberries, is picked directly into the con-tainer surrounded by the cooling collar with the container and cooling collar being placed in an outer box or other receptacle.
The modified atmosphere package may be sealed and palletized prior to vacuum cooling.

Description

Vd0 92/042~G fC'f'/LJ591/06~41 ~~'~~J~~
A '2ACKAGE FOFt PFFt2S~IiLE FOOD
APED HORTIC'GLTURAL FRODUCT~~
BACKGROUND OF 'fNE :INVENTION
The present invention relates to packaging for perishable products and in particular, to packaging usable in both cooling and protecting the: products.
Several methods are commonly used for cooling perishable products where rapid cooling is required.
These include hydrocooling, vacuum cooling, icing and forced air refrigeration. For. example, the so-called "Desert Water Hag" operates on the principle that the evaporation of water from fabric forming the bag cools the water in the bag.
In the produce field, it is common to pick heads of lettuce and place them in waxed boxes with the box of lettuce then being hosed down with water either before or after the boxes are loaded onto a truck. Although evaporation of water from the lettuce during transportation assists in cooling the lettuce, relatively insignificant am~unts of water are absorbed by the waxed boxes and cooling is limited.. Transportation of broecoli in waxed boxes filled with ice is also known.
In addition, vacuum cooling approaches have been used for cooling produce. sn accordance with this cooling technique, the warm pr~duct is loaded into an air tight chamber or tube which is su3asequen~tly evacuated my a mechanical or steam--ejector vacuum pump to establish a partial vacuum therein.. As the t~tal gas.pressure in the tube is reduced below 'the saturation pressure of water at the temperature of the warm product (the "flash point~').
watE;r on and within the product begins to evaporate rapidly. The thermal energy reguired to provide the heat of vaporization of.this water comes predominately from the WO 92/0~82j6 P~1"/11591 /Ofi3A 1 2p~2~~~ - 2 -sensible heat (e.g. °'field heat°°) of the product. k~s a result, the product temperature begins to fall as rapid evaporation begins. Because vacuum pumps are generally very inefficient movers of condensable gases, such as , water vapor, chilled coils are provided within the tube or chamber to condense and thereby remove the liberated water vapor. These coils are chilled usually by evaporation of liquid ammonia within, the ammonia being supplied by a conventional vapor-compression refrigeration unit.
In t'he absence of air or any other restriction to water vapor movement from the product to the chilled coil, the temperature of the product will in time equilibrate with that of the coil (the coil temperature in fact being commonly used as a control variable in vacuum cooling .
operations). Under these circumstances, the rate of thermal equilibration is largely determined by product characteristics. In general, products high in readily evaporated moisture content, with high thermal conductivity and high evaporative surface-to-volume ratio, will cool more rapidly under vacuum than do other types of products. For example, lettuce and other leafy vegetables cool well under vacuum (high moisture content and high surface-to-volume ratio), while melons do not (low evaporation rate and lour surface-to-volume ratio). In addition, strawberries have not been viewed as suitable for vacuum cooling because of damage to the surface of the berries under vacuum conditions and the relatively small rise in cooling rate resulting from the vacuum conditions a,s opposed to nonvacuum refrigeration type cooling.
pne example of a prior art vacuum cooling system is described in U.S. Patent No. 4,576,014.to Miller, et al.' In these approaches, water has been known to be added to the produce by sprinkling the produce before or while the vacuum is imposed to reduce the amount of moisture removed from the produce during cooling with the water r evaporated during cooling being supplied at least in part by the water added to the system instead of entirely by the produce. In these approaches known to the inventor, CVO 92/04256 fC~'/U~91/Ofi341 ~~'~~~9a the vacuum cooled produce sprinkled with water has been packed in waxed boxes which absorb very small amounts of water. All of these methods are significantly inhibited if product "exposure°' is restricted, a~ w h2n t h2 product is packed in a plastic bag; such i;s the case where modified atmosphere packaging is used.
Modified or controlled-atmosphere packaging of fresh produce has also been heretofore utilized and offers advantages to virtually all sectors of the industry, from l0 grower-shipper to food service and retail consumers.
Benefits include reduced waste due to spoilage, enhanced quality, extended shelf life and greater consumer convenience. The essential feature of the modified-atmosphere approach to packaging is to seal the product in a package that restricts, to a predetermined degree, the exchange of gases between the product and the surroundings. Many studies have been performed on the desired gas environments for various types of products.
In general, modified-atmosphere packaging retards the four mayor causes of produce quality loss, namely dehydration, respiration, microbial spoilage and enzyme attack. The quality of cut fruits or vegetables (e. g. florets]
deteriorates much more rapidly due to these factors than if the products remain uncut. Moisture~loss from produce is governed by Pick's law of diffusion which states that the rate of vapor lass increases in direct proportion to the vapor pressure difference between the surface of the produce and the surraunding air. since at a constant relative humidity, vapor pressure iv the air nearly doubles for each 10°C temperature rise, and vapor pressure at the surface of fresh praducs is nearly 100 percent, produce will~dehydr~te nearly four times faster. at rooan temperature than at a temperature near freez?ng,.,when .
exposed' to ',dry" a,ir. A ~raodified-atmasphere. packaging ~ with a' lord ~ioist;ure permeability will prevent this loss. .: .
All'~produc~ continues to respire.~fter harvest.
.. ...
During normal reapiratian; internal carbohydrates ire t'~, 1 / U~ l 1 / 1)UJ4 1 ~o~~~o~ - ~ -.
converted into carbon dioxide, water and energy (heat) according to:
(aerobic respiration) : C6HIZO6 + 602-->6C02 + 6F~z0 +
(heat) .
y This process generally results in a, progressive deterioration in product quality. If a harvested item is , stared in an oxygen depleted environment, anaerobic respiration occurs. This latter type of respiration is essentially a fermentation process that results in the production of an assortment of organic conipouxlds that lead to undesirable flavors and odors. Anaerobic respiration is described as follows:
(anaerobic respiration) : C6H12~'6-°'~lcohOls + Acids + COz + H20 -~ (heat) .
Aerabic respiration rates can vary greatly among commodities, among varieties and even among parts of the same plant. There can be further variability due to growing conditions and post-harvest injuries, such as knife cuts, bruises, chill damage, etc. The most 2~ significant factors effecting respiration rate are the stage of maturity of the produce, temperature and storage atmosphere.
The "law of mass action" in ah~~aistry states that the rake of a chemical reaction is proportional to the concentration of each of the reactants. Thus, aerobic respiration can be slowed by either decreasing the oxygen level or increasing the carbon dioxide level of the storage atmosphere. In practice, this relationship.:, appears--to hold with the result that increasing the CCZ
level is-equally as effective as decreasing the 02.1.evel and that the results are additive. Plant sens.itivitv to COZ ranges fro~a .low tolerance, .as with 'apples., ,to, high .
tolerance, as °.~it:h. strawberries.
~nzymas ax~e.organic catalysts present in abundance in produce. After harvest, these enzyfnes tend to "spill°' from damaged, cut, bruised, ~etc, cells of produce and can lead to rapid discolorization,of light colored surfaces, such as of mushrooms and cut apples.

WO 92/04256 d~Cl'/1J~91/Ofi341 ~0'~2J~
There are two basic ways to combat this enzyme activity.
The first is through the reduction of the oxygen level in a package. Enzymatic browning rate tends to vary nearly linearly with oxygen concentration. The second approacrA
is to use enzyme inhibitors. These are components that deactivate the browning enzyme. Svulfite, citric acid and ascorbic acid additives have been 'used for this purpose.
In addition, carbon monoxide in concentrations of one to ten percent is effective as an enzyme inhi.biter and as a microbicide. Items known to benefit from small (one to five percent) concentrations of carbon monoxide include cauliflower, avocados, strawberries, tomatoes, cherries and grapes. Items known to benefit from larger concentrations (five to tan percent) include lettuce, stone fruit, melons, cantaloupe, mushrooms and citrus products.
Although bacterial diseases can cause significant decay in vegetables, most post-harvest diseases are caused by fungi. Since these organisms respire in the:same manner as the cut plant, their growth in general is controlled by the same factors (e.g. high COZ
concentration, etc.). In addition, microbial decay is dramatically accelerated under high relative humidity conditions. There are a variety of chemical treatments 2.5 used to control these pathogens, including carbon monoxide and sulfur dioxide: )elated to controlling ~aicrobial decay of produce, is the control of insects, in particular with respect to exported products which are frequently subjected to quarantine fumigant treatments.-It i~ also known to inject or charge modified-atmosphere containers with gas of a desired.;~ompositi.on for the particular products. This approach has been used, for~example, in connection with bread.whereby brad is placed in~plast9.c wrappers'which are injected,with gas of the desired environment prior to sealing the bread in..the wrappers. In audition, poultry products are packaged in high COz environments and.red meat products are packaged i.n high OZ and COZ environanents.

