Patent Application
20080166458
1. Field of the Invention
This invention relates to packaging for harvested plant tissues.
2. Description of Related Art
Many plant tissues, including important agricultural products, ripen after harvest. For example, bananas harvested green and unripe continue to ripen during packaging, transportation and storage, consuming oxygen and releasing carbon dioxide in the process of respiration. Bananas also produce ethylene (although not all fruits do), and exposure to ethylene promotes the ripening of harvested bananas and other climacteric (ethylene-sensitive) fruits.
Agricultural industries are vulnerable to economic losses from the excessive ripening of agricultural products before those products reach the consumer. Many important agricultural products are harvested unripe or partially unripe to avoid damage, spoilage or decay en route to market. The storage and transportation environments for these products must be optimized for the products' preservation.
Technology that slows or effectively suspends ripening during the transportation and storage of plant products can reduce or prevent losses of the products due to overripening and spoilage. Further, technology that mitigates ripening can broaden the market horizons for agricultural and horticultural products, by allowing them to reach more distant consumers due to their improved longevity during transportation, or by allowing them to remain in storage longer before becoming unpresentable to consumers. For example, ripening-mitigation technologies may afford fruit and vegetable growers greater access to consumers in lands to which their products must travel by sea. Ripening-mitigation technologies may also extend the green-life, shelf-life, and effectively the season of availability of notoriously perishable fruits.
“Green life” refers to the period of time after harvest during which the plant product stays in a condition suitable for transportation. “Shelf life” refers to the period of time after the green life during which the product remains saleable. For example, upon arrival at an overseas shipping destination, green bananas are often processed in ripening rooms, in which ethylene is administered to achieve the plant products' uniform partial ripening before delivery to the retailer and consumer. For each type of plant product, there are conditions that typically induce ripening. For example, green bananas ripen while exposed to ethylene at a concentration of 100-150 parts per billion in a room held at 20 degrees Celsius and 90-95 percent relative humidity.
Currently available technologies for postponing or slowing ripening to lengthen the time available from the harvesting of plant products to their presentation to consumers include: harvesting fruit well before it is ripe, refrigeration, packaging fruit in “modified atmosphere” containers to retard respiration, and adding a powder that absorbs ethylene. Modified atmosphere packaging is a commonly used technique for preserving agricultural products, in which the oxygen content of the atmosphere inside a package is changed to retard respiration and other undesired processes. For example, hard, green (“preclimacteric”) bananas may be packaged in modified atmosphere packaging such as polyethylene bags that are 0.4 mm thick, in which the carbon dioxide content has been raised to five percent, and the oxygen content has been lowered to two percent. Potassium permanganate may be enclosed in the packaging to absorb ethylene emitted by the bananas. When stored in this manner and refrigerated at approximately 12 to 14 degrees C., preclimacteric bananas shipped at a relative humidity of about 90 to 95 percent may enjoy a shelf life of about two to three weeks.
Modified atmosphere packaging also may be achieved by placing a gas-permeable patch in what is otherwise standard, gas-impermeable packaging. For example, a gas-permeable or gas-transfer patch may consist of an array of microscopic pores, or may comprise a gas-permeable polymer. An example of a gas-permeable polymer is INTELIMER® by Landec Corporation, Menlo Park, Calif. An example of a polymer patch currently in use is the BREATHEWAY® membrane by BreatheWay in Guadalupe, Calif., which is selectively 3.8 times more permeable to carbon dioxide than to molecular oxygen, and which reversibly becomes markedly more gas-permeable when the temperature rises above a known level.
Refrigeration alone preserves plant products by slowing ripening and the growth of decay-causing microbes. Reduced-oxygen or controlled-atmosphere storage enhances the benefits of refrigeration. Controlled-atmosphere storage is a commonly used technique in which the oxygen content of the atmosphere inside a storage area is changed to promote the preservation of harvested agricultural products; the concentrations of other gases, temperature and humidity of the storage area are routinely controlled as well. Controlled-atmosphere storage requires specially equipped storage rooms that are costly to construct and operate, and maintaining a controlled atmosphere in a shipping container is very difficult and expensive. Moreover, because controlled-atmosphere environments may not support human life, they may only be entered by personnel with special equipment. In addition, ethylene-sensitive products (such as kiwi fruit) and ethylene-producing products (such as Oriental Pears) must be stored in separate rooms to prevent cross-ripening. Furthermore, even when a batch of ethylene-sensitive fruit is stored separately from other fruits, an entire batch of ethylene-sensitive fruit (e.g., all the fruit in a storage room or shipping container) can ripen prematurely if only a small amount of the fruit within it begins to ripen.
