Microwave vacuum dehydration apparatus with fractionally rotating container

Abstract

A microwave vacuum dehydration apparatus and method for drying organic materials in which baskets of the materials are moved through a vacuum chamber. The baskets holding, for example, pieces of food to be dried, are fractionally rotated in the clockwise and counterclockwise directions as they are moved through the vacuum chamber. The fractional rotation imparts a gentle rocking motion to the baskets. The baskets have an interior space, and the rocking gently moves the pieces of food on the bottom side of the horizontally- oriented baskets without tumbling them. The dried food pieces have an airy and open structure, and breakage is reduced.

Description

MICROWAVE VACUUM DEHYDRATION APPARATUS WITH FRACTIONALLY ROTATING CONTAINERField of the Invention

[0001] The invention pertains to apparatuses and methods for dehydrating organic materials such as food products in a vacuum chamber of the type in which the organic materials are transported through the vacuum chamber in a rotatable container.Background

[0002] Dehydration of organic materials such as foods and plant materials by microwave vacuum dehydration is well known in the art. In one type of these dehydration machines, organic materials are dried by transporting the materials through a microwave vacuum chamber in a rotating container (basket) in which they are tumbled during the irradiation. Examples are disclosed in WO 2009 / 049409 published April 23, 2009, WO 2014 / 085897 published June 12, 2014, and WO 2021 / 168522 published September 2, 2021 . This type of apparatus has some advantages over the type of microwave vacuum drying apparatus in which the organic materials are transported through the microwave vacuum chamber on trays. That type of dryer is disclosed, for example, in WO 2011 / 085467 published July 21 , 2011. The rotating basket system has higher throughput, requires less energy to dry the material, and requires less labour to load and unload the organic material. However, the rotating basket system also has limitations, particularly for drying certain types of organic materials, due to the fact that the pieces of organic material are tumbled and strike each other as the basket is rotated. This can result in the clustering of sticky, high moisture content materials, breakage causing reduced yield, more shrinkage causing higher density product which negatively affects the final texture of the products, and an undesirable, tightly-wrapped appearance of leafy greens such as Brussels sprouts and cannabis flowers. The rotating basket system is also not suitable for drying powdered materials due to the formation of dust by the full rotations of the basket.

[0003] There is a need in the dehydration industry for a vacuum microwave dehydrationapparatus of the type in which the organic materials are transported through the vacuum chamber in rotatable containers, but which overcome the limitations of the current systems.Summary

[0004] By means of the present invention, a basket of organic material moving through a microwave vacuum dryer is given a gentle rocking motion. This is achieved by applying a partial, clockwise and then counterclockwise rotation to the basket, i.e. , fractional rotation rather than full rotation. The pile of organic material in the basket, for example pieces of food, stays at the bottom side of the horizontally oriented basket, and the pieces are gently moved by the rocking motion so their spatial positions are constantly changing during the microwave vacuum drying process. The dried products exhibit an airier and more open structure and appearance than products subjected to tumbling in a rotating basket. Breakage and fines are greatly reduced, increasing the product yield. Also, due to the constant gentle movement of the food pieces, their surfaces do not touch each other constantly (as they would if sitting on trays), and the burning due to touched surfaces is eliminated. The process of the invention also permits drying of many materials that are difficult to dry using a microwave vacuum dehydration system that tumbles the food pieces, such as IQF carrot slices, partially air-dried banana coins and pineapple wedges. It also permits drying fine powder material, which cannot be done with full rotation of a basket due to the formation of airborne dust particles.

[0005] In some embodiments, the gentle rocking motion of the basket may be accomplished by programming the motors that drive gear assemblies coupled with a roller that supports and fractionally rotates the basket.

[0006] According to one aspect of the invention, there is provided an apparatus for dehydrating organic material, comprising: (a) a container having a cylindrical wall defining an internal space within the container for holding pieces of the organic material, the container having a longitudinal axis and being rotatable about its longitudinal axis; (b) a vacuum chamber having an input end for loading the container into the vacuum chamber, an output end for removing the container, and a longitudinal axis parallel to the longitudinal axis of the container; (c) means for fractionally rotating the container clockwise andcounterclockwise about the longitudinal axis; (d) means for moving the fractionally-rotating container horizontally through the vacuum chamber from the input end to the output end; (e) a microwave generator arranged for transmission of microwave radiation into the vacuum chamber; and (f) means for reducing pressure in the vacuum chamber to a pressure less than atmospheric.

