WO2000032052A1 - Methods and systems for reducing microbial populations - Google Patents

Methods and systems for reducing microbial populations Download PDF

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Publication number
WO2000032052A1
WO2000032052A1 PCT/US1999/028084 US9928084W WO0032052A1 WO 2000032052 A1 WO2000032052 A1 WO 2000032052A1 US 9928084 W US9928084 W US 9928084W WO 0032052 A1 WO0032052 A1 WO 0032052A1
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WO
WIPO (PCT)
Prior art keywords
chlorine dioxide
pad
treated
solution
products
Prior art date
Application number
PCT/US1999/028084
Other languages
French (fr)
Inventor
Timothy D. Wildman
Barry K. Speronello
James Aamodt
Original Assignee
Raytec Corporation
Engelhard Corporation, Inc.
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Publication date
Application filed by Raytec Corporation, Engelhard Corporation, Inc. filed Critical Raytec Corporation
Priority to AU17455/00A priority Critical patent/AU1745500A/en
Publication of WO2000032052A1 publication Critical patent/WO2000032052A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/153—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of liquids or solids
    • A23B7/158—Apparatus for preserving using liquids
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/144—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/144—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A23B7/152—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor in a controlled atmosphere comprising other gases in addition to CO2, N2, O2 or H2O ; Elimination of such other gases
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/153—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of liquids or solids
    • A23B7/157—Inorganic compounds
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/34—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals
    • A23L3/3409—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/34—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals
    • A23L3/3409—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A23L3/34095—Details of apparatus for generating or regenerating gases
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/34—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals
    • A23L3/3409—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A23L3/3445—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor in a controlled atmosphere comprising other gases in addition to CO2, N2, O2 or H2O
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/34—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals
    • A23L3/3454—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals in the form of liquids or solids
    • A23L3/358—Inorganic compounds
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47F—SPECIAL FURNITURE, FITTINGS, OR ACCESSORIES FOR SHOPS, STOREHOUSES, BARS, RESTAURANTS OR THE LIKE; PAYING COUNTERS
    • A47F3/00—Show cases or show cabinets
    • A47F3/001—Devices for lighting, humidifying, heating, ventilation
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47F—SPECIAL FURNITURE, FITTINGS, OR ACCESSORIES FOR SHOPS, STOREHOUSES, BARS, RESTAURANTS OR THE LIKE; PAYING COUNTERS
    • A47F7/00—Show stands, hangers, or shelves, adapted for particular articles or materials
    • A47F7/0071—Show stands, hangers, or shelves, adapted for particular articles or materials for perishable goods

Definitions

  • the present invention is generally directed to the employment of an antimicrobial agent alone, including chlorine dioxide, or a combination of antimicrobial agents, to extend the life of products such as produce, meat, dairy and floral items in environments such as retail grocery stores
  • an antimicrobial agent alone, including chlorine dioxide, or a combination of antimicrobial agents
  • the antimicrobial agent, or combination of antimicrobial agents is located in proximity to the product, for example in or on a disposable pad provided in a dnp pan located below the displayed products, and/or the products themselves are contacted with the anitimicrobial agent or the combination of antimicrobial agents
  • Antimicrobial agents die known in the art for the treatment and inhibition of the infestation and proliferation of microorganisms
  • Such agents e g , sodium hypochlo ⁇ te, lodophors, phenol, quaternary ammonium compounds, glutaraldehyde, peracetic acid and the like
  • can be used to kill a wide va ⁇ ety of microorganisms e g , Pseudomonas aeragtnosa Saccharamvas cerevisiae, and Staph ⁇ lococcus aureus
  • Chloride dioxide is also known in the art for the treatment and inhibition of the infestation and proliferation of microorganisms and can be used to kill a wide va ⁇ ety of microorganisms (e g , Pseudomonas aeruginosa, Saccharamyas cerevisiae, and Staphylococcus aureus
  • Food storage display cases often have a "dnp pan,” which is typically a metal tray (e g , aluminum), mounted underneath the display case to collect water and droppings of loose food product (e g , leaves of lettuce and the like)
  • the drip pan is designed to be easily removed for proper cleaning to maintain the food storage display cases in sanitary conditions
  • Display cases also frequently incorporate an air recirculation system comprising a fan and associated venting to provide the displayed food product with circulating an Without routine maintenance, a drip pan containing food droppings becomes a good environment for the growth and proliferation of microorganisms
  • the inventors believe that as the microorganisms grow, they enter the air recirculation system typically employed in such food storage and display cases The circulating air and the food product consequently becomes contaminated with microorganisms
  • chlo ⁇ ne dioxide in low concentrations has long been recognized as useful for the treatment of odors and microbes Its use is particularly advantageous where microbes and/or organic odorants are sought to be controlled on and around foodstuffs, because chlonne dioxide functions without the formation of undesirable side products such as chloramines or chlo ⁇ nated organic compounds that can be produced when elemental chlo ⁇ ne is utilized for the same or similar purposes
  • chlo ⁇ ne dioxide gas is also generally considered to be safe for human contact at the low concentrations that are effective for deodo ⁇ zation and most antimicrobial applications
  • Chlorine dioxide gas can be toxic to humans at concentrations greater than 1,000 ppm, and it can be explosive at pressures above about 0 1 atmosphere Therefore,
  • chlo ⁇ ne dioxide using mixtures of solid reagents
  • One system employs a solid mixture of a metal chlo ⁇ te and an acid in a liquid, aqueous environment.
  • a second system combines a metal chlo ⁇ te and a solid organic anhydride to generate a highly concentrated flow of chlo ⁇ ne dioxide which must be diluted with a constantly flowing stream of inert gas.
  • Each of these solid reagent systems is disadvantageous for any one or more of the following reasons: a) upon mixing there is normally a sudden, highly concentrated stream of chlorine dioxide generated; b) the mixture of reactants produces chlorine dioxide gas under dry conditions, thereby reducing the shelf life of the reactants, and c) an inert gas stream must be used to reduce the concentration of chlo ⁇ ne dioxide gas in the atmosphere.
  • Aqueous solutions of chlorine dioxide are also known in the art. Two types of synthesis processes are generally used to provide chlo ⁇ ne dioxide solutions for commercial uses, such as poultry chiller water purification, washwater purification, potable water treatment and as a teat dip for the control of non-human mammalian mastitis
  • the first type of synthesis process is based on the manual combination of two aqueous solutions, one containing a source of chlorite anions and another being acidic
  • the solution containing chlorite anions is usually a solution of sodium chlorite having a concentration of between about 100 ppm and about 5% by weight and having a pH of about 13
  • the acidic solution may contain any acid capable of providing a pH below about 8 5 after the solutions are mixed
  • Such acids include cit ⁇ c acid, lactic acid, hydrochloric acid, sulfu ⁇ c acid, and dissolved carbon dioxide ( ⁇ e., sodium bicarbonate)
  • the antimicrobial performance of the resultant solutions depends upon the degree to which the chlorite anions from the chlorite source solution are converted to free molecular chlo ⁇ ne dioxide ("Chlorine Dioxide") in the solution, as Chlo ⁇ ne Dioxide is the effective agent for both antimicrobial and deodo ⁇ zation activity
  • Such solutions having a pH of about 8 are generally referred to in the industry as "stabilized" chlorine dioxide solutions, and usually contain between about 100 ppm and 5% of a mixed solution of Chlorine Dioxide and unconverted chlo ⁇ te anion Because the acid concentration is relatively low at a pH of 8, the typical ratio of Chlo ⁇ ne Dioxide to chlonte anion in a stabilized chlo ⁇ ne dioxide solution is less than 0 01 Therefore, for a given initial concentration of chlo ⁇ te anion, stabilized chlorine dioxide solutions are relatively weak antimicrobial agents due to their low conversion of chlorite anion to Chlorine Dioxide Also, since they are typically supplied at a concentration of less than about 5% by weight sodium chlorite, they are relatively expensive to ship and store due to the high weight of water that must be transported as part of the solution
  • Chlorite anion is generally stable in stabilized solutions (pH 8), so they have an advantageously long shelf life To improve their effectiveness, however, they are typically activated just prior to use by the addition of a strong acid to lower their pH to below about 3 5 and convert more chlo ⁇ te anion to Chlo ⁇ ne Dioxide via the reaction shown above Since the activation process involves the addition of a strong acid to lower the pH, it requires a high le ⁇ el of operator skill to handle, measure and mix the acid with the stabilized chlo ⁇ ne dioxide solution Also, since the activation process results in a solution having a pH of less than about 3 5, such activated solutions are not well suited to work in combination with, for example, detergents which work best under alkaline or neutral pH conditions Contact of these solutions with many metals should also be limited because of possible metallic corrosion by the acidic solution
  • Such activated solutions typically have a ratio of Chlo ⁇ ne Dioxide to chlorite anion below about 0 05 when the solution is acidified to a pH of about 3 It is possible to achieve a higher ratio of Chlorine Dioxide to chlorite anion in such activated solutions, but doing so is dangerous and requires extreme operator skill Achieving a ratio of
  • Chlorine Dioxide to chlo ⁇ te anion above about 0 05 requires further acidification to a much lower pH than 3 (typically less than 2) and often requires that the further acidification be performed at concentrations of chlorite anion above about 5000 ppm Under such conditions of extremely low pH and high chlorite ion concentration it is possible to generate a sufficient chlo ⁇ ne dioxide concentration in solution such that the vapor pressure of gaseous chlo ⁇ ne dioxide in equilibrium with the solution approaches the explosive range Therefore, it is not common practice to produce solutions having a high ratio of Chlonne Dioxide to chlorite anion by manual acidification (i e , without chlorine dioxide generation equipment as discussed below)
  • chlorine dioxide solution is generated from either a sodium chlorite solution or stabilized chlonne dioxide solution using chlo ⁇ ne dioxide generation equipment at the point of use
  • the generated solution typically has a ratio of Chlorine Dioxide to chlorite anion of between about 10 and 25 and, as a result, such solutions are highly effective antimicrobial agents Since generated chlorine dioxide solution is typically used shortly after generation, the relatively high decomposition rate of chlo ⁇ ne dioxide in solution is unimportant Also, since aqueous sodium chlorite is commercially available at higher concentrations than are typically available in the form of stabilized chlo ⁇ ne dioxide solutions, the cost of stonng and shipping the aqueous sodium chlorite solutions can be lower when compared to stabilized chlorine dioxide solutions However, the high cost of the chlonne dioxide generation equipment and the high level of operator skill needed for its operation makes generated chlorine dioxide solution best suited to relatively large applications such as water treatment and poultry processing where the consumption of chlorine dioxide is sufficiently large
  • Chlorine dioxide is first produced in solution by conventional means, e g acid activation of a solution of sodium chlo ⁇ te Inert carrier gas, typically air or nitrogen, is then bubbled through the activated solution where it picks up some of the Chlorine Dioxide That gaseous mixture of Chlorine Dioxide and carrier gas is then bubbled through a second vessel containing water where the Chlorine Dioxide is dissolved to produce a solution of chlorine dioxide typically having a ratio of Chlorine Dioxide to chlorite anion between about 20 and about 50 While it is possible to produce substantially pure solutions of chlonne dioxide in this manner, it requires a very high level of operator skill and is rarely done outside of the laboratory
  • U.S. Patent 2,022,262 discloses stable stain removing compositions comprising a dry mixture of a water soluble alkaline chlorite salt, an oxalate, and an acid. Since alkaline chlorites are strong oxidizers and corrosively caustic, a relatively high level of user skill is needed to employ this process.
  • the pH of the resultant solution is acidic, so such acidic solutions of chlorine dioxide are not well suited for use in combination with detergents which work best under alkaline or neutral conditions.
  • the resultant solution contains contaminants including sodium chloride, and the solution byproducts of the oxalate and acid as contaminants.
  • U.S. Patent 2,071 ,091 discloses an improved fungicide and bactericide, and an improved sterilization process using chlorous acid and the salts of chlorous acid.
  • chlorous acid and the salts of chlorous acid includes aqueous solutions of soluble chlorite salts that have been acidified to an acidic pH. Such solutions contain mixtures of chlorine dioxide and chlorite anions with the ratio of Chlorine Dioxide to chlorite being higher when the pH of the solution is lower.
  • this process requires a relatively high degree of user skill to handle and measure the alkaline chlorite and acid. The requirement for an acidic pH limits the utility of this process when the preferred solution pH is alkaline, and the resultant solution is contaminated with sodium chloride and the solution byproducts of the acid.
  • U.S. Patent 2,071,094 discloses deodorizing compositions in the form of dry briquettes comprising a dry mixture of a soluble chlorite, an acidifying agent, and a filler of lower solubility.
  • Generation of chlorine dioxide begins as the briquette dissolves in water. This process is suitable for unskilled users, but still requires that the resultant solution be produced at an acidic pH, and it is still contaminated with the solution byproducts of the reagents.
  • the inert, low solubility filler leaves an insoluble residue paste that is difficult to handle and dispose of.
  • U.S. Patent 2,482,891 discloses stable, solid, substantially anhydrous compositions comprising alkaline chlorite salts and organic acid anhydrides which release chlorine dioxide when contacted with water.
  • the patent disclosure indicates that the prefe ⁇ ed solution is highly concentrated and consequently would have been at an acidic pH. As such, this process suffers from the same limitations as the '262 and '091 Patents mentioned above.
