Abstract:
An apparatus and method for pressure processing a pumpable substance, such as a pumpable food product. In one embodiment, the apparatus includes a plurality of coupled pressure vessels, each having an inlet port to receive the pumpable substance, an outlet port to remove the pumpable substance, an isolator to pressurize the pumpable substance and a high-pressure port for receiving pressurizing fluid to bias the isolator toward the pumpable substance. The apparatus can further include blocking valves to limit the travel of materials that may leak through the inlet and outlet valves, a heat exchanger to heat and/or cool the pumpable substance, and/or a gas controller to add gas to the pumpable substance or remove gas from the pumpable substance. Cleaning, rinsing, and/or sanitizing fluid can be pumped through the entire system, including through the isolator to cleanse and/or sanitize.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to methods and apparatus for pressure processing a pumpable substance, for example, food substances and the like.  
         BACKGROUND OF THE INVENTION  
         [0002]    Flowable substances, such as liquid food products, may be treated by exposure to ultrahigh-pressures. For example, liquid food products may be preserved or otherwise chemically or physically altered after exposure to ultrahigh-pressures. In one conventional process, the food substance is loaded into a pressure vessel where it is pressurized to a selected pressure for a selected period of time to achieve the desired physical or chemical change. The vessel is then depressurized and the contents unloaded. The pressure vessel may then be reloaded with a new volume of unprocessed substance and the process may be repeated.  
           [0003]    Although current systems produce desirable results, issues of product contamination can arise. Contamination is an important issue in certain applications, particularly those involving pressure-processing of food substances. Contamination can potentially result from contact between the food substance and the outside environment, or can potentially result from exposure of the pressure processed food product to the unprocessed food product.  
         SUMMARY OF THE INVENTION  
         [0004]    The invention relates to methods and apparatus for pressure-processing a pumpable substance, such as a food substance, in one or more pressure vessels. In one embodiment, the apparatus can include first and second high pressure vessels each having an inlet port, an outlet port and an isolator for isolating the pumpable substance from a repressurizing fluid. The pressure vessels are coupled to a controller to move the isolators according to a schedule such that the schedule for one isolator is delayed or offset relative to the schedule for the other isolator.  
           [0005]    The apparatus can further include first and second spaced apart valves coupled to the inlet port and/or the outlet port and movable between an open position and a closed position. A detector between the two valves is positioned to detect leakage of the pumpable substance past one of the valves when the valve is in its closed position. The detector can include any suitable device, such as a pressure sensor or a pH sensor.  
           [0006]    In another embodiment, the apparatus can include one or more devices coupled to the pressure vessels to further process the pumpable substance before and/or after it has been pressurized. For example, in one embodiment, the apparatus can include a heat exchanger coupled to the inlet port or the outlet port of one or more of the pressure vessels to transfer heat between the pumpable substance and the region external to the heat exchanger. In another embodiment, the apparatus can include a gas controller coupled to at least one of the inlet port and the outlet port for removing a gas from the pumpable substance.  
           [0007]    In yet another embodiment of the invention, the isolator in the pressure vessel can include a piston with a channel extending therethrough. The channel can include a first opening in fluid communication with the inlet port and a second opening in fluid communication with a high pressure fluid port. The piston can further include a valve positioned between the first and second openings of the channel to regulate flow from one side of the piston to the other. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a partially broken, partial cross-sectional side elevation view of an apparatus having a pressure vessel with a pumpable substance valve, a high pressure valve and an isolator in accordance with an embodiment of the invention.  
         [0009]    [0009]FIG. 2 is a partially schematic, detailed cross-sectional side elevation view of a portion of the vessel and the pumpable substance valve shown in FIG. 1.  
         [0010]    [0010]FIG. 3 is a detailed cross-sectional side elevation view of the high pressure valve shown in FIG. 1.  
         [0011]    [0011]FIG. 4 is a detailed cross-sectional side elevation view of the isolator shown in FIG. 1.  
         [0012]    [0012]FIG. 5 is a schematic view of an apparatus having heat exchangers, gas controllers and three vessels of the type shown in FIG. 1, in accordance with another embodiment of the invention.  
         [0013]    [0013]FIG. 6 is a cross-sectional side elevation view of an embodiment of the gas controller shown in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    The present invention is directed toward methods and apparatus for pressure-processing pumpable substances, such as food products. Details of certain embodiments of the invention are set forth in the following description, and in FIGS.  1 - 6 , to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, and that they may be practiced without several of the details described in the following description.  