[0007] Another aspect of the invention provides a method for dehydrating an organic material, comprising the step of: (a) reducing pressure within a vacuum chamber to a pressure less than atmospheric; (b) loading a container into the vacuum chamber, the container having a cylindrical wall defining an internal space holding pieces of the organic material within the container, the container having a longitudinal axis and being fractionally rotatable about its longitudinal axis; (c) fractionally rotating the container clockwise and counterclockwise about its longitudinal axis and thereby agitating the pieces of organic material in the internal space within the container; (d) moving the fractionally-rotating container horizontally through the vacuum chamber from an input end to an output end, while applying microwave radiation to dehydrate the organic material; and (e) removing the container of dehydrated organic material from the output end of the vacuum chamber.

[0008] Further aspects of the invention and features of specific embodiments of the invention are described below.Brief Description of the Drawings

[0009] Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[0010] Figure 1 is a cutaway side elevational view of the vacuum microwave drying apparatus according to one embodiment of the invention.

[0011] Figure 2A is a sectional view on the line 2-2 of Figure 1 , showing the input end of the vacuum chamber of the apparatus of Figure 1 , the output end being substantially identical thereto.

[0012] Figure 2B is a transverse cross-sectional view of the container for holding the organic material.

[0013] Figure 3 is an isometric sectional view, partly cutaway, of the vacuum chamber of the apparatus of Figure 1 .

[0014] Figure 4 is a schematic view of the apparatus of Figure 1 .Detailed Description

[0015] Referring to Figures 1 to 3, the apparatus of the invention is a microwave vacuum dehydration apparatus 20. It has a microwave generator 76 and a vacuum chamber 22, through which a container 24 of organic material is transported for microwave vacuum dehydration. The vacuum chamber 22 has a cylindrical wall 25 supported by a stand 21 , an input end 26 for loading the container 24 into the vacuum chamber, and an output end 28 for removing the container 24 from the vacuum chamber. A loading module 30 is provided at the input end 26 for loading the container 24 containing organic materials 61 to be dehydrated into the vacuum chamber. A discharge module 32 is provided at the output end 28 for receiving the container 24 holding the dehydrated organic materials upon removal from the vacuum chamber. The loading module 30 and the discharge module 32 each have a pair of airlock doors, respectively 33, 34 and 36, 37. These permit the containers 24 to be loaded into and unloaded from the vacuum chamber, while maintaining the vacuum chamber at the reduced pressure required for the dehydration process. The airlock doors are self-sealing doors that form an airtight seal in their closed positions. Airlock doors 34, 36 separate the respective loading module 30 and discharge module 32 from the vacuum chamber.

[0016] Means are provided within the vacuum chamber 22 for fractionally rotating the container 24, i.e. , applying a rocking motion to it, as explained below, and for moving it from the input end 26 to the output end 28.

[0017] In one embodiment, shown in Figure 1 , rollers 42A and 42B are longitudinal rodswhich align with each other and together extend along the length of the vacuum chamber 22. One end of roller 42A is mounted at the input zone 29 of the vacuum chamber. One end of roller 42B is mounted at the discharge zone 31 of the vacuum chamber. The other ends of the rollers 42A, 42B are supported together in alignment at a longitudinally-intermediate point in the vacuum chamber. The rollers 42A, 42B are rotatable about their longitudinal axis, which is parallel to the longitudinal axis of the vacuum chamber. Mounting plates (not shown) may be provided at the input zone 29 and discharge 31 zone for supporting the ends of the rollers 42A, 42B. The mounting plates are secured to a respective end support frame 86, 88, which is mounted on the inner side of the cylindrical wall 25 at the respective input 29 and discharge zones 31 of the vacuum chamber. The end support frames 86, 88 of the vacuum chamber define an opening 90, 92 respectively through which the container 24 is loaded into and removed from the vacuum chamber.

[0018] The rollers 42A, 42B have a circumferential surface 44 having spur gear teeth 46 extending along their length, parallel to the longitudinal axis of the rollers 42A, 42B. A gear 78 is mounted on the input zone mounting plate, below the roller 42A, to engage the spur gear teeth 46 of the roller 42A at one end, and a gear 82 is mounted on the discharge zone mounting plate, below the roller 42B, to engage the spur gear teeth 46 of the roller 42B at the other end. Gears 78, 82 are driven by a respective drive motor 48, 50. They may be programmed to fractionally rotate the rollers 42A, 42B about their longitudinal axis at the same speed. Alternatively, they may be programmed to fractionally rotate at different speeds for purposes of optimal drying of certain organic materials.