fcrrv u~9 w io~~m Because modified-atmUSphere packaging inhibits the action of these major causes of product quality loss, it has recently been a focus of much activity. In this regard, there is much data which de:~cribes the optimal , atmosphere for a variety of commodities. For example, the article entitled °°Post-Harvest Technology of Horticultural Crops°', by Kader, A. et al, special publication 3311, published by the University of Cali:Eornia at Davis in ' 1985, contains a table of optimal storage atmospheres for l0 a wide variety of types of prod~ice. Controlled atmosphere packaging has also been used for bakery, meat and other perishable food products. In general, it appears that one can deviate substantially prom an optimal atmosphere and still benefit. Modified-atmosphere packaging is also the subject of numerous patents, such as U.S. Patent Nos.
4,256,770 t0 Rainy; 4,515,266 to Myers; and 4,91.0,032 t0 Antoon, Jr.
Although these technologies exist, when produce is enclosed in a modified-atmosphere package, it becomes difficult to remove heat, such as heat in the produce and existing at the harvest site or field. In addition to this trapped field heat, the produce continues to warm due to the heat of respiration. As temperature rises, respiration increases exponentially, resulting in heat build up. This situation can readily lead to a loss of product quality that quickly negates 'the benefits intended with the modified-atmosphere package.
In the prior art,, due to the fact that controlled-atmosphere packaging involves the sealing of products iri'a package that restricts the exchange of gases between the''product and surroundings, conventional techniques for fi~eld.heat removal,.such,as forced-air cooling and hydro~cooling have been applied before the product is~sealed in its package and palletized. Because , 35~'tlae equipment associated with the cooling techniques is usually-a.ocated at a central location, the use of..
modified-atmosphere packaging systems generally requires that the product be shed-packed at a location remote from - ~ - ~~"~~~90 the picking location, in contradiction 'to recent trends in agriculture favoring field-packing of many fresh produce items. zn addition, if the ready escape of water vapor from the product surfaces a:.d/or its subsequent flow to a chilled condensing coil are restricted, the rate of cooling under vacuum may be significantly reduced, even in the case of otherwise readily-cooled items, such as lettuce. By their very nature as gas--flow regulating devices, typical modified-atmosphere packages would be expected to inhibit the vacuum cooling process, owing to the severely restricted rates of gas (water vapor) removal from the package.
Thus, the standard modified atmosphere approach far packing berries, such as strawberries, is to pick or harvest the berries into containers; palletize the containers of berries and refrigerate the pallets. After the berries are cooled, the pallets of berries axe wrapped in plastic and injected with an enriched COz mixture and shipped. 6~hen the pallets reach the distributors or end users, the pallets are broken apart and the benefit of the modified atmosphere packaging is lost at that point.
For most modified at~aosphere packaged produce other than berries, the produce is harvested and transported to a remote shed for cooling. The cooled produce is cut, processed and sorted. The cooled and now processed produce is theca packaged in a modified atmosphere container. This approach is costly and results in damage to the produce due to multiple handling steps and due to the delayed placement of the produce in a modified atmosphere package.
Therefore, a need eacists for a new package and packaging system for overcoming these and,othex disadvantages of the prior art. :.. : .
:.' c,pg~Y OIa, TFI~ INVFNT~~3~
.. .~ In accordance with one aspect of the. present invention, a package for perishable food. and horticultural products includ~,s a cooling element. A c~ntainer of the type providing a controlled flow of gas between the fC f/U~)1 /Ofi341 ~0"~2~~ - ~ - _ exterior and interior thereof when closed is positioned in thermal communication, and preferably in contact with, the cooling element. The cooling element may comprise a temperature heat sink element in proximity tca the exterior of the container for cooling the container. preferably, the heat sink element is in contact with or adjacent to a major portion of the exterior surface area of the exterior of the containers The heat sink element may comprise a chilled or frozen element, such.as in the for7:n of a collar. A frozen block of liquid, such as ice, may be used as the heat sink element. Vacuum cooling of the package enhances the cooling of the packaged product. Also, frozen or cooled phase change chemicals, such as potassium nitrate as water in a sealed container, may he used as the heat sixik.
Also, the heat sink may comprise a cooling element 'with a liquid holding portion which contains a liquid and which is exposed to the environment outside or exteriorly of the container such that evaporation of liquid from the liquid holding portion of the cooling element enhances the evaporative cooling of the product packed in the container. In this latter case, vacuum cooling of the cooling element enhances the evaporation of. the liquid from the cooling element and the gaoling of the exterior of the container and ~f the products packed therein even though this c~ntainer is closed to dorm a modified atmosphere environment.
The cooling element may comprise a collar which substantially surrounds the container. The cooling element and container may be integral. The cooling element cools the container such that a cold surface is provided within the container on whiclx water vapor from products within the container (assuming the products are the type whicka contain.waterj may condense. This accelerates the cooling of ahe products with or without an applied vacuum: _~
The cowta~.nar may be of a film or films or other material which controls the flow of oxygen and carbon tV0 92/()4256 fC('/US93/06341 ~~'~299c~
dioxide between the interior and exterior thereof and may also have a water permeable portion so as to permit water vapor to pass from the interior to the exterior of the container. .
In accordance with a specific aspect of the present invention, the liquid holding portion of a liquid evaporative type of cooling element may comprise a hydrophilic material, such as a wood pulp sheet. To increase the water holding capacity of this material, a superabsorbent material, such as a hydrogel, may be incorporated into the cooling element. For example, the container may be formed of a hydrophilic material, such as a cellulose based material with cellophane being one example such that the container itself holds water used in cooling the product. Similarly, the container may be coated with wood pulp or other hydrophilic material adhered to the container.
To enhance the bulk transfer of gas from the interior of the closed container to the exterior: thereof, for example when the container is placed under vacuum conditions, a bulk gas flow mechanism is provided for this purpose. In its simplest form, the bulk flow mechanism may comprise an aperture which is sized to control the flow of gas by diffusion between the interior and exterior of the container while permitting the bulk transfer of gas 'through the aperture upon subjecting the container to a vacuum. Typical. apertures are in the .form of a circle with a diameter of from about twewty~five microns to about six hundred and fifty microns per kilogram of packed product within the container. In another form of a bulk transfer enhancing mechanism, the container includes a valve~which selectively enhances the bulk transfer rate of gas from the intern.or to the exteriar of the container, for; example, upon the application of a vacuum to,the container .-Idiechanical valves, such as described in U.S.
Patent Noo 4,890,637 and used in connection with packaging coffee, may be used for this purpose. However, a specific preferred valve is formed by a flexible patch of an oxygen w~ <~?ioa2s~ Pc-~v us~~ r io~3a ~
- to - _ and carbon dioxide gas permeable material mounted to the container so as to overlay and close: an opening in the container, the container being of a substantially oxygen and carbon dioxide gas impermeable material. The patch may also be of a water vapor permeak~le material. The patch is mounted to the container ak:~a perimeter surrounding and spaced from the opening in the container.
Upon the application of a vacuum to the container, the area of the patch exposed to the interior of the container increases due a bubbling of the ~atc:h away from the opening so as to increase the surface area of the patch exposed to the interior of the container through the aperture and enhance the bulk transfer rate of gas through the patch from the interior to the exterior of. the container.
As another aspect of the present invention, the package includes a receptacle, which may be of a box-like configuration, for receiving the cooling element and container with these latter components of the package being positioned at least partially within the receptacle.
The cooling element may also be integral with the receptacle. In one specific form, the receptacle comprises a fluted or corrugated core of a la.~a~.d resistant material, such as wax impregnated medium, a hydrophilic material at one side of the core so as to form the interior of the receptacle and a sheet at the oppasite side of the core which forms the exterior of the receptacle. The hydrophilic material,, which may comprise wood pulp or ether suitable materials contains water for cooling the produce within the container by evaporation.
The liquid resistant core, due the corrugations or flutes, provides a path for the flow of air adjacent t.o.the hydrophilic materiah to aid in the evaporation of moisture from the~hydrophilic material and thus.the cooling of the container. The liquid resistant material also i~ibits the transfer of water from 'the hydrophilic material, to the cover sheet of the receptacle. The cover sheet may be printed, far example with brand identifications or 6vV vL~u~6L~6 fLI~U~H~~Ub.i~l1 advertising material, such that 'the entire package is suitable for display in a retail store. In addition, the package may be assembled in the field with the produce being harvested directly into the container to minimize the handling of the produce between harvest and display.
The receptacles may else be configured for stacking in tiers with the product in containers placed in proximity to, preferably in contact with, the cooling elements and in the receptacles. A vacuum may be applied to the containers so as to evaporate liquid from products within the containers. Ti the evaporative type cooling elements are used, liquid also evaporates from the cooling elements to cool the products within the containers. By making the containers of a flexible material, the containers tend to expand against the respective cowling elements during the application of the vacuum to enhance the conductive cooling through the container to the cooling elements.
Far effective cooling purposes, the liquid absorbent material of the evaporative type cooling element is typically designed for holding liquid, such as water, in an amount which is at least from about forty-five to about sixty-five grams of water for each kilogram of product within the container. Assuming the field temperature of the products is approximately 8~°F, evaporation of forty-five grams of water for each kilogram of the products within the container will cause a drop in temperature of about 45°F in the products, or to 35°F.
The additional water included in such cooling elements is used to assist in evaporatively cooling the products as they are picked in the field.
...The cooking element.may include plural .
passageways open at at least-one end.to which. gas.,may pass ..
to enhance the~rate of heat transfer, for example by enhancing the evaporative type evaporation of liquid from cooling elements. In a specific example, the cooling element may be formed of a corrugated board having a ~ PC'('/~JS911063~t I-~