  • U.S. Patent 4,585,482 discloses a long-acting biocidal composition comprising a chlorine dioxide liberating compound and a hydrolyzable organic acid-generating polymer. Methods are disclosed for producing dry polymer encapsulated microcapsules containing such compositions and water such that the resultant dry materials release chlorine dioxide gas.
  • the primary purpose of the polymer encapsulating film of the '482 Patent is to provide for hard, free flowing particles, and to protect against the loss of water from the interior of the microcapsule. If the micro capsules were to be immersed in water, they would produce a chlorine dioxide solution. Producing chlorine dioxide solution in this manner would eliminate the complications of measuring and mixing reagents and the cost of capital equipment that characterize the prior art.
  • the solution pH need not be acidic so it would be feasible to produce chlorine dioxide in a detergent solution.
  • the materials of the '482 Patent are not storage stable because they begin to release chlorine dioxide as soon as they are manufactured. Furthermore, they release chlorine dioxide over a period of several days, so they are unsuitable for quickly preparing a useable chlorine dioxide solution.
  • the microcapsules cannot be removed from the water in a simple fashion. Typically they must be separated by a process such as filtration.
  • the inventors have determined that chlorine dioxide alone, and various antimicrobial agents, alone, as well as combinations of chlorine dioxide and a select group of antimicrobial agents, in specified effective amounts, are effective for extending the storage and display life of products such as produce, meat, fish, dairy, and floral products. It would be a significant advance in the art to provide a method of extending the storage life of such products, especially in storage or display cases, by inhibiting the proliferation of microorganisms contained in the environment surrounding such products. The methods and systems would therefore serve not only to limit the proliferation of microorganisms in storage and display areas, but also to inhibit infestation of the products by microorganisms.
  • the present invention is generally directed toward extending the life of products including produce, meat, dairy, and floral products, and is more specifically directed toward the protection and/or treatment of food products to either inhibit infestation by and proliferation of microorganisms, and/or to treat the products which may already have microorganisms present.
  • a particular aspect of the present invention is directed toward methods and systems for protecting or treating products against infestation by and proliferation of microorganisms, said methods and systems involving treating the environment in proximity to such products with an antimicrobially effective amount of at least one Antimicrobial Agent, or chlorine dioxide, or a combination of chlonne dioxide in gaseous and/or liquid form, and at least one Antimicrobial Agent (hereinafter "Combinations")
  • the term, "Comb ⁇ nat ⁇ on(s),” when used herein, is intended to include chlorine dioxide in gaseous and/or solution forms in combination with one or more Antimicrobial Agent(s) in a gaseous, liquid (preferably aqueous solution), and/or solid form
  • pads or matting treated with at least one Antimicrobial Agent or chlorine dioxide, or a combination of chlorine dioxide in gaseous and/or liquid form and at least one Antimicrobial Agent are provided Such pads or matting are suitable for placement in the environment in proximity to a storage or display case, such as in a dnp pan
  • the chlorine dioxide gas is released under controlled conditions at low concentrations when in the presence of water vapor
  • the reactants generating the chlorine dioxide gas when combined to form a mixture, do not generate a significant amount of chlorine dioxide gas when water is not present
  • the reactants can therefore be stored for long pe ⁇ ods of time in a substantially dry atmosphere
  • the present invention is concerned with extending the life of products, including food and floral products, by introducing, alone or m va ⁇ ous Combinations, chlonne dioxide gas, aqueous solutions of chlorine dioxide, quaternary ammonium compounds, and other Antimicrobial Agents into the product storage and/or display environment.
  • Chlorine dioxide gas may be produced by a) forming a mixture of at least one metal chlorite and at least one matenal capable of reacting with the metal chlorite to produce chlorine dioxide gas in the presence of water but not in the substantial absence of water, and b) exposing the mixture to the atmosphere in proximity to displayed food products, the atmosphere comprising water vapor, to produce chlorine dioxide gas in a sustained concentration of from about 0 001 to 1 ,000 ppm, preferably from about 0 01 to 500 ppm, more preferably from about 0 01 to 100 ppm, and most preferably from about 0 01 to 10 0 ppm
  • the cho ⁇ ne dioxide gas is produced in a device which, when combined with water, allows the controlled passage of water into the device to initiate a reaction which generates chlorine dioxide gas
  • the gas is able to pass through the device into the body of water to form an aqueous solution of chlonne dioxide
  • the device may be in the form of a capsule or sachet, for example, and may be placed in the drip pan, wherein it is contacted with moisture and activated
  • An aqueous solution of chlorine dioxide may thus be produced by a) having liquid water in a first zone and at least one metal chlorite and at least one acid forming component in a second zone, said first and second zones being separated by a membrane, b) contacting the membrane with water from said first zone (e g , a drip pan), such that liquid water and/or water vapor passes through the membrane into the second zone, thereby facilitating the reaction between said at least one acid forming component and said at least one metal chlorite to produce chlonne dioxide,
  • a preferred embodiment of the present invention provides for the controlled release of chlo ⁇ ne dioxide, and thereby provides not only immediate antimicrobial treatment but sustained treatment as well
  • Figure 1 is a side elevational view of a typical display case for the display of food products in a retail grocery store
  • Figure 2 is a side elevational view of the display case shown in Figure 1 showing a system for treating the displayed food products and drip pan with an Antimicrobial
  • protection and/or treatment of products stored or displayed in cases is provided using an effective amount of an Antimicrobial Agent or chlorine dioxide alone, or a combination of Antimicrobial Agents, or a combination of chlo ⁇ ne dioxide in a gaseous and/or a liquid solution with a select group of Antimicrobial Agents (hereinafter "Combination")
  • the Combination of chlorine dioxide gas and/or solution and Antimicrobial Agent(s) may be applied to the products themselves, or may be released or dispersed to the environment in proximity to the products, including the area underneath the product and in a dnp pan generally found below the product which is used to catch droppings of loose food product
  • Antimicrobial Agent(s) shall mean agents which effectively reduce the proliferation of microorganisms in storage and display areas and also inhibit infestation of the products themselves by microorganisms
  • Antimicrobial Agents does not include chlorine dioxide and, components that, in the presence of water, can generate chlo ⁇ ne dioxide Examples of suitable Antimicrobial
  • Agents include, but are not limited to, sodium hypochlonte, sodium chlonte, -(p- nonylphenyl)-hydroxypoly (oxyethylene)- ⁇ odme complex, hydrogen peroxide, glutaraldehyde/phenol, acid glutaraldehyde, quaternary ammonium chlorides, phenol de ⁇ vatives, and combinations thereof, as disclosed in Journal of Industrial Microbiology, Vol 4, pp 145-154 (1989)
  • the products may be treated with at least one Antimicrobial Agent by forming a mixture of one or more Antimicrobial Agent(s) with a suitable solvent, preferably water
  • a suitable solvent preferably water
  • the mixture may then be sprayed directly onto the products, preferably as a fine mist, using conventional spraying equipment
  • the Antimicrobial Agent(s) is sufficient to inhibit the proliferation of microorganisms withm the food storage display case
  • the effective concentration of the Antimicrobial Agent(s) varies depending, in part, on the particular Antimicrobial Agent
  • the preferred concentration of sodium hypochlonte solution for treating displayed food products is from about 50 to 2,000 ppm, most preferably from about 100 to 1,500 ppm
  • the preferred concentration of glutaraldehyde solution is from about 0 01% to 5%, most preferably from about 0 1 to 3% by weight
  • suitable Antimicrobial Agents for use in the present invention and their relative strengths for determining a suitable concentration level are identified in Journal of Industnal Microbiology, Vol 4, pp 145-154 (1989), which is incorporated herein by reference in its entirety From the information contained withm this publication, and/or with the routine knowledge of those practicing in this art, a suitable concentration of a selected Antimicrobial Agent may readily be determined
  • waste pieces of loose products e g , leaves of lettuce
  • waste pieces of loose products e g , leaves of lettuce
  • a solution comprising an Antimicrobial Agent preferably an aqueous solution
  • concentration of the Antimicrobial Agent in aqueous solution for the treatment of waste pieces of food products is the same as discussed above for the treatment of the fresh food products
  • the food product display or storage area may be treated in whole or in part with an antimicrobially effective amount of an Antimicrobial Agent which imparts sustained antimicrobial activity to the treated surfaces of the area
  • an Antimicrobial Agent is an antimicrobial composition marketed as LNTERSEPT*, which is available from Interface Speciality Products Company.
  • the LNTERSEPT ® product includes the following active ingredients ethanol, 2,2' -(cocoimino) -bis, salt with phosphoric acid, bis (2-ethyl hexyl) ester ( 1 1), ethanol, 2,2' -(cocoimino) -bis, salt with mono (2-ehtyl hexyl) ester (1 1 ), and phosphoric acid, mono (2-ethyl hexyl) ester
  • Other suitable active ingredients ethanol, 2,2' -(cocoimino) -bis, salt with phosphoric acid, bis (2-ethyl hexyl) ester ( 1 1), ethanol, 2,2' -(cocoimino) -bis, salt with mono (2-ehtyl hexyl) ester (1 1 ), and phosphoric acid, mono (2-ethyl hexyl) ester
  • Antimicrobial Agents may be identified by those of ordinary skill in the art
  • chlorine dioxide alone, or in Combinations may be used to extend the life of food products, such as food and floral products stored and displayed in retail grocery store display cases
  • Chlo ⁇ ne dioxide may be used directly on the food products
  • Chlorine dioxide gas may be circulated tlirough a circulation system or generated in an area in proximity to stored or displayed products, and/or m the drip pan, to treat and/or inhibit the proliferation of microorganisms in the environment of a storage or display case
  • the employment of chlorine dioxide alone, or in Combinations is effective for controlling infestations a ⁇ sing from a va ⁇ ety of microorganisms, including microorganisms of the genus Salmonella
  • Chlorine dioxide gas and/or aqueous solutions of chlo ⁇ ne dioxide have the additional effect of reducing the ethylene content resulting from the natural ripening process of the food products such as fruits and vegetables
  • Ethylene is a gas which is produced naturally by food products such as fruits and vegetables dunng the npening process Because the ripening process accelerates as ethylene concentrations increase, the production of ethylene can result in the rapid ovempening of a batch of such food products Currently, up to about 20% of such food products may be lost due to premature
  • the chlo ⁇ ne dioxide gas is
  • Products may be treated with chlonne dioxide gas generated by forming a mixture of at least one metal chlorite and at least one material capable of reacting with the metal chlorite to produce chlorine dioxide gas in the presence of water but not in the substantial absence of w ater, and then by exposing the mixture to an atmosphere comp ⁇ sing water vapor to produce chlorine dioxide gas in a sustained concentration of from about 0 001 to
  • the chlorine dioxide gas may be generated as desc ⁇ bed above and directed to an enclosure containing the food products, such as through the air circulation system
  • the preferred concentration of chlorine dioxide gas for treating displayed food products is from about 0 01 to 500 ppm, more preferably from about 0 01 to 100 ppm, and most preferably from about 0 01 to 10 0 ppm
  • waste pieces of loose products (e g , leaves of lettuce) which may be in proximity to the food products, may be treated with chlorine dioxide gas as well
  • a drip pan located below the products in a storage or display area such as a food display case typically found in retail grocery stores, is provided with a pad or matting material.
  • the ingredients necessary to generate chlorine dioxide gas are provided in the region below the displayed food product, in the drip pan, or in a pad or matting provided in the drip pan.
  • the chlorine dioxide inhibits the proliferation of microorganisms in the drip pan and also helps to reduce the proliferation of microorganisms in the air recirculation system.
  • the ingredients for generating the chlorine dioxide may be contained within a sachet, such as disclosed, for example, in U.S. Patent No. 5,567,405.
  • the composition for generating chlorine dioxide gas may be in the form of a mixture of at least one metal chlorite and at least one Second Material.
  • the metal chlorites employed may generally be any metal chlorite.
  • Preferred metal chlorites are alkali metal chlorites, such as sodium chlorite and potassium chlorite.
  • Alkaline earth metal chlorites may also be employed. Examples of alkaline earth metal chlorites include barium chlorite, calcium chlorite, and magnesium chlorite. The most preferred metal chlorite is sodium chlorite.
  • the Second Material is a dry solid hydrophilic material, preferably a dry solid inorganic hydrophilic material.
  • the preferred dry solid hydrophilic material produces a pH of no more than about 10.5 when the aqueous portion of a 30 weight percent mixture of that material in deionized water is measured. More preferred solid hydrophilic materials produce a pH of less than 9 and most preferably less than 7.
