IL159400A - Method for storing a bulk commodity - Google Patents

Description

ΓΡΠ33 ΓΤΎΙΠΟ "pOTTlfc WW METHOD FOR STORING A BULK COMMODITY BACKGROUND OF THE INVENTION The present invention relates to storage of bulk commodities in loose or bagged form and, more particularly, to the long term storage of bulk commodities under a controlled environment.

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.

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 and various oxidation effects in the stored commodity.

Vacuum sealing of bulk commodities also has been rejected because of the perceived need for rigid and expensive pressure vessels.

It is accordingly, a general object of the invention to provide a method for long term storage of bulk commodities that obviates the above problems.

SUMMARY OF THE INVENTION In the present invention, to insure the rapid kill of biological contaminant(s), such as insects, as well as to protect the commodity from oxygen-effected deterioration such as the growth of fungi and micro-organisms, a oxidation, the commodity is sealed within the enclosure after which the atmosphere therein is evacuated to establish a vacuum. The vacuum is maintained during at least a portion of the long term storage of the bulk commodity. Handling of the bulk commodity it achieved through selectively opening and closing an airtight seal in the enclosure formed by the flexible, low gas-permeability sheet material.

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.

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.

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.

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.

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.

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.

Specifically, according to the teachings of the present invention there is provided a method for storing a bulk commodity under conditions wherein substantialy all biological contaminant(s) within the bulk commodity are killed during at least a portion of its storage, comprising; A) hermetically sealing the bulk commodity in a flexible, low gas-permeability sheet material enclosure to thereby store the bulk commodity, and thereafter; B) maintaining the bulk commodity at a temperature of at least 20 °C during the at least a portion of its storage in the flexible, low gas-permeability sheet material enclosure; C) substantially evacuating the atmosphere in the sealed flexible, low gas-permeability sheet material enclosure to establish a vacuum within the enclosure of about 25-100 mm of mercury during the at least a portion of its storage; D) maintaining, during the at least a portion of its storage, the vacuum at about 25-100 mm of mercury while the bulk commodity is maintained at the temperature of at least 20 °C to kill substantially all of the biological contaminant(s) without generating heat; and E) at the end of the storage opening a hermetic seal in the flexible, low gas-permeability sheet material enclosure in order to remove therefrom at least a portion of the bulk commodity.

In embodiments, the storage is a time period in which serious biologically-active damage would occur if the bulk commodity were not protected from damage. In embodiments, the damage is insect infestation by insects already in the bulk commodity before it is sealed, is produced at least in part by the effect of oxidation of the bulk commodity, is produced at least in part by the effect of heat produced by the bulk commodity, is produced at least in part by the effect of the growth of micro-organisms in the bulk commodity and/or is produced at least in part by the effect of the growth of fungi in the bulk commodity.

In embodiments, the bulk commodity has a weight in the range of one-half metric ton to two hundred metric tons.

In embodiments, the flexible, low gas-permeability sheet material enclosure is a plastic such as a UV resistant PVC. In embodiments, the plastic sheet material enclosure has a thickness of at least 0.032 inches.

In embodiments, the method further comprises maintaining the vacuum during the storage of the bulk commodity.

BRIEF DESCRIPTION OF THE DRAWINGS 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.

FIG. 1 is a flow diagram in block form of one embodiment of the invention.

FIG. 2 is a perspective view of a storage system in accordance with one embodiment of the invention.

FIG. 3 is a schematic of a vacuum system in accordance with one embodiment of the invention.

FIG. 4 is a flow diagram in block form of an embodiment of the method of the invention.

DESCRIPTION OF THE INVENTION The steps of the invention are depicted in FIGURE 4. A bulk commodity is hermetically sealed in a flexible container or enclosure, such as that formed from a 0.032 inch, low gas-permeability, UV resistant food grade PVC sheet material. A vacuum 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. An opening, which can be opened or closed by means such as a solenoid-controlled inlet valve, is fed to an ordinary vacuum pump, with, if needed, an appropriate filter at the hermetically sealed container end to prevent clogging or damage to the pump. The vacuum pump 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%. At this time the valve is closed, and the hermetically sealed container becomes a large "vacuum pack," with periodic pumping as required to compensate for residual infiltration of air, eliminating any of the respective causes of degradation named above due either to direct or indirect effects of oxygen. Further, any residual moisture in the absence of oxygen will not as easily cause moisture-produced damage. The damage to the commodity can be provided at least in part by the effect of heat produced by the commodity.

