Patent Application
20140338373
The present invention relates to the field produce storage chamber to reduce spoilage. More specifically, to a construction designed to fit on a counter top.
Due to various nutrient and antioxidant profiles, consumption of fresh produce is generally accepted as essential to a healthy diet. Regular consumption of fruit is associated with reduced risks of cancer, cardiovascular disease (especially coronary heart disease), stroke, Alzheimer's disease, cataracts, and some of the general functional declines associated with aging. Diets that include a sufficient amount of fruits and vegetables also help reduce the chance of developing kidney stones and may help reduce the effects of bone loss. Fruits are also low in calories and are often integral to weight loss plans and generally healthy, balanced diets.
Most fruits and vegetables ripen after they are removed from their associated plants and stalks. Such ripening often changes the characteristics of the produce, including altering sweetness levels, texture, and firmness. Consumption of fruits and vegetables at the optimal point in the ripening process helps maximize not only taste and enjoyment of these foods, but may also maximize their health benefits.
Ripening is a natural process which is primarily a result of the production of ripening enzymes, many of which are triggered by the release of ethylene by the produce. Ethylene is a simple hydrocarbon gas produced when a fruit ripens, and is known to promote the upregulation of genes that cause the expression of enzymes that foster ripening. These enzymes may change the color of the skin as chlorophyll is degraded, aid in the production of new pigments, foster the breakdown of acids that make fruit taste sour, convert starches into sweet sugars, and soften pectin.
Maintaining most fruits and vegetables in a sufficiently cold state after harvest helps extend and ensure shelf life, most notably by reducing the release of ethylene. However, storage of produce in an isolated area without refrigeration causes a build up of ethylene and results in faster ripening (and rotting) of fruits and vegetable.
Due to the costs and life spans of harvested fruits and vegetables, there have been many techniques developed to address storage to maintain this cold chain. One such example is U.S. Pat. No. 4,845,958 entitled “Method of and Apparatus for Preserving Perishable Goods” to Senda. The apparatus taught by Senda relates to a refrigerated housing that includes a humidifier and a compression system to cool the housing. The device also uses an ethyl alcohol spray to help odorize the ripening produce.
A second concept for preserving ripening produce is introduced by U.S. Pat. No. 5,661,979 entitled “Self-contained Refrigeration Device for Fruit” to Deboer. The Deboer patent teaches a self contained refrigeration unit that uses thermo-electric Peltier cooler, as well as a heat sink to dissipate the heat generated by the cooler so to maintain a cooled container to maintain produce. A double-headed fan facilitates airflow throughout the assembly to aid in the removal of ethylene through a vent tower.
Yet a third example of a system for preserving fruit and vegetables is found in U.S. Pat. No. 5,782,094 entitled “Refrigerated Countertop Snack Container” to Freeman. Akin to Daboer, Freeman uses a Peltier thermoelectric element (instead of a compressor) to cool a refrigeration container. Such container is insulated and includes a series of air outlet and intake vents to aide in circulating air about the produce in order to reduce ethylene build up. The device further uses a series of fins and baffles to aid in circulation.
Ozone is a pungent, naturally-occurring gas possessing strong oxidizing properties, and has a long history of safe use in the disinfection of water sources. Ozone rapidly attacks bacterial cell walls and is generally thought to be a more effective anti-pathogenic agent against plant spores and mammalian parasites than chlorine. Ozone is reported to have 1.5 times the oxidizing potential of chlorine, yet contact times for this antimicrobial action are typically 4-5 times less than that of chlorine, all without the unwanted byproducts associated with chlorine. Ozone is also known to degrade ethylene.
As shown by the foregoing references, there are certain limitations in current counter-top style devices used to maintain fruits and vegetables. First, these devices are limited to using the Peltier effect (or traditional vapor compression systems) in combination with airflow to ward off the effects of ethylene build up. Second, current designs are largely inefficient and consume large levels of energy. Third, most of these designs fail to provide effective treatment of the ethylene which is the root of rotting and spoilage of the produce. Fourth, there are no counter-top applications of produce storage that introduce ozone as a means of preventing produce spoilage. Accordingly, there is a need in the art of produce storage for an energy efficient and robust chamber for use with fresh fruits and vegetables.
In view of the foregoing background, it is therefore an object of the present invention to provide a table top, stackable, produce chamber comprising a chamber capable of encasing produce, having a refrigeration system, at least one ozone generation unit, and at least one ethylene scrubbers. The chamber is therefore capable of delaying postharvest produce deterioration using of temperature control, ozone generation, and ethylene scrubbing.
