WO1998031608A1

WO1998031608A1 - Insulated transport container

Info

Publication number: WO1998031608A1
Application number: PCT/AU1998/000026
Authority: WO
Inventors: Paul James Smart
Original assignee: Food & Packaging Centre Management Limited
Priority date: 1997-01-21
Filing date: 1998-01-20
Publication date: 1998-07-23
Also published as: AUPO469397A0; EP0961741A1; NZ336489A; CA2278748A1

Abstract

An insulating package for transporting chilled foodstuffs consisting of a product bag (3) having a reflective outer surface disposed within a lidded transport container (4) that has inward projection protrusions or baffles (5) of at least 1 cm in depth spaced apart to provide an insulating airspace between the product bag (3) and the base and walls of the lidded container. The reflective outer layer can be a metallised film or a foil laminated to a polymeric film. The lid is optionally baffled. The product bag (3) may be vacuum sealed. Ice placed with the product in the product bag takes longer to melt than with conventional insulated containers.

Description

INSULATED TRANSPORT CONTAINER

Field of the Invention This invention relates to the packaging of fresh foodstuffs for transportation in insulated containers to minimise heat gain to the contents. It is particularly concerned with the transport of foodstuffs cooled with ice.

Background to the invention

There is a trend toward consumers preferring to buy fresh unprocessed food. Difficulty is encountered when the transportation times from the point of harvest to the final retail outlet are more than a day and where transportation involves a number of loading and unloading steps. This degree of handling and can lead to delays and if the temperature of the product varies as well the quality of the product will deteriorate more rapidly. Freezing of foodstuffs aids in long term preservation and transportation but does cause a loss of flavour. The optimum transportation method is to use refrigerated transport and ensure that the products are maintained at a temperature below 4 ° C. Often ice is included with the fresh produce to achieve this temperature. To prevent heat gain insulated containers are generally employed. These containers usually need to meet a range of parameters such as cost, robustness, minimal wall thickness, to minimise storage space loss, and low weight.

Many attempts have been made to design suitable insulated containers. French patent 2697809 discloses a stackable container for transporting fish with a product basket insert which leaves an insulating air space between the external box and the internal basket. Japanese patent 6-32379 discloses an externally ribbed container that can be sheathed to once again provide an insulating air space. Japanese patent 8-53166 discloses a hollow walled container while USA patent 4896790 discloses a foldable thermo-box of plastic insulating material for use in transporting fish and meat. USA patent 5102004 discloses a foldable chill box wherein the insulating walls are of polyurethane foam with foil surfaces. Flexible insulating containers such as bags have also been proposed. USA patent 421 1267 discloses an insulating and shock absorbing bag formed of a laminate including a foam layer, a foil layer, polyethylene layer and optionally a cotton layer. GB patent 2085401 discloses a double wall bag having air or gas in the wall cavity and a foil layer in the outer wall.

All of these proposals address some of the requirements but many fail because of cost considerations, the container is too heavy or its wall thickness means it takes up too great a volume in the limited space available during transport.

It is an object of this invention to provide an insulated container that has good insulation performance without taking up excessive volume, or weighing too much in comparison to its contents.

Brief Description of the invention

To this end the present invention provides an insulated package combination which includes a product container having a reflective outer surface, said container being disposed within a transport container having internal protrusions on its bottom and sides to create an air space between the reflective outer surface of the product container and the transport container walls.

By providing an air space between the walls of the rigid transport container and the product container and incorporating a reflective surface on the outer surface of the product container, the insulating performance is enhanced without significant change to the packaging wall space or packaging weight.

In another aspect the present invention provides a method of transporting chilled food stuffs comprising the steps of a) placing the chilled product into a product container having an outer reflective surface b) placing said product container into a transport container which incorporates protrusions in the base and sides to create an air space between the walls of the transport container and the reflective surface of the product container c) placing sufficient coolant in either the product container or the transport container to maintain the product in a chilled state d) transporting the filled transport container to its destination before all the coolant has undergone a phase transition [e.g. - melted].