         [0015]    A pressure processing apparatus in accordance with one embodiment of the invention includes a plurality of pressure vessels, each having an internal inlet valve that opens to admit a pumpable substance into the vessel. The inlet valve then closes and the pumpable substance is compressed by a piston that is driven by an ultrahigh-pressure fluid. After the pumpable substance has been pressurized, an internal outlet valve opens to remove the pressurized pumpable substance. The inlet and outlet valves can be supplied with a control fluid that can reduce the likelihood of contaminating the pressurized pumpable substance by creating a fluid barrier between the pressurized and unpressurized pumpable substances. Blocking valves adjacent the inlet and outlet valves can prevent the purging fluid from contaminating the pumpable substance, and can prevent the unpressurized pumpable substance from contaminating the pressurized pumpable substance.  
         [0016]    [0016]FIG. 1 is a partial cross-sectional side elevation view of a pressure-processing apparatus  10  that includes a pressure vessel  15  having an internal surface  14  capable of withstanding high internal pressures. The pressure vessel  15  may include an open-ended cylinder  12  partially surrounded by an insulating layer  16  and a protective shield  17 . The cylinder  12  can firther include a pumpable substance valve  30  at one end and a high pressure valve  70  at the opposite end. A yoke  11  secures the pumpable substance valve  30  and the high pressure valve  70  in place when the pressure vessel  15  is subjected to high internal pressures. The pumpable substance valve  30  includes two ports  31 , shown in FIG. 1 as an inlet port  31   a  that admits unpressurized pumpable substance into the pressure vessel  15 , and an outlet port  31   b  that evacuates the pumpable substance from the pressure vessel once the pumpable substance has been pressurized. Each of the ports  31  can be sealed and unsealed with a valve body  40  (shown as an inlet valve body  40   a  and an outlet valve body  40   b ).  
         [0017]    The pumpable substance can be pressurized by an ultra high-pressure fluid that is separated from the pumpable substance by an isolator  80 . In one embodiment, the isolator  80  can be a piston that is driven by the ultrahigh-pressure fluid to move axially within the pressure vessel  15 . The ultrahigh-pressure fluid is supplied to the pressure vessel  15  through a high pressure conduit  71  in the high pressure valve  70 . The ultrahigh-pressure fluid is initially removed from the pressure vessel  15  through the high pressure conduit  71  until the pressure within the vessel  15  is low enough to allow a low pressure port  72  to open by moving a low pressure valve body  40   c . Once the low pressure port  72  is opened, the remaining ultra-high pressure fluid can be evacuated from the pressure vessel  15  at a higher rate of flow through the low pressure port.  
         [0018]    In one embodiment, the apparatus  10  can include a model number 012122 assembly available from Flow International Corp. of Kent, Wash. that includes the vessel  15 , yoke  11  and shield  17 , configured to withstand an internal vessel pressure of at least 100,000 psi. In other embodiments, the apparatus  10  can include other pressure vessels  15  and peripheral components configured to withstand an internal pressure of 100,000 psi or another suitable pressure, depending upon the selected pumpable substance and treatment. Such vessels and components are available from ABB Pressure Systems of Vasteras, Sweden, Autoclave Engineering of Erie, Pa., or Engineered Pressure Systems of Andover, Mass.  
         [0019]    [0019]FIG. 2 is a detailed partial cross-sectional elevation view of the pumpable substance valve  30  and a portion of the cylinder  12  shown in FIG. 1. As shown in FIG. 2, the pumpable substance valve  30  can include an inlet coupling  33   a  in fluid communication with the inlet port  31   a , and an outlet coupling  33   b  in fluid communication with the outlet port  31   b . The inlet coupling  33   a  may be coupled to a source of pumpable substance (discussed in greater detail below with reference FIG. 5), to supply the pumpable substance to the pressure vessel  15 . The outlet coupling  33   b  may be coupled to a container or a packaging device to package the pumpable substance once it has been pressure processed.  
         [0020]    As mentioned above, the flow of the pumpable substance through the inlet port  31   a  and the outlet port  31   b  is controlled by the inlet valve body  40   a  and the outlet valve body  40   b , respectively. Each valve body  40  is connected with a valve stem  50  to a valve piston  52  that drives the valve body  40  axially between an open position (shown by the position of the outlet valve body  40   b  in FIG. 2) and a closed position (shown by the position of the inlet valve body  40   a  in FIG. 2). Accordingly, each valve piston  52  has a forward face  55  adjacent an opening port  54  and a rear face  56  adjacent a closing port  53 . When pressurized control fluid is forced through the opening port  54 , it acts against the forward face  55  of the valve piston  52  to drive the valve body  40  axially to its open position. When the pressurized control fluid is forced through the closing port  53 , it acts against the rear face  56  of the valve piston  52  to drive the valve body  40  axially to its closed position.  
         [0021]    Each valve body  40  can include an external portion  41  that remains external to the corresponding port  31  when the valve body is in the closed position, and an internal portion  42  that extends into the port when the valve body is in the closed position. Each valve body  40  may also include one or more seals that restrict the motion of the pumpable substance past the valve body when the valve body is in the closed position. For example, the valve body  40  can include a flexible seal  43  around the periphery of the external portion  41 . The flexible seal  43  can be held in place by a lip  44  so as to seal against an internal surface  14   a  of the pumpable substance valve  30  adjacent the corresponding port  31 . The valve body  40  can also include an O-ring  45  around the internal portion  42  that seals against an internal surface  32  of the port  31 .  