fluted core and a fibrous mat on one surface thereof for purposes of absorbing liquid.
It is accordingly one object of the present invention to provide an improved ~:ontainer for packaging and cooling perishable food and horticultural products.
Another object of the present invention is to provide a package usable in field applications by which a field-packed modified-atmosphere car other wrapped container may still be effectively cooled, including l0 cooling under vacuum conditions.
Still another object of the present invention is to provide a package capable of. enhancing the effectiveness of cooling of a wide variety of products, including strawberries, and in which vacuum cooling may be utilized to enhance the cooling process.
Another object of the present invention is to provide a package which extends the duration of the peak quality of a product for eating or other use. This allows the picking of produce which is closer to full maturity, an expansion of marketing opportunities in that products may be economically shipped to more distant markets; and an extension of the market season in that seasonal products may beheld longer and still be at high quality when sold.
As another object of the present invention, efficiencies in processing the products are enhanced and costs arm reduced. ~'or example, waste (e. g. lettuce cores, broccoli stalks) can be removed and left in the field so that the product arrives ready to eat without 3~ additional processing being required. This reduces waste disposal costs and labor costs at the point of sale. In addition, losses due to-..spoilage of.the products are reduced. Moreaiver, transportation costs are reduced as much 'of the r~7L:~tively heavy..ice. used Vin, the ..
.. transportation i~f many types of products, sucta as , .
broccoli, can be ~elianinated.
As another object of the present invention, loads of various products not otherwise typically shipped N'O 92/04256 pCT/US91/U6341 ~0'~~~90 together, may be commingled. For e~cample, ethylene sensitive products, such as bananas, or odor absorbing products, such as strawberries, can be shipped with odor emitting products such as onions or ethylene emitting products, such as apples, pears and 'tomatoes.
As another object of the present invention, the products may be packaged and labeled in the field to minimize the possibility of misbranding of the products ' downstream in the distribution chain.
As an advantage of the present invention, a package is provided which increases the room temperature' tolerance of the products and enhances the duration of peak quality of such products even under such adverse conditions.
As yet another object of the present invention, a .
package is provided which minimizes the possibility of cross-contamination of products, for example pests found in some products migrating to other products during shipment.
2o The present invention relates to the above features, objects and advantages both individually and collectively. These and other objects, features and advantages of 'the present invention will become apparent .
with reference to the following description and drawings.
~'~21EF DESCRTPT:CON of TFiE DRP~WINGS
FIG. 1 is an exploded view of one form of package in.accordance with the present invention illustrating a produce container, a cooling eleynent and receptacle.
FIG. 2 is a cross-sectional view of a portion of one foz~n of cooling element in accordance with the present .
invention also showing a portion of an alterxaative form of rec~ptacle~'i.n accordance with the present invention in the event the cooling element and receptacle are combined.
FIG. 3 is cross-sectional view of a portion of an ..
~lternat~.ve for~rt of container-in accordance with the present invention in which-the container and cooling element are combined.

'WO 92/O~J2~j, r s ~~~ri~m9rio~3a~
~0 l ~9~~
- 14 ~- _ FIG. 4 is cross-sectional illustration of one form of mechanism for increasing the bulk flow of gas from the interior to the exterior of the container when the container is subjected to a vacuum.
FIG. 5 is an illustration similar to FIG. 4 showing the operation of the bulk gas transfer aaechanism when subjected to a vacuum.
FIG. 5(a) is a plan view of the gas transfer mechanism of Fig. 4.
~.0 FIG. 6 is a cross-sectional view of a portion of a container which illustrates an alternative bulk gas transfer mechanism.
FIG. ~ is an exploded view of an alternative form of container in accordance with the present invention.
FIG. 8 is a plan view of a cutout blank which may be formed into the cooling element of the package of FIG
7.
FIG. 9 is a plan view of a cutout blank which may formed into the receptacle of the package of FIG:7.
FIG. ~.0 is a schexuatic .illustration of the use of the package in a field packing applicati~n.
FIG. 13, is a cross-sectional view illustrating one form of mechanical fastening mechanism suitable for use in sealing containers of the present inventipn.
FTG. L2 illustrates palletized packages in accordance with the present invention and also illustrates heat sealing of the container used in such packages.
FIGS. ~.3 ° 15 are graphs illustrating the gas transfer axed perraeance characteristics of , selected types of media suitable for use in containers in acCOrdance with the present invention.
FIG. 1Ev is a graph illustrating oxygen and carbon ~d~.cixid~ concentrations.achievable in containers of various constrtactions . . . . .
w~v FIG. 1f is an explcaded view of a coxata:iner .and .
another form of cooling element in accordance with the .
present invention.

WO ~2/i)4256 pt:'T/~JSt)1/06341 FIG. 18 is a top perspective view of another form of receptacle and cooling element in accordance with the present invention.
DETAILED -DES CFIPTION CF PREF;EP.~?ED E:~3CDIt~ENTS
The package, packaging system, and method of the present invention is applicable to the packaging of a wide variety of perishable food and horticultural products.
These products include both respiring and nonrespiring types. Respiring products include, but axe not limited to, cut and uncut fruits and vegetables and other horticultural. products such as cut flowers. Nonrespiring products include, but are not limited to, bakery products, meats, poultry and fish. Although the invention has wide applicability to the packaging of perishable food and horticultural products in general, the invention offers particular advantages in conjunction with packaging arid cooling products, including tl2ose products benefited by a modified atmosphere environment.
For purposes of convenience, and not to be construed as a limitation, the invention will be described in an application involving the harvesting and packaging of strawberries (a respiring product' and in which a modified atmosphere. environment is utilized.
With reference to FCC. 1,, the illustrated package includes a modified atmosphere container 10 enclosing strawberries 12 therein, a cooling element in the form of a cooling collar 3.4 within which the container 10 :is positioned when the packaged is asseanbled, and a box-like receptacle,l6 for receiving both the cooling collar and ~O container. The illustrated receptacle ~.6 is subdivided by a wall 18 into a first compartment 20 and a second compartment'22. Although only one cooling collar l4'and container 1.0 is ,shown in FIG..,1, plural such elements are typically provid~pd with one.containex:and collar being positioned in co~mpartment.20 and..another such Container and c~llax being positioned in compartment 22. As explained.below, the receptacle 1.6 is typically of a corrugated kraft board material assembled to provide wc) 9zioazs~ r~~°riusd)~iob~a~

reinforced corners and the central wall, with upper planar shelves, some being numbered as 26, 28, to facilitate stacking of product containing receptacles on top of one another.
The container has a produce containing interior and an exterior and is preferably of the type which is closable with product to provide a controlled flow of gas between the interior and exterior of the container when closed. The material used for the container is selected l0 to provide a desirable gas environment for the particular product being contained. Suitable environments and storage conditions are found in the literature, for example in the previously mentioned article by Kader, A.
et al. entitled °°Post Harvest Technology of Horticultural Crops." The Kader article mentions that a desirable environment for broccoli is one to two percent 02 and five to ten percent COZ, and that a desired environment for strawberries is ten percent OZ and fifteen to twenty percent CO2.
l~Iost gases will dissolve in plastic films. Once dissolved, the gases diffuse through the film and eventually evaporate frown the opposite surface. With films, this process has been shown to follow an '°Arrehenius'° relationship, whereby their permeab~.lity increases with temperature. For most non-gas°barrier films, this temperature change a~aaounts to approximately doubling the permeability when the temperature rises from freezing to room temperature. The:perx~eability of a plastic film cars-be inoreas~d with the.addition of.
plasticiz~rs. Water vapor is a strung plastici~~.ng agent for hydrophilic polymers, such as cellophane, nylon and ethylene vinylralcohol~.thus, permeabilities of these films tend to be highly dependent upon relative. humidity.
Permeability is ;s~anewhat rtlifferent for each gas depending 35-upon its salubilit;~ and molecular size. , Pea-zaeabality ratios, howev~x~ are remarkably constant across a broad spectrum of polymers. As a rule of thumb,...O2 and nitrogen permeabilities through film are four and eight times lower WO 92/04256 P~ i'/U591 /()6341 _ 17 ~Orl~~~
than carbon dioxide, respectively. Each gas diffuses independent of the others in the mix so that the transfer of a single gas through a film or membrane is dependent on its partial pressure drop across t:he membrane.
Gas permeability of plastic films is measured in accordance with ASTM Standard D1434, commonly referred to as the Dow cell Method. The water vapor transmission rate of plastic fihus is generally mea:aured in accordance with ASTPi Standard E9fi. Typical permea~nce and water vapor transmission data for plastic films can be obtaixled from the suppliers of these films with one needing only to select a film that provides the desired environment. In general, the Higher the water vapor transmission rate, the lower the gas permeance of a film. Typical film permeance properties of a number of films are set forth in the table below.
TA1BL~ I
Permeant;e (1) Flm CO2" O' N~ , W~'I'R~~

a ' Polyethylene (!err density) 1,500 100 ~ 1 Potyptopylene 350 ?3 ~G 1 Silicone 350,000 70,OQU30,000.d 1 .

