AU2020100322A4

AU2020100322A4 - Vapour heat treatment apparatus and method

Info

Publication number: AU2020100322A4
Application number: AU2020100322A
Authority: AU
Inventors: Alastair Scott
Original assignee: Hannay Douglas Pty Ltd
Current assignee: Hannay Douglas Pty Ltd
Priority date: 2020-01-20
Filing date: 2020-03-04
Publication date: 2020-04-09
Anticipated expiration: 2028-03-04
Also published as: AU2020100299B4; AU2020100299A4; AU2020100322B4; AU2020100411A4; AU2020100411B4

Abstract

An apparatus for supplying heated and humidified air to fresh produce is described. The apparatus comprises a treatment chamber for holding a plurality of produce containers and that has a ceiling and an exhaust hood below the ceiling so as to define a plenum air space between the exhaust hood and the ceiling. There is at least one exhaust fan mounted in the hood for drawing air from the treatment chamber into the plenum air space and an air flow restriction arrangement mounted to the hood below the at least one exhaust fan. The apparatus also has a heating chamber for heating air and the heating chamber is in fluid communication with the plenum air space for receiving exhausted air and is also in fluid communication with the treatment chamber for introducing heated floor for the supply of heated air into the treatment chamber. Figure 10 ?000 Q50 _0 AxZ/ lo 00A rntI S (00 C> -nUl00 ccr ½~D~b~Q0obc ro~ooiO 0 -_ - - - - - T-1 N---- -. O cP II ----D I , I >00 L Figure 10 6/-7 if)7 q p 400a rr

Description

VAPOUR HEAT TREATMENT APPARATUS AND METHOD

TECHNICAL FIELD

The present disclosure relates to an apparatus and method for insect disinfestation of fresh produce such as fruits and vegetables.

DEFINITION

In the present specification and claims the term “comprising shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

BACKGROUND

Many fruit and vegetables are hosts to insect pests and in particular fruit flies. In order to export to countries or locations with a fruit fly quarantine barrier, the produce must be subjected to a disinfection treatment approved by the importing country.

Chemical fumigation with agents such as diethylene bromide and methyl bromide is an effective disinfestation treatment and was traditionally the most widely used. However, chemical fumigation is being phased out as a result of concerns relating to toxicity and worker safety. Irradiation is also an effective disinfestation treatment but is relatively expensive, has poor consumer acceptance and significant adverse physiological effects, reducing shelf life and often cosmetic degradation over time as a result of necrosis.

Insect pests such as fruit fly may also be killed by temperature treatment to temperatures above or below that at which the insect larva may survive. Temperature treatment has the advantages of avoiding use of toxic chemicals or irradiation and has a high consumer acceptance. Cold storage holds fruit or vegetables at temperatures below 3° for about two to three weeks. Cold storage also has the advantage of preserving the produce. Heat treatment heats the fruit or vegetables to temperatures such that the internal temperature reaches above about 45°C for a predetermined period of time. Heat treatment can however adversely affect produce quality and may be a high cost treatment.

Some fruits and vegetables are sensitive to cold temperature and cold temperature treatment cannot be used as a disinfestation treatment. Tropical fruits are especially sensitive. For example, mangos suffer chill damage at below 13° C.

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The temperature and time to which fruits or vegetables are heated and held is determined by the quarantine regulations of the importing country. For example some regulations require heating fruit to 46.5°C for twenty minutes whilst others require heating to 47°C for 15 minutes.

In order to minimise heat damage to the treated fruit it is desirable to raise the temperature as quickly and accurately as possible. Heat treatment at high humidity, known as vapour heat treatment or VHT is particularly effective. As water vapour condenses on the fruit, it gives up its latent heat and efficiently heats the fruit thereby facilitating heating rate.

VHT treatment is conventionally carried out by placing fruit in large plastic bins, stacking the bins and placing the bins in a sealed treatment chamber. The plastic bins have ventilation openings so as to allow air flow about the produce. Heated air is introduced into the chamber with a relative humidity of 90 to 100%. The plastic bins are configured to hold a maximum of about 500kg of produce.