         [0022]    An advantage of a valve body  40  having two seals (e.g., the flexible seal  43  and the O-ring  45 ) is that the seals reduce the likelihood that the pumpable substance will flow past the valve body when the valve body is in the closed position. For example, the two seals may reduce the likelihood that the pumpable substance will escape past the outlet valve body  40   b  and enter the outlet port  31   b  when the outlet valve body  40   b  is in the closed position and the pumpable substance is pressurized. Such a condition is undesirable because the escaping pumpable substance may not be fully pressure processed, and may therefore contaminate the fully processed substance that subsequently passes through the open outlet port  31   b . Furthermore, the two seals on the inlet valve body  40   a  may prevent unpressurized pumpable substance from passing out of the inlet port  31  a and directly into the outlet port  3  lb without being pressurized, for example when the inlet valve body  40   a  is in the closed position and the outlet valve body  40   b  is in the open position.  
         [0023]    The valve body  40  can also include a purging zone  60  that may further reduce the likelihood that the fully processed pumpable substance will be contaminated with unprocessed or under-processed pumpable substance. As shown in FIG. 2, the purging zone  60  can be positioned between the O-ring  45  and the flexible seal  43 . The purging zone  60  can be further bounded by the internal portion  42  of the valve body  40  and by the inner surface  32  of the port  31 . The control fluid can enter the purging zone  60  through one or more orifices  58  located in the valve body  40  adjacent the purging zone. The orifices can be coupled to a source of control fluid (discussed in greater detail below with reference to FIG. 5) via a passage  51  in the valve stem  50 . Accordingly, the control fluid can enter the passage  51  via a passage entrance  57  when the valve body  40  is in the closed position and flow through the valve stem  50  to the purging zone  60 . When the valve body  40  is in the open position, the valve piston  52  blocks the passage entrance  57 , preventing the control fluid from entering the passage  51  and therefore preventing the control fluid from flowing freely into the pressure vessel  15 .  
         [0024]    While in the purging zone  60 , the control fluid can entrain particles of unprocessed or under-processed pumpable substance that might enter the purging zone by escaping past the flexible seal  43  and/or the O-ring  45 . Accordingly, the purging zone  60  forms a fluid barrier between a region containing fully processed pumpable substance and a region containing unprocessed or only partially processed pumpable substance. For example, the purging zone  60  surrounding the outlet valve body  40   b  may prevent pumpable substance that has not been fully pressure processed from escaping the pressure vessel  15  before the processing cycle is complete. Furthermore, the purging zone  60  surrounding the inlet valve body  40   a  may prevent unprocessed pumpable substance from flowing past the inlet valve body and out through the outlet port  3  lb when the outlet valve body  40   b  is opened to remove the pumpable substance from the vessel  15 .  
         [0025]    The control fluid can exit the purging zone  60  through an exit channel  61  to convey unpressurized or under-pressurized pumpable substance away from the corresponding port  31 . The exit channel  61  can include a check valve  62  that prevents the control fluid from re-entering the purging zone  60  when the pressure in the purging zone drops. For example, the check valve  62  can include a flexible elastomeric ring that expands in diameter away from the exit channel  61  to allow the control fluid to escape, and collapses on the exit channel to prevent the control fluid from re-entering the purging zone  60 . The escaping control fluid can pass into an annulus  64  and away from the pressure vessel  15  through a relief valve  63 . The relief valve  63  can be adjusted to maintain a pressure in the annulus  64  that is low enough to allow the control fluid to escape and high enough to prevent the pumpable substance from passing out of the pressure vessel  15  between the cylinder  12  and the pumpable substance valve  30 .  
         [0026]    The control fluid may include any suitable fluid that can drive the valve bodies  40  back and forth and purge the pumpable substance from the purging zones  60 . In one embodiment, the control fluid may also include a compound that contains iodine to clean and/or sanitize the surfaces adjacent the purging zone  60  as the control fluid passes through the purging zone  60 . Alternatively, the control fluid may be selected to contain any substance that cleanses the purging zone  60  without adversely affecting the characteristics of the pumpable substance. Accordingly, the control fluid may further reduce the likelihood that the fully pressure processed pumpable substance is contaminated by under-pressurized or unpressurized pumpable substance. In addition, the control fluid may reduce the likelihood that particulates (which might be included in the pumpable substance) will become lodged between the valve body  40  and the port  31  where they can prevent the valve body from fully closing.  