2 5 Ceflop6ane < 1 < 1 75 .( 1 Nylon s a ~ 1 to Polyrattronate sso ~s s iso styrene s~ iso 3o s pvc s,soa sso irs is . ' ( 1 ) mml',/hr - atm - mZ ( 1 mm thickrae~a, room ta~mperature ) (2) ~en,lm~/day (1 9~~ IiFI, room temperature) mm thickness, 35 For products which are not sensitive to the presence of water, suck( as broccoli, a film container of a material such as polyethylene may be selected. However, f~r packaging praducts which are sensitive to relative -rlumidity and the presence of water, for example fruit and 40 sugar co><ztaining produce such as apples and strawberries, a material with a higher.-water vapor transmission,.xats, such as cellophane is preferred., However,.a.container entirely of cellophane or of anotl~ler gas barrier film, as is apparent from the above table, would in most cases not 45 provide the desired controlled atmosphere environment in W~ 92/04256 PCT/ US91 /06341 - 18 - , the container for respiring type products as cellophane tends to be a gas°barrier to carbon dioxide, oxygen and nitrogen.
It should also be noted that for nonrespiring products, barrier type films are preferred with the containers being charged with desired mixes of gases during packaging.
A number of options exist for providing a container with a modified atmosphere environment and which l0 allows the escape of water vapor. In one basic approach, the container may be made of more than one material, one of the materials permitting the passage of~wa'ter vapor and the other material controlling diffusion of gases. This approach, which may be called a window technique, may be accomplished by, for example, the inclusion of a section or patch of porous or nonporous material in the container, the patch being of the type which controls the desired diffusion'of gas between the interior and exterior of the container. Another approach, as explained below,: is to include one or more apertures in the container which are sized to control the diffusion of gases through the aperture. As explained below, the use of a patch of porous material or an apertured container is helpful in vacuum cooling applications as the apertures and porous material facilitate the bulk transfer of gas from the container when the container is subjected 'to a vacuum.
In connection with the window approach, one container material may be relatively water permeable and a gas barrier, such 'as cellophane or ethylene vinyl alcohol copolymers. Another container material may be a nonporous material selected to control the gas transfer by diffusion between the interior and exterior..of the container so as to establish the desired controlled atmosphere environment.- One approach for accomplishing this result is to make the cowtainer 10 in the form of a bagP ~..
portion of which is indicated at-30 in FIG. 4, of a water vapor permeable gas barrier material with an aperture 32 being provided in the bag. The aperture is covered with a WO 92/042>~ PC1'/US9 i /06341 patch 34 having a permeance which establishes the desired gas environment within the container. For example, the patch 3~ may be of silicone such that gas diffuses through the patcY~ unti'i the oxygen and car:aon dioxide concentrations reach the desired relative levels within the container. If the product is respiring, equilibrium levels in the container will differ from air in that the oxygen concentration is reduced and the carbon dioxide concentration is increased. Yet, the overall bag material 30 permits the removal of water and water vapor through this portion of the container. As another option far removing excess water from witha.n the container, desiccants, such as in the form of one or more package inserts, may be included within the container.
Referring again to fIG. 4, the patch 34 is typically sealed, as by an adhesive 36 (or mechanically, or heat sealed,-or otherwise sealed) to the container to v.
close the aperture 32. As shown in FIG. 5A, the adhesive 36 is typically placed so as to form a perimeter:seal at a location spaced from the boundary of the aperture 32 for purposes explained below. ' Another window approach involves the use of a porous patch for the window. These porous mtambranes control the bulk diffusion of~gas between the interior and exterior of the container so as to control the atmosphere within the container as desired. l~xampl.es of suitable porous patch materials and the measured gas transfer coefficients through apertures of selected dimensions covered with a number of such porous materials are indicated in Table II below.
TABLE II

Diameter ylembrane .. ~ndition fMLlhr-ahnl . fcmL
yj _ .

Nuclepore (3 D~ . . 695 . . .. . , . .
micron) . 0,69 .

Wet ~ 0.69 650 - -.

4 0 veratec Dry 1.0 1,120 58.1# Polyester Wet 1.0 8s(1 42# Bleached Dry 1.0 155 Liner Wet 1.0 265 ~~~0 92/01256 PC'!'/U~91/06341 33# Kraft Liner Dry 1.0 500 Wet 1.0 480 Teslin Synthetic Papcr (PPG) (10 mil) Dry 1.0 655 Wet 1.0 480 Tyvek #1059B Dry 5° 7,580 *Large diameter required due to rnaterial ncynuniformity.
Yet another way of achieving the desired modified atmosphere environment within the container 10 has been discovered. with reference to FIG. 5, perforating the container 10 with a small aperture or hole 60 has been found to work effectively in these applications.
Ordinary molecular diffusion occurs through perforated or porous.membranes whose pore diameters are large relative to the mean free path of the gas. For atmospheric gases, relatively large pores refers to pore sizes larger than about 0.5 microns in diameter, l~lthough ordinary molecular diffusion increases with absolute temperature to the 1.75 power, there is little temperature dependence over the relatively small range of interest to modified atmosphere packaging. There is, however, a slight dependence on gas composition, since X32 and N2 diffuse approximately thirty percent more readily than CUZ
and H20 vapor diffuses approximately sixty percent more readily than CO2. However, it has been found that the gas transfer coefficient increases proportionately with the circumference of an aperture rather than the area of the aperture. ~'T~~. 13, 14 and 15 illustrate these observations for 'three different types of materials. This finding has provided a basis for selecting aperture sizes which result in the desired gas environment while still permitting the enhanced bulk transfer of gas under vacuum conditions. ,apertures havzng an area of that of a circle of a diameter of from. about.twen~,y_-five microns to about six hundred and fifty microns per k~.logram of, packed product have proven to maintain, the desired -aontroll~d atmosphere with packages having,.in the range,of up to.

WO 92/04266 PCt'/U~91/06341 2l - 2~'~2~~J
about one-half to ten kilograms of packed product having been tested to date.
Another gas transfer mechanism is Knudsen diffusion through porous membranes whose pore diameters are small relative to the mean free path of the gas. For atmospheric gases, this means pores smaller than about 0.5 microns in diameter. In Knudsen diffusion, gas permeance is related to the inverse of the molecular weight of the gas. Thus, theoretically, Knudsen diffusion will result in oxygen and nitrogen permeabilities twenty percent and thirty percent higher than carbon dioxide, respectively.
It is also possible to further modify the internal atmosphere of a modified atmosphere container using an assortment of gas scrubbing materials. Scrubbing products are commercially available for ethylene, carbon dioxide, oxygen and water vapor. In particular, silica gel and clay are commonly used to scrub water vapor, iron oxide is commonly used to scrub oxygen, lime is commonly used to scrub carbon dioxide, and potassium permanganate is commonly used to scrub ethylene from the controlled atmosphere environment. In addition, humectants are sometimes used ~o control the humidity in a controlled atmosphere container.
nesignia~g a modified atmosphere package simply involves throttling the incoming oxygen and outgoing carbon dioxide streams so that respiring produce becomes starved for oxygen and flooded with carbon dioxide. At a steady state, in general, all of the oxygen being consumed by the respiring produce must pass through the package.
This oxygm will pass through at a rate dependent upon the gas transmission rate of the film and the partial pressure drop across it. Thus, when respiring produce is packed in a controlled atmosphere package, the oxygen level will continue to dre~i-and the carbon dioxide and water vapor levels will continue to rise until.the respiration rate is in balance with the gas transfer rate of the film.
As previously mentioned, most plastic films are more permeable t:o carbon dioxide than they are to oxygen.