The treatment chambers used for VHT treatment were originally based upon configurations used in conventional forced-air cooling chambers. With forced air cooling, produce is placed in ventilated plastic bins and placed in a refrigeration unit. The refrigeration units includes a fan system in a plenum to pull cold air through the bins. Air flow may be either horizontal or vertical. The plenum is generally provided with spaced rectangular outlets covered by a grill. The stacked bins are carefully aligned relative to an outlet so as to optimise cold air flow through the bins.

With VHT treatment it is critical that all produce is subjected to the “kill temperature” for the regulated period of time. Failure to do so can result in incomplete disinfestation if not all produce reaches the required temperature and/or for less than the regulated time. The result is that the entire load is rejected for quarantine purposes. On the other hand if the temperature is too high, a significant percentage of produce may be lost due to heat damage. Either scenario represents a significant commercial loss.

The treatment process is carefully monitored to ensure the internal (pulp) temperature of all produce being treated reaches the required temperature for the required period of time. Probes are placed into the largest fruits at different heights and locations within the chamber. The treatment is continued until the sensor at the coldest location reaches the regulated temperature and held for the regulated minimum time. The “cold spots” or spots with the longest heat up time are determined during a certification procedure for each treatment chamber.

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In practice this means that a significant amount of the fruit is held at a higher temperature for longer. This can adversely affect fruit quality. There may be up to about 20 to 30% loss of fruit after a VHT process.

It is therefore desirable to produce uniform airflow and efficient heating so that all fruit is heated to the same temperature at the same time. There are a number of variables that may affect airflow within a treatment chamber, including air flow pattern such as vertical flow or horizontal flow through the chamber, lateral flow, design and arrangement of the plastic bins, relative sizes of fruit and the packing of the fruit into the plastic bins.

It is therefore desirable to provide an alternative apparatus and method for VHT treatment for disinfestation of fruits and/or vegetables.

SUMMARY

According to a first aspect of the disclosure there is provided an apparatus for supplying heated and humidified air to fresh produce comprising;

a treatment chamber for holding a plurality of produce containment containers, the treatment chamber comprising a ceiling and an exhaust hood below the ceiling so as to define a plenum air space between the exhaust hood and the ceiling;

at least one exhaust fan mounted in the hood for drawing air from the treatment chamber into the plenum air space;

an airflow restriction arrangement mounted to the hood below the at least one exhaust fan;

a heating chamber for heating air, the heating chamber being in fluid communication with the plenum air space for receiving exhausted air and also in fluid communication with the treatment chamber for the supply of heated air into the treatment chamber.

The present inventor has surprisingly discovered that by providing an air flow restriction arrangement in the exhaust hood can improve evenness of airflow within the treatment chamber.

The airflow restriction arrangement may be any suitable arrangement that may restrict airflow from the treatment chamber into the hood.

The air flow restriction arrangement suitably has a sheet type body with a having a plurality of air flow openings separated by land areas such that air flow is restricted to flow through the openings. Suitably the air flow openings are uniformly spaced

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Such types of restriction arrangements are characterised by the % open area. The open area is a ratio that reflects how much of the sheet is occupied as holes normally expressed as percent.

The air flow restricted arrangement may be a perforated sheet or grid having holes or slots through which air may pass.

The open area of the restriction arrangement is generally between about 10% to about 80%, suitably between about 15% to about 60%, suitably between about 20% to about 50%, suitably between about 25% to about 45%. In an embodiment the open area is about 30%.

The restriction arrangement may be in the form of a metal grill.

Suitably, the air flow restriction arrangement is a perforated metal sheet. Suitably the sheet is perforated with round holes. However, it will be appreciated that other hole configurations such as square, oblong, hexagonal or otherwise may be suitable.

In a preferred aspect, the exhaust hood is mounted to the ceiling and is able to be raised or lowered so as to be placed immediately above the uppermost produce crate or bin. Such placement is desirable to optimise air flow. In this way, stacks of different size bins or stacks of less or more numbers of bins may be accommodated.

