The invention pertains to apparatuses and methods for the treatment of organic materials such as food products in a vacuum chamber of the type in which the organic materials are transported through the vacuum chamber on a conveyor belt.

Background of the Invention

Treatment of organic materials in a vacuum chamber is a known process in the processing of food products and biologically-active materials. An example of such treatment is dehydration, which is usually done in order to preserve the products for storage, or to create a product that is used in the dehydrated form, such as dried herbs and various kinds of chips. Vacuum microwave dehydration is an effective method of dehydration. Examples in the patent literature include WO 201 1/085467 A1 , Fu et al., published July 21 , 201 1 ; WO 2013/010257 A1 , Fu et al. , published January 24, 2013; and WO 2014/085879 A1 , Durance et al. , published June 12, 2014. Vacuum microwave-drying is a rapid method that can yield products with improved quality compared to air-dried and freeze-dried products. Because the drying is done under reduced pressure, the boiling point of water and the oxygen content of the atmosphere are lowered, so components sensitive to oxidation and thermal degradation, such as some food and medicinal components, can be retained to a higher degree than by air-drying.

In machines for the treatment of organic materials in a vacuum chamber, including vacuum microwave dehydration, where the process is a continuous-throughput rather than a batch process, the material being treated is typically carried through the vacuum chamber using a conveyor belt. In one type of these machines, the organic material is carried directly on the belt, causing the belt to become contaminated with product residues and require periodic cleaning. This

necessitates shutting down the machine and opening up its interior for

maintenance access. Production time is lost, and the labour cost of doing the maintenance is incurred. This problem is reduced to some extent in machines which employ containers such as trays to carry the material on the conveyor belt, protecting it from contamination. However, in this container-type prior art machine, the loaded containers have to be moved in and out of the vacuum chamber, typically through an airlock chamber with two movable doors, and the cycle time required to move them through the vacuum locks is a limitation on the production capacity of the machine. It limits the maximum microwave power and processing speed that can be employed.

The present invention is directed to an improved apparatus which reduces these disadvantages of conventional vacuum chamber machines.

Summary of the Invention

The invention provides a continuous-throughput vacuum chamber apparatus in which the organic material to be treated in the chamber is carried directly on the conveyor belt, avoiding the production limitations of the container-type machines. The apparatus has a cleaning station for cleaning the conveyor belt as the machine operates, reducing the need to shut down the machine for cleaning. The cleaning station is external to the vacuum chamber, avoiding contamination of the chamber by removed material residues or cleaning preparations, and permitting a more thorough cleaning than if the cleaning station were inside the chamber. The apparatus also makes it possible to monitor the status of contamination of the conveyor belt from the outside of the vacuum chamber.

One aspect of the invention provides apparatus for treatment of organic material, comprising: a vacuum chamber for operation at a pressure less than atmospheric; means for producing treatment conditions, such as microwave radiation, within the vacuum chamber; means for continuous loading of the organic material into the vacuum chamber; a conveyor belt for transporting the organic material through the vacuum chamber, the conveyor belt forming a closed loop and extending outside of the vacuum chamber such that one part of the conveyor belt is inside the vacuum chamber and another part is outside the vacuum chamber; means for continuous unloading of the treated organic material from the vacuum chamber; and means for cleaning the conveyor belt during operation of the apparatus, located outside the vacuum chamber. Another aspect of the invention provides a method for treatment of organic material in a vacuum chamber, comprising the steps of: loading the organic material continuously onto a conveyor belt inside the vacuum chamber, the vacuum chamber being at a pressure less than atmospheric, the conveyor belt forming a closed loop, one part of the conveyor belt being inside the vacuum chamber and another part being outside of the vacuum chamber; moving the organic material through the vacuum chamber on the conveyor belt; treating the organic material on the moving conveyor belt by exposing it to conditions within the vacuum chamber, such as microwave radiation; unloading the treated organic material continuously from the vacuum chamber; and cleaning the moving conveyor belt at a location outside the vacuum chamber. Further aspects of the invention and features of specific embodiments of the invention are described below.

Brief Description of the Drawings

Figure 1 is a partly cutaway view of a dehydration apparatus according to one embodiment of the invention. Figure 2 is an isometric view of the apparatus of Figure 1 .

Figures 3A and 3B are sectional views of the conveyor belt inlet and outlet, respectively, of the vacuum chamber.

Figure 3C is a schematic view of the belt washer of the dehydration apparatus.

Figure 4 is an elevational view, partly broken away, of the input end of the apparatus of Figure 1 .

Figure 5 is a schematic view of the apparatus of Figure 1 .

Figure 6 is a schematic view of a pasteurization apparatus according to another embodiment of the invention.