Removal of the commodity from the sealed enclosure can be made through a commercially available hermetic "zipper", such as, the zipper sold by ITW under the trademark MAXIGRIP, that is provided on the hermetic enclosure.

In a particular embodiment, a vacuum in the range of 25-100 mm of mercury is established in the enclosure at 20°C or higher as a function of a biological contaminant(s) and a desired kill time of the biological contaminant(s). The commodity can have a weight in the range of one-half to two hundred metric tons.

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.

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 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.

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.

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%.

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.

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.

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.

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 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.

Insect Species Life Stage 25°C 33°C 37°C 40°C Tribolium castaneum Eggs 27.62 h 16.31 h 1 1.17h 4.12 h (Red Flour Beetle) Larvae 3.46 h 3.29 h 2.56 h 1.94 h Pupae 12.73 h 11.48 h 9.35 h 3.83 h Plodia interpunctella Eggs 28.35 h 6.21 h 4.00 h 2.49 h (Indian Meal Moth) Larvae 3.99 h 2.69 h 2.07 h 2.10 h Pupae 5.35 h 2.65 h 2.44 h 1.64 h Rhyzopertha dominica Eggs 176.32 h 85.98 h 46.32 h 11.24 h (Lesser Grain Borer) Larvae 83.80 h 49.58 h 19.45 h 6.47 h Pupae 98.28 h 56.20 h 22.14 h 8.65 h 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.

It has been found that a vacuum of between about 35-50 mm Hg and a temperature above about 18 °C, and particular in the range of about 25-40 °C, works particularly well in the storage of some commodities.

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.

It is important to note that those portions of the specification which do not fall within the scope of the claims do not belong to the invention.

Claims (12)

- 9 - 159400/3 What is claimed is:

1. A method for storing a bulk commodity under conditions wherein substantially all biological contaminant(s) within the bulk commodity are killed during at least a portion of its storage, comprising; A) hermetically sealing said bulk commodity in a flexible, low gas-permeability sheet material enclosure to thereby store said bulk commodity, and thereafter; B) maintaining said bulk commodity at a temperature of at least 20 °C during said at least a portion of its storage in said flexible, low gas-permeability sheet material enclosure; C) substantially evacuating the atmosphere in said sealed flexible, low gas- permeability sheet material enclosure to establish a vacuum within the enclosure of about 25-100 mm of mercury during said at least a portion of its storage; D) maintaining, during said at least a portion of its storage, said vacuum at about 25- 100 mm of mercury while said bulk commodity is maintained at the temperature of at least 20 °C to kill substantially all of said biological contaminant(s) without generating heat; and E) at the end of the storage opening a hermetic seal in said flexible, low gas- permeability sheet material enclosure in order to remove therefrom at least a portion of said bulk commodity.

2. The method of claim 1 wherein said storage is for a time period in which serious biologically-active damage would occur if said bulk commodity were not protected from damage.

3. The method of claim 2 wherein said damage is insect infestation by insects already in said bulk commodity before it is sealed.

4. The method of claim 2 wherein said damage is produced at least in part by the effect of oxidation of said bulk commodity.

5. The method of claim 2 wherein said damage is produced at least in part by the effect of heat produced by said bulk commodity. 159400/2 - 10 -

6. The method of claim 2 wherein said damage is produced at least in part by the effect of the growth of micro-organisms in said bulk commodity.

7. The method of claim 2 wherein said damage is produced at least in part by the effect of the growth of fungi in said bulk commodity.

8. The method of claim 1 wherein said bulk commodity has a weight in the range of one-half metric ton to two hundred metric tons.

9. The method of claim 1 wherein said flexible, low gas-permeability sheet material enclosure is a plastic.

10. The method of claim 9 wherein said plastic sheet material enclosure is a UV resistant PVC.

11. The method of claim 9 wherein said plastic sheet material enclosure has a thickness of at least 0.032 inches.

12. The method of claim 1 further comprising maintaining said vacuum during said storage of said bulk commodity. 1 1 Menahem Begin Street 52 521 Ramat Gan