In one embodiment, the present invention contemplates a portable produce chamber comprising a housing having a size and dimension to fit on a kitchen countertop, the housing comprising a chamber capable of encasing produce. In one embodiment, the chamber is shaped so that one chamber will securely stack on another chamber of the same type. At least one ethylene scrubber is fitted within the chamber capable of reducing chamber ethylene gas concentrations to delay postharvest produce deterioration. The chamber is in communication with a refrigeration system for the purpose of maintaining a chamber temperature that delays postharvest produce deterioration. Additionally, the refrigeration system maintains a chamber relative humidity that delays postharvest produce deterioration. Lastly, an ozone generator in communication with the chamber maintains a chamber ozone concentration for the purpose of delaying postharvest produce deterioration.
The invention also contemplates a method of reducing postharvest produce deterioration comprising the steps of: placing produce in a chamber; encasing the produce within the chamber; cooling the chamber to a temperature from about 10° C. to 20° C.; introducing gaseous ozone into the chamber to maintain a chamber ozone concentration between approximately 0.005 ppm and approximately 0.35 ppm; and maintaining a relative humidity within the chamber ranging from about 70% to 100% relative humidity.
For a fuller understanding of the invention, reference is made to the following detailed description, taken in connection with the accompanying drawings illustrating various embodiments of the present invention, in which:
In the Summary of the Invention above and in the Detailed Description of the Invention and in the accompanying drawings, reference is made to particular features (including method steps) of the invention. It is to be understood that the disclosure of the invention in this specification includes all possible combinations of such particular features. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects and embodiments of the invention, and in the invention generally.
The term “comprises” is used herein to mean that other elements, steps, etc. are optionally present. When reference is made herein to a method comprising two or more defined steps, the steps can be carried in any order or simultaneously (except where the context excludes that possibility), and the method can include at least one steps which are carried out before any of the defined steps, between two of the defined steps, or after all of the defined steps (except where the context excludes that possibility).
In this section, the present invention will be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the invention to those skilled in the art.
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A top hinge 390 connects the top edge 301 of the door 300 with the top edge 351 of the back panel 350. As shown, the top hinge 390 allows the door 300 to swivel open and allow access the various fruits and vegetables within the produce chamber 100. Optionally, the back panel 350 may include an insulating layer 380. This insulating layer can be sandwiched between the back panel 350 and an interior panel 385. Such insulating layer 380 increases the efficiency of the system and reduces the need for the refrigeration system 400 to constantly run to provide cooled air within the produce chamber 100.
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As a third duty, the controller 500 can also opt to circulate already cooled air within the produce chamber through a scrubber 490—for purposes of removing toxins such as ethylene which may lead to premature ripening of the fruits and vegetables contained within the produce chamber 100.
To foster ethylene removal from the produce chamber 100, media for the purpose of scrubbing ethylene from the air is present in the produce chamber 100. The media is at least one of activated alumina, vermiculite, zeolite, and silica gel. The media is impregnated with potassium permanganate (KMnO4). The mass of media utilized is tailored to the size of the produce chamber 100. Media pore size, pore volume, surface area, and bulk density is also tailored to the size of the produce chamber 100. Media with lower bulk density is desired over the same mass of media possessing a higher bulk density, due to the greater surface area of the lower bulk density media providing greater availability of KMnO4 to ethylene gas. The mass, pore size, pore volume, surface area, and bulk density required for the produce chamber 100 will be readily apparent to those skilled in the art. The media performs two primary functions: 1) to provide an absorptive surface to trap ethylene gas molecules, and 2) to provide a substrate on which KMnO4 is carried. KMnO4 is an oxidizing agent that reacts with ethylene, oxidizing it to ethylene glycol which does not markedly affect produce ripening. The produce chamber 100, in a preferred embodiment, comprises at least one sachet containing 5 mg KMnO4 impregnated zeolite. Besides or in conjunction with sachets, KMnO4 impregnated filters and pellets may be used in the chamber 100. In another embodiment, ultraviolet light mediated photcatalysis of titanium oxide reduces ethylene levels in the produce chamber 100 (the ultraviolet light source is optically sequestered from the produce). In one embodiment of the produce chamber 100, at least one dedicated pocket, bag, shelf, hook, or net provides a location for at least one sachet containing ethylene scrubbing media.