Detailed Description Referring first to Figures 1 to 4, in one embodiment, the treatment apparatus of the invention is a vacuum-microwave dehydration apparatus 20. This comprises a processing unit 22, in which organic material is vacuum microwave-dried, having an input end 24 and an output end 2G, with an input module 28 at the input end and an output module 30 at the output end. The input module 28 has a housing 60, fastened and sealed to the input end 24 of the processing unit 22. Similarly, the output module 30 includes a housing 62 fastened and sealed to the output end 26 of the processing unit. The processing unit 22 and modules 28, 30 are supported on a frame 32 with legs.

A vacuum chamber 34 extends the length of the processing unit 22 and the interior of the input and output modules 28, 30. Microwave-transparent windows 36, separated by short panel sections 38, form the bottom wall of the processing unit portion 22 of the vacuum chamber 34. The vacuum chamber has a cover 40 and side walls 42. Microwave chamber modules 44 are arranged below the windows 36, each module 44 having a microwave generator 46 and a microwave chamber 48. Each microwave chamber has side walls 50 and a floor 52, with one of the microwave-transparent windows 36 forming the upper wall of each microwave chamber, separating it from the vacuum chamber 34. The microwave chambers 48 are not sealed from the atmosphere and are thus air-filled and at atmospheric pressure.

A microwave-transparent conveyor belt 54 for transporting the organic material through the vacuum chamber extends along the windows 36. The conveyor belt extends into the input and output modules 28, 30, and forms a continuous loop.

The belt 54 runs over a roller 56 in the input module and over a roller 58 in the output module 30. The belt 52 is driven by a power-driven roller 90 that engages the belt 52 in the belt-washer, as described below.

The input module 28 has a rotary vacuum valve 64 for feeding the organic material to be dried into the processing unit. The valve 64 is motor-driven and permits the continuous feeding of the material from a hopper 66, at atmospheric pressure, into the interior of the vacuum chamber, at reduced pressure. Material passing through the valve 64 falls through a chute 68 onto a motor-driven spreader 70, which is arranged to distribute the material across the conveyor belt 54.

The output module 30 has a motor-driven rotary vacuum valve 72, for continuous removal of the dried material from the vacuum chamber. The rotary vacuum valve 72 is arranged below an outlet chute 74 such that dried material dropping off the end of the conveyor belt 54 as the belt passes around the roller 58 drops into the chute 74 and is gravity-fed into the rotary vacuum valve 72 for release from the apparatus into a container at atmospheric pressure.

Apertures 78, 82 for airtight passage of the conveyor belt 54 are provided in the output and input modules respectively, whereby a portion 54A of the continuous loop formed by the conveyor belt is inside the vacuum chamber and a portion 54B is outside it, at atmospheric pressure. The portion 54B of the conveyor belt outside the vacuum chamber is supported by rollers 84 on the frame 32

underneath the microwave chamber modules 44.

As seen in Figure 3B, a vacuum seal 76 is fitted in the aperture 78 in the housing 62 of the output module 30. After the dried material is dropped from the conveyor belt 54 into the outlet chute, the conveyor belt passes out of the vacuum chamber through the vacuum seal 76. Likewise, as shown in Figure 3A, a vacuum seal 80 is fitted in the aperture 82 in the housing 60 of the input module 28, and the conveyor belt passes back into the vacuum chamber 34 through this vacuum seal. The seals 76, 80 thus permit passage of the conveyor belt out of and back into the vacuum chamber 34 without loss of the vacuum pressure inside the vacuum chamber. The seals 76, 80 may be solid or inflatable silicon rubber seals, for example as marketed by The Rubber Company. The material of the conveyor belt 54 may be Teflon-coated fiberglass, which minimizes friction with the seals 76, 80.

Referring to Figure 3C, a belt washer 86 is attached to the frame 32 outside the vacuum chamber 34. It is arranged below the vacuum chamber for cleaning of the conveyor belt 54 after it exits the vacuum chamber through the aperture 78 in the output module 34 and before it re-enters through the aperture 82 in the input module 28. The belt washer has a housing 88 having a cleaning fluid drain 89, a power-driven roller 90 around which the belt passes, and two power-driven brushes 92, 94 positioned to brush against each respective side of the belt. A sprayer 96 is arranged to spray a cleaning solution onto the belt as it passes against the brushes. By means of the belt washer 86, the conveyor belt is cleaned, at atmospheric pressure, after each traverse through the vacuum chamber 34. The dehydrating apparatus 20 includes the components conventionally required for the operation of vacuum microwave driers. As illustrated schematically in Figure 5, a vacuum pump 98 is operatively connected through a condenser 100 and via a vacuum distributor 102 to vacuum ports 108 in the vacuum chamber and the input and output modules. The condenser condenses water vapor produced during dehydration of the organic material. A refrigeration unit 104, comprising a compressor, cooling fan and refrigerant pump, conveys refrigerant to the condenser 100 to maintain the condenser at a desired temperature. A water load system 106 may be provided in the vacuum chamber to absorb extra microwave energy, by means of a water pump and conventional piping within the vacuum chamber. The dehydration apparatus 20 includes a programmable logic controller (PLC) 110, programmed and connected to control the operation of the system, including controlling the drive motors, the microwave generators, the vacuum pump, the refrigerant pump and the belt washer.