         [0027]    As is also shown in FIG. 2, the pumpable substance valve  30  can be coupled to pumpable substance conduits  34  (shown as an inlet conduit  34   a  coupled to the inlet coupling  33   a  and an outlet conduit  34   b  coupled to the outlet coupling  33   b ). Each conduit  34  can include a blocking valve  35  (shown as an inlet blocking valve  35   a  and an outlet blocking valve  35   b ) spaced apart from the corresponding valve body  40 . Between each blocking valve  35  and the corresponding valve body  40  is positioned a detector  36  shown as an inlet detector  36   a  and an outlet detector  36   b . If the pumpable substance inadvertently leaks past either valve body  40  when the valve body is in its closed position, the corresponding blocking valve  35  prevents the pumpable substance from passing any further in the corresponding conduit  34 . Furthermore, the detector  36  can detect the presence of the leak by detecting a change in a characteristic of the pumpable substance in the conduit between the valve body  40  and the blocking valve  35 . For example, the detector  36  can include a pressure transducer that detects an increase in pressure if the pumpable substance leaks past the valve body  40 . In other embodiments, the detector  36  can include an opacity meter that detects a change in the color characteristics of the material in the conduit, or a pH detector that detects a change in the pH of the material in the conduit caused by leakage of the pumpable substance through the closed valve body  40 . In still further embodiments, the detector  36  can include other devices capable of detecting the presence of a leak between the valve body  40  and the blocking valve  35 .  
         [0028]    The outlet conduit  34   b  can further include a diverter valve  37  positioned between the outlet blocking valve  35   b  and the outlet valve body  40   b . In its closed position, the diverter valve  37   b  allows the pressurized pumpable substance to pass through the outlet conduit  34   b  and through the blocking valve  35   b  for packaging or other post-pressurization processing. In its open position, the diverter valve  37  can divert the pumpable substance either to a dump or back to the source of the unpressurized pumpable substance. Accordingly, in the event that the apparatus  10  pressurizes the pumpable substance by less than a selected amount, the diverter valve  37  can be moved to its open position to either dispose of the partially pressurized pumpable substance or return the pumpable substance to its source, from which it can be reintroduced to the cylinder  15  for further pressurization.  
         [0029]    [0029]FIG. 3 is a detailed partial cross-sectional side elevation view of the high pressure valve  70  and the high pressure conduit  71  shown in FIG. 1. The high pressure conduit  71  can be coupled to a source of ultrahigh-pressure fluid to drive the isolator  80  in the pressure vessel  15 . The ultrahigh-pressure fluid can be supplied by a device such as a model No. 25XQ 100 available from Flow International Corp. of Kent, Wash., which includes a 150 Hp motor driving four hydraulic intensifiers, each capable of pressurizing water to 100,000 psi at a rate of 0.9 gpm. Other devices capable of generating pressures higher or lower than this value may be suitable as well, so long as the pressure is sufficient to produce the desired effect on the pumpable substance.  
         [0030]    The ultrahigh-pressure fluid is evacuated from the pressure vessel  15  through the low pressure port  72  as the pressure vessel is filled with the pumpable substance. The low pressure port  72  may be opened and closed with the low pressure valve body  40   c  in a manner similar to that discussed above with reference to the inlet and outlet valve bodies  40   a  and  40   b  shown in FIG. 2. In one embodiment, the low pressure valve body  40   c , the valve stem  50 , and the valve piston  52  shown in FIG. 3 may be identical to the valve bodies, valve stems and valve pistons shown in FIG. 2 to provide for commonality of parts. However, because the low pressure port  72  is not exposed to the pumpable substance, the high pressure valve  70  need not include a purging zone  60  (FIG. 2) or an exit channel  61  (FIG. 2).  
         [0031]    As shown in FIG. 3, the high pressure valve  70  can include a sealing flange  65  that is sealably coupled to an internal surface  14   b  of the cylinder  12  to seal the high pressure valve  70  within the cylinder. The sealing flange  65  is spaced apart from the internal surface  14   b  to accommodate an O-ring  67  that sealably engages both the internal surface  14   b  and the flange  65 . The high pressure valve  70  can also include an elastomeric seal  68  adjacent the O-ring, and an anti-extrusion ring  69  adjacent the elastomeric seal, both of which are seated against an aft surface  73  of the sealing flange  65 . The elastomeric seal  68  may comprise a polymer, such as an ultra-high molecular weight polyethylene, and the anti-extrusion ring  69  may include a metal, such as bronze. The aft surface  73  of the sealing flange  65  may be inclined so that as the elastomeric seal  68  is forced aft in the direction indicated by arrow A (for example, when the pressure vessel  15  is pressurized), the elastomeric seal  68  forces the anti-extrusion ring  69  outward toward the cylinder  12 , to prevent the elastomeric seal  68  from extruding into a small gap that might exist between the high pressure valve  70  and the cylinder  12 . This arrangement may be advantageous because it reduces wear on the elastomeric seal  68 . A similar arrangement may be used to seal the pumpable substance valve  30  (FIG. 2) to the cylinder  12 .  