  • dry solid hydrophilic materials suitable for reacting with the metal chlorites include, but are not limited to, synthetic zeolites, such as A, X, Y and mordenite; natural zeolites such as chabazite and clinoptilolite; hydrous clays, such as bentonite, kaolin, attapulgite and halloysite; calcined clays, such as metakaolin, spinel phase kaolin, calcined bentonite, calcined halloysite, and calcined attapulgite; acidified synthetic zeolites, such as A, X, Y, and mordenite that have been contacted with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid, or other acidic compound (e.g., calcium chloride) so that the pH of the resulting aqueous phase of the mixture is below 10.5; acidified natural zeolites such as chabazite and clinoptilolite; acid
  • the chlorine dioxide may be used in the form of a solution to treat and/or prevent infestation of microorganisms
  • Chlonne dioxide in the form of an aqueous solution may be produced by a) having liquid water in a first zone and at least one metal chlorite and at least one acid forming component in a second zone, the first and second zones being separated by a membrane, b) contacting the membrane with water from the first zone (e g , a dnp pan), such that liquid water and/or water vapor passes through the membrane into the second zone, thereby facilitating the reaction between the at least one acid forming component and the at least one metal chlonte to produce chlonne dioxide, and c) allowing the chlorine dioxide produced in the second zone to pass through the membrane to the first zone, into the liquid water, to form an aqueous solution
  • a device which generates chlorine dioxide in the presence of water, but not in the substantial absence of water may be employed
  • the device when placed in liquid water, may be used to generate an aqueous solution containing chlo ⁇ ne dioxide on demand
  • the device may comp ⁇ se a membrane defining, at least in part, an enclosed space, the enclosed space containing at least one metal chlonte and at least one acid forming component
  • the membrane is made of a material which permits (a) liquid water and/or water vapor to pass therethrough into the enclosed space to allow the at least one metal chlorite and at least one acid forming component to react to produce chlo ⁇ ne dioxide, and (b) the so produced chlonne dioxide to pass therethrough out into the liquid water to produce the product solution containing chlorine dioxide
  • the liquid water needed to induce the formation of aqueous chlonne dioxide may be provided by the water present in the drip pan of the food storage display case
  • the present invention can be adapted to provide the controlled release of chlonne dioxide by employ
  • Embodiment B the at least one metal chlorite and at least one acid forming component are initially separated from the liquid water by a membrane which does not substantially dissolve du ⁇ ng the generation of chlorine dioxide
  • This embodiment produces chlorine dioxide solutions of higher purity than Embodiment A because at least a portion of the reaction byproducts from the reaction between the metal chlorite and acid forming component are substantially retained by the membrane which is at least substantially insoluble and therefore the byproducts do not enter the product aqueous solution containing chlorine dioxide in appreciable quantities
  • Embodiments A and B are preferred, however, the invention also contemplates that substantially insoluble reactants may be used w ith substantially soluble membranes and substantially soluble reactants may be used with substantially insoluble membranes and that mixtures of insoluble and soluble reactants may be used with either type of membrane
  • Other methods for generating aqueous solutions of chlonne dioxide are known to those skilled in the art and may be adapted for use in the methods and systems of the present invention
  • reaction rate i e , the rate of generation of chlo ⁇ ne dioxide
  • desired pu ⁇ ty of the resulting aqueous solution containing chlorine dioxide the ease of handling and disposal of the reaction waste products. If reaction rate is of primary importance, then it is preferred to select reactants which are more water soluble and membrane materials which are more permeable to both water and chlorine dioxide.
  • reactants and membrane materials can be chosen so that the membrane and all of the reaction byproducts are substantially water soluble, the aqueous solution of chlorine dioxide does not have to be further processed to remove either membrane residue or the insoluble byproducts of the reactants.
  • the membrane employed in the present device serves several functions. First, it must provide for the controlled passage of liquid water and/or water vapor from a source (typically the body of water that is to be treated to form an aqueous chlorine dioxide solution) into the device so that the metal chlorite and the acid forming component can react with each other to produce chlorine dioxide. Second, in the absence of a source of water, the membrane must protect the reactants form ambient humidity so that the reactants have a desirable shelf life. Third, the membrane must allow the passage of chlorine dioxide gas out into the body of water to be treated once water has contacted the reactants and the chlorine dioxide generating reaction has commenced.
  • a source typically the body of water that is to be treated to form an aqueous chlorine dioxide solution
  • the membrane materials can be selected from substantially water soluble materials when rapid reaction is important and dissolved byproducts are acceptable. Substantially insoluble membrane materials are appropriate when it is desirable to avoid introducing species other than chlorine dioxide (such as soluble membrane constituents to the product solution).
  • Preferred substantially water soluble membrane materials include gelatin, polyvinyl alcohol, cellulose, and derivatives of cellulose including but not limited to hydroxypropyl methyl cellulose. Other such materials will be known to those skilled in the art.
  • the preferred substantially water soluble membrane materials, such as gelatin, once contacted with liquid water are quickly water softenable and at least partially water soluble.
  • the membrane is water soluble to the extent that after the reaction between the metal chlorite and acid forming component has been completed and the chlorine dioxide gas has been released, the membrane continues to solubilize. As a result, the membrane material is fully dissolved in the aqueous solution of chlorine dioxide and does not have to be removed therefrom after use. In this manner, if water soluble reactants are utilized, there are no undissolved byproducts to be removed from the body of water.
  • the preferred membrane material is gelatin, preferably in the form of capsules, such as Capsugel manufactured by Warner-Lambert Co. and Vegecaps manufactured by G.S. Technology.
  • a membrane material which is not substantially soluble is preferred when it is desired to limit the introduction of species other than chlorine dioxide into the product solution.
  • the purity of the aqueous solution can be further enhanced by incorporating into the enclosed space containing the reactants one or more materials which form an insoluble phase with at least one otherwise soluble reaction byproduct. As a result, the at least one otherwise soluble reaction byproduct cannot escape out through the membrane into the aqueous solution containing chlorine dioxide because the at least one otherwise soluble reaction byproduct is tied up in at least one insoluble phase.
  • the preferred substantially insoluble membrane materials which permit passage of water vapor into contact with the contained reactants also provide a barrier to keep insoluble reactants and reaction products from entering the aqueous solution of chlorine dioxide that is produced.
  • Such materials include microporous nonwoven hydrophobic polymer sheet materials including nonwoven polyethylene (e.g., TYVEK ® brand sold by
  • sustained concentration means that at all times during production, the concentration of chlorine dioxide gas is within the range 0.001 to 1 ,000 ppm.
  • the generation of chlorine dioxide gas need not be at a constant rate. It is permissible to have a fluctuating rate so long as the chlorine dioxide gas concentration does not exceed 1,000 ppm, and is within the range of from about 0 001 to 1,000 ppm for a sustained period of time
  • the generation of chlonne dioxide gas within the specified range will vary depending on the relative humidity of the surrounding atmosphere, the ratio of the reactants in the mixture, the diluent gas flow rate (e g , air) through the treated space if any, and the ratio of the amount of chlorine dioxide gas releasing material to the volume of the treated space Generally, the higher the relative humidity the higher the rate of production of chlorine dioxide gas The lower the flow of the diluent gas through the treated space, the higher the resultant chlo ⁇ ne dioxide gas concentration The higher the ratio of the chlorine dioxide gas releasing matenal to the volume of the treated space, the higher the chlorine dioxide gas concentration
  • the sustained amount of chlo ⁇ ne dioxide gas is from about 0 01 to 500 ppm, more preferably from about 0 01 to 100 ppm Especially good results are obtained when the chlo ⁇ ne dioxide gas production is in the range of from about 0 01 to 10 ppm
  • the amount of each of the metal chlorite and the matenal which reacts with the metal chlonte will depend on several factors, including, but not limited to, the quantity of chlorine dioxide gas needed for a particular application, the basicity of the metal chlo ⁇ te and the acidity of the matenal which reacts with the metal chlonte In general, it is preferred to use as much chlorite as possible consistent with a sufficient rate of release
  • the yield of chlo ⁇ ne dioxide gas per unit mass of the mixture is maximized
  • the weight ratio of the metal chlonte and the matenal which reacts with the metal chlorite is in the range of from about 0 01 to 0 25 1 0 It is withm the skill of the art to choose the proper ratio for a particular application
  • the mixture formed in accordance with the present invention may optionally contain a desiccant which absorbs water to minimize or eliminate an initial brief duration production of chlorine dioxide gas due to residual water vapor present m the atmosphere or in the solids when the mixture is packaged
  • Suitable desiccants include but are not limited to calcium chloride, activated calcium sulfate, activated zeolite X and zeolite A, activated bentonite clay, activated silica gel, activated attapulgite and mixtures thereof
  • the term "activated" means that the particular matenal has been substantially dehydrated, for example, by heating at 300 C for one hour
  • the total amount of desiccant may vary depending on several factors, for example, the ambient humidity when the matenal is packaged, the water permeability of the packaging material and the desired shelf life of the product.
  • the desiccant is present in a total amount from about 0.1% to 25% by weight based on the total weight of the mixture.
  • the relative humidity of the atmosphere to which the composition is exposed during use can range from low to high humidity conditions.
  • the method of the present invention can be conducted at low humidity (e.g., 10% relative humidity) up to 100% relative humidity.
  • low humidity e.g. 10% relative humidity
  • the amount of chlorine dioxide gas generated per given amount of the mixture will depend, in part, on the relative humidity of the surrounding atmosphere. In general, higher humidity will result in a higher concentration of chlorine dioxide gas.
  • one of the constituents of the composition of the present invention may be present in excess and the second of the constituents may be added as needed.
  • the mixture can contain an excess of an organic acid anhydride and periodically additional amounts of metal chlorite can be added.
  • the mixture of the metal chlorite and the material which reacts with the metal chlorite can be formulated in several ways. The preferred method is to prepare in a dry atmosphere an intimate physical mixture of fine powders of both constituents having particle sizes, preferably below about 200 um. Larger particles may be used and may achieve a slower rate of chlorine dioxide gas release in certain instances.
  • the mixture can be formed by combining one of the constituents in liquid form with other constituent(s).
  • a slurry of a fine powder of calcined kaolin microspheres in a nonpolar liquid such as dodecane may be combined with the metal chlorite.
  • the mixture is then dried to remove the nonpolar liquid. If water is used as the liquid, then the mixture should be dried to a sufficient extent to prevent excessive release of chlorine dioxide gas
  • the reaction ot the metal chlo ⁇ te and the material which reacts with the metal chlorite can last for a sustained period of time
  • sustained period of time shall mean that the chlorine dioxide gas will be generated during a short period of time (several minutes) to a long penod of time spanning many hours
  • the length of the sustained pe ⁇ od of time will depend, for example, on the relative amounts of the constituents in the mixture Eventually, of course, one of the reacting constituents (either the metal chlonte or the material which reacts with the metal chlorite) will be spent and the reaction will cease However, during the course of the reaction for however long it lasts, chlonne dioxide gas will be produced in a sustained concentration as defined herein
  • a preferred composition for producing a slow release rate of long duration is a mixture of about 5% sodium chlorite and about 95% metakaolin microspheres
  • a preferred composition for a shorter duration, higher rate of generation of chlorine dioxide is a mixture of about 5% sodium chlo ⁇ te, about 10% activated calcium chlo ⁇ de and the balance acid-treated metakaolin microspheres
  • the length of time of the reaction is also dependent, in part, on how much water vapor is present in the atmosphere contained within the packaging
  • desiccants to minimize chlonne dioxide gas production in the packaging can ensure that the mixture w ill react for the longest pe ⁇ od of time when exposed to water vapor under operating conditions
  • the presence of a desiccant may delay the desired onset of production of the chlorine dioxide gas when the mixture is exposed to water vapor
  • the mixture of metal chlorite and a matenal which can react with metal chlo ⁇ te in the presence of water vapor may be packaged for shipment and storage m containers made of mate ⁇ als which are resistant to the passage of liquid water and water vapor
  • mate ⁇ als which are resistant to the passage of liquid water and water vapor
  • Example of such materials include metal cans, glass jars, foil pouches, and barrier layer polymer laminates
  • the mixture of the metal chlorite and the material which reacts with the metal chlorite may be used as a powder, used as formed shapes, or packaged and retained for use in any material which is gas permeable Examples of such matenals include
  • TYVEK ® and GORTEX ® These materials enable water vapor to enter into the package and react with the mixture and also enable the resulting chlorine dioxide gas to be released from the package and enter the atmosphere Such matenals are liquid water impervious
  • the metal chlorites employed in the present invention can generally be any metal chlorite, as well as mixtures thereof
  • Preferred metal chlo ⁇ tes are water soluble and include alkali metal chlorites, such as sodium chlorite and potassium chlo ⁇ te as well as alkaline earth metal chlorites
  • alkaline earth metal chlontes include ba ⁇ um chlorite, calcium chlo ⁇ te, and magnesium chlorite
  • the most preferred metal chlonte is sodium chlorite, especially dry technical grade sodium chlonte containing about 80% by weight of sodium chlorite and 20% of sodium chlonde available from Energia E Indust ⁇ as Aragonesas, S A of Madrid, Spain
  • the acid forming component is preferably a dry solid hydrophilic matenal which does not react with the metal chlorite during dry storage The acid forming component does, however, react with the metal chlorite to form chlorine dioxide when in the presence of liquid water and/or water vapor
  • the term "acid forming component” shall mean a dry solid matenal which is itself acidic or produces an acidic environment when in contact with liquid water and/or water vapor and metal chlonte
  • the acid forming component may be water soluble or substantially insoluble
  • the preferred acid forming mate ⁇ als are those which produce a pH of below about 7, most preferably below about 5 when the aqueous portion of a concentrated mixture of the solid in deiomzed water is measured
  • Examples of preferred acid forming components include water soluble solid acids such as bone acid, citnc acid, tartanc acid and water soluble acid salts such as calcium chloride, magnesium chloride, magnesium nitrate, lithium chloride, magnesium sulfate, aluminum sulfate, sodium acid sulfate (NaHSO 4 ), sodium dihydrogen phosphate (NaH : PO 4 ), potassium acid sulfate (KHSO 4 ), potassium dihydrogen phosphate (KH PO 4 ), and water soluble organic acid anhydrides such as maleic anhydride, and mixtures thereof
  • the most prefe ⁇ ed acid forming component is sodium acid sulfate
  • the amount of acid forming component should be sufficient to provide an excess of acid beyond that needed to neutralize the alkalinity of the metal chlorite and the incoming water
  • the amount of the acid forming component should be sufficient to maintain a pH of less than about 5 and more preferably less than about 3 5 when in contact with the metal chlo ⁇ te
  • Calculation of the amount of metal chlonte, specifically sodium chlorite can be computed by methods well known in the art based on the reaction:
  • Other constituents may be included within the enclosed space in addition to the reactants and phases that form insoluble phases with otherwise soluble phases.
