Abstract:
A method and system for storing of a bulk commodity utilizes a flexible, low air-permeable sheet material enclosure in which the bulk commodity is hermetically sealed. The atmosphere in the sealed flexible sheet material enclosure is evacuated to establish a vacuum therein. The vacuum is maintained during at least a portion of the storage of the commodity to ensure a significant reduction of the commodity. The temperature of the commodity is maintained sufficiently high to ensure substantial total kill of infesting insects within a desired time period. At least a portion of the commodity can be removed from the enclosure by opening a hermetic seal therein.

Description:
RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of application Ser. No. 09/667,481, filed Sep. 22, 2000. The entire teachings of the above application are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Commodities stored in bulk which are degradable in the presence of oxygen such as coffee, grains, fruits, cocoa, and the like, are subject to deleterious effects including extensive loss caused by insects in the commodity during storage, the effects of oxygen during storage produced, for example, by the growth of micro-organisms such as aerobic bacteria and/or fungi in the commodity, and other impacts on the quality, nutritional purposes, safety, purity, appearance, taste, aroma and freshness of the commodity.  
           [0003]    A well known method for storage of a bulk biologically-active commodity utilizes a hermetically sealed enclosure formed from a flexible, low air-permeable sheet material employing the slow depletion of oxygen by respiration of live insects present in the commodity, and by the commodity itself. However, this process can take significant time and can rely on a significant level of infestation to deplete the oxygen. In addition, after the insects die, the oxygen level gradually rises due to infiltration of oxygen through the enclosure, thereby permitting various oxidation and oxygen-related effects in the stored commodity, including the growth of fungi, and hence the growth of undesirable aflatoxins.  
         SUMMARY OF THE INVENTION  
         [0004]    In accordance with the present invention, to ensure the rapid kill of insects as well as to protect the commodity from oxygen-effected deteriorations such as the growth of fungi, micro-organisms, and oxidation, the commodity is sealed within an enclosure after which the atmosphere therein is evacuated to establish a vacuum. The vacuum is maintained during at least a portion of the storage of the bulk commodity. Handling of the bulk commodity is achieved through selectively opening and closing an airtight seal in the enclosure formed by a flexible, low air-permeable sheet material. The temperature of the commodity is maintained sufficiently high within substantially all portions of the commodity to ensure substantial total kill of infesting insects within a desired time period. In alternative embodiments, the method can include opening a hermetic seal in the sheet material enclosure in order to remove therefrom at least a portion of the commodity.  
           [0005]    A system for storing a commodity is also provided which includes a flexible, low air-permeable sheet material enclosure for substantially hermetically enclosing the commodity. A vacuum pump coupled to the enclosure establishes a vacuum therein for at least a portion of the storage of the commodity. The temperature of the commodity is maintained sufficiently high within substantially all portions of the commodity to ensure that substantially all of the infesting insects are killed within a desired time period.  
           [0006]    A method for storing a bulk food commodity which can be degraded by insects is also provided which includes hermetically sealing the food commodity in a flexible, low air-permeable sheet material enclosure, evacuating the atmosphere in the sealed sheet material enclosure to establish a vacuum therein, and maintaining the vacuum during at least a portion of the storage of the food commodity. The method also includes maintaining a temperature sufficiently high within substantially all portions of the food commodity to ensure substantial total kill of all infesting insects within a desired time period.  
           [0007]    An alternative method for storing a bulk commodity which is degradable in the presence of oxygen is provided which includes hermetically sealing the commodity in a flexible, low air-permeable sheet material enclosure, evacuating the atmosphere in the sealed sheet material enclosure to establish a vacuum therein, and maintaining the vacuum during at least a portion of the storage of the commodity to ensure a significant reduction in the production of aflatoxins. The method also includes maintaining a temperature sufficiently high within substantially all portions of the commodity to ensure substantial total kill of infesting insects within a desired time period.  
           [0008]    Another method for storing a bulk commodity which is degradable in the presence of oxygen is provided which includes hermetically sealing the commodity in a flexible, low air-permeable sheet material enclosure, evacuating the atmosphere in the sealed sheet material enclosure to establish a vacuum therein, and maintaining the vacuum during at least a portion of the storage of the commodity to significantly reduce the growth rate of bacteria which can degrade the commodity. The method also includes maintaining a temperature sufficiently high within substantially all portions of the commodity to ensure substantial total kill of infesting insects within a desired time period.  
           [0009]    Yet another method for storing a bulk commodity which is degradable in the presence of oxygen is provided which includes hermetically sealing the commodity in a flexible, low air-permeable sheet material enclosure, evacuating the atmosphere in the sealed sheet material enclosure to establish a vacuum therein, and maintaining the vacuum during at least a portion of the storage of the commodity to ensure a significant reduction in chemical degradation of the commodity. The method also includes maintaining a temperature sufficiently high within substantially all portions of the commodity to ensure substantial total kill of infesting insects within a desired time period.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0011]    [0011]FIG. 1 is a flow diagram in block form of one embodiment of the invention.  
         [0012]    [0012]FIG. 2 is a perspective view of a storage system in accordance with one embodiment of the invention.  
         [0013]    [0013]FIG. 3 is a schematic of a vacuum system in accordance with one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    A description of preferred embodiments of the invention follows. One embodiment of the invention is illustrated in FIGS.  1 - 3 . In step  10 , a commodity is hermetically sealed in a flexible container or enclosure  18 , such as that formed from a 0.813 mm (0.032 inch), low air-permeable, ultraviolet-resistant food grade polyvinyl chloride sheet (PVC) material. In one embodiment, the container can include a PVC enclosure marketed by GrainPro, Inc. of Concord, Mass. under the trade name Cocoons™. The commodity can be packaged in individual jute bags  22  and stored on pallets  24  within the enclosure  18 .  