[0019] In some embodiments, instead of two rollers 42A, 42B, there is a single roller extending the full length of the vacuum chamber. This embodiment does not provide the option of different rotation speeds in different sections of the vacuum chamber.

[0020] The container 24 is a basket made of a microwave-transparent material, such as high density polyethylene, with a closed bottom wall 54, a cylindrical wall 56 and a removable lid 58. As shown in Fig 2B, the inner side of the cylindrical wall 56 defines an empty space 59 in the container for holding the pieces of organic material 61. The cylindrical wall 56 may optionally include baffles 63 extending into the space 59 along part of the length of the basket. Such optional baffles may be arranged at a 90 degree angle toadjacent baffles, as illustrated in Fig. 2B.

[0021] The cylindrical wall 56 of the container has spur gear teeth 60 extending along part or all of its outer circumferential surface, parallel to the longitudinal axis of the container 24. The spur gear teeth 46 of the rollers 42A, 42B are aligned to mesh with the spur gear teeth 60 of the container 24 to fractionally rotate the container about its longitudinal axis as the rollers 42A, 42B are driven to fractionally rotate about their longitudinal axis.

[0022] Means are provided within the vacuum chamber 22 for holding the container 24 on the rotating rollers 42A, 42B. As shown in Figure 2A, a pair of guide members 72, 74 is secured to opposite sides of the opening 90 defined by the end support frame 86, circumferentially spaced from the roller 42A, at the input zone 29, and to opposite sides of the opening 92 defined by the end support frame 88, circumferentially spaced from the roller 42B, at the discharge zone 31. The guide members 72, 74 extend longitudinally through the length of the vacuum chamber 22 from the input zone 29 to the discharge zone 31 , parallel to the longitudinal axis of the vacuum chamber. The guide members 72, 74 are flat rectangular plates, arranged adjacent to opposing sides of the cylindrical wall 56 of the container 24, for guiding the container as it moves along the fractionally rotating rollers 42A, 42B.

[0023] Chamber dividers 94, each extending across the internal, lateral cross-sectional area of the vacuum chamber 22, separate the vacuum chamber into a plurality of vacuum chamber modules (shown as modules 22a, 22b, 22c in Figure 1). The chamber dividers 94 act as microwave chokes to minimize cross interference between chamber modules. For convenience of illustration, the vacuum chamber is shown with only three modules, but it will be understood that it can have any number of modules suitable for a particular application, for example ten modules. In Figure 1 , roller 42A extends through modules 22a and 22b, and roller 42B extends through module 22c. In an embodiment with ten modules, the roller 42A could extend, for example, through the first six modules, and the roller 42B could extend through the last four modules.

[0024] Each of the chamber dividers 94 has openings 96, 97, shown in Figure 3, through which the guide members 72, 74 and the rollers 42A, 42B respectively extend, forsupporting the guide members and rollers through the intermediate portions of the vacuum chamber 22 between the end support frames 86, 88 at the input 29 and discharge 31 zones. Each of the chamber dividers 94 also has an opening 99 for providing a passageway between adjacent vacuum chamber modules for movement of the containers 24 from one module to an adjacent module.

[0025] Means are provided at the input module 30 for moving the container 24 through the vacuum chamber 22, and at the discharge module 32 for removing the container 24 from the vacuum chamber. Figure 1 illustrates an example mechanism. A pushing cylinder 64 is affixed to the input module 30 for pushing the container 24 through the input end 26 of the vacuum chamber, and a pulling cylinder 66 is affixed to the discharge module 32 for pulling the container 24 out of the vacuum chamber at the output end 28. The pushing cylinder 64 and the pulling cylinder 66 may be air cylinders, with a piston 68, 70 respectively, that is moveable between a position extending into the vacuum chamber through the respective loading 30 and discharge modules 32 and a retracted position.Connection means may be provided at the bottom wall 54 and the lid 58 of the container 24 to secure the container 24 to the respective piston 68, 70.

[0026] A plurality of containers 24, each loaded with organic materials, such as pieces of food 61, can be concurrently supported on the rollers 42A, 42B. The containers 24 are sequentially introduced into the vacuum chamber 22 and arranged to be moved, one after another, along the length of the rollers 42A, 42B. The containers abut one another on the rollers, such that each downstream container is pushed by the adjacent upstream container.