Alternatively, if the produce containers are sufficiently sealed so as to prevent or minimise air loss around them, the hood may be stationary and/or sit above the stack of containers.

The hood has at least one exhaust fan. Suitably there are a plurality of exhaust fans equally spaced along the length of the hood.

Suitably the spacing of the exhaust fans is such that an exhaust fan will be directly above the centre of a stack of crates or bins.

In an embodiment, there is provided an apparatus for supplying heated and humidified air to fresh produce comprising;

a treatment chamber for holding a plurality of produce containment containers, the treatment chamber comprising a ceiling and an exhaust hood below the ceiling so as to define a plenum air space between the hood and the ceiling;

2020100322 04 Mar 2020 at least one exhaust fan mounted in the hood for drawing air from the treatment chamber into the plenum air space;

wherein the hood is mounted to the ceiling for movement towards and away from the ceiling;

In an embodiment there is a method for vacuum heat treatment of produce comprising placing at least one stack of crates containing the produce into a treatment chamber as disclosed, lowering the exhaust hood until the lower part of the hood meets the top of the uppermost crate of the stack and introducing heated air into the treatment chamber.

The heating chamber is in fluid communication with the treatment chamber for introducing a supply of heated air into the treatment chamber.

Suitably the heated air is introduced into the lower part of the treatment chamber so that the heated air may travel up through the containers for contacting the produce.

In one aspect, the apparatus has opposing side walls and two end walls. The heating chamber may be located along a side wall and separated from the treatment chamber by an internal dividing wall. The heating chamber and treatment chamber may share a common floor. The lower edge of the dividing wall may be spaced from the common floor so as to define an air inlet space through which heated air may be delivered into the treatment chamber. In this way, the heated air is distributed such that it flows across the floor.

In this aspect, the apparatus may include a grate located above the floor such that the containers may sit on top of the grate so as to allow heated air to travel upwards through the bottom of the lower most container.

It is important that the plastic bins that are used for VHT treatment have ventilation slots or holes so as to allow the heated and humidified air to contact the produce. Typical bin dimensions are square with sides between about 800mm to about 1200mm and a height of between about 750 to about 1000mm.

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The bins that are used for VHT treatment are plastic bins designed for fruit and vegetable transport and cold storage. The bins are provided with side vents so as to facilitate cooling when the produce is refrigerated.

Wooden crates and cardboard produce boxes are unsuitable for use in VHT treatment as they absorb moisture when subjected to the heat and humidity of the VHT treatment. Plastic bins are easy to clean and can tolerate chemical washing.

Large plastic bins are however unsuitable for storage and transport of many types of produce as it may result in compression damage over time. Further the produce on the lowermost layer is in contact with the ventilation holes and is subject to further compression damage resulting in indentions complimentary to the ventilation holes.

The types of produce that are subject to compression damage include mangos, paw paw and tomatoes. Produce of this type is generally transported in stackable cardboard trays. Mangos in particular are transported in single layer cardboard trays. The base of the trays may be contoured and/or lined to resist compression damage.

In practice, in order to treat produce such as mangos, the fruit is manually unloaded from the cardboard trays at the VHT treatment facility and loaded into bulk plastic bins such as field bins or crates for treatment. After treatment, the fruit is unloaded form the bulk bin, placed into new (sterile) cardboard trays and then covered with fruit fly resistant mesh in a quarantined area. It is important that the fruit is not left in the bulk bins for any length of time post treatment. This is because, the fruit on the lowest layer that is in contact with the ventilated base of the bin is damaged by the by contact with the edges of the ventilation slots.

There are other practical problems associated with the use of bulk bins for VHT treatment. For some types of produce, or produce that may be at a riper stage than usual, the propensity to damage may limit the number of layers of produce that may be stacked on top of one another in a bin. In some instances, there may be simply insufficient produce for treatment to fill all the bins.

This incomplete filling of a bin may create problems with encouraging uneven airflow. Airflow will follow the path of lower pressure. This may be a particular problem with a horizontal air flow configuration as shown in Figures 1 and 2. Figure 1 shows that the air A will tend to flow in the free space in the bin 1 above the fruit 2 rather than through the fruit as shown in Figure 2.