  • desiccant materials may be included to increase the storage stability of the reactants by protecting them from humidity (which can cause humidity induced premature reaction to form chlorine dioxide).
  • Deliquescent materials may also be included in the enclosed space to accelerate the onset of the chlorine dioxide forming reaction once the membrane is contacted with water. Deliquescent materials absorb water vapor and convert it to liquid water. Consequently, soluble reactants can dissolve and begin rapidly to react to form chlorine dioxide even before liquid water has penetrated the membrane.
  • Calcium chloride is both the preferred desiccant material and preferred deliquescent material. Additional materials having these characteristics will be known to those skilled in the art and are included within the scope of the present invention.
  • the solid metal chlorite and the solid acid forming component can be in any physical form which can be contained within the device.
  • the solid reactants can be in the form of powders, granules, pellets, tablets, agglomerates and the like. In a preferred aspect of the invention, one or both of the reactants are present in the form of relatively large agglomerates (as defined below).
  • the agglomerates do not contain mixtures of metal chlorites and acid forming components.
  • one type of agglomerate contains only one or more metal chlorites or a mixture of metal chlorite(s) and one or more non- acid forming additive(s) (e.g., silica gel desiccant, paraffin wax tableting binder, and/or sodium sulfate filler).
  • the second type of agglomerates is substantially free of the metal chlorite, and at least one type of them comprises the acid forming component as defined herein, and may also contain one or more metal chlorite-free additives (e.g., Ion Exchangers, tableting binders, and/or desiccants).
  • the preferred composition also does not contain constituents that deliquesce upon exposure to ambient humidity.
  • This aspect is the preferred aspect when it is desired that the materials be resistant to premature conversion to chlorine dioxide as a result of ambient humidity (i.e., when it is desirable for the materials to react to form chlorine dioxide substantially only when they are exposed to liquid water).
  • Large agglomerates allow less costly packaging materials to be used for packaging of the device. Specifically, if powdered mixtures of reactants are exposed to high levels of ambient humidity for an extended period of time during storage, they undergo humidity activated premature reaction to form chlorine dioxide. To prevent such premature reaction, powdered reactants can be packaged in humidity barrier materials such as foil pouches, glass bottles, and metal cans.
  • Such packaging is expensive and its use can be reduced or eliminated if the physical form of the reactants inhibits them from undergoing excessive premature humidity activated reaction, i.e., if they are in the form of large agglomerates.
  • Applicants have discovered that when the particles of metal chlorite and the acid forming component have a particle size of up to about 80 microns in diameter when in intimate contact may react due to exposure to humidity. Larger particles, probably because of their reduced interfacial contact area, react more slowly upon exposure to humidity. Consequently, in a situation where humidity activated chlorine dioxide formation is undesirable, large particles (i.e., 80 microns) are preferred because the resultant reactant mixture will undergo less premature humidity activated reaction.
  • agglomerates having a particle size of at least 80 microns preferably above about 100 microns (0.1 mm), more preferably above about 500 microns (0.5 mm), and most preferably above about 1 ,000 microns ( 1 mm).
  • a mixture of reactants when present in such preferred particle size will exhibit a reduced rate of humidity activated chlorine dioxide release when compared to being present in smaller particle sizes, but can dissolve and will react in contact with liquid water to produce an aqueous solution of chlorine dioxide.
  • one or more materials which form an insoluble phase with at least one otherwise soluble reaction byproduct may be included with the reactants or may itself be a reactant.
  • an acid forming component can be used which is primarily present as a source of acidity, but which also reacts with cations which may be present to form an insoluble phase which is retained by the membrane.
  • the practice of this embodiment permits the production of highly pure aqueous solutions containing chlorine dioxide.
  • Such materials (“Ion Exchangers") are preferably solid, water insoluble H * ion exchangers having a high selectivity for cations in the reactants and reaction byproducts, e.g., cations of the metal chlorite.
  • the Ion Exchangers capture the cations by ion exchange with H r .
  • the predominant resultant soluble reaction product is therefore only chorine dioxide with a possible trace amount of hydrogen chloride.
  • Ion Exchangers include, but are not limited to, synthetic molecular sieves such as synthetic zeolite Y, dealuminated zeolite Y, mordenite and ZSM-5 which have been converted to the substantially H" exchange forms; acid ion exchange resins such as Amberlite ® brand resins (sold by Rohm and Haas); DowexTM HCR-S resins (sold by Dow Chemical Company); acid treated clays such as acid treated bentonite; and acid treated calcined clays such as acid treated spinel calcined kaolin and acid treated metakaolin including metakaolin microspheres which are nominally spherical particles having an average particle size of from about 50 to 100 microns and mixtures thereof.
  • the preferred Ion Exchanger for this embodiment of the invention is the acid form of synthetic zeolite Y. Additional Ion Exchangers will be known to those skilled in the art and are included within the scope of the present invention.
  • Ion Exchangers are not the only materials suitable for forming insoluble phases by reacting with otherwise soluble phases.
  • ionic calcium is an otherwise soluble phase
  • the preferred phases containing sulfate and/or phosphate are the acid forming components sodium acid sulfate and sodium dihydrogen phosphate.
  • aqueous solutions of chlorine dioxide for cleaning and disinfecting purposes contain from about 0.5 ppm to 200 ppm of chlorine dioxide. If, for example, a liter solution containing 100 ppm of chlorine dioxide gas were desired, the required amount of the metal chlorite (specifically sodium chlorite) would be about 170 mg.
  • a drip pan which may be located below the products in a storage or display area (e.g., a food product storage or display case typically found in retail grocery stores), may be provided with a treated pad or a mat containing an antimicrobially effective amount of one or more Antimicrobial Agent(s).
  • the antimicrobially effective amount of the selected Antimicrobial Agent is within the skill of the art to determine.
  • a microbially effective amount may be from about 0.5% to about 5.0%, by weight, (preferably from about 2.0% to 4.0%), based on the weight of the matting material.
  • an antimicrobially effective amount of an Antimicrobial Agent such as ⁇ NTERSEPT E used in connection with a pad, may be from about 0.005 to about 5.0 gm/ft , more preferably from about 0.1 to about 1.0 grn/ft 2 .
  • the Antimicrobial Agent may be provided in a dry, solid form, or it may be provided as a dry, water soluable agent that, when contacted with moisture, forms an antimicrobial solution that remains in the drip pan to reduce the presence and proliferation of microorganisms.
  • the Antimicrobial Agent inhibits the proliferation of microorganisms in the drip pan and also helps to reduce the proliferation of microorganisms in the air recirculation system.
  • the matting material may be selected to provide one or more of the following functions: (1 ) to provide a physical barrier which prevents the deposition and accumulation of waste and food debris on the drip pan; (2) to provide a substrate for the incorporation of one or more adhering or chemically bonding Antimicrobial Agent(s) to prevent or reduce the growth of microorganisms, including bacteria and fungi, on the matting and the drip pad; and (3) to provide a water absorbant material that collects moisture from a humidification and/or misting system and assists in maintaining a high relative humidity in the product environment, generally a display or storage case for fresh food or floral products.
  • a suitable pad or matting material for use in the present invention may have varying degrees of liquid absorbency.
  • the matting material may be comprised of at least one absorbent sheet (i.e., a sheet capable of absorbing one or more Antimicrobial Agents) made of absorbing materials such as wood fiber, cotton fiber, synthetic fiber and the like, as well as mixtures thereof.
  • the pad or matting material may be composed of multiple layers of individual sheet materials, including alternating layers of sheet materials having different absorption properties.
  • the Antimicrobial Agent(s) may be uniformly distributed throughout the matting matenal, or may be confined to selected regions of the pad according to either a random or systematic arrangement (e g , as a checkerboard)
  • a suitable matting matenal compnses multiple layers of materials having different properties, including two outer layers having generally non-absorbent properties
  • An Antimicrobial Agent preferably a broad spectrum biostat agent having demonstrated efficacy against bacteria and fungi and having no toxicity, such as the LNTERSEPT ® antimicrobial agent descnbed above, is preferably applied to one or both outer layers of the matting material by spraying, coating, soaking, impregnating, or any suitable means
  • one or more intermediate matting layers is also provided The intermediate layer(s) preferably has greater liquid absorbency properties than the outer layers and may be treated with the same or a complementary Antimicrobial Agent
  • the matting treated with one or more Antimicrobial Agent(s) may be provided in any convenient form for placement in dnp pans or similar receptacles located in proximity to products such as meat, produce, dairy, and floral items
  • the matting may be provided in selected standardized sizes for placement in dnp pans or other receptacles, or it may be piovided in one or more sizes and cut to fit to dnp pan or other receptacle dimensions
  • the treated matting may be provided in a continuous roll form with perforations or markings or other indications marking standard or selected predetermined dimensions Perforations are preferred, so that mats having standard or selected predetermined sizes may simply be separated from a roll of matenal
  • the "Combination" of chlorine dioxide gas and/or chlo ⁇ ne dioxide aqueous solution and one or more Antimicrobial Agents may be applied to the food products themselves, and/or to the environment in proximity to the food products, including the region above and/or below the food products and the drip pan
  • the components of the Combination may be applied together to the food products and/or the surrounding environment, or they may be applied separately
  • chlo ⁇ ne dioxide gas is circulated through the air recirculation system of the food display case, while one or more Antimicrobial Agent(s) alone, or in combination with an aqueous solution of chlo ⁇ ne dioxide, is applied to the dnp pan
  • Other applications of the Combination to storage and display cases are within the purview of the present invention.
  • Food product display cases of the type used in large grocery stores and supermarkets can extend to 50 foot lengths or more.
  • a single location of the components of the Combination may be insufficient to treat and/or prevent infestation of microorganisms throughout the full length of the display case. It is therefore desirable to provide a plurality of locations for the Combination.
  • units of the Combination are placed about 6 to 7 feet from each other along the length of the display case. An amount of the Combination sufficient to treat and/or prevent the proliferation of microorganisms is then generated for each 6 or 7 foot length of the display case.
  • Display case 2 comprises housing 4 having a vertical wall 6, a horizontal wall 8 and a slanted display counter 10, as more fully described below, which is supported by the vertical and horizontal walls 6, 8.
  • Slanted counter 10 has an outer slanted display surface 12 which can be tailored to provide appropriate storage and display areas for a variety of products 13, including produce, meat, dairy and floral items.
  • Slanted counter 10 may have ridges, spaced apart boards, and the like, to provide support for storage and display of food products on slanted display surface 12 so that the food products 13 can be displayed in an attractive manner.
  • Slanted counter 10 contains openings 14 of sufficient size to enable broken and/or withered portions of the food products 9 to fall therethrough into the region 15 below the slanted counter 10.
  • a drip pan 16 At the bottom of the region 15 and generally spaced above the horizontal wall 8 is a drip pan 16 for catching the droppings of food products as they fall through the region 15.
  • the drip pan 16 is generally made of lightweight metal (e.g., aluminum) so that it can be readily removed from the display case 2 for cleaning and to remove the loose droppings 9 therein.
  • a drip pan containing droppings of food product becomes an ideal environment for the growth and proliferation of microorganisms. As the microorganisms grow, they contaminate the food product stored above on slanted counter 10.
  • a fan assembly 18 including a fan 20 which draws air into the display case through an opening 22 and thereby maintains a circulation of air throughout the display case including the food products being displayed.
  • the fan assembly 18 can be conveniently located to provide adequate air circulation.
  • the region 15 or drip pan 16 is contaminated with microorganisms, these microorganisms enter the circulation system provided by the fan assembly 18 and thereby come into contact with the stored food product in the display case. This can result in infestation of the displayed food products and premature spoilage of the displayed food product.
  • the present invention provides methods and systems for reducing and/or inhibiting the infestation by and proliferation of microorganisms in the area of a display or storage case, thereby reducing infestation and spoilage of the displayed food products.
  • the methods and systems of the present invention also improve the shelf life of the displayed products and substantially eliminate unpleasant odors.
  • drip pan 16 is provided with a treated pad 30.
  • the pad 30 may be provided with ingredients, in accordance with the present invention, that are necessary to generate chlorine dioxide in a gaseous or solution form.
  • Treated pad 30 may, for example, comprise a metal chlorite and an acid component which, when they are brought together in the presence of water vapor (i.e., relative humidity), are capable of generating chlorine dioxide gas.
  • the treated pad 30 may contain liquid water which causes the reactants to form an aqueous solution of chlorine dioxide, which remains in drip pan 16 to kill microorganisms.
  • the components for generating chlorine dioxide gas may be provided in the pad, or in the drip pan directly, or contained within a sachet as previously described.
  • Pad 30 may be additionally treated with at least one Antimicrobial Agent, which may be in dry, solid or other suitable form, in an antimicrobially effective amount.
  • treated pad 30 may contain a dry, water soluble Antimicrobial Agent.
  • an antimicrobial system of the present invention contemplates the use of the treated pads, described above, in combination with a system for dispersing an Antimicrobial Agent and/or chlorine dioxide in a liquid or gaseous form.
  • capsules or sachets containing ingredients that generate chlorine dioxide in a liquid or gaseous form are used in combination with a treated pad.
  • dry ingredients that, upon activation, generate chlorine dioxide gases which are confined by a gas permeable membrane, such as TYVEK ® , and placed in proximity to a treated pad.