wo ~zioazs~ ~~criu~~~iob~a~
~~~~~~~7 - zz - _ In addition, respiring produce consumes approximately the same volume of oxygen as the volume of carbon dioxide it emits. Because of these properties, produce in a sealed plastic film container will reach a stable atmosphere in which the oxygen deficit is higher than the carbon dioxide buildup. As shown in Table I, permeance ratios (COZ:oz) for "commodity'° film materials range from about three to one (styrene) to ten to one (polyvi.nyl chloride). With a sealed polystyrene wrap, it is thus possible to achieve ZO any atmosphere along the line AD of: FIG. 16. Similarly, with a PVC wrap, one can achieve any atmosphere along AB.
Thus, using the sealed commodity films listed in Table I, it is possible to achieve any atmosphere within the triangle ABD of FIG. ~.6. With other materials, the area within the triangle may be varied.
Within the ABD range of FIG. ~.6, the carbon dioxide and oxygen levels do not add to twenty-one percent. This means that a partial vacuum is created within the package. As a result, any °'pin hole":leak in such a package will result in nitrogen enrichment to make up the pressure difference. This in effect provides the basis for an enlargement of the design range by using perforated barrier wraps. As previously discussed, if the perforations are large (relative to .5 microns), bulk diffusion dominates so that it is possible~to achieve any internal atmosphere along AE in FIG.,16. Similarly, if the perforations are small (relative to 0.5 microns), ~Cnudsen diffusion dominates so that it is possible to achieve any internal atmosphere along line AC.
By combining these mechanisms, (e. g. perforating a gas permeable film) one can obtain any. atmosphere within tine triangle ABC of FIG. 1.6.
Thus, a mechanism is described for readily selecting materials for obtaining a desired controlled a°tmrisphere environment for a wide variety of products.
By'circumventing the inherent restrictions placed on the outward water vapor flow bar modified-atmosphere packages, affective cooling of products sealed in such wo 9~io~2ss ~crvus~iio~~m z3 ~~'~2~-~
packages is permitted. This cooling is accomplished by locating a heat sink or cooling element in proximity to the outside wall of the container 10. The heat sink is in close enough proxiwity to the outside wall so as to facilitate heat transfer between the exterior of the container and the heat sink. Most preferably the heat sink is in direct contact with such. outside wall of the container. It is also preferred that the heat sink contact is proximate to a major portion of the surface area of the exterior of the container. A major portion means for purposes of this description at least from about thirty to about fifty percent of 'the exterior container wall surface area.
To facilitate use of the invention in the field, it is preferred that the package, including the cooling element, be of a size and weight which makes them easily manually portable. Consequently, harvesters can carry these packages with them as they move about a field and harvest produets. Typically, the receptacles, cantainers, cooling elements and packed produce in a package of the present invention weigh less than fifty pounds to facilitate manual carrying of the package.
The cooling element may take nnany forms to produce the desired heat sink at the exterior of. the container. AS shown in FIG. 17, the cooling element may comprise a collar 14b, such as of a liquid impermeable plastic film ~e.g. polyethylene) which seals a liquid therein,' such as water or a phase change cooling chemical, with potassium nitrate being one example. The illustrated collar 14b has plural liquid containing compartments 15a, 15b, 15c and 15d which are.jained 't~gether by,hinge funning portions,-such.as indicated at 17. The components may be formed, for.. example,.: by sealing the outer pouch forming cover malterial together at the hinge locations, to separate the collar 14b into the indiva.diaal cooling material c~nthining compartments.
The collar 14b is typically frozen and placed in a receptacle 3.~ with the container 10 opened and AVO 92/04256 ~CT/US91/~D6341 2~'~~~~~ - 2~ -positioned within the collar in tree Field. Produce is harvested into the container. When the container is full, the container is closed, as explained below, for example in the field. The collar 14b acts as a heat sink to cool , the exterior wall of the container and the packed product, which may then subsequently be vacuum cooled to substantially accelerate the coola..ng, such as explained by example in conjunction with Table T1T, below. The collar 14b gray be removed prior to shipment of the cooled produce and refrazen for subsequent reaise in the field harvesting operation. Other forms of heat sinks or cooling elements may also be used, provided the heat sink offers a sufficient thermal mass to accomplish the desired cooling.
preferably the thermal mass is such that it is capable of dropping the temperature of packed produce in the field under normal field temperatures and container filling times from about 80° l: to about 35° F. In general, it is preferred that the thermal mass be capable of one BTU
(British Thermal Unit) per pound of packed product in the container per degree of cooling desired. Thus, for a temperature drop ~f from 80° F to about 35° ~', the thermal capacity of the collar preferably is at least about 45 BTU
per pound of packed product. By providing excess thermal capacity (e.g. another 5 BTU per pound of packed product), the cooling collar also compensates somewhat for the time the container is exposed to field temperatures as the container is being filled.
The cooling element array also be of the type which permits the evaporatian of ,liquid therefrom;to provide the heat sink in this manner. Evaporation of a cooling liquid in proximity to the exterior wall of the container x0 ~~ coolsvthe contents of the container by,~v~aporation and _ tra.n~fer of heat ~ frown the . products in the ;.container.
through the container wall-a . .. Water vapor within the. .., .
package, for~~xample, from moisture containing products, tends to coxadenw;e on the chilled inner surface of the _ .
package wall (wh.ich is also true when other types of cooling el~ment~o are used), reducing the water vapor WO 9/04256 fCf/US9i/06341 Z5 - .. .
pressure inside the package and promoting further evaporation of water from the moist product. This evaporation from both the cooling element and packed product is enhanced under ~:~acu»m Jonditions and results in a rapid cooling of the product. Thus, cooling, and in particular a vacuum cooling approach can be applied to the product within a modified-atmosphe~:°e package. Cooling is accomplished by a series evaporation-candensation-evaporation process that is facilitated by the moisture l0 source in proximity to or contact with the exterior container wall.
Although FIB. 1 illustrates one form of a separate cooling element which is capable of holding a volatile liquid, such as water, ethanol or the like, against the container wall, other approaches may be used.
For example, by making the container of a hydrophilic material, such as of a cellulose based material (e. g.
nylon, cellulose acetate, cellophane or other dissolved cellulose based films) or other absorbent material, the .
container 10 itself may function as a cooling element with liquid evaporating from the container to facilitate the cooling of its contents. Polysaccharide films, hydrogels (such as the so-called superabsorbent particles Goanmon in the disposable diaper art) adhered to film, fibrous materials such as wood pulp adhered t~ the film, water pouches or pockets on the container, are yet other examples of mechanisms for incorporating liquid into the container for purposeswof evaporative cooling. For example, FTC. 3 illustrates a film 30 with adhered wood pulp particles 40, the wood pulp particles holding water for use in evaporative cooling of the contents of the container. " .. -The required oapacity of the moisture source, whether it be a substrate ors ttie coaatainer l0 or ~c~isture holding substrate in a separate coating element such as;-collar 14, depends Japan the mass of the product within the package. Edith water being the cooling liquid, a rule of thumb indicates that one percent of the product mass is WO 92/04256. P(~'T/U~91/Ofi341 lost to evaporation for every 10°F of vacuum cooling. To minimize evaporation of moisture from the product itself during cooling, the moisture source is typically designed to provide ~t least this minimum mass. In a typical field , packing operation, one can assume an average air temperature of about 80°F, Therefore, to drop the , temperature of products from 80°F to 35°F would require about forty-five grams of water for each kilogram of product in the container. However, in accordance with the method of the present invention, and to gain benefits of cooling during harvesting of the produce, water is , typically added to the cooling element or package in advance of harvesting the praduce such that the produce is harvested into a container already provided with this added moisture. Because evaporation can take place, and is encouraged for cooling purposes, during actual picking .
of the strawberries or other products, excess water is typically included so that enough water remains in the container for purposes of subsequent evaporative: cooling, ~0 such as under vacuum conditions. Therefore, a preferable cooling container is designed to hold an excess amount of water, such as about sixty-five grams of water for each kilogram of product in the container., .Also, in general, the greater the proportion of the c~ntainer in contact with the moisture source, the more effective the pooling.
In addition, relatively thin moisture containing substrates offer a low resistance to the transfer of heat from the condensing surface at the interior of the , container to the evaporating moisture.in the substrate and thereby increase cooling effectiveness.
To accommodate this relatively. large quantity of moisture, the moisture is most conveniently placed in a substrate with the..substrate being.positioned in contact .: With the container: wall. - ~.lso, , by utilising a container 35.:::1~ of a flexible material,-'the container expands against the substrate during the applica~t~.on of a vacuum. This advantage is also obtained by usa.ng a flexible container with the other forms of cooling elements. This is due to wo oziaazs~ ~c.-ri t ~a a -z~-'the delay in evacuating the air from the container and the fact that the container tends to inflate against. the cooling element, thereby enhancing the contact between rheas components and enhancing the resulting heat transfer.
Any moisture absorbing material may be utilized,' such as blotter pads, absorbent fluff pulp, superabsorbent polymers, paper, molded fiber and combinations thereof.
The location of the moisture containing substrate with respect to the container 10 may be varied, such as ' underneath, along side, or on top of the container.
In the design of a cooling element such as collar ~.4 shown in FIG. 1, the substrate material is indicated at 50 and positioned at the interior of the collar 14. Zn ,.
FIG. 2, the water containing substrate 50 comprises a sheet which is positioned at a surface of the collar 14 and which is incorporated into the collar. Again, the sheet may be of any suitable liquid containing material, such as wood pulp. Also as shown in FIG. 2, the:collar ~.4 may include a conventional corrugated corer indicated at 52, such as of corrugated Kraft paper. T'he corrugations define passageways or flutes, some being indicated at 54 in FIG. 2, which permit the passage of air or otherwise expose the back side of the sheet 50. Consequently, evaporation of liquid from the back side of the sheet is enhanced. This can be important, especially if the container is pressing against the exposed surface 56 of the sheet so as to limit evaporation at the area of contact between the container and sheet. To limit the possible transmission of liquid to-an exterior sheet 5~ of the collar 14, the core 52 may be formed of a water r~sistent or water impermeable material. Wax, impregnated medium, such as a ~iaxed paper, is one specific.~xample of a medium which may be utilized for this purpose. although migration of liquid through'the liner and the.;core..52 to the sheet 58 is~typically limited in any event, the use of a water resistent core 52 minimizes the potential wetting of 'the sheet 58.

WO 92/04256 fCT/iJS91/06341 ' 28 -- _ The receptacle 16 may be a separate element as indicated at FTG. 1, or may be combined with the cooling element 14. One convenient approach for combining these elements is to utilize the structure of FIG. 2 for the receptacle, in which case the interior surface of the receptacle comprises the water holding or carrying ,material, such as the sheet 50. Also, with a water resistant core 52, the sheet 58 remains substantially dry.
Therefore, the sheet 52 may be preprinted with brand to identification or other advertising material so that the receptacle 16 is usable as the display container for the produce, such as in a retail establishment. Of course, a separate receptacle 16 may also be used for this purpose.
with the optional construction utilizing a water resistant .
core 52, the receptacle 16 remains strong enough for stacking and carrying the products as well as for protecting the products during shipment even though the sheet 50 is wet.
In applications wherein the package is to be vacuum cooled, cooling is greatly assisted if a path is provided fox removal of air from the inside of the package during the evacuation period. otherwise the pressure of air within the package inhibits the condensation of. water vapor from the product onto the cold package wall. pne way of providing the pathway is to utilize the small window or patch of porous filtration material which allows the bulk transfer of air from within the container during the application of the Vacuum while.still peranitting _.
diffus3an to control the gas balance within.the container during storage:' However, to increase the gas transfer rate during evaporative cooling, mechanical Valves, such as thewvalve described in U.S. 1?atent.No. 4,890,67 or the like;-..~a~ be included in the: wall.of the,. container, 10.
w Although suitable; mechanical valves,tend..;to add to,the , expenseo of the packaging.system. . . ....
. '~s another approach for increasing the bulk.