The produce which most benefits from the present invention are pharmaceuticals and higher value fresh foods, which are subjected to extended travel and storage. All seafoods including lobsters, crayfish, oysters, fish such as salmon, fresh cut flowers, fresh herbs, vegetables such as broccoli, cauliflower, lettuce, spinach, carrots, brussel-sprouts and fruits that benefit from chilled storage and transportation including tomatoes, stone fruits, melons, grapes, mangoes, strawberries, pears, bananas and kiwifruit. The product container may conveniently be a flexible bag of reflective foil. For applications where the product container needs to be liquid tight a laminate of a polymeric film and a reflective layer is used to form the product bag. The function of the protrusions on the inner wall of the rigid transport container is to prevent the inner product container from contacting the greater portion of the wall surface so that an air space is formed between the outer surface of the product container and the inner surface of the lidded container. The protrusions may be a series of upstanding ribs or baffles arranged on the base and the side and end walls of the transport container. These can be aligned horizontally, vertically or both, although in moulded containers a vertical orientation is easier to form. The height of the ribs from the base or walls is preferably in the range of 1 to 3 cm. Below 1 cm the air gap provides insufficient insulating performance while above 3 cm the loss of useable interior volume affects economic performance of the package. The spacing between the ribs should be at least 1cm and the upper limit will vary according to the dimensions of the product bag and whether portions of it can enter the air space. Baffles or ribs can be provided on the lid but, as there is usually an air gap between the product container and the lid, these baffles are generally superfluous.

The material of the transport container can be any suitable insulating material such as wood, moulded plastic such as polystyrene, plastic foams such as expanded polystyrene [EPS], or polyurethane, corrugated cardboard or combinations of these. The baffles need not be formed of the same material as the container. Polystyrene foam or cork baffles arranged horizontally and/or vertically on the walls of a corrugated cardboard box are examples. The air space could also be created by an open sided honeycomb structure of cardboard or plastic. Cardboard strips of 1 to 3 cm in width interlocking at right angles can be inserted on the bottom and sides to provide air spaces of 1 to 3 cm in depth. The advantage of using such a cardboard grid is that the thickness of the board does not reduce the volume of the airspace which can be a problem with cork or polystyrene ribs or projections.

It is preferred that the lidded transport container is enclosed within a shipping cover which also provides insulation. This cover may be foil covered. The product container may be rigid but is preferably flexible. Conveniently the product container is a foil coated bag made from a foil laminate such as reflective aluminium/polyethylene. For non-water proof applications only foil need be used. An alternative to a foil/film laminate is metallised polymeric film suitable for packaging such as metallised polyethylene, polyester.or polypropylene. Inside the product container there may be a product tray or other ancillary packaging materials used for the particular product. The product container may be vacuum evacuated and sealed.

Coolant preferably water ice, is also included inside the product container or the transport container. The coolant must be present in sufficient quantity and at an initial temperature which ensures that it is not completely melted before the produce is ready for presentation. Preferably the coolant is present in an amount from 10% to 40% by weight of the produce. Alternative coolants to _1 to -2 °C ice are :

• low temperature freshwater/saltwater ice[-20 to -30 °C] • Frozen aqueous glycol mixtures

• Frozen hydrated polyacrylamide gel packs such as that sold as "TECHNI-ICE"

• Dry ice [solid carbon dioxide]

• Liquid Nitrogen

If the ice or coolant is in contact with the fish or other produce it is preferably at a temperature above that at which the produce itself becomes frozen to prevent undesirable tissue damage. For fish, and in particular, salmon the ice is preferably added at a temperature of -2 to -5°C. An alternative is to store the coolant in a compartment above the produce so that much lower coolant temperatures can be used. Thus the coolant can be arranged on the internal face of the lid or on a stand to elevate it above the produce within the product bag. For fish the melted ice flowing over the surface of the fish is a desirable flushing action particularly favoured in some countries such as Japan. For this reason the coolant is preferably stored within the product bag.

Detailed Description of the Invention A preferred embodiment of the invention designed for use with fish will now be described with reference to the drawings in which; figure 1 is a schematic exploded end view of the package of this invention; figures 2 and 3 are a plan view and a side view of the longer wall of the lidded container. Referring to figure 1 the package consists of an outer cover 1 , a lidded container 4 and a product bag 3. The external cover 1 is a foil coated 1.5mm fluted cardboard cover dimensioned to fit over the container 4. The container 4 is of polystyrene with a polystyrene lid 2. The base and walls of the container 4 include internal baffles 5 which are 10mm in depth to create the 10mm deep air spaces 6 in the container walls and base.

The product bag 3 is a polyethylene/aluminium foil laminate with an outer reflective surface which abuts the air spaces 6 when it is full. Alternatively a metallised polypropylene film with the outer surface being reflective can be used. For transporting fish the product bag includes a drainage tray 7 and an absorbent pad 8 to absorb melted ice and fluids. The fish is placed on the tray and a quantity of ice is placed on the fish and the bag is then closed. The flushing action of the melted ice flowing over the surface of the fish enhances its appearance.