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In the case of a vertical flow configuration, the airflow may be diverted out through the upper side vents 3 rather than through the path of the produce and out through the bottom vents 4 as shown schematically in Figures 3 and 4. In practice, in order to reduce or avoid loss of air through side vents as shown in Figure 3, tarps or other covering material may be placed over the side vents so as to channel the air flow. It will be appreciated this is an additional step that adds to the commercial cost of the treatment.

Another disadvantage where the filling of the bin is limited so as to avoid damage is that the HVT treatment procedure can only treat half the maximum capacity of produce which is a commercial loss.

It is also impractical for a number of reasons to stock a range of different sized bins so as to accommodate different load sizes.

The present inventor has therefore proposed that by providing plastic stackable produce containers that are configured to hold up to a maximum of five layers of produce, suitably three, more suitably two layers and most suitably a single layer of produce may make a substantial contribution to the working of an HVT procedure.

The contribution may include the reduction or avoidance of compression damage and/or loss of air flow through side vents

According to another aspect, there is provided a method of subjecting fresh produce to heat and vapour treatment, comprising the steps of;

providing a plurality of plastic containers having a height dimension for holding between one to five vertical layers of an article of fresh produce, the crates being configured to be stacked one on top of the other and each crate comprising side walls and a floor, the floor containing flow through openings for allowing air to flow therethrough;

loading each container with the fresh produce;

stacking a plurality of containers one on top of the other so as to form at least one stack of containers;

placing the or each stack in a treatment chamber;

introducing heated and humidified air into the treatment chamber to heat the produce to a predetermined temperature and removing the containers from the treatment chamber.

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The plastic containers or crates have a height suitable for up to five layer of produce to be placed therein. It will be appreciated that the height may vary depending upon the produce. For example, mangoes, tomatoes, papayas, eggplants and the like are of different dimensions. A person skilled in the art would readily be able to calculate the required height for a specific produce.

The foot print dimensions of the crates are generally similar to those of transport boxes or trays as used for that produce in the respective industry. Such trays and boxes are dimensioned for stacking onto conventional transport palettes.

Transport boxes and trays are generally made from cardboard. Cardboard boxes and trays are readily supplied in flat pack form to the packaging site. Virgin cardboard is a sterile material and the boxes do not require cleaning or other sanitation prior to packaging at the source. Cardboard boxes are also easily disposable after use and may be readily recycled. The cardboard trays are generally packed on site at the farm and then transported to the VHT treatment facility. As mentioned above, cardboard is incompatible with VHT treatment.

In the present method, the loading of the plastic crates is suitably carried out on site at the farm or other packing facility. This avoids the further manual handling steps at the VHT treatment facility.

The floor of the crate comprises ventilation openings for air flow. Suitably the ventilation openings are configured to minimise or avoid hard edges that may damage the produce.

In some aspects, a resilient insert may also be placed on the floor of the crate so as to provide additional cushioning to the produce. The insert is suitably a thermoplastics material that is stable under the temperature and humidity of the HVT treatment. A suitable material is a polyolefin foam such as polyethylene. Suitably the insert may have apertures, slots or holes that allows heated and humidified air to flow through. Suitably the apertures, holes or slots may overlap or be consistent with the dimensions of the openings in the floor.

This may be compared with conventional fruit packing plastic crates have a floor with rectangular grid configuration with sharp or thin edges. This grid floor design is essentially concerned with minimising weight and material rather than protection of the contents. Byway of example, the grid may comprise rectangular openings between of about 30mm x 20mm with a land area between the openings of about 1mm to 5mm.

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This may minimise diversion of air flow out of the crate as shown in Figure 1.

After the produce in the crates has been heated to the predetermined temperature and held for the specified time, the crates are removed from the treatment chamber. The crates and treated produce may then be covered with fruit fly resistant mesh in compliance with quarantine requirements. It will be appreciated that the plastic crate will also be sterilised from the VHT treatment process. The treated and covered crate of produce may then be exported.