         [0032]    [0032]FIG. 4 is a detailed cross-sectional side elevation view of a portion of the pressure vessel  15  and the isolator  80  shown in FIG. 1. The isolator  80  can be in the form of a piston having seals  85  that slideably and sealably engage the inner wall of the cylinder  12 . The isolator  80  can further include flow passages  81  (shown as an upper flow passage  81   a  and a lower flow passage  81   b ). Each flow passage  81  can include a relief valve  82  (shown as an upper relief valve  82   a  and a lower relief valve  82   b ). The relief valves  82  include stoppers  83  that are biased to a closed position by a biasing device  84 , such as a spring.  
         [0033]    In a preferred embodiment, each of the check valves  82  allows flow to pass in the direction opposite of the other check valve. For example, as shown in FIG. 4, the upper relief valve  82   a  allows flow to pass from the left side of the isolator  80  to the right side of the isolator  80  when the difference in pressure between the left side of the isolator  80  and the right side of the isolator  80  exceeds a certain value. Similarly, the lower relief valve  82   b  can allow fluid to pass through the isolator  80  from the right side of the isolator to the left side of the isolator when the pressure differential across the isolator  80  from right to left exceeds a selected value. In one embodiment, the isolator  80  can include two flow passages  81 , as shown in FIG. 4, and in other embodiments, the isolator  80  can include more than two flow passages, so long as the structural integrity of the isolator  80  is maintained. In yet another embodiment, the isolator can include a single flow passage  81  having a single relief valve  82  for passage of fluids in only one direction.  
         [0034]    The flow passages  81  and check valves  82  in the isolator  80  can perform a variety of functions. For example, when the pressure vessel  15  is cleaned, the isolator  80  can be moved to the extreme right side of the cylinder  12  against the pumpable substance valve  30  (FIG. 1). Fluid at high pressure can then be pumped through the upper relief valve  82   a  and into a region between the isolator  80  and the pumpable substance valve  30  for cleaning this region. Similarly, the isolator  80  can be driven to the left end of the cylinder  12  against the high pressure valve  70  (FIG. 1) and cleaning fluid can be forced through the lower passage  81   b  and lower relief valve  82   b  to clean the region between the isolator  80  and the high pressure valve  70 . In another procedure, the flow passages  81  and relief valves  82  can be used to relieve pressure which may build up during the course of operating the pressure vessel  15 . In yet another procedure, the isolator  80  can be moved back and forth within the cylinder  12  to clean the cylinder without fluid passing through the flow passages  81 . For example, the isolator  80  can scrub the walls of the cylinder  12  by pressurizing the isolator  80  with a cleaning fluid. The isolator  80  moves back and forth within the cylinder  12 , the isolator  80  transports the cleaning fluid along the walls of the cylinder  12 , while at the same time providing a mechanical scrubbing action as the seals  85  slide along the walls.  5  Operation of an embodiment of the apparatus  10  is best understood with reference to FIGS. 1 and 2. Beginning with FIG. 2, the outlet valve body  40   b  is closed by supplying control fluid through the corresponding closing port  53 . The control fluid acts against the rear face  56  of the corresponding valve piston  52  to draw the outlet valve body  40   b  into the outlet port  3  lb. The O-ring  45  seals against the internal surface  32  of the port  31  and the flexible seal  43  seals against the internal surface  14   a  of the pumpable substance valve  30 . The control fluid enters the purging zone  60  of the outlet valve body  40   b  through the corresponding control fluid passage  51 , and exits the purging zone through the corresponding exit channel  61 . The control fluid continues to flow as long as the outlet valve body is in the closed position. The outlet blocking valve  35   b  is also closed. The inlet blocking valve  35   a  is opened and the inlet valve body  40   a  is then moved to its open position by applying control fluid to the corresponding opening port  54 . The control fluid acts against the forward face  55  of the corresponding valve piston  52  to drive the inlet body  40   a  to the open position.  
         [0035]    Referring now to FIG. 1, the low pressure valve body  40   c  is moved to its open position in a manner similar to that discussed above with reference to the inlet valve body  40   a . The pumpable substance is then introduced through the inlet port  31  a and into the pressure vessel  15  to move the isolator  80  toward the high pressure valve  70 , driving residual high pressure fluid located between the isolator  80  and the high pressure valve  70  out through the low pressure port  72 . The low pressure valve  40   c , the inlet valve body  40   a  and the inlet blocking valve  35   a  are then closed and the ultrahigh-pressure fluid is introduced to the pressure vessel  15  through the high pressure conduit  71 . The ultrahigh-pressure fluid drives the isolator  80  toward the pumpable substance valve  30  to compress the pumpable substance within the vessel. When the desired pressure is obtained, the flow of ultrahigh-pressure fluid is halted and the pumpable substance is allowed to remain at an elevated pressure for a selected period of time. If, during this time, either detector  36  detects a pressure leak, the process can be halted and the partially pressurized pumpable substance can either be disposed of or reintroduced to the pressure vessel  15 .  