The dehydrating apparatus 20 operates according to the following method. The vacuum pump, refrigerant pump, water pump, microwave generators and the motors to drive the conveyor belt and the rotary vacuum valves are actuated, all under the control of the PLC. The vacuum chamber is brought to reduced pressure. Operating pressures may be in the range, for example, of about 30 to 300 Torr (3.9 to 39.9 kPa), or 0.1 to 30 Torr (0.13 to 4.0 kPa). The organic material, in pieces small enough to be fed through the rotary vacuum valves, is fed into the hopper. Within the vacuum chamber 34, the material is dehydrated by the radiation from the microwave generators that passes through the windows 36. The conveyor belt 54 is operated at such speed, and the generators 44 at such power level, that the organic material is dehydrated to the desired moisture level during its traverse through the vacuum chamber. The dried material falls into the outlet chute 74 and is collected outside the unit from the rotating outlet valve 72. The conveyor belt is washed continuously by the belt washer 86, after each traverse of the vacuum chamber.

Examples of materials suitable for dehydration by the apparatus 20 include fruit, either frozen or un-frozen, including banana, mango, papaya, pineapple, melon, apples, pears, cherries, berries, peaches, apricots, plums, grapes, oranges, lemons, grapefruit; vegetables, either fresh or frozen, including peas, beans, corn, carrots, tomatoes, peppers, herbs, potatoes, beets, turnips, squash, onions, garlic; cannabis; pre-cooked grains including rice, oats, wheat, barley, corn, flaxseed; hydrocolloid solutions or suspensions, vegetable gums; vaccines, enzymes, protein isolates; amino acids; injectable drugs, pharmaceutical drugs, natural medicinal compounds, antibiotics, antibodies; composite materials in which a hydrocolloid or gum surrounds and encapsulates a droplet or particle of a relatively less stable material as a means of protecting and stabilizing the less sensitive material; meats, fish and seafoods, either fresh or frozen, and dairy products such as cheese, whey proteins isolates and yogurt.

The inventive arrangement of a conveyor belt washer that is external to a continuous-throughput vacuum chamber also applies to processes in which the organic material is processed in a vacuum chamber by a treatment other than dehydration, for example by heating or pasteurization. Figure 6 schematically illustrates a pasteurization apparatus 200 for the pasteurization of solid food products using microwave radiation and steam for heating. The apparatus 200 is substantially the same as the dehydration apparatus 20, but includes a steam conduit 202 connected to a source of steam 204, for feeding steam into the vacuum chamber 34. A pressure sensor 206 controls the operation of a steam supply valve 208, to add steam into the vacuum chamber if the pressure drops below a set level. Heating of the material in the vacuum chamber to pasteurize it is done by means of both the steam and the microwave radiation from the microwave generators 46, under the control of the PLC 110. The apparatus is otherwise the same as the dehydration apparatus 20, and is operated in the same manner.

Example 1

Blanched onion rings were processed in a vacuum microwave dehydration apparatus of the type illustrated in Figures 1 to 5. The initial moisture content was 88 wt.%. Processing was done at a microwave power level of 80 kW and a vacuum pressure of 32 Torr. After 25 minutes of processing, the output product had a moisture content of 84 wt.% and a temperature of 28 degrees C. The conveyor belt was continuously cleaned by the belt washer. Example 2

Pre-dried blueberries having an initial moisture content of 40 wt.% were processed in a vacuum microwave dehydration apparatus of the type illustrated in Figures 1 to 5. Processing was done at a microwave power level of 100 kW and a vacuum pressure of 32 Torr. After 35 minutes of processing, the output product had a moisture content of 3 wt.% and a temperature of 75 degrees C. The conveyor belt was continuously cleaned by the belt washer.

Throughout the foregoing description and the drawings, in which corresponding and like parts are identified by the same reference characters, specific details have been set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail or at all to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof. Some examples include the following:

• The belt washer can take many forms, and include additional types of cleaning, such as irradiation.

• The belt washer can be operated intermittently, depending upon the material being treated and the needs of a particular application.

• Piston vacuum valves can be used as the airlock valves instead of rotary vacuum valves.

• The conveyor belt can pass over the vacuum chamber, rather than under it, after exiting the vacuum chamber.

• The microwave generators and window can be above rather than below the vacuum chamber, or both above and below, or the microwave generators can be inside the vacuum chamber.

• The processing unit can include any desired and practical number of modules, including a single module.

• Each microwave chamber module may hold two or more microwave generators rather than only one. • The means for reducing the pressure in the vacuum chamber can include any means for applying a vacuum to the vacuum chamber, such as connection to the central vacuum system of a plant.

Accordingly, the scope of the invention is to be construed in accordance with the following claims.