The crate is suitably made from a thermoplastics material that is readily able to be recycled. An example of such a material is virgin polypropylene or polyethylene. The crate may be granulated and added to a plastics masterbatch.

Suitably the crate is collapsible so as to minimise transport costs to the initial loading site.

Also disclosed herein is a plastic container for holding items of fresh produce comprising walls and a floor wherein the floor comprises ventilation openings that have a rounded rectangular shape.

The above method is particularly applicable for use with the treatment chamber as disclosed in the first aspect in which the ceiling panel can be lowered to meet the top of the uppermost crate. This may avoid the problem as shown in Figure 3 above in which there is an open air space between the upper layer of produce and the air outlet.

BRIEF DESCRIPTION OF DRAWINGS

Figures 1 to 4 are schematic drawings showing air flow through prior art VHT treatments;

Figure 5 is a perspective view of a VHT chamber as disclosed herein;

Figure 6 is an end view of the VHT chamber shown in Figure 6;

Figure 7 is a section A-A of Figure 6;

Figure 8 is a section B-B of Figure 6;

Figure 9 is a schematic internal front elevation of the VHT chamber;

Figure 10 is a section C-C from Figure 9;

Figure 11 is a schematic top plan view of the VHT chamber;

Figure 12 is a schematic view of a model of a VHT chamber as used to conduct air flow trials;

Figure 13 is a top perspective view of a container as disclosed herein and

Figure 14 is a bottom perspective view of the container as shown in Figure 12.

DETAILED DESCRIPTION

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Figure 5 is a perspective view of a VHT chamber 10 as disclosed herein. The chamber is an insulated container with a similar general construction to that of refrigerated containers that are known in the refrigeration transport art as Reefer units or containers. Reefer units are designed for bottom flow delivery of chilled air that is cooled by a refrigeration unit at one end.

The floor has a T-shaped decking floor to allow cool air to flow into the chamber through or around the cooled produce and warmed air is returned to the cooling system in the space between the top of the produce and the container ceiling.

The VHT chamber 10 is to be constructed using the bodies of three 40 ft Reefer containers.

A first container is modified by removing the refrigerator unit at one end, removing wall sheeting along one side and removing the roof panel to provide main section 12.

A second container is cut in half lengthways and the roof removed. One lengthways half provides side section 14.

A third container is cut in half through the horizontal axis. The upper half provides upper left section 16. The other half is cut again to provide upper right section 18.

The four sections are welded together to provide container 10. Doors 8 are installed at each end.

Figure 7 shows the section A-A as shown in Figure 6. The section has the T section floor 20 of the original Reefer container. The upper section 16 provides a ceiling space that will be described further below.

Figure 8 shows the section B-B as shown in Figure 6. Section 14 defines a space for heating coils or heating chamber. Section 12 defines a space for holding produce to be treated, a treatment chamber. The treatment chamber 12 and the heating chamber 14 are separated by an internal dividing wall 13. The internal dividing wall 13 has a bottom edge that is spaced form the floor 20 as will be discussed further with reference to Figure 10.

Figure 9 is a schematic side elevation view of the exhaust hood arrangement 22 that draws heated air upwardly from the floor 20 and through the produce. The hood arrangement 22 has a housing 24 that is trapezoidal in cross section. A series of exhaust fans 26 are mounted in the hood 22.

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The housing 24 is mounted to the ceiling 30 by a winch arrangement such that the housing 24 may mover vertically towards and away from the roof. The housing 24 is closed off at the lower end by a 30% perforated steel sheet 32. The perforations are staggered round holes.

Figure 10 shows the section C-C from Figure 9 and schematically shows the air flow within the chamber 10.

Figure 11 is a plan view showing that there are two rows of nine fans 26 extending along each side of the chamber 10.

Heating coils 34 are housed within heating chamber 14 and provide a source of heated air HA. There is also a source of water to provide the required degree of humidity as is known in the art. The internal dividing wall 30 has a bottom edge 40 that is spaced from floor 20 so as to define a longitudinal air flow passage 44 that allows heated air HA to enter the treatment chamber 12 across and perpendicular to the T floor 20.