Modified atmosphere packaging provides a low-oxygen environment to its contents, allowing them to be stored or transported in a regular-atmosphere environment. It would be desirable to use modified atmosphere packaging for ethylene-sensitive products, so that these products could be stored and shipped in proximity to ethylene-producing products, minimizing concerns of cross-ripening (and cross-contamination of other kinds) between separately packaged products. However, undesired ripening and microbial contamination within each package remains problematic. The packaging traps ethylene, which thus accumulates within the package. The rate of ripening of ethylene-sensitive plant products in packaging that traps ethylene is faster than that which occurs in storage conditions that allow ethylene to escape.
What is desired is packaging for plant tissues that can more effectively retard or arrest ripening and spoilage during transportation and storage. The present invention provides an improved technology to mitigate the excessive ripening and spoilage of plant tissues.
The present invention provides improved packaging for harvested plant tissues, such as agricultural products. In some embodiments harvested plant tissues are placed in a package that contains either at least one hole, or a gas-permeable patch. The hole or patch is in turn covered by an adjustable aperture. The present invention improves currently available packaging methods by providing an additional level of control over the gas composition inside the package over the entire course of transportation and storage of the packaged plant tissues. Some embodiments of the present invention also mitigate damage to harvested plant tissues due to excessive ripening and spoilage, by contacting the plant tissues with ozone during transportation and storage. In some embodiments, harvested plant tissues are treated with ozone before packaging. The present invention also reduces costs by enabling the same package or kind of package to be used for different contents that have different atmospheric requirements for optimal protection from excessive ripening and spoilage.
The present invention provides improved packaging for harvested plant tissues, such as agricultural products. In some embodiments harvested plant tissues are placed in a package that is made of standard, gas-impermeable packaging material except for either one or more holes, or a gas-permeable patch. The hole or patch is in turn covered by an aperture that is adjustable from a fully closed to fully open position, so that the gas-permeability of the packaging may be altered by closing or opening the aperture by a desired amount. The one or more holes may be a macroscopic hole (visible to the naked eye), or microscopic or invisible pores that allow gases to flow across the packaging with relatively little selectivity. The gas-permeable patch may be made of an array of micropores, or may be made of a gas-permeable polymer with or without selectivity. The polymer may but need not be temperature sensitive, that is, the permeability of the polymer patch may but need not change substantially as a function of temperature.
An aperture may be made of any material (such as plastic or metal) and adjustable in any way (such as dialing or sliding). The aperture may be affixed to the package by any means that does not alter the permeability of the package (such as gluing to the package with an adhesive that does not dissolve the packaging material).
The use of an adjustable aperture improves currently available packaging methods by providing an additional level of control over the gas composition inside the package over the entire course of transportation and storage of the packaged plant tissues. By closing the aperture, one effectively converts modified atmosphere packaging into standard, gas-impermeable packaging. By opening the aperture, one effectively converts standard, gas-impermeable packaging (when the aperture is closed) into modified atmosphere packaging. By modulating the degree to which the aperture is open, one increases (by opening further) or decreases (by closing further) the gas permeability of the entire package.
In addition to those illustrated in
To provide a convenient guideline for adjustment of gas transfer, the adjustable aperture may comprise one or more markings at predetermined positions, and the aperture may be adjusted according to the markings. For example, a box for storing fruit under low-oxygen conditions to slow down ripening may have markings corresponding to the optimal gas transfer for a certain amount of fruit, such as a marking to use if the box contains one peach, another marking if the box contains two peaches, and so on. Alternatively, an adjustable aperture for use on a reusable box designed to contain different kinds of fruit may have markings indicating one scale reflecting optimal gas-transfer areas for pears, and another for bananas.
