BACKGROUND ART At the present time, the shelf life of foods such as fruit and vegetables can be extended by refrigeration, freezing, canning/bottling, chemical treatments and/or gas flushing.

Refrigeration of produce slows the deterioration/degradation process. A significant difference in the texture, taste and appearance of the refrigerated produce occurs after a period compared to the fresh produce when initially refrigerated.

The freezing of vegetables prolongs their shelf life, however the thawing of these vegetables removes their fresh appearance and the fresh flavour available from fresh vegetables.

The initial freezing, storage and transport of frozen produce is expensive.

The canning of fruits and vegetables extends their shelf life but is suitable for only certain varieties of produce, and the storage and disposal of the containers before and after use can become problematic.

The chemical treatment of fruits and vegetables to extend their shelf life is common practice the techniques used being largely unknown to the public.

Gas flushing to create a modified atmosphere within a package containing foodstuffs is also common practice however there are significant capital and running costs involved in the provision of suitable equipment.

Each of the processes referred to above are suitable for a variety of foodstuffs including fruit and vegetables, however each method is limited by the physical and aesthetic qualities of the produce required by the customer.

The appearance of fruit and vegetables is a major factor in the

eyes of purchasers and it is important that at the point of sale, food retains its natural appearance after processing and packaging to the point of sale.

OBJECT OF THE INVENTION It is an object of the present invention to provide a process and apparatus for extending the shelf life of various products such as foodstuffs including fresh fruit and vegetables.

A further objective of the present invention is to provide an intermediate process between fresh-cut foodstuff processing where cells are still living and traditional foodstuff canning where cellular functions and all microbial growth has been arrested. Such a process will offer the advantages in fresh texture and taste without the myriad of different storage needs of fresh cut product.

Further objects and advantages of the present invention will become apparent from the ensuing description which is given by way of example.

DISCLOSURE OF INVENTION According to the present invention there is provided a method of processing products comprising the steps of conveying the products within communicable heating and cooling chambers and controlling temperatures and elevating pressures within the chambers during the period of residence of the products.

The control of temperature within the chamber can be in two distinct phases, heating and then cooling.

The heating of the product can be by microwave.

Cooling of the product is by refrigeration.

Conveyance of the product within the chamber is by screw or belt conveyors and/or free fall systems.

Pressures within the chamber are elevated to be greater than 1.5 bar (150 Kpa), while the product is heated and subsequently cooled.

Product is microwave heated to above 500C and then cooled below the critical temperature point of the produce.

The residence time of the product within the chamber can be

less than twenty minutes.

According to a further aspect of the present invention there is provided processing apparatus comprising a processing chamber, an inlet to the processing chamber adjacent one end thereof and an outlet from the processing chamber at/or adjacent an opposite end of the chamber, means for conveying product throughout the chamber, means for heating a first portion of the chamber and means for cooling a second downstream portion of the chamber, and means for controlling temperature, residence time and pressure within the chamber as product is conveyed within the chamber.

The apparatus can include water jacket microwave locks at both an inlet to and outlet from the first portion of the chamber.

The means for heating the first portion of the chamber can be a microwave generator.

The processing chamber can comprise a heating chamber and a downstream cooling chamber interposed by tower and conveying means for conveying product throughout the apparatus.

The apparatus can have positive displacement paddle valves at the inlet to and outlet from the processing chamber.

BRIEF DESCRIPTION OF THE DRAWINGS Aspects or the present invention will now be described by way of example only with reference to the accompanying drawings in which Figure 1 is a diagrammatic representation of one form of apparatus in accordance with the present invention, and Figure 2 is a displacement/temperature curve illustrating changes in pressure temperature as product is conveyed throughout the apparatus of figure 1, and Figures 3 and 3a are plan and part sectional views of heating and cooling chambers of an apparatus in accordance with one aspect of the present invention, and

Figures 4 and 4a are plan and part sectional views of a heating chamber for the apparatus of figures 3 and 3a, and Figure 5 is a sectional view of a typical microwave guide for the heating apparatus of figures 4 and 4a, and Figure 6 is a sectional view of a typical cooling chamber for the apparatus of figures 3 and 3a, and Figures 7 and7a are sectional drawings of a typical rotary valve for apparatus of the present invention, and Figure 8 is a sectional drawing showing the positioning of a temperature sensor for the apparatus of the present invention, and Figures 9 and 9a are part sectional plan and side views of an intermediate cooling tower for apparatus of the present invention.