The stacks of crates 36 are placed above the floor 20 on a grid 42. This enables the hot air HA to be drawn upwardly through crates 36 of produce so as to heat the produce to the required temperature. After the hot air HA has passed through the crates 36 and drawn into the ceiling plenum space 16, the cooler air CA is recycled back to the heating chamber 14.

It may be seen that the hood housing 24 is directly above the crates 36.

The housing 24 is able to be lowered or raised to accommodate crate 36 stacks of different heights.

Trials

Air flow tests were conducted on a model hood arrangement 50 that is shown in Figure 12. The model hood arrangement 50 includes a hood 51 with a single extraction fan placed over a stack of crates. The hood 51 has a depending collar 53 that receives the upper end of the uppermost crate 36. The crates used for the tests were conventional produce crates that are used for refrigerated transport and thus have side vents for allowing flow through of chilled air. The crates were empty.

As explained above, air flow through crate sides is undesirable for HVT treatment. For the purpose of the tests, the crates were wrapped in a plastic film. Thus the combination of the

2020100322 04 Mar 2020 plastic film and hood 51 fitting closely over the uppermost crate36, the flow of air is limited to up flow through the crates.

The crates 36 were placed on a slatted palette 52 that was in turn placed on empty crates 36 so as to space the bottom most crate from the ground.

The cross section of the crate stack 36 was divide into nine sections in a 3 x 3 grid. The exhaust fan 26 was turned on and air flow was measured (m/s) by placing an anemometer below the lower crate at a location corresponding to each of the nine sections.

Trial 1

A first trial was conducted without any means of flow restriction between the uppermost crate and the extraction fan.

The results are shown in Table 1.

Table 1

2.00	•1.94	2.00
A	B	C
2.38	2.68	2.59
D	E	F
2.03	1.91	2.16
G	H	I

Maximum Air Flow =	(E)	2.68
Minimum Air Flow =	(H)	1.91
Maximum differential =		0.77
Air flow differential % =		40

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Trial 2

A second trial was conducted with a 30% perforated steel mesh (staggered round hole configuration) placed at the lower part of the hood 51 immediately above the collar 53.

The results are shown in Table 2.

Table 2

30% Perforation Restriction

2.08 A	2.03 B	1.97 C
2.21	2.27	2.24
D	E	F
2.03	1.97	2.08
G	H	I
Maximum Air Flow	= (E) 2.27
Minimum Air Flow	= (H) 1,97
Maximum differential	= 0.30
Air flow differential %	= 15

The results from both trials show that the centre section E had the highest airflow being 2.68 and 2.27 respectively. The results also show that section H displayed the minimum airflows of 1.91 and 1.97 respectively.

The airflow differential % of Trial 1 at 40% was significantly higher than the airflow differential of 15% for Trial 2.

As discussed in the background section, a HVT treatment process is strictly monitored to ensure that the internal temperature of all produce is heated to the specified temperature and

2020100322 04 Mar 2020 is held at that temperature for the specified period of time. In practice, it is not possible to measure each produce item. To ensure compliance for all produce, temperature probes are placed in produce that is located at those parts of the HVT chamber that are the coolest. In practice, this means that the produce in the hottest parts of the HVT chamber are subjected to higher temperatures for longer and the overheated produce is subject to heat damage. Constancy of temperature across the HVT chamber is highly desirable. Constancy of flow of hot air through the produce is one factor in achieving such consistency.

Turning now to the trials above, the sections of lowest airflow would correspond to the cooler parts of a HVT chamber. Thus in practice, temperature probes would be placed in produce located in sections B and H. For trial 1, the produce in section E would be subjected to considerably higher air flow and this higher temperatures than produce in sections B and H.

Trial 2 shows the differences in maximum and minimum air flow to be significantly less. This would convert in practice to a lesser difference between the in temperatures of the treated produce in sections E and H.

The present inventor has surprisingly and unexpectedly discovered that by providing an air flow restriction below the exhaust fan, air flow differential may be reduced.