Currently, it must be determined in advance how much and what type of plant tissue is to be placed in, for example, a plastic box with a polymer patch, so that the size of the patch may be optimized to mitigate excessive ripening of the contents. See, e.g., http://www.breatheway.com/overview/difference.aspx. By covering the patch with an adjustable aperture, some embodiments of the present invention allow a box with a patch of arbitrary size to be used for a variety of agricultural products with differing respiration properties. For example, the same box or type of box may be loaded with bananas in one instance, and kiwi fruit in another, and the atmosphere modification propertied of the box tailored to each commodity by adjusting the aperture. Thus, the present invention can reduce packaging costs by enabling the same package or kind of package to be used for different contents that have different atmospheric requirements for optimal protection from excessive ripening and spoilage.
Even when a prefabricated box is to be used for only one variety of agricultural product, the adjustable aperture confers additional ability to tailor the atmosphere inside the package to the needs of the contents. For example, while a temperature-sensitive polymer patch allows greater gas permeability once a single temperature threshold has been reached, without an aperture, no additional control over the gas-permeability of the package is provided. By setting the aperture to more open positions as temperature increases, and to more closed positions as temperature drops, the gas-permeability of the package may be adjusted in increments as finely as may be desired. This ability to tailor and fine-tune the atmosphere inside the package provides greater protection to the packaged plant tissues.
In an exemplary embodiment, bananas are stored in a plastic box, which includes a gas-permeable polymer patch covered with an adjustable aperture. As the ambient temperature rises through a given temperature (say, 35° C.), the polymer comprising the patch switches from a crystalline to an amorphous state, so that the gas-permeability of the patch increases significantly. As the box proceeds through various stages of transportation and storage, the ambient temperature my rise above or fall below the given temperature repeatedly. In addition to the one-step switching of the polymer between two permeability states (much less and much more), adjusting the size of the aperture provides greater and less gas flow in a way that is much more responsive to changes in ambient temperature that do not involve the given temperature.
In some embodiments, the aperture covers a gas-permeable patch of microscopic pores, rather than a temperature-sensitive polymer patch. Again, the aperture modulates the flow of gases through the patch by adjusting the area of patch that is available for gas transfer, tailoring the modified atmosphere packaging to the needs of its specific contents. Some embodiments combine the use of an aperture and a macroscopic hole, so that, for example, when the aperture is open, the aperture exposes a hole on an otherwise substantially closed package. The package may be a bag, box, or other container of any material or size.
Some embodiments of the present invention also mitigate damage to harvested plant tissues due to excessive ripening and spoilage by contacting the plant tissues with ozone during transportation and storage, as described in Provisional Patent Application Ser. No. 60/879,716 filed on Jan. 9, 2007 (cited above). The ozone is added to the atmosphere surrounding the package. In some embodiments, the ozone enters the package through the aperture. In some embodiments, the ozone may permeate the packaging material independently of the aperture, which may cover a hole, set of holes, or patch having gas permeability characteristics that differ from those of the packaging material. In some embodiments; harvested plant tissues are treated with ozone before packaging further to promote their freshness (also as described in the cited application).
In some embodiments, plant tissues also are treated with ozone before the products are packaged, for example, by exposure of the plant tissues to ozone gas or to ozonated water, for instance, in a hydro-cooler. Such ozone pre-treatment affords additional benefits, such as destroying or retarding the growth of microorganisms on or around the plant products even before ozone is introduced to the atmosphere in which the packaged plant tissues will be loaded.
It will be understood by one skilled in the art that embodiments of the present invention are applicable to any form of packaging that can include a patch or hole that can be covered with an aperture, and that virtually any kind of plant tissues may be so packaged. While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments.
The present application claims benefit and priority from U.S. Provisional Patent Application Ser. No. 60/879,716 filed on Jan. 9, 2007, Attorney Docket # PA4101PRV entitled, “Improved Modified Atmosphere Packaging Process,” which is herein incorporated by reference, and from pending U.S. patent application Ser. No. ______ [not yet assigned] filed on Jul. 26, 2007, Attorney Docket # PA4175US entitled, “Improved Plant Tissue Packaging Process,” which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60879716 | Jan 2007 | US |