BEST MODE With respect to figure 1 of the drawings the drawing product such as foodstuffs can be prepared for processing at a preparation area 1 and be transferred manually to a hopper 2, or alternatively the foodstuff may be automatically transferred to the hopper by conveying means 3. The hopper 2 is provided with a valve 4 which allows the foodstuff to be displaced into a heating and pressure chamber generally indicated by arrow 5.

The heating chamber 5 contains fore and aft microwave locks designated 6 on the drawing, and is communicable with a microwave generator 7. The microwave generator 7 is mounted on a rearwardly inclined entry chamber 8 and, as indicated by the path arrows, foodstuffs are conveyed to and from the heating and pressure chambers by conveying means (not shown).

A tower 9 is interposed between the heating and pressure chamber 5 and a cooling chamber generally indicated by arrow 10. At the outlet from the cooling chamber 10, a valve 11 similar to valve 4 is positioned.

Within the tower 9 a fan and cooling unit (not shown) can be accommodated.

Elevating conveyor means 12 transports processed foodstuffs to a dispersal valve 13. A packaging station 14 may be positioned adjacent the valve 13. Valves 4,11 and 13 may be similar in construction and function.

The path arrows indicate the passage of the foodstuffs via tower 9, the cooling chamber 10 and elevating conveyor 12 to valve 13.

It is to be appreciated that the layout and relative positioning of the elements of the apparatus may vary from that illustrated, depending on such factors as the variety of produce to be processed, handling requirements and central temperatures, site/floor space restrictions and production rates.

The heating and cooling chambers may be in an in-line, parallel, over and under, at right angles to one another or in any other configuration determined by a particular site.

Activation and control means designated 15,16 and 17 are provided to control the environment within the apparatus and, in particular, pressure, temperature and residence periods. Such means can readily be computer programmed and controlled and should include environment measuring equipment and a shut-down facility in the event of malfunction.

Pressures within the heating and cooling chambers of the apparatus can be increased using proprietary pressure pumps.

Figure 2 of the drawings are temperature/displacement and pressure/displacement curves which illustrate graphically temperature and pressure variations as product is conveyed from the heating to the cooling chambers of an apparatus according to the present invention. The upper graph shows that product enters heating chamber 5 at ambient temperature and as it progresses through the heating chamber its temperature is elevated and as product progresses through the cooling chamber 10 its temperature is lowered. The lower graph shows that pressures within the communicable heating and cooling chambers are elevated from ambient/atmospheric pressure to a predetermined level and gradually returned to ambient/atmospheric pressure as product progresses within the conveyor 12.

The apparatus controls the molecular temperature of product as it is conveyed and the heating process polarises the product in proportion to elevated pressures within the heating chamber.

With respect to figures 3 and 3a of the drawings the particular apparatus illustrated is in an L-shaped layout with a heating chamber 5

branching from tower 9 and a cooling chamber 6 also branching from tower 9 at right angles to the heating chamber 5.

Product can be fed to a heating chamber conveyor 17 via a valved entry 18 and progresses to conveyor 19 within the cooling chamber 6 and later exits the apparatus.

The heating chamber 5 is shown in enlarged detail by figures 4 and 4a of the drawings. The heating chamber 5 illustrated comprises an elongate tubular outer body having an open end 21 from which conveyor 17 extends and a closed end 22 which can include a removable cap.

Microwave generators (not shown) are mounted a plurality of guides generally indicated by arrow 23.

Temperature sensors generally indicated by arrow 24 are positioned strategically on the topside of the body 20.

Rotary valves generally indicated by arrow 25 are positioned adjacent entry 18 above the infeed end of the conveyor 17, at the outlet from the cooling chamber and at the outlet from the apparatus.