  • the dry ingredients are activated by exposure to moisture, or aqueous solutions, to generate chlorine dioxide on a controlled, sustained release basis.
  • the treated or untreated absorbent pad may be provided with markings indicating suitable locations for sachets containing the dry ingredients.
  • the treated pads and sachets may furthermore be provided with attachment means, such as adhesives, hook and loop fasteners, or the like, the provide attachment of a sachet to a pad at selected locations.
  • Packets or sachets containing such ingredients in a gas permeable membrane maybe placed, at selected intervals, on the treated pad.
  • the size and composition of the packet or sachet, the ingredient, and the number of sachets used in a selected area may be chosen to deliver the desired sustained chlorine dioxide gas release and concentration.
  • systems of the present invention contemplate the combination of a pad or matting treated with an Antimicrobial Agent with a device containing a chlorine dioxide generating system, such as one or more sachets that, upon activation, provide sustained release of chlorine dioxide gas at an appropriate concentration.
  • a device containing a chlorine dioxide generating system such as one or more sachets that, upon activation, provide sustained release of chlorine dioxide gas at an appropriate concentration.
  • the treated pad or matting may be marked to indicate suitable locations for such chlorine dioxide devices.
  • the treated pads and/or the chlorine dioxide devices may furthermore be provided with attachment means, such as adhesives, hook and loop fasteners, and the like, that provide attachment of the device(s) to a treated pad at a selected location.
  • the circulatory system is provided with at least one Antimicrobial Agent as a gas and/or solution from the storage vessel 40.
  • the Antimicrobial Agent is passed into a conduit 42 having openings 44 which allow the Antimicrobial Agent to be passed into the region 14 as a fine mist or gas and thereby treat microorganisms both in the drip pan 16 and on food product resting on the slanted counter 10.
  • a circulatory system for chlorine dioxide gas may be provided, or a system in which a chlorine dioxide solution is provided from a storage vessel 40 and then passed into a conduit 42 having openings 44 which allow the chlorine dioxide solution to be passed into the region 15 as a fine mist, to kill microorganisms both in drip pan 16 and on product 13 resting on the slanted counter 10.
  • a chlorine dioxide solution is provided from a storage vessel 40 and then passed into a conduit 42 having openings 44 which allow the chlorine dioxide solution to be passed into the region 15 as a fine mist, to kill microorganisms both in drip pan 16 and on product 13 resting on the slanted counter 10.
  • a display case in a retail grocery store of the type shown in Figure 1 was provided with a quantity of typical fruits and vegetables as shown in Table 1.
  • the display had a fan which was operated on a constant basis to provide air circulation. After nine days, the amount of spoiled food product was measured and an estimate of the total revenue loss was calculated. The results are shown in Table 1.
  • a display of the type desc ⁇ bed m Example 1 is treated in accordance with the present invention by placing in the drip pan, an absorbent pad which was treated with about 2% by weight of a quaternary ammonium compound produced by Interface Research of Atlanta, Georgia and sold under the trademark LNTERSEPT ® Thereafter, the display case was sprayed with an aqueous solution of chlorine dioxide in a concentration sufficient to provide 5 ppm of chlorine dioxide The combination of chlorine dioxide and the quaternary ammonium compound was sufficient to reduce the proliferation of microorganisms in the dnp pad and the environment proximate to the displayed food products
  • a quantity of sodium hypochlonte was added to a quantity of water sufficient to provide a concentration of 1,000 ppm
  • the solution was sprayed over a display case of the type show n in Figure 1 containing fruits and vegetables, sufficient to cover but not drench the same
  • the fruits and vegetables were tested for the presence of microorganisms Few, if any, microorganisms were detected
  • Example 4 A quantity of a solid quaternary ammonium compound, namely methyl dimethylammonium chloride, was added to the dnp pad of a display case of the type shown in Figure 1 The amount of the antimicrobial agent was about 1-2% by weight, based on the weight of the drip pad The drip pad containing discarded leaves of vegetables was tested for the presence of microorganisms Few, if any, microorganisms were detected

Abstract

Method and system for treating and/or protecting food and floral products (13) while stored or displayed such as in a display or storage case (2), against infestation by and proliferation of microorganisms with an antimicrobially effective amount of chlorine dioxide gas or chlorine dioxide in solution, or with a combination of an antimicrobial agent and chlorine dioxide. A kit (40, 42, 44) and treated pad (30) for use in the food storage and/or display environments are also disclosed.

Description

METHODS AND SYSTEMS FOR REDUCING MICROBIAL POPULATIONS
Field of the Invention The present invention is generally directed to the employment of an antimicrobial agent alone, including chlorine dioxide, or a combination of antimicrobial agents, to extend the life of products such as produce, meat, dairy and floral items in environments such as retail grocery stores The antimicrobial agent, or combination of antimicrobial agents, is located in proximity to the product, for example in or on a disposable pad provided in a dnp pan located below the displayed products, and/or the products themselves are contacted with the anitimicrobial agent or the combination of antimicrobial agents
Background of the Invention Antimicrobial agents die known in the art for the treatment and inhibition of the infestation and proliferation of microorganisms Such agents (e g , sodium hypochloπte, lodophors, phenol, quaternary ammonium compounds, glutaraldehyde, peracetic acid and the like) can be used to kill a wide vaπety of microorganisms (e g , Pseudomonas aeragtnosa Saccharamvas cerevisiae, and Staphγlococcus aureus) in diverse applications such as hard surface disinfection, clean in place sanitation, and medical and dental instrument sterilization Chloride dioxide is also known in the art for the treatment and inhibition of the infestation and proliferation of microorganisms and can be used to kill a wide vaπety of microorganisms (e g , Pseudomonas aeruginosa, Saccharamyas cerevisiae, and Staphylococcus aureus) in diverse applications such as hard surface disinfection, clean in place sanitation, and medical and dental instrument sterilization
Typically, retail grocery stores lose a significant amount of food product in food storage display cases as a result of moisture evaporation and spoilage Moisture fogging and misting systems are used to help reduce the loss of food products due to water evaporation However, the loss of food product as a result of the presence and proliferation of microorganisms remains undesirably high
Food storage display cases often have a "dnp pan," which is typically a metal tray (e g , aluminum), mounted underneath the display case to collect water and droppings of loose food product (e g , leaves of lettuce and the like) The drip pan is designed to be easily removed for proper cleaning to maintain the food storage display cases in sanitary conditions Display cases also frequently incorporate an air recirculation system comprising a fan and associated venting to provide the displayed food product with circulating an Without routine maintenance, a drip pan containing food droppings becomes a good environment for the growth and proliferation of microorganisms The inventors believe that as the microorganisms grow, they enter the air recirculation system typically employed in such food storage and display cases The circulating air and the food product consequently becomes contaminated with microorganisms
Gaseous chloπne dioxide in low concentrations (i e , up to 1 ,000 ppm) has long been recognized as useful for the treatment of odors and microbes Its use is particularly advantageous where microbes and/or organic odorants are sought to be controlled on and around foodstuffs, because chlonne dioxide functions without the formation of undesirable side products such as chloramines or chloπnated organic compounds that can be produced when elemental chloπne is utilized for the same or similar purposes For example, if a low concentration of chlorine dioxide gas is maintained in contact with fresh produce for several days duπng shipping from the farm to the local retailer, the rate of spoilage of the produce is decreased In addition, chloπne dioxide gas is also generally considered to be safe for human contact at the low concentrations that are effective for deodoπzation and most antimicrobial applications Chlorine dioxide gas can be toxic to humans at concentrations greater than 1,000 ppm, and it can be explosive at pressures above about 0 1 atmosphere Therefore, chloπne dioxide gas is not manufactured and shipped under pressure like other industπal gases, and conventional methods of on-site manufacture require not only expensive generation equipment, but also high levels of operator skill to avoid generating dangerously high concentrations These problems have substantially limited the use of chlorine dioxide to large commercial applications, such as pulp and paper bleaching, water treatment and poultry processing, where the consumption of chlorine dioxide is sufficiently large that it can justify the capital and operating costs of expensive equipment and skilled operators for on-site manufacture Commercially, chlorine dioxide is produced from a vaπety of aqueous solutions of certain chlorine-containing salts, as disclosed for example in U S Patent No 5,009,875
Attempts have also been made to produce chloπne dioxide using mixtures of solid reagents Generally, the prior art has focused on three systems for chlorine dioxide production using solid reagents. One system employs a solid mixture of a metal chloπte and an acid in a liquid, aqueous environment. A second system combines a metal chloπte and a solid organic anhydride to generate a highly concentrated flow of chloπne dioxide which must be diluted with a constantly flowing stream of inert gas. Each of these solid reagent systems is disadvantageous for any one or more of the following reasons: a) upon mixing there is normally a sudden, highly concentrated stream of chlorine dioxide generated; b) the mixture of reactants produces chlorine dioxide gas under dry conditions, thereby reducing the shelf life of the reactants, and c) an inert gas stream must be used to reduce the concentration of chloπne dioxide gas in the atmosphere.
Aqueous solutions of chlorine dioxide are also known in the art. Two types of synthesis processes are generally used to provide chloπne dioxide solutions for commercial uses, such as poultry chiller water purification, washwater purification, potable water treatment and as a teat dip for the control of non-human mammalian mastitis
The first type of synthesis process is based on the manual combination of two aqueous solutions, one containing a source of chlorite anions and another being acidic The solution containing chlorite anions is usually a solution of sodium chlorite having a concentration of between about 100 ppm and about 5% by weight and having a pH of about 13 The acidic solution may contain any acid capable of providing a pH below about 8 5 after the solutions are mixed Such acids include citπc acid, lactic acid, hydrochloric acid, sulfuπc acid, and dissolved carbon dioxide (ι e., sodium bicarbonate) The antimicrobial performance of the resultant solutions depends upon the degree to which the chlorite anions from the chlorite source solution are converted to free molecular chloπne dioxide ("Chlorine Dioxide") in the solution, as Chloπne Dioxide is the effective agent for both antimicrobial and deodoπzation activity
In one variation on this synthesis process the pH of the sodium chlorite solution is reduced from about 13 to about 8 using the acidic solution Chloπte anion is thus converted to Chloπne Dioxide according to the following reaction.
5C1O, + 5H' => 4C1O, + HC1 + 2H.0 Such solutions having a pH of about 8 are generally referred to in the industry as "stabilized" chlorine dioxide solutions, and usually contain between about 100 ppm and 5% of a mixed solution of Chlorine Dioxide and unconverted chloπte anion Because the acid concentration is relatively low at a pH of 8, the typical ratio of Chloπne Dioxide to chlonte anion in a stabilized chloπne dioxide solution is less than 0 01 Therefore, for a given initial concentration of chloπte anion, stabilized chlorine dioxide solutions are relatively weak antimicrobial agents due to their low conversion of chlorite anion to Chlorine Dioxide Also, since they are typically supplied at a concentration of less than about 5% by weight sodium chlorite, they are relatively expensive to ship and store due to the high weight of water that must be transported as part of the solution
Chlorite anion is generally stable in stabilized solutions (pH 8), so they have an advantageously long shelf life To improve their effectiveness, however, they are typically activated just prior to use by the addition of a strong acid to lower their pH to below about 3 5 and convert more chloπte anion to Chloπne Dioxide via the reaction shown above Since the activation process involves the addition of a strong acid to lower the pH, it requires a high le\ el of operator skill to handle, measure and mix the acid with the stabilized chloπne dioxide solution Also, since the activation process results in a solution having a pH of less than about 3 5, such activated solutions are not well suited to work in combination with, for example, detergents which work best under alkaline or neutral pH conditions Contact of these solutions with many metals should also be limited because of possible metallic corrosion by the acidic solution
Such activated solutions typically have a ratio of Chloπne Dioxide to chlorite anion below about 0 05 when the solution is acidified to a pH of about 3 It is possible to achieve a higher ratio of Chlorine Dioxide to chlorite anion in such activated solutions, but doing so is dangerous and requires extreme operator skill Achieving a ratio of
Chlorine Dioxide to chloπte anion above about 0 05 requires further acidification to a much lower pH than 3 (typically less than 2) and often requires that the further acidification be performed at concentrations of chlorite anion above about 5000 ppm Under such conditions of extremely low pH and high chlorite ion concentration it is possible to generate a sufficient chloπne dioxide concentration in solution such that the vapor pressure of gaseous chloπne dioxide in equilibrium with the solution approaches the explosive range Therefore, it is not common practice to produce solutions having a high ratio of Chlonne Dioxide to chlorite anion by manual acidification (i e , without chlorine dioxide generation equipment as discussed below)
In the second type of chloπne dioxide solution synthesis process, chlorine dioxide solution is generated from either a sodium chlorite solution or stabilized chlonne dioxide solution using chloπne dioxide generation equipment at the point of use The generated solution typically has a ratio of Chlorine Dioxide to chlorite anion of between about 10 and 25 and, as a result, such solutions are highly effective antimicrobial agents Since generated chlorine dioxide solution is typically used shortly after generation, the relatively high decomposition rate of chloπne dioxide in solution is unimportant Also, since aqueous sodium chlorite is commercially available at higher concentrations than are typically available in the form of stabilized chloπne dioxide solutions, the cost of stonng and shipping the aqueous sodium chlorite solutions can be lower when compared to stabilized chlorine dioxide solutions However, the high cost of the chlonne dioxide generation equipment and the high level of operator skill needed for its operation makes generated chlorine dioxide solution best suited to relatively large applications such as water treatment and poultry processing where the consumption of chlorine dioxide is sufficiently large that it can justify the capital and operating costs
In addition to the two types of commercial synthesis processes for chloπne dioxide solution discussed above, it is also possible to generate solutions containing chlorine dioxide and having a high ratio of Chloπne Dioxide to chloπte anion by absorption of gaseous chlorine dioxide into water Chlorine dioxide is first produced in solution by conventional means, e g acid activation of a solution of sodium chloπte Inert carrier gas, typically air or nitrogen, is then bubbled through the activated solution where it picks up some of the Chlorine Dioxide That gaseous mixture of Chlorine Dioxide and carrier gas is then bubbled through a second vessel containing water where the Chlorine Dioxide is dissolved to produce a solution of chlorine dioxide typically having a ratio of Chlorine Dioxide to chlorite anion between about 20 and about 50 While it is possible to produce substantially pure solutions of chlonne dioxide in this manner, it requires a very high level of operator skill and is rarely done outside of the laboratory
Attempts have been made to reduce the cost of generating chlonne dioxide solutions by using mixtures of alkaline chlorite salts and acidic dry powders which, upon addition to water, acidify the water and generate chloπne dioxide via reaction described above. U.S. Patent 2,022,262, discloses stable stain removing compositions comprising a dry mixture of a water soluble alkaline chlorite salt, an oxalate, and an acid. Since alkaline chlorites are strong oxidizers and corrosively caustic, a relatively high level of user skill is needed to employ this process. Furthermore, the pH of the resultant solution is acidic, so such acidic solutions of chlorine dioxide are not well suited for use in combination with detergents which work best under alkaline or neutral conditions. Finally, the resultant solution contains contaminants including sodium chloride, and the solution byproducts of the oxalate and acid as contaminants.