         [0015]    In the context of a hermetic enclosure, low air-permeable can be defined as low air-permeability through the enclosure compared to the initial consumption of air by the insects. If a vacuum is used, low air-permeable can be defined as low air permeability through the enclosure compared to the pumping capability of the vacuum at a designated pressure. In one embodiment, the enclosure is 15 m 3  with a ten metric ton capacity, and has an infiltration rate of less than about 10 liters/minute at 40 mm Hg. Even lower infiltration rates can be achieved with different materials that form the low air-permeable enclosures.  
         [0016]    In step  12 , a vacuum  20  is established in the enclosure by using a conventional commercial vacuum pump and set point regulator. The flexible container or enclosure prevents excessive stresses when evacuated as would occur with a rigid container by conforming to the shape of the enclosed commodity. The vacuum  20 , as shown in FIG. 3, can include a vacuum pump  26  driven by a motor  28 . Tubing or hose  38  connects the enclosure  18  to the vacuum pump  26 .  
         [0017]    An opening in the enclosure  18 , which can be opened or closed by means such as a solenoid-controlled inlet valve, is fed to the vacuum pump  26  with, if needed, an appropriate filter  30  in line  38  to prevent clogging or damage to the pump. In a particular embodiment, the vacuum pump  26  is allowed to run for an extended period of time so that either or both oxygen and interstitial moisture inside are substantially removed, typically down to a vacuum of 25-100 mm Hg at room temperature representing an oxygen level equivalent to normal pressure of 3-13%.  
         [0018]    At this time, the inlet valve is closed, and the hermetically sealed enclosure becomes a large “vacuum pack” (step  14 ), with periodic pumping as required to compensate for residual infiltration of air, eliminating any of the respective causes of degradation named above due to either direct or indirect effects of oxygen. Further, any residual moisture in the absence of oxygen will not as easily cause moisture-produced damage. The vacuum  20  can be controlled by control panel  34  coupled to a pressure sensor  32  to maintain a desired vacuum level. In alternative embodiments, the vacuum pump  26  runs continuously during storage of the commodity and is turned on and off by an on/off switch.  
         [0019]    The time, temperature, and vacuum conditions for removing biologically-active contaminants are a function of the type of contaminant, e.g., the type of insect infestation, temperature, and the desired kill time. For example, it has been found that a 100% kill of insects in coffee and cocoa beans can be achieved in three days using a vacuum in the range of 30-50 mm Hg at room temperature. In some applications, it is desirable to remove the oxygen from the stored commodity to preserve the freshness which affects the taste of the commodity. In other applications, it is desirable to remove the oxygen from the stored commodity so that growth of fungi is curtailed and hence the production of aflatoxins. Thus, in step  16 , the temperature of the commodity is maintained sufficiently high to ensure substantial kill of infesting insects within a desired time period. Generally, the higher the temperature, the faster the insects will die as they respire more rapidly to deplete air within the hermetic enclosure  18 .  
         [0020]    In alternative embodiments, an insecticidal gas, such as propylene oxide, ozone, etc., can be injected into the hermetic enclosure  18 , before or after applying a vacuum to the enclosure, to accelerate the kill time of the insects. In a particular embodiment, the insecticidal gas is injected into the hermetic enclosure prior to applying a vacuum to the enclosure  18 . Of course, when additional gases are injected into the hermetic enclosure  18 , care must be taken to avoid gas mixtures which are flammable, explosive, etc.  
         [0021]    Removal of the commodity from the sealed enclosure can be made through a commercially available hermetic “zipper,” such as the zipper sold by ITW Maxigrip Specialty Applications Group under the trademark MAXIGRIP, that is provided on the hermetic enclosure.  
       EXAMPLE 1  
       [0022]    It has been shown experimentally that the kill time for various life stages and species of insects varies as between life stages and species and is a strong function of ambient temperature. As shown in the Table below, for 3 common insect pests, the kill time varies between the insects, and between the different life stages of the same insect. In these experiments, a commodity was placed in a hermetic enclosure  18  and a vacuum of 35 mm Hg was applied.  
                                                                                                   Life            Insect Species   Stage   25° C.   33° C.   37° C.   40° C.                      Tribolium     Eggs   27.62 hours   16.31 hours   11.17 hours   4.12 hours         castaneum         (Red Flour   Larvae   3.46 hours   3.29 hours   2.56 hours   1.94 hours       Beetle)           Pupae   12.73 hours   11.48 hours   9.35 hours   3.83 hours         Plodia     Eggs   28.35 hours   6.21 hours   4.00 hours   2.49 hours         interpunctella         (Indian Meal   Larvae   3.99 hours   2.69 hours   2.07 hours   2.10 hours       Moth)           Pupae   5.35 hours   2.65 hours   2.44 hours   1.64 hours       Rhyzopertha   Eggs   176.32 hours   85.98 hours   46.32 hours   11.24 hours       dominica       (Lesser Grain   Larvae   83.80 hours   49.58 hours   19.45 hours   6.47 hours       Borer)           Pupae   98.28 hours   56.20 hours   22.14 hours   8.65 hours                  
 
         [0023]    It has been discovered that the minimum temperature needed to ensure substantial total kill of all infesting insects within a desired time period is reached at substantially all portions of the commodity. Thus, one must maintain the coolest part of the commodity at or above a given temperature, for example, with a heated warehouse, in the hermetic enclosure  18  for the greatest time period of the 3 life stages to kill the desired species.  
         [0024]    It has been found that a vacuum of between about 35-50 mm Hg and a temperature above about 18 degrees Celsius, and particular in the range of about 25-40 degrees Celsius, works particularly well in the storage of some commodities.  
         [0025]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.