transfer ~f hir fxom the interior of .a container under vacuum conditions, reference should be made to FIGS. 4, 5 WO 92/04256 PL f/1JS91 /Ofr3A l 2~N~~~9 and 5a. As previously explained, the patch 34 is typically secured, as by adhesive, to the container wall 30 about a perimeter 35 which is spaced from 'the boundary of the aperture 32. Under vacuum conditions, the patch 34 tends to form a bubble, as shown in FIG. 5, whereas in the absence of the vacuum, the patch tends to lay flat against the container wall as shown in FIG.. 4. In comparing FIGS.
4 and 5, it is apparent that the area of the underside of the patch 34 exposed to the aperture 32 is increased under l0 vacuu~a conditions as opposed to the case when a vacuum is not being applied. Due to the increase in exposed area of the patch 34, the gas transfer rate through the patch 34 is increased under vacuum conditions. Consequently, a more rapid escape of air fram within the container is permitted when a vacuum is applied and, as a result, more effective cooling of the product contained therein takes place.
Also, the use of an aperture in the container (See FIG. 6) enhances the bulk gas flow under vacuum conditions.
In connection with bulk flow of gases, gases are transferred from the high pressure side of the package to the low pressure side independently of the partial pressure differences of each gas component. For example, if air is bulk transferred from the outside of a package to the inside, enrichment is in the constant ratio of seventy-nine parts nitrogen to twenty-one parts oxygen (the composition of air), regardless of what the internal partial cancentrations of these gases are.
As previously mentioned, the package of the present invention can be utilized in conjunction wit?a various means of achieving evaporative co~la.ng. For example, water vapor may siaaply be allowed to evaporate from an ewapora~:ive type Gaoling collar. ~an:addi~tion, ~ offirmative waX>orative cooling rnay be accomplished: by .
moving air acro~a~such a cooling collage pressure cooling may also be utilized, involving use of dry air at a higher temperature. In addition, and offering particular wo 9zionzs~ ~c rvus~ r io~3~ l ~~~~~)~~3 - 30 - -advantages, vacuum cooling may be employed to cause the flashing of water vapor from the produce and from an evaporative type cooling collar when air is removed as a vacuum is applied. ' .
It is also possible to charge the package with a desired gas environment. For example, the vacuum may be' relieved by charging the vacuum chamber with a desired gas atmosphere having a gas balance wr;~ich differs from air.
For a nonrespiring product in a gas barrier film, the l0 modified atmosphere within the container remains at the charged gas composition for a substantial period of time. .
For example, the atmosphere may be enriched in carbon dioxide. This charging gas will pass into the container and effectively precharge the container with gas of the 25 desired environment. The charging gases may include a fumigant for destroying fungi, bacteria, insects and other pests that might otherwise damage the packaged product. A
number of known fumigants can be used, such as methyl bromide gas for mite control to satisfy export 20 requirements, such as the case for strawberries being shipped to a number of foreign countries. In addition, gases such as carbon monoxide may be used to inhibit enzymes responsible for browning of lettuce, mushrooms and other products. Again, any number of suitable fumigants 25 may be utilised, with other examples indluding sulfur dioxide and sulfite based materials. Other chemicals for these purposes may be added in liquid or solid fore.
FIG. 7 illustrates another form of package in accordance with the present invention with corresponding 30 elements being assigned the same numbers as in ~'IG. 1, but with the added subscript '°a". In this case, a ,omewhat smaller container 10a, in comparison to the container 10 ~~ FIG. 1,' is shown with strawberriesl2a therein. .The .
cooling cellar W4a in this case is formed.into a box-like 35 configuratio~i with.a water absorbi~g.:s~bstrate a~a at one surface of this form of cooling element. ~n the FIG. 7 package,.the receptacle 1~ is comprised of a first receptacle ~.6a for receiving the container 10a and cooling - ~1 ~ ~~i'~~~~~
collar 14a therein and a larger receptacle 16b for receiving plural, in this case four, of the containers 16a and contents.
FIG. 8 illustrates a corrugated board blank used in forming the cooling collar 14a o:f FIG. 7. When folded along perforations 60, 62, 64, 66, 68 and '70, the cooling collar 14a takes the form of a box 'which may include the water holding substrate 50 on all of its interior surfaces. During use, the collars 14a, as well as collars of the form 14 shown in FIG. 1,'and 14c in FIG. 18, are typically inverted (substrate 50, 50a, 50c side down]
and floated in a pool of liquid, such as water, so that these collars become at least partially saturated. To expedite this wetting procedure, the blanks used to form the collars 14, 14a and 14c may be carried by a~cOnveyer across the surface of a pool of water with the substrate 50 in contact with the water so as to wet the substrate without wetting the remaining surfaces o~ the collar, However, the entire collar nay be wetted if desired.
FIG. 9 illustrates a corrugated board blank for one of the receptacles ~.6a which, if folded along perforations 80 - 94 forms another box-like structure for receiving the cooling collar and container.
With reference to FIG. 10, a typical method in accordance with the present invention will be described.
In this case, at a location x.00 a cooling lic~uuid, such as water, is added t0 the cooling collar. This x~ay be accomplished by at least partia~.ly saturating the Substrate 50 Of the cooling Collars 1.4, lea, Or 3.4c (FIGS.
1, 7, 18). Liquid is typically added to the cooling collars in the field, that is at the location where the products are to be harvested. Following the addition of the cooling liquid,"~(or in the case. of the collar 14b.
~foll.ing the chilling 'or freezing;-Of the collar) the- .:.
35. packages are typically assemblede' That is,.;open-..
containers 10, l.Oa are placed a.n respective cooling collars 14, 14a, 14b, 14c and in the receptacles 16 ar 16a and 16b. The assembled containers, one being indicated at ~'O 92/0d256 fCT/1hi91 /~)6:~A i 102 in FTG. 10, are 'then taken by the produce harvesters and filled with produce, such as strawberries from a row 104. The strawberries are sorted by the picker and placed directly into ~,he open containers 10, 10a. Evaporation of liquid from the cooling collars 14, 14a, 14c (and heat transfer to the chilled collar 14b if this 'type of collar is used) helps to cool the berries as they are being harvested.
In a typical commercial strawberry field, plastic or other ground covering 106 is placed on the ground between the plants so that the berries are clean. Thus, the berries being placed in the containers 10, 10a are clean and attractive for marketing purposes. The picker, when containers 10 and ~.oa are full, typically takes the filled package to a sealing location, indicated at 108, at which time the controlled atmosphere packages 10, 10a are closed.
The containers may be provided with mechanical fastening mechanisms for use in sealing the containers.
One such mechanism is shown in FIG. 1.1 and is indicated by number 110 as comprising a common "zip-lock" type mechanism having an elongated bead 112 which fits within and mates with an elongated groove 3~.4 formed in the container 10. This mechanism may be provided in a strip of material secured to the container. Although mechanical seals may provide the sole sealing for the containers 10, 10a, films of this type are typically of a heat sealable material. .."Consequently, as shown. in FIG. 1.2, a filled package x.02 may simply be placed on a table l~.s with the open end af'the container 10, 1.0a being exposed,for positioning between heating elements x.20, 122 of an j electrically powered heater a24. With the end 118 of the bag clasped betweenwthe bars,120,and..122, the bag is ' closed by'heat s~ealing~:..Of course,:.~~trasonic and other .
sealing approach~eswmay;alsp be.used. For example, commercially available cable ties, such as Part No. X54?6~
ties~from Consolidated Plastics Comgany of Twinsburg, Ohio have proven suitable. In addition, the mechanical WC) )2/04256 PC.'C/U~91/063~i fastening mechanism 110, although helpful in preliminarily closing the bags so that ends 118 may be oriented easily for heat sealing, is not necessary. After sealing, the now sealed end of the bag 118 is typically tucked into the receptacle.
As shown in FIG. 12, the receptacles may be printed with brand identifying indicia or advertising material, as indicated at 130, so that the produce can be displayed at its end destination, such as at retail stores, in these receptacles. As also shown in FIGS. 10, 12, following sealing, the packaged products may be palletized, that is, stacked in tiers on a pallet 138 as shown in FIG. 12. fihis approach minimizes the number of times that the produce is handled following harvest. mhat is, the only direct handling of the produce occurs at the time it is picked and initially placed in the container and then again at the restaurant or other end location when the produce is actually used. Also, the modified atmosphere container typically remains in tact until the individual containers of produce are used. Although the produce has been placed in modified atmosphere containers, evaporation of liquid from the form of cooling collars 14, lea coxttinues to cool the produce. In a like manner, heat transfer to the FIG. 17 form of cooling collar 14b also continues to cool the produce.
Following the optional palletizing step, the packaged product is moved to a vacutam cooler of a conventional type. The vacuum cooler may be located at the field, that is in proximity to the location where the product is harvested, ox at a remote site. I'he packaged product is subjected to vacuum cooling to further cool the prodixct until tr=msported, as indicated by vehicle 142 in F"IG.~10, during distribution of the product.
~:.. . ~: F~.~$llyo to provide a further explanation the.
present invention; a"specific example is_described below.
In connection with this example, a four~unit retail flat of the type showrnvin FIG. ~' was used. Each container 10a of this flat was packed with approximately one thousand WO 92/0d256 fL t'/U~91/06341 grams of strawberries. The film utilized in 'the container 10a was ethylene vinyl alcohol (EVO~) having a twelve micron thickness and being approximately of a twelve inch by five and one-half inch by six inch size. The patch 34 (FIG. 4) comprised forty-two pound bleached liner paper in the form of a one and one-fourth inch by one and one-fourth inch label with a one-quarter inch diameter adhesive-free circular area applied positioned over a one-sixteenth inch diameter perforation in the film (the l0 perforation corresponding to aperture 32 in FIG. 5). Over the aperture, the gas transfer coefficient (diffusion) was measured as 80 mL/hr/atm while the Gurly (bulk flow) was measured at 560 sec/100mL. In addition, the cooling collar 14a (FIG. 7) was partially saturated with approximately 100 grams of water with the assembly being placed in one of the containers 16a. Testing revealed the steady-state internal atmosphere of this container was approximately seven percent COZ and sixteen percent 02 at ~0°F.
When a package of this type including a cooling collar is stored in a well-ventilated area, tae temperature of the cooling collar approaches the wet bulb temperature of the surrounding air. For example, in Watsonville, California, where the average high temperature in June is 70°F and the average relative humidity is fi.a~ty percent, the wet bulb temperature is approximately 60°F. It has been found that after two hours under these conditions, strawberry packages with a cooling collar as described above are on the average 3.5°F
cooler than those without collars.
When subaected to a vacuum, to minimize bursting problems of the container 10a, the. porous membrane typically has aw~Gt~rly flow of greater than-0.2 mL~/sec (100 mL/560 sec). This Gnarly flow is also achieved by placing an oversized porous~label,:for example one-quarter inch in diameter, over a one-sixteenth inch diameter perforation in the film. As previously explained, under vacuum conditions this label bubbles out to expose the entire WO 92/092~i6 PC'r/U~9H/f163~S1 2~~~~~9~
one-quarter inch diameter porous material, but then returns to a flat position under ambient conditions.
Also, as previously explained, a small aperture may be used for this purpose.
In a conventional vacuum cooling process (e.g. no cooling collar or other cooling element), all of the heat removed from a product is contained in the water vapor and is removed from the product or from any water sprayed onto the product. With: a modified atmos;~here package, ttae removal rats of heat from the product would therefore be limited by the rate at which water vapor would pass through the porous membrane, which in turn is related to its Gurly number, or to the rate water vapor is otherwise collected within the container. If a cooling collar is used, a condensing surface is created on an interior surface of the modified atmosphere container. This allows .
the water vapor inside the container to give up its heat (while condensing) to the cooling collar sa as to enable a much ars~ore rapid heat transfer. In addition, the cooling collar removes heat by conduction at points of contact with the container. Tt has been observed that after either a fifteen minute or thirty minute vacuum cycle, tile temperature drop of a package which comzbines a modified atmosphere container with a cooling dollar is three to 2~ four times greater than the case sai.thout a cooling collar.
Iw addition, it has been observed that this method of cooling (utilizing a cooling eleanent in coanbination with a modified atmosphere package) appears to be gentler on strawberries than a conventional vacuum cooling process.
Although the reason is not entirely clear, it is quite possible that evacuation shock and cell rupture of the berries is reduced and that freezing is minimized since no berry can be colder than the coating collar.
Also, after about fifteen ~ainutes in a vacuum tube,.(an open, e.g. conventional modified atmosph~re~
package) would be approximately 6° cooler if a cooling collar is used than if one is not used. Thus, a cooling collar may be used to speed up the cycle time of vacuum ~vo ~2ioazsrs ~cPrius~~io63a~