U.S. Patent 2,071 ,091 discloses an improved fungicide and bactericide, and an improved sterilization process using chlorous acid and the salts of chlorous acid. The term "chlorous acid and the salts of chlorous acid" includes aqueous solutions of soluble chlorite salts that have been acidified to an acidic pH. Such solutions contain mixtures of chlorine dioxide and chlorite anions with the ratio of Chlorine Dioxide to chlorite being higher when the pH of the solution is lower. As with the '262 Patent discussed above, this process requires a relatively high degree of user skill to handle and measure the alkaline chlorite and acid. The requirement for an acidic pH limits the utility of this process when the preferred solution pH is alkaline, and the resultant solution is contaminated with sodium chloride and the solution byproducts of the acid.
U.S. Patent 2,071,094 discloses deodorizing compositions in the form of dry briquettes comprising a dry mixture of a soluble chlorite, an acidifying agent, and a filler of lower solubility. Generation of chlorine dioxide begins as the briquette dissolves in water. This process is suitable for unskilled users, but still requires that the resultant solution be produced at an acidic pH, and it is still contaminated with the solution byproducts of the reagents. Furthermore, the inert, low solubility filler leaves an insoluble residue paste that is difficult to handle and dispose of.
U.S. Patent 2,482,891 discloses stable, solid, substantially anhydrous compositions comprising alkaline chlorite salts and organic acid anhydrides which release chlorine dioxide when contacted with water. The patent disclosure indicates that the prefeπed solution is highly concentrated and consequently would have been at an acidic pH. As such, this process suffers from the same limitations as the '262 and '091 Patents mentioned above.
U.S. Patent 4,585,482 discloses a long-acting biocidal composition comprising a chlorine dioxide liberating compound and a hydrolyzable organic acid-generating polymer. Methods are disclosed for producing dry polymer encapsulated microcapsules containing such compositions and water such that the resultant dry materials release chlorine dioxide gas. The primary purpose of the polymer encapsulating film of the '482 Patent is to provide for hard, free flowing particles, and to protect against the loss of water from the interior of the microcapsule. If the micro capsules were to be immersed in water, they would produce a chlorine dioxide solution. Producing chlorine dioxide solution in this manner would eliminate the complications of measuring and mixing reagents and the cost of capital equipment that characterize the prior art. In addition, the solution pH need not be acidic so it would be feasible to produce chlorine dioxide in a detergent solution. However, the materials of the '482 Patent are not storage stable because they begin to release chlorine dioxide as soon as they are manufactured. Furthermore, they release chlorine dioxide over a period of several days, so they are unsuitable for quickly preparing a useable chlorine dioxide solution. Finally, once mixed in water the microcapsules cannot be removed from the water in a simple fashion. Typically they must be separated by a process such as filtration.
The inventors have determined that chlorine dioxide alone, and various antimicrobial agents, alone, as well as combinations of chlorine dioxide and a select group of antimicrobial agents, in specified effective amounts, are effective for extending the storage and display life of products such as produce, meat, fish, dairy, and floral products. It would be a significant advance in the art to provide a method of extending the storage life of such products, especially in storage or display cases, by inhibiting the proliferation of microorganisms contained in the environment surrounding such products. The methods and systems would therefore serve not only to limit the proliferation of microorganisms in storage and display areas, but also to inhibit infestation of the products by microorganisms.
Summary of the Invention
The present invention is generally directed toward extending the life of products including produce, meat, dairy, and floral products, and is more specifically directed toward the protection and/or treatment of food products to either inhibit infestation by and proliferation of microorganisms, and/or to treat the products which may already have microorganisms present. A particular aspect of the present invention is directed toward methods and systems for protecting or treating products against infestation by and proliferation of microorganisms, said methods and systems involving treating the environment in proximity to such products with an antimicrobially effective amount of at least one Antimicrobial Agent, or chlorine dioxide, or a combination of chlonne dioxide in gaseous and/or liquid form, and at least one Antimicrobial Agent (hereinafter "Combinations") The term, "Combιnatιon(s)," when used herein, is intended to include chlorine dioxide in gaseous and/or solution forms in combination with one or more Antimicrobial Agent(s) in a gaseous, liquid (preferably aqueous solution), and/or solid form According to another aspect of the present invention, pads or matting treated with at least one Antimicrobial Agent or chlorine dioxide, or a combination of chlorine dioxide in gaseous and/or liquid form and at least one Antimicrobial Agent are provided Such pads or matting are suitable for placement in the environment in proximity to a storage or display case, such as in a dnp pan located underneath the case, and may be used in combination with systems for generating chlorine dioxide m a gaseous or solution form, or with other Antimicrobial Agents
In one system for generating chlonne dioxide gas, the chlorine dioxide gas is released under controlled conditions at low concentrations when in the presence of water vapor The reactants generating the chlorine dioxide gas, when combined to form a mixture, do not generate a significant amount of chlorine dioxide gas when water is not present The reactants can therefore be stored for long peπods of time in a substantially dry atmosphere Thus, the present invention is concerned with extending the life of products, including food and floral products, by introducing, alone or m vaπous Combinations, chlonne dioxide gas, aqueous solutions of chlorine dioxide, quaternary ammonium compounds, and other Antimicrobial Agents into the product storage and/or display environment.
Chlorine dioxide gas may be produced by a) forming a mixture of at least one metal chlorite and at least one matenal capable of reacting with the metal chlorite to produce chlorine dioxide gas in the presence of water but not in the substantial absence of water, and b) exposing the mixture to the atmosphere in proximity to displayed food products, the atmosphere comprising water vapor, to produce chlorine dioxide gas in a sustained concentration of from about 0 001 to 1 ,000 ppm, preferably from about 0 01 to 500 ppm, more preferably from about 0 01 to 100 ppm, and most preferably from about 0 01 to 10 0 ppm
In another aspect of the present invention, the choπne dioxide gas is produced in a device which, when combined with water, allows the controlled passage of water into the device to initiate a reaction which generates chlorine dioxide gas The gas is able to pass through the device into the body of water to form an aqueous solution of chlonne dioxide In use, the device may be in the form of a capsule or sachet, for example, and may be placed in the drip pan, wherein it is contacted with moisture and activated An aqueous solution of chlorine dioxide may thus be produced by a) having liquid water in a first zone and at least one metal chlorite and at least one acid forming component in a second zone, said first and second zones being separated by a membrane, b) contacting the membrane with water from said first zone (e g , a drip pan), such that liquid water and/or water vapor passes through the membrane into the second zone, thereby facilitating the reaction between said at least one acid forming component and said at least one metal chlorite to produce chlonne dioxide, and c) allowing the chlonne dioxide produced in the second zone to pass through the membrane to the first zone, into the liquid water to form said aqueous solution
Other methods for generating chlorine dioxide gas and/or aqueous solutions are known to those skilled in the art, and may be adapted for use in connection with methods and systems of the present invention A preferred embodiment of the present invention provides for the controlled release of chloπne dioxide, and thereby provides not only immediate antimicrobial treatment but sustained treatment as well
Brief Description of the Drawings The following drawings, in which like reference characters indicate like parts, are illustrative of embodiments of the invention and are not intended to limit the invention as encompassed by the claims forming part of the application
Figure 1 is a side elevational view of a typical display case for the display of food products in a retail grocery store, and Figure 2 is a side elevational view of the display case shown in Figure 1 showing a system for treating the displayed food products and drip pan with an Antimicrobial
Agent in accordance with the present invention Detailed Description Of The Invention
In the methods and systems of the present invention, protection and/or treatment of products stored or displayed in cases is provided using an effective amount of an Antimicrobial Agent or chlorine dioxide alone, or a combination of Antimicrobial Agents, or a combination of chloπne dioxide in a gaseous and/or a liquid solution with a select group of Antimicrobial Agents (hereinafter "Combination") The Combination of chlorine dioxide gas and/or solution and Antimicrobial Agent(s) may be applied to the products themselves, or may be released or dispersed to the environment in proximity to the products, including the area underneath the product and in a dnp pan generally found below the product which is used to catch droppings of loose food product
As used herein, the term "Antimicrobial Agent(s)" shall mean agents which effectively reduce the proliferation of microorganisms in storage and display areas and also inhibit infestation of the products themselves by microorganisms The term "Antimicrobial Agents" does not include chlorine dioxide and, components that, in the presence of water, can generate chloπne dioxide Examples of suitable Antimicrobial
Agents include, but are not limited to, sodium hypochlonte, sodium chlonte, -(p- nonylphenyl)-hydroxypoly (oxyethylene)-ιodme complex, hydrogen peroxide, glutaraldehyde/phenol, acid glutaraldehyde, quaternary ammonium chlorides, phenol deπvatives, and combinations thereof, as disclosed in Journal of Industrial Microbiology, Vol 4, pp 145-154 (1989)
The products, particularly food products such as produce, meat, and dairy products, as well as floral items, may be treated with at least one Antimicrobial Agent by forming a mixture of one or more Antimicrobial Agent(s) with a suitable solvent, preferably water The mixture may then be sprayed directly onto the products, preferably as a fine mist, using conventional spraying equipment The effective concentration of the
Antimicrobial Agent(s) is sufficient to inhibit the proliferation of microorganisms withm the food storage display case The effective concentration of the Antimicrobial Agent(s) varies depending, in part, on the particular Antimicrobial Agent For example, the preferred concentration of sodium hypochlonte solution for treating displayed food products is from about 50 to 2,000 ppm, most preferably from about 100 to 1,500 ppm
The preferred concentration of glutaraldehyde solution is from about 0 01% to 5%, most preferably from about 0 1 to 3% by weight Information regarding suitable Antimicrobial Agents for use in the present invention and their relative strengths for determining a suitable concentration level are identified in Journal of Industnal Microbiology, Vol 4, pp 145-154 (1989), which is incorporated herein by reference in its entirety From the information contained withm this publication, and/or with the routine knowledge of those practicing in this art, a suitable concentration of a selected Antimicrobial Agent may readily be determined
Alternatively, or in addition to treating the products themselves, waste pieces of loose products (e g , leaves of lettuce) that are in proximity to the product may be treated with a solution comprising an Antimicrobial Agent, preferably an aqueous solution The concentration of the Antimicrobial Agent in aqueous solution for the treatment of waste pieces of food products is the same as discussed above for the treatment of the fresh food products
The food product display or storage area may be treated in whole or in part with an antimicrobially effective amount of an Antimicrobial Agent which imparts sustained antimicrobial activity to the treated surfaces of the area Such a Antimicrobial Agent is an antimicrobial composition marketed as LNTERSEPT*, which is available from Interface Speciality Products Company. Atlanta, Georgia The LNTERSEPT® product includes the following active ingredients ethanol, 2,2' -(cocoimino) -bis, salt with phosphoric acid, bis (2-ethyl hexyl) ester ( 1 1), ethanol, 2,2' -(cocoimino) -bis, salt with mono (2-ehtyl hexyl) ester (1 1 ), and phosphoric acid, mono (2-ethyl hexyl) ester Other suitable
Antimicrobial Agents may be identified by those of ordinary skill in the art
In another embodiment, chlorine dioxide alone, or in Combinations, may be used to extend the life of food products, such as food and floral products stored and displayed in retail grocery store display cases Chloπne dioxide may be used directly on the food products Chlorine dioxide gas may be circulated tlirough a circulation system or generated in an area in proximity to stored or displayed products, and/or m the drip pan, to treat and/or inhibit the proliferation of microorganisms in the environment of a storage or display case The employment of chlorine dioxide alone, or in Combinations, is effective for controlling infestations aπsing from a vaπety of microorganisms, including microorganisms of the genus Salmonella
Chlorine dioxide gas and/or aqueous solutions of chloπne dioxide have the additional effect of reducing the ethylene content resulting from the natural ripening process of the food products such as fruits and vegetables Ethylene is a gas which is produced naturally by food products such as fruits and vegetables dunng the npening process Because the ripening process accelerates as ethylene concentrations increase, the production of ethylene can result in the rapid ovempening of a batch of such food products Currently, up to about 20% of such food products may be lost due to premature
5 ripening This problem of overproduction of ethylene occurs throughout the food processing chain from harvest to the point of consumption and can occur while the food products are displayed in a display case The chlorine dioxide gas alone or as an aqueous solution, in accordance with the present invention, effectively reduces ethylene gas concentrations in contact with ripening food products to thereby help reduce rapid
10 ovempening
Various methods and systems for generating chloπne dioxide in a gaseous or liquid form may be used alone, or in connection with the Combinations of the present invention Exemplary reactants, packaging systems, and the like, are described below
In one system for generating chlorine dioxide gas, the chloπne dioxide gas is
I D released under controlled conditions at low concentrations when m the presence of water vapor The reactants generating the chloπne dioxide gas, when combined to form a mixture, do not generate a significant amount of chloπne dioxide gas in the absence of water The reactants may therefore be stored for long peπods of time in a substantially dry atmosphere
20 Products may be treated with chlonne dioxide gas generated by forming a mixture of at least one metal chlorite and at least one material capable of reacting with the metal chlorite to produce chlorine dioxide gas in the presence of water but not in the substantial absence of w ater, and then by exposing the mixture to an atmosphere compπsing water vapor to produce chlorine dioxide gas in a sustained concentration of from about 0 001 to
25 1 ,000 ppm The chlorine dioxide gas may be generated as descπbed above and directed to an enclosure containing the food products, such as through the air circulation system The preferred concentration of chlorine dioxide gas for treating displayed food products is from about 0 01 to 500 ppm, more preferably from about 0 01 to 100 ppm, and most preferably from about 0 01 to 10 0 ppm
30 Alternatively, or in addition to treating the products themselves, waste pieces of loose products (e g , leaves of lettuce) which may be in proximity to the food products, may be treated with chlorine dioxide gas as well In a preferred embodiment of the present invention, a drip pan located below the products in a storage or display area such as a food display case typically found in retail grocery stores, is provided with a pad or matting material. The ingredients necessary to generate chlorine dioxide gas are provided in the region below the displayed food product, in the drip pan, or in a pad or matting provided in the drip pan. The chlorine dioxide inhibits the proliferation of microorganisms in the drip pan and also helps to reduce the proliferation of microorganisms in the air recirculation system. The ingredients for generating the chlorine dioxide may be contained within a sachet, such as disclosed, for example, in U.S. Patent No. 5,567,405.