Microwave chokes generally indicated by arrow 26 are positioned at opposite ends of the body 20 as indicated. The conveyor 17 can be a roller belt conveyor as illustrated.

The microwave guides 23, sensors 24, valve 25 and chokes 26 are shown in more detail by figures 5 through to 8.

With respect to figure 5 each of the microwave guides 23 can comprise an angled divergent sleeve 27 mounted in an opening 28 in the body 20 of the heating chamber via a base 29. A flanged joint 30 enables the connection of a microwave infeed conduit 31 and also provides a means of fitting a microwave permeable window 32.

The number, position, usage and inclination o the microwave guides 23 may vary depending on the product being processed.

Figure 6 of the drawings illustrates one possible form of microwave choke 26. Conveyor frame members 33 provide for the centralised positioning of belt conveyor 17.

Upper and lower water jackets 34 are supported by mounting

flanges 35 and a centralised water jacket 36 is supported by the frame 33.

Troughed sections 37 of the upper and lower water jackets 34 provide passages of predetermined size for the belt conveyor 17. The balance of the area within the body and between the water jackets can be partitioned.

Figures 7 and 7a of the drawings illustrate the valves 25 in more detail.

The valve 25 which is illustrated is a rotary positive displacement valve comprising a journalled hub 38, paddles 39 within a circular casing 40.

Product passes through the valves 25 an entry port 41 and exit port 42.

The hub 38 and paddles 39 may be free-wheeling, or manually or mechanically driven.

Figure 8 of the drawings illustrates a possible temperature sensor mounting arrangement for the heating chamber.

Conveyor 17 is supported by the frame 33 as previously described and sensor units (not shown) can be mounted on a flanged entry 43.

The sensors which are used may be infra-red temperature sensors such as those supplied by the Cobra Corporation of the United States of America.

It is necessary to screen the sensors from the internal environment of the heating chamber and this can be achieved by the provision of high density mesh screens 44. The infra-red sensor"profile"is represented by the shaded triangular image 45 directed at the central longitudinal axis of the conveyor 17.

Figures 9 and 9a of the drawings illustrate one possible arrangement for a refrigeration tower 9 of the present invention. The tower 9 can be a domed vessel provided with connecting sleeves 47,48 for the connecting the bodies of the heating and cooling chambers respectively.

An inspection hatch 49 provides access to the interiors of the

tower which can also accommodate a cooling blower 50 and other elements 51 of a refrigeration plant.

Foodstuffs processed by the apparatus of the present invention still retain natural appearance after processing and packaging without the addition of chemicals. Produce such as fruit and vegetables can be prepared (sliced or diced) into the desired form, processed and then packaged into conventional packaging.

The present invention extends the fresh appearance and taste of processed produce to an extent not available from other processes previously mentioned.

Refrigeration after processing extends the shelf life of the processed produce.

Product degradation is now measurable under refrigeration compared to alternative refrigerated storage procedures.

Reduced storage and handling facilities are an added benefit to the process as product can be packaged and handled on a greater mass per unit volume basis.

The elimination of the need for frozen storage and transport is also a significant economic benefit. The present invention eliminates significantly the bacterial loads in produce which under normal circumstances are the cause of product degradation.

The elimination/reduction of the bacterial load of the prepared product is achieved as a result of the produce being rapidly heated using microwave energy (greater than 2 giga hertze) from ambient temperature (20°C approximately) to a temperature greater than 50°C while under pressure greater than 1.5 bar (150KPa).

While under the same pressure, the produce is then cooled at the same or a slower rate of cooling back to ambient temperature.

Upon exiting the apparatus, product may then be vacuum packaged utilizing a sparging and packaging unit.

The pressure chamber can be fabricated in stainless steel and the inlet and the outlet valves such as described allow a continuous flow of

produce to be processed.

The conveyors within the cooling chamber 9 may tumble produce several times to assist in its cooling.

Whilst the present invention is primarily designed to extend the shelf life of product such as foodstuffs the process and apparatus may be used for the beneficial processing of product which is not for human consumption.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.