~~~~JJ
cooling. In~~addition, with such a cooling collar, cooling has been observed to continue for several hours after removal from the vacuum tube as heat continues to transfer to the collar. Early observations suggest that the equilibrium (two-hour) temperature drop using a liquid evaporative type cooling collar in combination with a fifteen minute vacuum cycle is com~aarable to that from the use of a thirty m'z.nute vacuum cycle without a cooling collar.
~.0 Mature (full color) strawberries packaged in this manner have maintained their peak quality for eating up to three weeks from packaging. Presently, the maximum strawberry life is about seven to ten days even if the berries are less mature when picked (green). Although this example has been described in connection with strawberries, the invention is not limited to this particular type of produce. ~s another specific example, broccoli packaged in this manner has maintained its quality and freshness for the duration of a twenty-one day test period, with the maximum duration not yet having been determined.
To provide further evidence ~f the effectiveness of the present invention, room te~tperature strawberries were placed in a xnodif led ataaosphere container and the container was closed. The container was then subjected to cooling for thirty minutes under conditions indicated by Table I~T belaw and with the results being set forth in this table. ' :. T~I"E Iu 3 0 STItAVJ~BERRY COOLING IN A
CLOSED MODIFIED ATMOSPFIERE CONTAINER
(EVOII F">lm with an Aperture) Cooling Elcmtnt Vacuum Applied ' ' Average Packed Strawberry 3 5 Type Area' During Cooling Temperature . .. , ,. . : Initial Fenal C2Sange ..
Frozen .Scale! Cooling ' .. - . .
Collar (14b type)°° 120 ~ No ,' 66.6 52.0 14.6 4A ~ - .... . .... , ,. . , .
Froaen Sealod Cooling _ _...
Collar (14b type)°° 120 Yes . 65.1D 36.8 , . 28.2 Wet yber Cooling ~ 5 Collar (14a type) 50 Yes ' . 67.8 ~ 37.2 30.6 WO 9?/042Sfi fC'f/US91/()f>34i ~~'~Z~~~
None Yes 66.9 59.6 7.3 In square inches per pound of packaged fruit ~' Commercially a~railablc Blue lca"' packaged sealed cooling elemeW s frozen at a tamperalure of 15° F.
From the above table i.t~iu apparent that vacuum cooling of room temperature strawberries is simply ineffective without a cooling collar. Also, the use of a' sealed cooling element without vacuum cooling of the strawberries offered an improvement over the cooling element-less vacuum cooling approach. Moreover, the combination of vacuum cooling with a cooling element (of either the sealed or evaporative cooling type) was extremely effective in cooling the strawberries. Also, the evaporative cooling type of cooling element required far less surface area than the sealed type cooling element to accomplish the substantially same result.
FIaving illustrated and described the principles of our inventian with reference to several preferred embodiments, it should be apparent to those of ordinary skill in the art that the invention may be modif~.ed in arraaigement and detail without departing from such principles. We claim as our invention all such modifications which fall within the scope of the following claims.