Figures 13 and 14 show top and bottom perspective views of a produce container 100 as disclosed herein. The container is formed from polypropylene that is resistant to the temperature and humidity of a HVT treatment.

The container 100 has an open top and is rectangular with two side walls 102, 104, two end walls 106, 108 and a floor 110.

The container 100 is intended for use for the transport and treatment of mangos. The container 100 is therefore sized similar to conventional cardboard mango trays. The crate 100 may be stacked on top of another crate. Spaced ribs 112 are provided on the bottom of the floor to facilitate stacking as is known in the art.

The floor 110 has a plurality of vent openings 114 uniformly distributed across the floor 110. The openings 114 are rounded rectangles. Thus there are no hard corners that may damage the mango skin. The openings 114 are separated by a land section 116.

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It may be appreciated that the density of the openings 114 and width of the land 116 provides for minimal damage to mango skin. This may be compared to conventional crates that have larger openings with thin lands between them that may easily damage a mango.

The side walls 102, 104 and end walls 106, 108 have recesses 120 to allow for manual stacking and unstacking of containers. On either side of the recesses 120 are two parallel longitudinal rows of further ventilation openings 122. At each corner of the tray, each wall has a vertical row of ventilation openings 124. The end walls 106, 108 have a further lateral row 130 of ventilation openings along the bottom edge.

The ventilation openings 122, 124 are also rounded rectangles. The openings 122, 124 allow for cold air to flow through the trays when they are placed in a chilled container for transport. The wall openings are the minimum required to allow for chilling or cooling. This minimises heated air passing out through the sides as is shown in Figure 3. On the other hand the openings 114 in the floor optimise vertical air flow though the floor.

The outer face of each wall also has pick-up points 126 for automated robotic vacuum handling devices.

The tray 100 is collapsible to facilitate cost effective transport. The collapsed containers may be readily transported to a packing site and easily assembled prior to packing.

The collapsed containers may be transported to a packing site or on site at a farm. The containers 100 are packed with produce and stacked on pallets for transportation to the site of the VHT chamber. The pallets with stacked containers thereon may be placed directly in the VHT chamber without requiring manual unpacking of the produce from the crates into which they were packed at the farm into crates used only for the VHT treatment.

The VHT chamber has doors at each end that allows for loading the VHT chamber at one end with produce to be treated and unloading at the other end to a quarantine space of the treated produce. The treated produce does not need to be unpacked and loaded into sterile containers fortransport. The treated produce and present containers may simply be covered with mesh as required by quarantine regulations and transport to the point of sale site in the same container.

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It will be appreciated that the ability of using the same container from the farm, through the VHT treatment and transport to point of sale may enable efficient tracking of produce from the farm all the way through to point of sale that may be in a different country.

It will be appreciated that various changes and modifications may be made to the invention as described and claimed herein without departing from the spirit and scope thereof.

Claims

1. An apparatus for supplying heated and humidified air to fresh produce comprising;

a treatment chamber for holding a plurality of produce containers, the treatment chamber comprising a ceiling and an exhaust hood below the ceiling so as to define a plenum air space between the exhaust hood and the ceiling;

a heating chamber for heating air, the heating chamber being in fluid communication with the plenum air space for receiving exhausted air and also in fluid communication with the treatment chamber for introducing heated floor for the supply of heated air into the treatment chamber.

2. The apparatus of claim 1, wherein the open area of the restriction arrangement is between about 15% to about 60%, preferably between about 20% to about 50%, and more preferably between about 25% to about 45%.

3. The apparatus of any one of claims 1 to 3, wherein the air flow restriction arrangement is a perforated metal sheet.

4. The apparatus of any one of claims 1 to 3, wherein the exhaust hood is mounted to the ceiling and is able to be raised or lowered relative to a vertical stack of produce containers.

5. The apparatus of any one of claims 1 to 4, wherein the apparatus comprises opposing side walls, two end walls and a base floor, the heating chamber is located along one side wall and separated from the treatment chamber by an internal dividing wall, the internal dividing wall has a lower part that is be spaced from the base floor so as to define an air inlet space through which heated air may be delivered into the treatment chamber above the base floor.