Titanium dioxide is known to be a photocatalyst under ultraviolet (UV) light. When Titanium dioxide is spiked with nitrogen ions or doped with metal oxide like tungsten trioxide, it is also a photocatalyst under either visible or UV light. The titanium dioxide photocatalytic reaction breaks down ethylene gas into carbon dioxide and water vapor. Additionally, photocatalytic oxidation provides the added benefir of reducing bacteria, molds, and odors. In one embodiment of the invention, a titanium dioxide photocayalyst is in communication with the produce chamber 100 for the purpose of scrubbing ethylene gas and preventing the premature ripening and spoiling of the fruits and vegetables contained within the produce chamber 100.
Ozone cannot be stored and transported like most other industrial gases, so must therefore be locally produced. Ozone can be produced in a number of ways known in the art. The most common methods are by the use of ultraviolet light and coronal discharge.
In one embodiment of the invention ozone is generated with an ultraviolet (UV) lamp. A UV lamp emitting light at approximately 185 nm in the presences of air (which is approximately 21% oxygen) will cause some diatomic oxygen (O2) molecules to split, resulting in single oxygen atoms (O−) that bind to other diatomic oxygen molecules to form ozone (O3). UV mediated ozone generation is advantageous in the current invention, for it is not susceptible to nitric oxide formation, as are some corona discharge-based devices operating in a humid environment.
The coronal discharge method of ozone is employed for many industrial and personal uses. While multiple variations of the “hot spark” coronal discharge method of ozone production exist, these units usually work by means of a coronal discharge tube. Coronal discharge tubes are typically cost-effective and do not require an oxygen source other than the ambient air to produce ozone. In one embodiment of the invention, ozone is generated with a corona discharge device. In such a device, air passes through an electrical field wherein ozone is generated. The preferred embodiment of an ozone generator is a variation of the coronal discharge method.
A suppression (“snubber”) circuit comprising a resister R4 and capacitor C2 protect the silicon controlled rectifier Q1 from overvoltage damage. Gate turn-on current is supplied by resister R2. Diodes D2 and D3 complete the full wave circuit. Capacitor C1 provides alternating current isolation as well as adequate current to drive the circuit 80.
A glass electrode 82 in communication with the circuit 80 is ultimately responsible for the production of ozone. As the primary winding of the transformer T001 is excited, the secondary winding of the transformer T001 drives a high voltage potential into a coiled metal element inside the electrode 82 that exceeds the dielectric breakdown of dry air, which in turn excites electrons to produce a positive corona that is initiated by an exogenous ionization event in a region of high potential gradient. The electrons resulting from the ionization are attracted toward the coiled electrode, and the positive ions repelled from it. By undergoing inelastic collisions closer and closer to the curved electrode, additional molecules are ionized in an electron cascade. The electron collisions excite the positive ions so that photons of short wavelength light are emitted. It is this that gives a blue-purple corona discharge its characteristic glow. These photons play an important part in producing the new seed electrons which are required to sustain the corona and for ozone to be continuously produced. The levels of ozone produced by this circuit and electrode combination, when installed in the produce chamber are between approximately 0.005 ppm and approximately 0.35 ppm ozone, and preferable from approximately 0.05 to approximately 0.15. Because of the high reactivity of ozone, materials employed in electrode construction include stainless steel (quality 316L), titanium, aluminum (as long as no moisture is present), glass, polytetrafluorethylene, or polyvinylidene fluoride. Silicone rubbers may also be employed since ozone concentrations in the present invention are relatively low.
The present invention contemplates a method of reducing the severity of postharvest produce deterioration. The method preferably utilizes the produce chamber 100 described herein. The method includes the step of placing of produce in a chamber of a suitable size and dimension to encase the produce. The produce chamber 100 is capable of being substantially sealed. The chamber is cooled to a temperature ranging from 10° C. to 20° C., with the preferred temperature being 13° C. Additionally, ozone is introduced into the chamber so that a chamber ozone concentration is maintained from approximately 0.005 ppm to approximately 0.35 ppm, with a preferred concentration range between approximately 0.05 ppm and approximately 0.15 ppm. A high cutoff point of approximately 0.3 ppm ozone may be maintained to ensure that ozone levels remain below permissible levels as established by Occupational Health and Safety Administration (OSHA) regulations. In a preferred embodiment, the ozone is introduced into the chamber 100 by an ozone generator that is installed within the chamber. In one embodiment, ethylene is scrubbed from the chamber environment. In a preferred embodiment, ethylene concentrations within the chamber remain below 0.015 ppm. Preferably, 5-gram sachets of potassium permanganate are placed within the chamber 100 for the purpose of ethylene scrubbing, though other methods of ethylene scrubbing will be clear to those skilled in the art. The step of maintaining a relative humidity from 70% to 100% within the chamber is also contemplated with a preferred relative humidity level being about 95%. The chamber 100 is placed on a counter top surface, such that as found in a residential or commercial kitchen environment. In an alternative embodiment, one chamber 100 is stacked on another chamber 100 so that multiple chambers form a stacked chamber array.