         [0036]    When the selected period of time has elapsed, the pressure within the pressure vessel  15  is relieved by initially passing the ultra-high pressure fluid out of the pressure vessel  15  through the high pressure conduit  71 . The outlet blocking valve  35   b  and the valve bodies  40   b  and  40   c  are then opened and low pressure fluid is supplied through the low pressure port  72  to move the isolator  80  toward the outlet valve body  40   b  and remove the pumpable substance from the pressure vessel  15  through the outlet port  3  lb. The cycle can then be repeated with a new quantity of pumpable substance.  
         [0037]    One advantage of an embodiment of the apparatus  10  shown in FIGS.  1 - 4  is that the blocking valves  35  restrict the motion of pumpable substance which may inadvertently leak past the valve bodies  40 . In addition, the detectors  36  can detect the presence of such a leak.  
         [0038]    Another advantage is that the plurality of seals on each valve body  40  reduces the likelihood that the valve body will leak and contaminate pressure processed pumpable substance with unpressurized or under-pressurized pumpable substance. Yet another advantage is that the two seals may define a purging zone  60  between the fully pressurized pumpable substance and the unpressurized pumpable substance. A control fluid may be passed through the purging zone  60  to remove under-pressurized pumpable substance from the purging zone, creating a fluid barrier between the pressurized pumpable substance and the unpressurized or under-pressurized pumpable substance. Furthermore, the control fluid may sanitize the surfaces of the apparatus in the purging zone. Both the purging function and the sanitizing function can be completed while the apparatus is pressurized and without having to access the interior of the pressure vessel  15 .  
         [0039]    Still another advantage of the apparatus  10  shown in FIGS.  1 - 4  is that the seal  68  between the cylinder  12  and the valves  30  and  70  may include an anti-extrusion ring  69  positioned adjacent an inclined surface of the valves. The anti-extrusion ring  69  moves outward under pressure to reduce wear on the seal and to reduce the likelihood of a leak developing between the cylinder  12  and the valves  30  and  70 .  
         [0040]    [0040]FIG. 5 is a schematic view of a semicontinuous processing apparatus  10   a  that includes three coupled apparatus  10 , such as are shown in FIG. 1. Accordingly, each apparatus  10  includes a pressure vessel  15  surrounded by a yoke  11  and each pressure vessel  15  includes a movable isolator  80 , an inlet valve body  40   a , an outlet valve body  40   b , a low pressure valve body  40   a , and a high pressure conduit  71 , as was discussed above with reference to FIGS.  1 - 4 . As will be discussed in greater detail below, the motion of the valves and isolators is controlled by a computer  130  so that each apparatus  10  operates according to a schedule (such as was discussed above with reference to FIGS.  1 - 4 ) that is offset or staggered from the schedule of the other apparatus  10 . Accordingly, the semicontinuous processing apparatus  10   a  can operate in the manner of a multi-cylinder internal combustion engine to produce a semicontinuous flow of pressurized pumpable substance. In the embodiment shown in FIG. 5, the apparatus  10   a  includes three pressure vessels  15 , and in other embodiments the apparatus  10   a  can include more or fewer pressure vessels  15  (for example, one pressure vessel  15 ), to produce a semicontinuous flow of pressurized pumpable substance.  
         [0041]    The apparatus  10   a  includes a pumpable substance source  90  for supplying the pumpable substance to each of the three pressure vessels  15 . The pumpable substance can include an abrasive slurry, a food stuff, such as juice, partially liquefied fruits or vegetables, or any substance that can be pumped through the devices included in the apparatus  10   a . For purposes of clarity, the path followed by the pumpable substance is shown in heavy solid lines in FIG. 5, while the paths followed by the control fluid and high pressure fluid are shown in dashed and phantom lines, respectively. Cleaning solutions follow the path of the pumpable substance shown in heavy solid lines as well as the path shown in heavy dashed lines.  
         [0042]    The pumpable substance can pass from the source  90  to a pre-processing heat exchanger  92   a  for heating the pumpable substance. It may be advantageous to heat the pumpable substance before pressurization for a variety of reasons. For example, heating the pumpable substance may, in conjunction with pressurization, reduce or eliminate microorganisms in the pumpable substance. In one aspect of this embodiment, the pressure to which the pumpable substance is subjected and/or the time during which the pumpable substance remains under pressure can be reduced by heating the pumpable substance in the heat exchanger  92   a  prior to pressurization. In another embodiment, the heat exchanger  92   a  can be used to cool the pumpable substance for a beneficial effect with certain food items. In either case, the heat exchanger  92   a  can be a scrape surface heat exchanger (to prevent the pumpable substance from adhering to the walls of the heat exchanger where it may bum), such as a model number 4X120 available from Cherry-Burrel of Little Falls, N.Y., or another suitable device having a channel for receiving the pumpable substance and a heat exchanger surface for transferring heat to and/or from the pumpable substance.  