In figures 2 and 3 a variation of the lidded container is shown. It consists of side walls 11 , end walls12 and base 13 each of 2cm thick polystyrene. The lid 17 is also 2cm thick. Baffles 14 are vertically arrayed on the side walls 11 and end walls 12 and these extend the full height of these walls. The baffles 14 are 1cm square in end section and are spaced at least 2cm apart. Baffles 15 on the base 13 are similarly dimensioned and spaced apart. This means that air spaces 16, which are 1cm deep and at least 2cm wide, surround the product bag on 3 sides. The product bag is dimensioned so that when it is full there is at least a 1cm air space between it and the lid 17.

It is important that, relative to the mass of the full product bag, the baffles not be easily compressed so that the air space is not diminished during transportation.

Comparative Examples

The insulation performance of a package can be measured by its R value which is a measure of the heat transfer through the package walls. Another method is to measure the time taken for a given mass of ice to melt.

Example 1

Various cardboard boxes were constructed with various product bags and in each bag 4.5Kg of -1 °C ice was placed and the time taken for the ice to melt to 0°C with an external temperature of 20 °C was measured, and the R value for the package was calculated.

Box A was a one piece cardboard box with 3mm flutes having an average surface area of 1.0m² and the product bag was a lOOmicron thick polyethylene bag. [non inventive comparison box ] Box B was a one piece cardboard box with 3 mm flutes and 2cm thick baffles on the internal surfaces of the base, walls and lid. The external surface was covered with a laminate of reflective aluminium foil over a 3mm thick plastic bubble wrap. The average surface area was 0.89m² and the product bag was a 70micron thick aluminium foil/polyethylene laminate bag. [invention] Box C was a two piece 3mm fluted cardboard box including an enveloping cover, having of average surface area of 1.0m² . The product bag is of lOOmicron polyethylene. [non inventive comparison box]

Box D was a two piece 3mm flute corrugated cardboard box with 2cm thick expanded polystyrene baffles on inner walls, base and lid. The external surface coated with a laminate of reflective foil over 3mm thick plastic bubble wrap. The average surface area was 0.89m . The product bag was composed of 70 micron thick reflective aluminium foil/polyethylene laminate. [invention]

Table 1

The two packages according to the invention [B and D] out performed the prior art boxes and enable less ice to be needed with the consequence that the package weight can be reduced.

Example 2 Polystyrene fish boxes of the prior art and the invention were tested with and without fish under the same conditions as in example 1. Again 4.5 Kg of -1 °C ice was placed in the bag and in the second trial 16 Kg of fish chilled to 0 -1 °C was also included.

Box E was an expanded polystyrene box with 2cm thick base, walls and lid. A 1.5mm fluted corrugated cardboard cover fits over the box. Average surface area was 0.9m². The product bag was 100 micron thick polyethylene. [prior art]

Box F was the same as box E, with 1.0 cm thick expanded polystyrene baffles on the inner walls, base and lid. The external surface of the cover was covered with reflective aluminium foil . Average surface area was 0.85m². The product bag was made of a 70 micron thick laminate of reflective aluminium foil and polyethylene, [invention] Table 2

*only 4 Kg of ice was added with the 16Kg of fish

Again this demonstrates the effectiveness of the package construction of the invention and shows that less ice can be used and still have a better performance.

Example 3 Four cardboard boxes were tested with ice only to gauge the effect of baffles alone, a reflective product bag alone, as well as a container with neither feature and one with both. The conditions were the same as in example 1 with 4.5Kg of -1 °C ice being used and the ambient temperature being 20°C.

Box K is the same as box C. Box L is a two piece 3mm fluted cardboard box including an enveloping cover. Baffles 2cm thick are arranged on the inner walls base and lid. The average surface area is 0.89m². The product bag was 100 micron thick polyethylene.

Box M is a two piece 3mm cardboard box including an enveloping cover.The average surface area is 1.0m². The product bag is 70micron thickreflective aluminium foil and polyethylene.

Box N is the same as box D. Table 3

These figures show a dramatic improvement when the combination of reflective bag and baffled container is used.

Example 4

Four expanded polystyrene boxes were used one with a reflective product bag, but without baffles one with baffles, one with the reflective bag and one with the combination. Both -1 °C ice only and ice plus 16 Kg of fish chilled to 0-1 °C, were used in each box. The quantity of ice only was 4.5Kg unless otherwise specified. The conditions were as in example 2 except that the ambient temperature was 22°C.

Box W was the same as box E

Box X was the same as box E with 1cm thick expanded polystyrene baffles on the inner wall, base and lid. The average surface area was 0.85m². The product bag was 100 micron thick polyethylene. Only 4Kg of ice was added with the fish.