The following experimental data compared the postharvest degradation of bananas and tomatoes in various conditions. The control (“room condition”) temperatures ranged from approximately 22° C. to 25° C., while experimental refrigerated temperatures ranged from approximately 12° C. to 15° C. Relative humidity for control groups was maintained at approximately 25% RH to 50% RH, while experimental groups were maintained between approximately 85% RH to 100% RH. Ethylene gas concentrations were maintained in control groups between approximately 0.02 ppm and 0.035 ppm, while some experimental groups were maintained between approximately 0.0 ppm and 0.01 ppm. Ozone was not introduced in control groups, while some experimental groups were maintained between approximately 0.08 ppm and approximately 0.095 ppm ozone, which is within the acceptable level range allowed by the Occupational Safety and Health Administration (OSHA) regulations for such an application.
Bananas and tomatoes were generally weighed every 2 days to track moisture loss. Table 1 summarizes the amount of moisture lost per individual banana or tomato for each storage condition. There was only a minimal discrepancy between the amount of moisture lost in the two 13° C. storage treatments. Moisture loss was lower in the treatment with additional ethylene scrubbing for both bananas and tomatoes, but the difference was within the standard error and thus was not statistically significant. However, fruit left exposed to the ambient/room temperature conditions were found to lose much more moisture. From these results, it can be concluded that lower temperatures with higher RH result in improved water retention in these fruit. Furthermore, it is possible that the removal of additional ethylene using ethylene scrubbing sachets may improve the water retention.
Table 2 shows that bananas in both of the 13° C. storage treatments exhibited improved preservation of firmness over bananas in ambient/room conditions. This is indicated by higher force values for the bananas stored at 13° C., particularly with the bananas in the ozone with ethylene scrubbing treatment. Thus, the treatment with ozone and ethylene scrubbing provided better preservation of firmness over the treatment with ozone only.
Table 3 shows that tomatoes in the 13° C. storage treatments generally exhibited improved preservation of firmness compared with tomatoes in the ambient/room temperature treatment. This is indicated by elevated force values for the tomatoes stored in 13° C. storage conditions compared with the lower force values observed with tomatoes stored in the ambient/room conditions. Minimal distinction can be seen between the firmness in tomatoes stored in the ozone treatment and the treatment with ozone and ethylene scrubbing.
Ozone concentration in the 13° C. storage treatments were effectively regulated and maintained within permissible levels as established by OSHA regulations. The presence of ozone in the 13° C. treatments effectively reduced the ethylene concentration by about ⅔, while the treatment with additional ethylene scrubbing further reduced the ethylene concentration to essentially negligible levels.
The tomatoes and bananas that were held in the ambient/room temperature conditions on the countertop were observed to be exceptionally shriveled and soft after only 6 and 12 days, respectively. Tomatoes in this storage condition were also found to have mold growth after 14 days particularly near the stem end. It was also determined that produce exposed to the ambient/room temperature conditions lost a significant amount of moisture over the 21 day trial. Furthermore, firmness measurements using a Texture Analyzer Plus (Stable Micro Systems) found that both the bananas and tomatoes had severely softened in the room temperature storage condition. Thus, storage in the ambient/room temperature treatment resulted in considerably diminished produce quality.
Bananas and tomatoes held at 13° C. exhibited significantly better maintenance of quality compared with produce stored in the ambient/room temperature conditions. Water retention was further improved in the treatment using ozone with additional ethylene scrubbing. Better color retention was also observed for both the bananas and tomatoes that received ozone with ethylene scrubbing. Greater levels of brown-spotting were observed in the bananas treated with only ozone than those treated with ozone and ethylene scrubbing. Additionally, more extensive shriveling and tearing of tomato flesh was observed with only ozone than with ozone plus ethylene scrubbing. Banana firmness was also best preserved in the fruit stored in the ozone with ethylene scrubbing treatment. Thus, storage at 13° C. using ozone with additional ethylene scrubbing resulted in the highest quality produce.
This application is a Continuation-in-Part application claiming priority to International Application Number PCT/US2013/25151, filed Feb. 7, 2013, which is a Continuation of U.S. patent application Ser. No. 13/368,195, filed on Feb. 7, 2012, which is a Continuation-in-Part application claiming priority to U.S. patent application Ser. No. 13/013,327 filed on Jan. 25, 2011, the contents of which are incorporated by reference herein.