[0027] The dehydrating apparatus 20 includes the components required for the operation of the vacuum microwave dryer. As illustrated schematically in Figure 4, a vacuum pump 98 is operatively connected through a condenser 100 and via a vacuum distributor 102 to vacuum ports in the vacuum chamber. 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 optionally be provided in the vacuum chamber 22 to absorb excess microwave energy, by means of a water pump and conventional piping within the vacuum chamber.

[0028] The dehydration apparatus 20 includes a programmable logic controller (PLC) 110, programmed and connected to control the operation of the system, including the microwave generators 76, the vacuum pump 98, the refrigerant pump, the airlock doors 33, 34, 36, 37, the pushing and pulling cylinders 64, 66, and controlling the drive motors 48, 50 to fractionally rotate the rollers 42A, 42B. The PLC is programmed to drive the motors 48, 50 so as to impart fractional rotation to the containers 24 on the rollers 42A, 42B.

[0029] The dehydrating apparatus 20 operates according to the following method. The vacuum pump 98, refrigerant pump, water pump, microwave generators 76 and the motors 48, 50 to fractionally rotate the rollers are actuated, all under the control of the PLC 110. The vacuum chamber 22 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). A container 24 of organic material to be dehydrated is loaded into the loading module 30, whose pressure is then equalized with the vacuum chamber. The airlock door 34 is lifted, and the container 24 is pushed by the piston 68 through the opening 90 of the end support frame 86 at the input end 26 into the vacuum chamber, supported by and moving along the fractionally rotating rollers 42A, 42B.

[0030] The airlock door 34 is then closed and the piston 68 is retracted. The second container is loaded in the same manner as the first container. Once the second container is in the loading module 30, the airlock door 34 is opened, and the piston 68 pushes it onto the fractionally rotating roller 42A. This pushes the second container against the first container, displacing the first container farther down the vacuum chamber towards the output end 28 by the length of one container. The process is repeated by loading additional containers in the same manner, each container displacing the previously-loaded ones in the vacuum chamber. Once the first container is at or near the output end 28, the airlock door 36 is opened, and the pulling cylinder 66 is actuated to move the piston 70 into the vacuum chamber through the output end 28, and pull the first container into the discharge module 32. The airlock door 36 is then closed, and the piston 70 is retracted. The discharge module 32 is brought to atmospheric pressure and the first container is removed through airlock door 37. The discharge module 32 is then sealed and its pressure equalized with the vacuum chamber. The process is again repeated by removing additional containers from the vacuum chamber in the same manner.

[0031] As it moves along the rollers 42A, 42B, each container 24 is fractionally rotated about its longitudinal axis within the vacuum chamber by engagement of the spur gear teeth 60 on its outer circumferential surface with the spur gear teeth 46 on the outer circumferential surface of the rotating rollers 42A, 42B. In some embodiments, the fractional rotation may be through an angle in the range of 1 to 90 degrees, alternatively in the range of 5 to 30 degrees, in each of the clockwise and counterclockwise directions. The container may be fractionally rotated in each direction for a time in the range of 1 to 10 seconds, alternatively in the range of 3 to 6 seconds.

[0032] The selection of the angle of fractional rotation may be based on the loading weight and the size, structure and thus the thermal dissipating nature of the materials being dried. The goal is to provide minimal agitation while minimizing heat accumulation in the material cluster. The fractional rotation time depends on the rotation speed of the basket. For example, if the rotation speed is 1 rpm, the angular speed will be 6 degrees per second. One example of material loading weight is 1 to 15 kg, in a basket having a length of about 50 cm and an inner diameter of about 43 cm. An example of organic material sizes for pieces in the shape of a cube or sphere is less than about 25 mm.

[0033] The container may be fractionally rotated at one speed while being moved through a first longitudinal section of the vacuum chamber, i.e., modules 22a, 22b, on roller 42A, and at a second speed while being moved through a second longitudinal section, i.e., module 22c, on roller 42B. The lowest roller speed to achieve gentle agitation and sufficient heat dissipation is preferred. This depends on the loading weight per basket and also the size and nature of the materials being dried. A slower speed on the second roller 42B than the first roller 42A is preferred due to the reduced weight in the baskets towards the end of drying process, to minimize the breakage when the product is getting more brittle. However, in some embodiments, the speed of fractional rotation is uniform throughout the length of the vacuum chamber.