Box Y was the same as box E. The average surface area was 0.9m². The product bag is 70micron thick reflective aluminium foil and polyethylene.

Box Z is the same as box F. Only 4Kg of ice was added with the fish. Table 4

The higher ambient temperature has a significant effect on the time taken to melt the ice. Even with less ice the combination out performed the other boxes when fish was present.

Example 5

A series of experiments was conducted to assess the effect of using low temperature ice. The following tables show the time for the ice to melt when various initial ice temperatures and varying container combinations are used.

Table 5A

Cardboard boxes containing 16.8 Kg. chilled salmon.

[external temperature 19-20°C]

Table 5B

Expanded polystyrene boxes containing 16.8Kg chilled salmon

[external temperature 19-20 °C]

Table 5C

Expanded polystyrene boxes [ box E ] containing 4.5Kg ice only

[external temperature 22 °C]

Table 5D Expanded polystyrene boxes [ box E ] containing 16-17Kg chilled salmon _ plus 4.5 Kg ice [external temperature 22 °C]

The results of set out in tables 5A to 5D show the significant improvement achieved when low temperature ice is used.

Example 6

A series of experiments was conducted to assess the difference in performance of metallised films as the external reflective layer of the product bags as compared with foil laminate bags. The metallised films tested were either 12micron metallised P E T [polyethylene terephthalate] film or 30 micron metallised BOPP [bi-axially oriented polypropylene] film. These were compared with the foil laminate bags of the kind described in the above examples.

Table 6

Metallised film bags vs Foil/Polymer laminate bags

These results demonstrate that the metallised films extend the ice melt time for a period longer than the foil/polyethylene laminate. Care needs to be taken with the metallised films as they are not as robust as the foil /PE laminate. Example 7

A series of experiments was conducted to assess the utility of vacuum evacuation and sealing of the product bags.

A 60 micron LDPE [low density polyethylene] film was heat sealed to form product bags. These were filled with chilled fish and ice and placed inside an EPS box [box E]. The bags were evacuated to remove air surrounding the fish and ice, then sealed. The heat transfer properties of of these bags were compared with that of lOOmicron LDPE bags that were unsealed and not evacuated inside an EPS box [box E].

In a second part of the experiment 30 micron metallised BOPP sheet was heat sealed to form product bags. These were filled with fish and ice and placed inside B flute cardboard boxes [box B]. One bag was vacuum evacuated and sealed and then its heat transfer properties compared with those of a similar unsealed metallised bag in box B.

Table 7

Evacuated bag comparisons

These results show a 7% improvement by the evacuated LDPE bag.

For the metallised film there was only a slight improvement gained with evacuation. The 30micron metallised BOPP films are less reliable in terms of vacuum sealing and leak resistance than the thicker LDPE bags. This may explain the reduced performance enhancement with evacuation of metallised films compared with LDPE. The metallised bags could be made more robust in terms of tear resistance and vacuum sealing if a layer of LDPE was laminated to the non reflective BOPP surface.

From the foregoing description it can be seen that the combination, of an inner container having an external reflective surface and an outer container having inward protrusions on its base and walls to create an insulating air space, provides a cost effective improvement in chilled transportation.

Claims

1) An insulated package combination which includes a product container having a reflective outer surface, said product container being disposed within a transport container having internal protrusions on its base and sides to create an air space between the reflective outer surface of the product bag and the container walls.

2) A package as claimed in claim 1 wherein the protrusions create an air space between the product bag and the inside of the transport container 1 to 3 cm in depth. 3) A package as claimed in claim 1 wherein the product container consists of a film or laminate having a metallised outer layer or a metal foil/polymer film laminate where the outer face is reflective.

4) A package as claimed in claim 3 wherein the transport container includes a lid.

5) A package as claimed in claim 4 wherein there is an air space between the lid of the transport container and the outer reflective surface of the product container.

6) A package as claimed in claim 1 wherein the product package contains fish and ice.

7) A package as claimed in claim 1 wherein the product container is vacuum sealed.

8) Use of a package as claimed in any one of claims 1 to 7 for storing or transporting chilled food produce.

9) A method of transporting chilled food stuffs comprising the steps of e) placing the chilled product into a product container having an outer reflective surface f) placing said product container into a transport container which incorporates protrusions in the base and sides to create an air space between the walls of the transport container and the reflective surface of the product container g) placing sufficient coolant in either the product container or the transport container to maintain the product in a chilled state h) transporting the filled transport container to its destination before all the coolant has undergone a phase transition.

10) A method as claimed in claim 7 wherein the coolant is ice and is placed in the product container at a temperature below its freezing point but above the temperature at which the produce freezes.