The composition for generating chlorine dioxide gas may be in the form of a mixture of at least one metal chlorite and at least one Second Material. The metal chlorites employed may generally be any metal chlorite. Preferred metal chlorites are alkali metal chlorites, such as sodium chlorite and potassium chlorite. Alkaline earth metal chlorites may also be employed. Examples of alkaline earth metal chlorites include barium chlorite, calcium chlorite, and magnesium chlorite. The most preferred metal chlorite is sodium chlorite.
The Second Material is a dry solid hydrophilic material, preferably a dry solid inorganic hydrophilic material. The preferred dry solid hydrophilic material produces a pH of no more than about 10.5 when the aqueous portion of a 30 weight percent mixture of that material in deionized water is measured. More preferred solid hydrophilic materials produce a pH of less than 9 and most preferably less than 7. Examples of such dry solid hydrophilic materials suitable for reacting with the metal chlorites include, but are not limited to, synthetic zeolites, such as A, X, Y and mordenite; natural zeolites such as chabazite and clinoptilolite; hydrous clays, such as bentonite, kaolin, attapulgite and halloysite; calcined clays, such as metakaolin, spinel phase kaolin, calcined bentonite, calcined halloysite, and calcined attapulgite; acidified synthetic zeolites, such as A, X, Y, and mordenite that have been contacted with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid, or other acidic compound (e.g., calcium chloride) so that the pH of the resulting aqueous phase of the mixture is below 10.5; acidified natural zeolites such as chabazite and clinoptilolite; acidified clays, such as bentonite, kaolin, attapulgite and halloysite that have been contacted with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid, or other acidic compounds (e.g., lanthanum chloride) so that the pH of the resulting aqueous phase of the mixture is below 10.5; acidified calcined clays, such as metakaolin, spinel phase kaolin, calcined bentonite, calcined halloysite, and calcined attapulgite that have been contacted with one or more acidic solutions containing sulfuric acid, hydrochlonc acid, nitπc acid, or other acidic compounds (e g , acetic acid) so that the pH of the resulting aqueous phase of the mixture is below 10 5, salts, such as aluminum sulfate, magnesium sulfate, calcium carbonate, and particularly deliquescent acidic salts, such as calcium chlonde, magnesium chlonde, lithium chloπde, and magnesium nitrate, solid acids, such as bone acid, tartanc acid and citnc acid, organic acid anhydrides such as phthahc anhydnde, maleic anhydride, succinic anhydride and glutaπc anhydride, and mixtures thereof A preferred Second Material is metakaolin microspheres As used herein the term "microspheres" shall mean nominally spherical particles having an average particle size of from about 50 to 100 microns
The chlorine dioxide may be used in the form of a solution to treat and/or prevent infestation of microorganisms Chlonne dioxide in the form of an aqueous solution may be produced by a) having liquid water in a first zone and at least one metal chlorite and at least one acid forming component in a second zone, the first and second zones being separated by a membrane, b) contacting the membrane with water from the first zone (e g , a dnp pan), such that liquid water and/or water vapor passes through the membrane into the second zone, thereby facilitating the reaction between the at least one acid forming component and the at least one metal chlonte to produce chlonne dioxide, and c) allowing the chlorine dioxide produced in the second zone to pass through the membrane to the first zone, into the liquid water, to form an aqueous solution
A device which generates chlorine dioxide in the presence of water, but not in the substantial absence of water, may be employed In a preferred aspect, the device, when placed in liquid water, may be used to generate an aqueous solution containing chloπne dioxide on demand In particular, the device may compπse a membrane defining, at least in part, an enclosed space, the enclosed space containing at least one metal chlonte and at least one acid forming component The membrane is made of a material which permits (a) liquid water and/or water vapor to pass therethrough into the enclosed space to allow the at least one metal chlorite and at least one acid forming component to react to produce chloπne dioxide, and (b) the so produced chlonne dioxide to pass therethrough out into the liquid water to produce the product solution containing chlorine dioxide The liquid water needed to induce the formation of aqueous chlonne dioxide may be provided by the water present in the drip pan of the food storage display case The present invention can be adapted to provide the controlled release of chlonne dioxide by employing reactants and membranes which readily dissolve in water ("Embodiment A"), or by employing membranes and optionally reactants which are more resistant to dissolution ("Embodiment B") In Embodiment A, the resultant chlonne dioxide containing solution compπses chlorine dioxide, solubilized membrane, and the soluble byproducts of the reaction between the metal chlorite and the acid forming component In this embodiment, separation, handling and disposition of undissolved solid waste products is substantially eliminated because the device and its contents substantially dissolve in the product chlorine dioxide containing solution However, the product solution will contain small amounts of dissolved impurities (e g , typically less than 1000 ppm) as discussed above
In Embodiment B, the at least one metal chlorite and at least one acid forming component are initially separated from the liquid water by a membrane which does not substantially dissolve duπng the generation of chlorine dioxide This embodiment produces chlorine dioxide solutions of higher purity than Embodiment A because at least a portion of the reaction byproducts from the reaction between the metal chlorite and acid forming component are substantially retained by the membrane which is at least substantially insoluble and therefore the byproducts do not enter the product aqueous solution containing chlorine dioxide in appreciable quantities For purposes of the present invention, Embodiments A and B are preferred, however, the invention also contemplates that substantially insoluble reactants may be used w ith substantially soluble membranes and substantially soluble reactants may be used with substantially insoluble membranes and that mixtures of insoluble and soluble reactants may be used with either type of membrane Other methods for generating aqueous solutions of chlonne dioxide are known to those skilled in the art and may be adapted for use in the methods and systems of the present invention
The selection of the reactants (metal chloπte and the acid forming component) as well as the membrane material separating the reactants for the formation of an aqueous solution of chlorine dioxide depends, in part, on the relative importance of several factors to the particular end use of the chlorine dioxide containing solution The factors include reaction rate (i e , the rate of generation of chloπne dioxide), the desired puπty of the resulting aqueous solution containing chlorine dioxide, and the ease of handling and disposal of the reaction waste products. If reaction rate is of primary importance, then it is preferred to select reactants which are more water soluble and membrane materials which are more permeable to both water and chlorine dioxide. If purity of the resultant product solution is of primary importance, then it is preferred to select reactants which produce byproducts which are not substantially water soluble and membrane materials which are also not substantially water soluble. If elimination or reduction of waste product handling and disposal is of primary importance, then it is preferred to select membrane materials and reactants whose byproducts are substantially water soluble.
The selection of water soluble reactants facilitates rapid dissolution and reaction of the reactants to produce chlorine dioxide in the presence of liquid water. A more highly permeable membrane material allows more rapid transfer of the water into contact with the reactants as well as the rapid release of the thus produced chlorine dioxide back into the body of water. If desired reactants and membrane materials can be chosen so that the membrane and all of the reaction byproducts are substantially water soluble, the aqueous solution of chlorine dioxide does not have to be further processed to remove either membrane residue or the insoluble byproducts of the reactants.
The membrane employed in the present device serves several functions. First, it must provide for the controlled passage of liquid water and/or water vapor from a source (typically the body of water that is to be treated to form an aqueous chlorine dioxide solution) into the device so that the metal chlorite and the acid forming component can react with each other to produce chlorine dioxide. Second, in the absence of a source of water, the membrane must protect the reactants form ambient humidity so that the reactants have a desirable shelf life. Third, the membrane must allow the passage of chlorine dioxide gas out into the body of water to be treated once water has contacted the reactants and the chlorine dioxide generating reaction has commenced.
As previously indicated, the membrane materials can be selected from substantially water soluble materials when rapid reaction is important and dissolved byproducts are acceptable. Substantially insoluble membrane materials are appropriate when it is desirable to avoid introducing species other than chlorine dioxide (such as soluble membrane constituents to the product solution). Preferred substantially water soluble membrane materials include gelatin, polyvinyl alcohol, cellulose, and derivatives of cellulose including but not limited to hydroxypropyl methyl cellulose. Other such materials will be known to those skilled in the art. The preferred substantially water soluble membrane materials, such as gelatin, once contacted with liquid water are quickly water softenable and at least partially water soluble. In a preferred form of the invention, the membrane is water soluble to the extent that after the reaction between the metal chlorite and acid forming component has been completed and the chlorine dioxide gas has been released, the membrane continues to solubilize. As a result, the membrane material is fully dissolved in the aqueous solution of chlorine dioxide and does not have to be removed therefrom after use. In this manner, if water soluble reactants are utilized, there are no undissolved byproducts to be removed from the body of water. The preferred membrane material is gelatin, preferably in the form of capsules, such as Capsugel manufactured by Warner-Lambert Co. and Vegecaps manufactured by G.S. Technology.
A membrane material which is not substantially soluble is preferred when it is desired to limit the introduction of species other than chlorine dioxide into the product solution. The purity of the aqueous solution can be further enhanced by incorporating into the enclosed space containing the reactants one or more materials which form an insoluble phase with at least one otherwise soluble reaction byproduct. As a result, the at least one otherwise soluble reaction byproduct cannot escape out through the membrane into the aqueous solution containing chlorine dioxide because the at least one otherwise soluble reaction byproduct is tied up in at least one insoluble phase.
The preferred substantially insoluble membrane materials which permit passage of water vapor into contact with the contained reactants also provide a barrier to keep insoluble reactants and reaction products from entering the aqueous solution of chlorine dioxide that is produced. Such materials include microporous nonwoven hydrophobic polymer sheet materials including nonwoven polyethylene (e.g., TYVEK® brand sold by
Dupont) and expanded polytetrafluoroethylene (e.g., GORTEX® brand sold by W.L. Gore). Other such materials will be known to those skilled in the art.