         [0043]    From the heat exchanger  92   a , the pumpable substance can pass to a gas controller  140   a . In one embodiment, the gas controller  140   a  can include a de-aerator that removes air or other gasses from the pumpable substance prior to pressurization, such as a model number  16  available from Aro-Vac (Division of Cherry Burrell) of Little Falls, N.Y. It may be advantageous to remove air and other gasses from the pumpable substance to prevent hydrocarbons present in the food from detonating under pressure, which may, in turn, cause the food to bum and thereby reduce the quality of the food. In one embodiment, the gas controller  140   a  is positioned downstream of the heat exchanger  92   a  because the pumpable substance is more likely to out-gas after it has been heated.  
         [0044]    In one embodiment, the gas controller  140   a  can include a gravity fed device, such as is shown in FIG. 6. The gas controller  140   a  accordingly includes an entrance port  141  positioned above an exit port  142 . A vacuum port  143  is positioned between the entrance port  141  and the exit port  142  and is coupled to a vacuum source (not shown). In operation, the pumpable substance enters the gas controller  140   a  through the entrance port  141  and as the pumpable substance descends toward the exit port  142 , air or other gasses are extracted from the pumpable substance and passed through the vacuum port  143 .  
         [0045]    Returning to FIG. 5, the gas controller  140   a  can also be operated to introduce a gas to the flow of pumpable substance. For example, in one embodiment, the gas controller  140   a  can introduce carbon dioxide to the pumpable substance which can reduce the amount of bacteria therein. In other embodiments, other gasses can be added to the pumpable substance to produce the same or other beneficial effects.  
         [0046]    The pumpable substance is pumped from the gas controller  140   a  through a cleaning solution valve  97  (discussed in greater detail below) to each of the three pressure vessels  15 , where it is processed according to the steps discussed above with reference to FIGS.  1 - 4 . The pressurized pumpable substance is then removed from the pressure vessels  15  through the outlet valves  40   b  from which it can pass to a post-processing gas controller  140   b . The post-processing gas controller  140   b  can be used to remove gas from the pressurized pumpable substance. For example, if carbon dioxide was added to the pumpable substance before pressurization, the post-processing gas controller  140   b  can be used to remove the carbon dioxide once pressurization has been completed.  
         [0047]    From the post-processing gas controller  140   b , the pressurized pumpable substance can pass to a post-processing heat exchanger  92   b . In one aspect of this embodiment, the post-processing heat exchanger  92   b  and the heat exchanger  92   a  can be coupled in the manner of a regenerative heat exchanger such that the heat extracted from the pressurized pumpable substance in the post-processing heat exchanger  92   b  is used to increase the temperature of the unpressurized pumpable substance in the heat exchanger  92   a . The pressurized pumpable substance then passes to a pressurized pumpable substance reservoir  91  where the pressurized pumpable substance can be packaged or otherwise prepared for end use.  
         [0048]    If, for any reason, the pressurized pumpable substance is not to be delivered to the reservoir  91 , the valves  37  can be adjusted to divert the pressurized pumpable substance away from the reservoir  91 . A dump valve  38  can then be selectively positioned to dump the pressurized pumpable substance or return the pressurized pumpable substance to the pumpable substance source  90  for repressurization.  
         [0049]    In a preferred embodiment, a cleaning system  93  is coupled to the pumpable substance source  90  for cleaning the pumpable substance source  90 , the vessels  15 , and the pressurized pumpable substance reservoir  91 , as well as the intermediate devices and connecting hardware. In one aspect of this embodiment, the cleaning system  93  can include a caustic solution reservoir  94  (containing a fluid such as citric acid or acidified water), a rinse solution reservoir  95  (containing rinse liquids, such as water), and a sanitizing resolution reservoir  96  (containing sanitizing fluid, such as those available from Echo Labs of Portland, Oreg.). The solutions contained in each of the reservoirs  94 - 96  can be sequentially pumped through the apparatus  10   a  to both clean and sanitize the apparatus. For example, each of the solutions can be pumped through the pumpable substance source  90 , the heat exchanger  92   a , the gas controller  140   a  and into the cleaning solution valve  97 .  
         [0050]    During cleaning, the cleaning solution valve  97 , which normally directs the pumpable substance past the inlet valve bodies  40   a  and into the upper portion of each of the vessels  15 , can be positioned to direct the cleaning solutions into both the upper portions of each vessel  15 , and via a cleaning inlet valve  98 , into the lower portion of each pressure vessel  15 . Accordingly, the cleaning solutions can be used to clean the pressure vessel  15  both above and below the isolator  80 . The cleaning solution in the upper portion of each pressure vessel  15  then flows past the outlet valve body  40   b  through the post-processing gas controller  140   b , the post-processing heat exchanger  92   b , and into the pressurized pumpable substance reservoir  91  to clean these components and connecting hardware. The cleaning solution in the lower portions of the pressure vessels  15  can be returned to the pumpable substance source  90  via a cleaning outlet valve  99  positioned at the bottom of each pressure vessel  15 .  