Claims (55)

CLAIMS:

1. A package for food and horticultural products comprising:
(a) a closable container defining a modified atmosphere environment for enclosing the food and horticultural products therein, the container having an interior and an exterior and means for transferring heat between the interior and exterior when the container is closed; and (b) a cooling element located outside of the modified atmosphere environment in close proximity to at least a portion of the exterior of the container, wherein said cooling element accepts heat from the interior of the container when the container is closed.

2. A package according to claim 1 wherein the cooling element comprises a liquid holding portion located in proximity to at least a portion of the exterior of the container and wherein the container permits a controlled flow of gas between the interior and exterior when the container is closed, whereby evaporation of liquid from the liquid holding portion of the cooling element enhances the cooling of the container and the products therein.

3. A package according to claim 2 in which the container is of a material which controls the flow of oxygen and carbon dioxide between the interior and exterior thereof, the container including a water permeable portion which is also substantially impermeable to the passage of oxygen and carbon dioxide.

4. A package according to claim 2 in which the cooling element comprises a collar which substantially surrounds the container.

5. A package according to claim 2 in which the liquid holding portion of the cooling element comprises hydrophilic material.

6. A package according to claim 1 in which the liquid holding portion comprises wood pulp sheet.

7. A package according to claim 2 in which the cooling element and container are integral.

8. A package according to claim 2 in which the container includes an aperture which is sized to control the flow of gas by diffusion between the interior and exterior of the container while permitting the bulk transfer of gas through the aperture upon subjecting the container to a vacuum.

9. A package according to claim 8 in which the aperture has an area of that of a circle with a diameter of from about twenty-five microns to about six hundred and fifty microns per kilogram of packed product.

10. A package according to claim 2 in which the container includes a bulk gas transfer rate enhancing valve operable to selectively enhance bulk gas transfer rates from the interior to the exterior of the container.

11 A package according to claim 10 in which the valve comprises a vacuum responsive valve operable in response to a vacuum at the exterior of the container to enhance the bulk gas transfer rates from the interior to the exterior of the container.

12. A package according to claim 11 in which the valve comprises a flexible patch of an oxygen and carbon dioxide gas permeable material mounted to the container so as to overlie and close an opening in the container, the container being of a substantially oxygen and carbon dioxide gas impermeable material, the patch being mounted to the container at a perimeter surrounding and spaced from the opening, whereby the area of patch exposed to the interior of the container increases in response to a vacuum at the exterior of the container to enhance the bulk gas transfer rates from the interior to the exterior of the container.

13. A package according to claim 1 including a receptacle, the cooling element and container being positioned at least partially within the receptacle.

14 A package according to claim 2 including a receptacle, the cooling element and container being positioned at least partially within the receptacle.

15. A package according to claim 3 including a receptacle, the cooling element and container being positioned at least partially within the receptacle.

16. A package according to claim 4 including a receptacle, the cooling element and container being positioned at least partially within the receptacle.

17. A package according to claim 13 wherein the cooling element and the receptacle are integral.

18. A package according to claim 17 in which the integral cooling element and receptacle comprises a corrugated core of a liquid resistant material, a hydrophilic material at one side of the core so as to form the interior of the receptacle, and a sheet at the opposite side of the core forming the exterior of the receptacle.

19. A system of packaging fresh horticultural products comprising:
(a) plural stackable receptacles configured for stacking in tiers;
(b) controlled atmosphere product receiving containers each having an interior and an exterior and each being positioned in a receptacle, the containers providing a controlled rate of gas flow between the interior and exterior thereof;
(c) cooling elements including a liquid absorbing material positioned within the receptacles exteriorly of the containers for evaporatively cooling products in the containers; and (d) means for applying a vacuum to the containers and cooling elements so as to evaporate liquid from horticultural products within the containers and from the cooling elements to cool the horticultural products within the containers.

20. A system according to claim 19 in which the cooling elements comprise a water absorbing portion of the containers.

21. A system according to claim 20 in which the cooling elements comprise water absorbing material positioned within the receptacles adjacent to the containers.

22. A system according to claim 20 in which the cooling elements comprise plural collars, each collar being associated with a respective one of the containers, each collar substantially surrounding the associated container, each collar having a liquid absorbing material positioned against the associated container.

23. A system according to claim 22 in which the liquid absorbing material comprises wood pulp.

24. A system according to claim 22 in which each container is of a flexible material so as to expand against the respective associated collar in response to a vacuum at the exterior of the containers.

25. A package according to claim 1 wherein the cooling element includes a liquid absor-bent material capable of holding water in an amount which is at least from about forty-five to sixty-five grams of water for each kilogram of the products within the container.

26. A package according to claim 25 in which the cooling element includes plural passageways open at at least one end through which gas may pass to enhance the rate of evaporation of liquid from the cooling element.

27. A package according to claim 25 in which the cooling element is formed of a corru-gated board having a fluted core and a fibrous mat on one surface thereof as the liquid absorbent material.

28. A package according to claim 27 in which the fibrous material comprises wood pulp.

29. A package according to claim 25 in which the container abuts a portion of the liquid absorbent material of the cooling element.

30. A package according to claim 25 including a receptacle and in which the cooling element and container are positioned at least partially in the receptacle.

31. A package according to claim 25 in which the cooling element comprises a rectangular box receptacle for the container.

32. A package according to claim 31 in which the cooling element includes a control fluted core of a water resistent material, an interior surface adjacent to the container of a hydrophilic material, and an exterior sheet material at the opposite side of the core.

33. A package according to claim 27 including a hydrophilic organic polymer in the fibrous mat.

34. A package according to claim 25 in which the container is of a flexible material which expands against at least a portion of the liquid absorbent material upon the application of a vacuum to the container.

35. A cooling element for evaporative cooling of horticultural products in a container, the cooling element comprising corrugated board having a fluted core and a sheet of nonwoven fibrous material on one surface thereof, the cooling element being foldable into a configuration for receiving the products container therein, the cooling element holding at least from about forty-five to about sixty-five grams of water for each kilogram of product in the container.

36. A package according to claim 3 in which the material is a film of ethylene vinyl alcohol.

37. A system according to claim 24 in which the flexible material is a film of ethylene vinyl alcohol.

38. A package according to claim 34 in which the flexible material is a film of ethylene vinyl alcohol.

39. A package according to claim 1 wherein the container permits a controlled flow of gas between the interior and exterior when the container is closed and wherein the cooling element is positioned in direct contact with a major portion of the exterior surface of the container so as to lower the temperature of the container and condense water vapor within the container against the interior surface of the container to enhance the cooling of the container and the products therein.

40. A package according to claim 1 wherein the container permits a controlled flow of gas between the interior and exterior when the container is closed and wherein the cooling element is frozen.

41. A package according to claim 40 in which the cooling element comprises a sealed element contained a phase change material or liquid.

42. A package according to claim 41 in which the cooling element comprises a collar which substantially surrounds the container.

43. A package according to claim 42 in which the collar is in contact with a major portion of the surface area of the exterior of the container.

44. A package according to claim 40 including means for enhancing the bulk gas flow rate from the container under vacuum conditions.

45. A package according to claim 40 including a receptacle, the cooling element and container being positioned at least partially within the receptacle.

46. A package according to claim 1 wherein the container permits a controlled flow of gas between the interior and exterior when the container is closed and wherein the cooling element is chilled, a major portion of the exterior of the container being positioned in contact with the cooling element.

47. A package according to claim 46 which includes a receptacle within which the cooling element and container are positioned.

48. A package according to claim 47 which is sized for manual transportation in the field.

49. A package according to claim 47 which is sized for manual transportation in the field.

50. A package according to claim 47 in which the cooling element comprises a cooling collar which is capable of absorbing one BTU per pound of product in the container per degree of cooling of the product.

51. A package according to claim 50 in which the cooling collar is capable of absorbing at least 45 BTU's per pound of product in the container.

52. A package according to claim 1 further comprising a receptacle, wherein the container and the cooling element are positioned within the receptacle, the container permitting a controlled flow of gas between the interior and exterior when the container is closed, and wherein the package further comprises means for applying a vacuum to the container and cooling element so as to evaporate liquid from horticultural products within the container to cool the horticultural products within the container.

53. A system according to claim 52 in which the cooling element comprises a sealed element containing liquid or a phase change material.

54. A system according to claim 52 in which the cooling element comprises a heat sink in proximity to a major portion of the container.

55. A system according to claim 52, in which the cooling element comprises a heat sink in contact with a major portion of the container.