[0034] In some embodiments, the container may be rotated in one direction in pulsed fractional rotation steps, with pauses between the steps. In some embodiments, the fractional rotation may be through an angle in the range of 5 to 10 degrees in the clockwise direction and no rotation in the counterclockwise direction. The time of each fractional rotation may be in the range of 1 to 2 seconds.Examples

[0035] In the following examples the drying apparatus used was a 10 kW nutraREV™ batch microwave vacuum dryer manufactured by EnWave Corporation, having a microwave power range of 100 to 10,000 W and an absolute chamber pressure range of 10 to 250 Torr.Example 1

[0036] A 10 kg sample of fried Brussels sprouts having an initial moisture content of about 78 wt.% was subjected to microwave vacuum dehydration using a rocking motion in the manner described above. The vacuum pressure was in the range of 20-25 Torr. The microwave power levels and times of application in the vacuum chamber were 10 kW for 1239 seconds, 8 kW for 930 seconds, 6 kW for 620 seconds, and 4 kW for 340 seconds. The total energy used was 6.737 kWh. The container was subjected to rocking time sequences of 6 seconds in each direction. The angle of rocking was 45°. The final dried sample weight was 2250 g and the moisture content about 4 wt.%. The product was observed to have a soft and crispy texture, an open structure and a loose wrapped appearance and with no burning.Example 2

[0037] An 8 kg sample of IQF apple cubes with 40 g of vegetable oil, having an initial moisture content of about 85 wt.% was subjected to microwave vacuum dehydration using a rocking motion in the manner described above. The vacuum pressure was in the range of 20-25 Torr. The microwave power levels and times of application in the vacuum chamber were 10 kW for 976 seconds, 8 kW for 610 seconds, 6 kW for 407 seconds, 4 kW for 915 seconds, 2 kW for 1800 seconds, and 1.5 kW for 941 seconds. The total energy used was 7.0 kWh. The container was subjected to rocking time sequences of 3 seconds in each direction. The angle of rocking was 45°. The final dried sample weight was 1200 g and the moisture content about 3 wt.%. The product was observed to have little shrinkage and no burning.Example 3

[0038] A 10 kg sample of IQF crinkle cut carrot slices (coins) with 75 g of vegetable oil, having an initial moisture content of about 90 wt.% was subjected to microwave vacuum dehydration using a rocking motion in the manner described above. The vacuum pressure was in the range of 20-25 Torr. The microwave power levels and times of application in the vacuum chamber were 10 kW for 1674 seconds, 8 kW for 837 seconds, 6 kW for 837 seconds, 4 kW for 837 seconds, 2 kW for 1376 seconds, and 1 .5 kW for 300 seconds. The total energy used was 9.497 kWh. The container was subjected to rocking time sequences of 3 seconds in each direction. The angle of rocking was 45°. The final dried sample weight was 1000 g and the moisture content about 3 wt.%. The product was observed to be similar to a tray-dried product, with little shrinkage, no damage and no burning.

[0039] 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.

[0040] 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. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

Claims

Claims1. An apparatus (20) for dehydrating organic material, comprising:(a) a container (24) having a cylindrical wall (56) defining an internal space (59) within the container for holding pieces of the organic material (61), the container having a longitudinal axis and being rotatable about its longitudinal axis;(b) a vacuum chamber (22) having an input end (26) for loading the container into the vacuum chamber, an output end (28) for removing the container, and a longitudinal axis parallel to the longitudinal axis of the container;(c) means (40, 50, 78, 82, 42A, 42B, 110) for fractionally rotating the container clockwise and counterclockwise about the longitudinal axis;(d) means (64, 66) for moving the fractionally-rotating container horizontally through the vacuum chamber from the input end to the output end;(e) a microwave generator (76) arranged for transmission of microwave radiation into the vacuum chamber; and(f) means (98) for reducing pressure in the vacuum chamber to a pressure less than atmospheric.

2. The apparatus of claim 1 , wherein the means for fractionally rotating the container about its longitudinal axis is configured to rotate the container through an angle in the range of 5 to 30 degrees in each of the clockwise and counterclockwise directions.

3. The apparatus of claim 1 , wherein the means for fractionally rotating the container about its longitudinal axis is configured to rotate the container through an angle in the range of 1 to 90 degrees in each of the clockwise and counterclockwise directions.

4. The apparatus of any one of claims 1-3, wherein the means for fractionally rotating the container about its longitudinal axis is configured to rotate the container in each direction for a time in the range of 1 to 10 seconds.