         [0051]    The apparatus  10   a  can further include a control fluid controller  110  that supplies and regulates the flow of control fluid to several of the valves of the apparatus. As was discussed above with reference to FIGS.  1 - 4 , the control fluid can be used to clean the valves and provide a fluid barrier between pressurized and unpressurized portions of the pumpable substance. As will be discussed in greater detail below, the control fluid can also be used to diagnose the operation of the pressure vessels  15 .  
         [0052]    The control fluid controller  110  can be coupled to a fluid supply  113  that supplies a suitable fluid for operating and cleaning the valves of the apparatus  10   a . In one embodiment, the fluid supply can supply citric acid or another liquid having a non-zero pH, and in other embodiments, other suitable fluids can be used. The fluid supply  113  can be filled with such cleaning solutions before initial startup of the apparatus  10   a  and/or at selected intervals after initial startup. In one embodiment, the fluid supply  113  can be sequentially filled with a caustic solution, a rinse solution and a sanitizing solution to clean the components powered by the control fluid in a manner similar to that discussed above with reference to the cleaning system  93 .  
         [0053]    The control fluid passes from the fluid supply  113  to a heater  114  for sterilizing the control fluid, and then to a cooler  115  to cool the control fluid to a suitable operating temperature. From there, the control fluid controller  110  directs the control fluid to various portions of the apparatus  10   a . For example, the control fluid can be directed to the yoke  11  of each pressure vessel  15  to control opening and closing of the yoke for access to the pressure vessel  15 . The control fluid can also be directed to the inlet valve body  40   a  and the outlet valve body  40   b  to power these valves in the manner described above with reference to FIGS.  1 - 3 . As was discussed above with reference to FIG. 2, the relief valve  63  can be coupled to the outlet valve body  40   b  to regulate the flow of the control fluid through the outlet valve body  40   b . In one embodiment, a bypass valve  63   a  can be positioned to bypass the relief valve  63  so that the control fluid can be run at low pressure through the valve body  40   b  and up to the relief valve  63  for cleaning.  
         [0054]    The control fluid can control the low pressure valve body  40   c  (as discussed above with reference to FIGS. 2 and 3), and can also drive the isolators  80  at low pressures, for example, to fill and empty the pressure vessels  15 . Accordingly, the low pressure valve body  40   c  can be coupled to a selector valve  100  that can be moved to a first position which allows the control fluid to enter the pressure vessel  15  (for purging the pumpable substance after pressurization has been completed), and can be moved to a second position which allows the control fluid to drain from the pressure vessel  15  (for filling the pressure vessel  15  with the pumpable substance ).  
         [0055]    In one embodiment, the pressure vessel  15  can include two detectors  18  (shown as a lower detector  18   a  below the isolator  80  and an upper detector  18  to above the isolator  80 ) to detect an inadvertent leak of the control fluid into the pressure vessel  15 . As discussed above with reference to the detectors  36  shown in FIG. 2, the detectors  18  can include pressure sensors, pH sensors, opacity sensors and/or any sensor configured to detect a leak of the control fluid into the pressure vessel  15 .  
         [0056]    In one embodiment, the control fluid entering each pressure vessel  15  as the pumpable substance is purged from the vessel can pass through a purge flowmeter  112 . The purge flowmeter  112  can detect the rate at which the control fluid enters each pressure vessel  15 , as well as the total amount of control fluid entering each pressure vessel  15  Accordingly, the purge flowmeter  112  can be used as a diagnostic tool to determine whether each pressure vessel  15  is filling at the desired rate and/or when the pressure vessel  15  has been completely filled. Similarly, the control fluid leaving each pressure vessel  15  during the fill cycle can pass through a fill flowmeter  111  which, in a similar manner to that discussed above, can be used to determine the rate and/or total volume of pressurized substance entering the pressure vessel  15 .  
         [0057]    As was discussed above, the isolator  80  can be driven by a high pressure pump  120  during the pressurization step of the pressurizing process. The high pressure pump  120 , the control fluid controller  110 , and the other components that control the motion of the pumpable substance, the control fluid, and the cleaning fluids can be controlled by the computer  130 . For purposes of clarity, only the connections between the computer  130  and the high pressure pump  120  and the control fluid controller  110  are shown in FIG. 5. The computer  130  can include a conventional personal computer coupled to a programmable logic controller, both of which are programmed to operate the apparatus  10   a  in an automatic, or semi-automatic mode, and to display and print out diagnostic or summary information related to the processing steps carried out by the apparatus  10   a.    
         [0058]    From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.