5. The apparatus of claim 5, wherein the time is in the range of 3 to 6 seconds.

6. The apparatus of any one of claims 1-5, wherein the means for fractionally rotating the container comprises at least one roller (42A, 42 B) which supports the container.

7. The apparatus of any one of claims 1-5, wherein the means for fractionally rotating the container comprises at least a first roller (42A) which supports the container in a first longitudinal portion of the vacuum chamber, and at least a second roller (42B) which supports the container in a second longitudinal portion of the vacuum chamber, and means (48, 50, 78, 82, 110) for fractionally rotating the first and second rollers at the same speed or at different speeds.

8. An apparatus (20) for dehydrating organic material, comprising:(a) a container (24) having a cylindrical wall (56) defining an internal space (59) within the container for holding pieces of the organic material (61), the container having a longitudinal axis and being rotatable about its longitudinal axis;(b) a vacuum chamber (22) having an input end (26) for loading the container into the vacuum chamber, an output end (28) for removing the container, and a longitudinal axis parallel to the longitudinal axis of the container;(c) means (40, 50, 78, 82, 42A, 42B, 110) for rotating the container about its longitudinal axis in one direction in pulsed fractional rotation steps, with pauses between the pulsed fractional rotation steps;(d) means (64, 66) for moving the rotating container horizontally through the vacuum chamber from the input end to the output end;(e) a microwave generator (76) arranged for transmission of microwave radiation into the vacuum chamber; and(f) means (98) for reducing pressure in the vacuum chamber to a pressure less than atmospheric.

9. A method for dehydrating an organic material, comprising the steps of:(a) reducing pressure within a vacuum chamber (22) to a pressure less than atmospheric;(b) loading a container (24) into the vacuum chamber, the container having a cylindrical wall (56) defining an internal space (59) holding pieces of the organic material (61) within the container, the container having a longitudinal axis and being fractionally rotatable about its longitudinal axis;(c) fractionally rotating the container clockwise and counterclockwise about its longitudinal axis and thereby agitating the pieces of organic material in the internal space within the container;(d) moving the fractionally-rotating container horizontally through the vacuum chamber from an input end (26) to an output end (28), while applying microwave radiation to dehydrate the organic material; and(e) removing the container of dehydrated organic material from the output end of the vacuum chamber.

10. The method of claim 9, wherein the container is fractionally rotated through an angle in the range of 5 to 30 degrees in each of the clockwise and counterclockwise directions.11 . The method of claim 9, wherein the container is fractionally rotated through an angle in the range of 1 to 90 degrees in the clockwise direction and an angle in the range of 1 to 90 degrees in the counterclockwise direction.

12. The method of any one of claims 9-11 , wherein the container is fractionally rotated in each direction for a time in the range of 1 to 10 seconds.

13. The method of claim 12, wherein the time is in the range of 3 to 6 seconds.

14. The method of any one of claims 9-13, wherein the container is rotated at a first speed while being moved through a first longitudinal section of the vacuum chamber, and at a second speed while being moved through a second longitudinal section of the vacuum chamber.

15. The method of any one of claims 9-14, wherein the pieces of organic material (61) have a diameter in the range of 0.1 to 25 mm.

16. A method for dehydrating an organic material, comprising the steps of:(a) reducing pressure within a vacuum chamber (22) to a pressure less than atmospheric;(b) loading a container (24) into the vacuum chamber, the container having a cylindrical wall (56) defining an internal space (59) holding pieces of the organic material (61) within the container, the container having a longitudinal axis and being rotatable about its longitudinal axis;(c) rotating the container about its longitudinal axis in one direction in pulsed fractional rotation steps, with pauses between the pulsed fractional rotation steps, and thereby agitating the pieces of organic material in the internal space within the container;(d) moving the rotating container horizontally through the vacuum chamber from an input end (26) to an output end (28), while applying microwave radiation to dehydrate the organic material; and(e) removing the container of dehydrated organic material from the output end of the vacuum chamber.

17. The method of claim 16, wherein the frequency of the pulsed fractional rotation steps is in the range of 2 to 12 seconds.

18. The method of claim 16, wherein the frequency of the pulsed fractional rotation steps is in the range of 1 to 2 seconds.

19. The method of any one of claims 16-18, wherein each pulsed fractional rotation step rotates the container through an angle in the range of 1 to 90 degrees.

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