As previously indicated, the generation of chlorine dioxide gas under controlled conditions in the presence of water vapor is made in sustained concentrations of from about 0.001 to 1 ,000 ppm. The phrase "sustained concentration" means that at all times during production, the concentration of chlorine dioxide gas is within the range 0.001 to 1 ,000 ppm. The generation of chlorine dioxide gas need not be at a constant rate. It is permissible to have a fluctuating rate so long as the chlorine dioxide gas concentration does not exceed 1,000 ppm, and is within the range of from about 0 001 to 1,000 ppm for a sustained period of time
According to the present invention, the generation of chlonne dioxide gas within the specified range will vary depending on the relative humidity of the surrounding atmosphere, the ratio of the reactants in the mixture, the diluent gas flow rate (e g , air) through the treated space if any, and the ratio of the amount of chlorine dioxide gas releasing material to the volume of the treated space Generally, the higher the relative humidity the higher the rate of production of chlorine dioxide gas The lower the flow of the diluent gas through the treated space, the higher the resultant chloπne dioxide gas concentration The higher the ratio of the chlorine dioxide gas releasing matenal to the volume of the treated space, the higher the chlorine dioxide gas concentration In a preferred embodiment of the invention, the sustained amount of chloπne dioxide gas is from about 0 01 to 500 ppm, more preferably from about 0 01 to 100 ppm Especially good results are obtained when the chloπne dioxide gas production is in the range of from about 0 01 to 10 ppm
The amount of each of the metal chlorite and the matenal which reacts with the metal chlonte will depend on several factors, including, but not limited to, the quantity of chlorine dioxide gas needed for a particular application, the basicity of the metal chloπte and the acidity of the matenal which reacts with the metal chlonte In general, it is preferred to use as much chlorite as possible consistent with a sufficient rate of release
As a consequence, the yield of chloπne dioxide gas per unit mass of the mixture is maximized In general, the weight ratio of the metal chlonte and the matenal which reacts with the metal chlorite is in the range of from about 0 01 to 0 25 1 0 It is withm the skill of the art to choose the proper ratio for a particular application The mixture formed in accordance with the present invention may optionally contain a desiccant which absorbs water to minimize or eliminate an initial brief duration production of chlorine dioxide gas due to residual water vapor present m the atmosphere or in the solids when the mixture is packaged Suitable desiccants include but are not limited to calcium chloride, activated calcium sulfate, activated zeolite X and zeolite A, activated bentonite clay, activated silica gel, activated attapulgite and mixtures thereof
The term "activated" means that the particular matenal has been substantially dehydrated, for example, by heating at 300 C for one hour The total amount of desiccant may vary depending on several factors, for example, the ambient humidity when the matenal is packaged, the water permeability of the packaging material and the desired shelf life of the product. Generally, the desiccant is present in a total amount from about 0.1% to 25% by weight based on the total weight of the mixture.
In practice of the present invention, the relative humidity of the atmosphere to which the composition is exposed during use can range from low to high humidity conditions. The method of the present invention can be conducted at low humidity (e.g., 10% relative humidity) up to 100% relative humidity. As previously indicated, the amount of chlorine dioxide gas generated per given amount of the mixture will depend, in part, on the relative humidity of the surrounding atmosphere. In general, higher humidity will result in a higher concentration of chlorine dioxide gas.
For example, it has been observed that the production of chlorine dioxide gas will approximately double when the relative humidity is increased from about 10% to about 80% at room temperature. It has also been observed that at ambient room temperature compared to 32° F, there is no significant change in the production rate of chlorine dioxide.
It will be understood that for a given unit of the mixture, a sustained amount of chlorine dioxide gas will be produced. For commercial applications, it may be desirable to employ multiple units of the mixture. In some cases it will be desirable to initiate the production of chlorine dioxide gas from one or more units of the mixture and then to have a second group or multiple groups of units of the mixture be added at a later time.
Furthermore, one of the constituents of the composition of the present invention may be present in excess and the second of the constituents may be added as needed. For example, the mixture can contain an excess of an organic acid anhydride and periodically additional amounts of metal chlorite can be added. The mixture of the metal chlorite and the material which reacts with the metal chlorite can be formulated in several ways. The preferred method is to prepare in a dry atmosphere an intimate physical mixture of fine powders of both constituents having particle sizes, preferably below about 200 um. Larger particles may be used and may achieve a slower rate of chlorine dioxide gas release in certain instances. The mixture can be formed by combining one of the constituents in liquid form with other constituent(s). For example, a slurry of a fine powder of calcined kaolin microspheres in a nonpolar liquid such as dodecane may be combined with the metal chlorite. The mixture is then dried to remove the nonpolar liquid. If water is used as the liquid, then the mixture should be dried to a sufficient extent to prevent excessive release of chlorine dioxide gas
The reaction ot the metal chloπte and the material which reacts with the metal chlorite can last for a sustained period of time The term "sustained period of time" shall mean that the chlorine dioxide gas will be generated during a short period of time (several minutes) to a long penod of time spanning many hours The length of the sustained peπod of time will depend, for example, on the relative amounts of the constituents in the mixture Eventually, of course, one of the reacting constituents (either the metal chlonte or the material which reacts with the metal chlorite) will be spent and the reaction will cease However, during the course of the reaction for however long it lasts, chlonne dioxide gas will be produced in a sustained concentration as defined herein
A preferred composition for producing a slow release rate of long duration is a mixture of about 5% sodium chlorite and about 95% metakaolin microspheres A preferred composition for a shorter duration, higher rate of generation of chlorine dioxide is a mixture of about 5% sodium chloπte, about 10% activated calcium chloπde and the balance acid-treated metakaolin microspheres
The length of time of the reaction is also dependent, in part, on how much water vapor is present in the atmosphere contained within the packaging The optional use of desiccants to minimize chlonne dioxide gas production in the packaging can ensure that the mixture w ill react for the longest peπod of time when exposed to water vapor under operating conditions However, the presence of a desiccant may delay the desired onset of production of the chlorine dioxide gas when the mixture is exposed to water vapor
The mixture of metal chlorite and a matenal which can react with metal chloπte in the presence of water vapor may be packaged for shipment and storage m containers made of mateπals which are resistant to the passage of liquid water and water vapor Example of such materials include metal cans, glass jars, foil pouches, and barrier layer polymer laminates
The mixture of the metal chlorite and the material which reacts with the metal chlorite may be used as a powder, used as formed shapes, or packaged and retained for use in any material which is gas permeable Examples of such matenals include
TYVEK® and GORTEX® These materials enable water vapor to enter into the package and react with the mixture and also enable the resulting chlorine dioxide gas to be released from the package and enter the atmosphere Such matenals are liquid water impervious
The metal chlorites employed in the present invention can generally be any metal chlorite, as well as mixtures thereof Preferred metal chloπtes are water soluble and include alkali metal chlorites, such as sodium chlorite and potassium chloπte as well as alkaline earth metal chlorites Examples of alkaline earth metal chlontes include baπum chlorite, calcium chloπte, and magnesium chlorite The most preferred metal chlonte is sodium chlorite, especially dry technical grade sodium chlonte containing about 80% by weight of sodium chlorite and 20% of sodium chlonde available from Energia E Industπas Aragonesas, S A of Madrid, Spain
The acid forming component is preferably a dry solid hydrophilic matenal which does not react with the metal chlorite during dry storage The acid forming component does, however, react with the metal chlorite to form chlorine dioxide when in the presence of liquid water and/or water vapor As used herein, the term "acid forming component" shall mean a dry solid matenal which is itself acidic or produces an acidic environment when in contact with liquid water and/or water vapor and metal chlonte The acid forming component may be water soluble or substantially insoluble The preferred acid forming mateπals are those which produce a pH of below about 7, most preferably below about 5 when the aqueous portion of a concentrated mixture of the solid in deiomzed water is measured
Examples of preferred acid forming components include water soluble solid acids such as bone acid, citnc acid, tartanc acid and water soluble acid salts such as calcium chloride, magnesium chloride, magnesium nitrate, lithium chloride, magnesium sulfate, aluminum sulfate, sodium acid sulfate (NaHSO4), sodium dihydrogen phosphate (NaH:PO4), potassium acid sulfate (KHSO4), potassium dihydrogen phosphate (KH PO4), and water soluble organic acid anhydrides such as maleic anhydride, and mixtures thereof The most prefeπed acid forming component is sodium acid sulfate
The amount of acid forming component should be sufficient to provide an excess of acid beyond that needed to neutralize the alkalinity of the metal chlorite and the incoming water Preferably the amount of the acid forming component should be sufficient to maintain a pH of less than about 5 and more preferably less than about 3 5 when in contact with the metal chloπte Calculation of the amount of metal chlonte, specifically sodium chlorite, can be computed by methods well known in the art based on the reaction:
5NaC10: + 5H~ = 4ClO2 + HC1 +2H2O + 5Na^ Other constituents may be included within the enclosed space in addition to the reactants and phases that form insoluble phases with otherwise soluble phases. For example, desiccant materials may be included to increase the storage stability of the reactants by protecting them from humidity (which can cause humidity induced premature reaction to form chlorine dioxide). Deliquescent materials may also be included in the enclosed space to accelerate the onset of the chlorine dioxide forming reaction once the membrane is contacted with water. Deliquescent materials absorb water vapor and convert it to liquid water. Consequently, soluble reactants can dissolve and begin rapidly to react to form chlorine dioxide even before liquid water has penetrated the membrane. Calcium chloride is both the preferred desiccant material and preferred deliquescent material. Additional materials having these characteristics will be known to those skilled in the art and are included within the scope of the present invention.
The solid metal chlorite and the solid acid forming component can be in any physical form which can be contained within the device. The solid reactants can be in the form of powders, granules, pellets, tablets, agglomerates and the like. In a preferred aspect of the invention, one or both of the reactants are present in the form of relatively large agglomerates (as defined below).
In this prefeπed aspect of the invention, the agglomerates do not contain mixtures of metal chlorites and acid forming components. Thus one type of agglomerate contains only one or more metal chlorites or a mixture of metal chlorite(s) and one or more non- acid forming additive(s) (e.g., silica gel desiccant, paraffin wax tableting binder, and/or sodium sulfate filler). The second type of agglomerates is substantially free of the metal chlorite, and at least one type of them comprises the acid forming component as defined herein, and may also contain one or more metal chlorite-free additives (e.g., Ion Exchangers, tableting binders, and/or desiccants). In this preferred embodiment the preferred composition also does not contain constituents that deliquesce upon exposure to ambient humidity. This aspect is the preferred aspect when it is desired that the materials be resistant to premature conversion to chlorine dioxide as a result of ambient humidity (i.e., when it is desirable for the materials to react to form chlorine dioxide substantially only when they are exposed to liquid water). Large agglomerates allow less costly packaging materials to be used for packaging of the device. Specifically, if powdered mixtures of reactants are exposed to high levels of ambient humidity for an extended period of time during storage, they undergo humidity activated premature reaction to form chlorine dioxide. To prevent such premature reaction, powdered reactants can be packaged in humidity barrier materials such as foil pouches, glass bottles, and metal cans. Such packaging is expensive and its use can be reduced or eliminated if the physical form of the reactants inhibits them from undergoing excessive premature humidity activated reaction, i.e., if they are in the form of large agglomerates. Applicants have discovered that when the particles of metal chlorite and the acid forming component have a particle size of up to about 80 microns in diameter when in intimate contact may react due to exposure to humidity. Larger particles, probably because of their reduced interfacial contact area, react more slowly upon exposure to humidity. Consequently, in a situation where humidity activated chlorine dioxide formation is undesirable, large particles (i.e., 80 microns) are preferred because the resultant reactant mixture will undergo less premature humidity activated reaction.
The term "relatively large agglomerates" as used herein shall mean agglomerates having a particle size of at least 80 microns preferably above about 100 microns (0.1 mm), more preferably above about 500 microns (0.5 mm), and most preferably above about 1 ,000 microns ( 1 mm). A mixture of reactants when present in such preferred particle size will exhibit a reduced rate of humidity activated chlorine dioxide release when compared to being present in smaller particle sizes, but can dissolve and will react in contact with liquid water to produce an aqueous solution of chlorine dioxide.
As previously indicated, one or more materials which form an insoluble phase with at least one otherwise soluble reaction byproduct may be included with the reactants or may itself be a reactant. In a prefeπed embodiment an acid forming component can be used which is primarily present as a source of acidity, but which also reacts with cations which may be present to form an insoluble phase which is retained by the membrane. The practice of this embodiment permits the production of highly pure aqueous solutions containing chlorine dioxide. Such materials ("Ion Exchangers") are preferably solid, water insoluble H* ion exchangers having a high selectivity for cations in the reactants and reaction byproducts, e.g., cations of the metal chlorite. The Ion Exchangers capture the cations by ion exchange with Hr. The predominant resultant soluble reaction product is therefore only chorine dioxide with a possible trace amount of hydrogen chloride.
Examples of such Ion Exchangers include, but are not limited to, synthetic molecular sieves such as synthetic zeolite Y, dealuminated zeolite Y, mordenite and ZSM-5 which have been converted to the substantially H" exchange forms; acid ion exchange resins such as Amberlite® brand resins (sold by Rohm and Haas); Dowex™ HCR-S resins (sold by Dow Chemical Company); acid treated clays such as acid treated bentonite; and acid treated calcined clays such as acid treated spinel calcined kaolin and acid treated metakaolin including metakaolin microspheres which are nominally spherical particles having an average particle size of from about 50 to 100 microns and mixtures thereof. The preferred Ion Exchanger for this embodiment of the invention is the acid form of synthetic zeolite Y. Additional Ion Exchangers will be known to those skilled in the art and are included within the scope of the present invention.
Ion Exchangers are not the only materials suitable for forming insoluble phases by reacting with otherwise soluble phases. For example, when ionic calcium is an otherwise soluble phase, it is useful to include constituents comprising soluble sulfate and/or phosphate anions in the enclosed space with the reactants. Sulfate and phosphate anions will react with ionic calcium to form the insoluble phases calcium sulfate and calcium phosphate, respectively, and consequently prevent the escape of the calcium out of the membrane into the product solution. The preferred phases containing sulfate and/or phosphate are the acid forming components sodium acid sulfate and sodium dihydrogen phosphate. Other combinations of materials that react with otherwise soluble phases to yield insoluble phases are known to those skilled in the art and are included within the scope of the invention. The amounts of the metal chlorite and the acid forming component must be sufficient to generate a quantity of chlorine dioxide gas sufficient to combine with the body of water to form the aqueous solution of chlorine dioxide in the desired concentration. Generally, aqueous solutions of chlorine dioxide for cleaning and disinfecting purposes contain from about 0.5 ppm to 200 ppm of chlorine dioxide. If, for example, a liter solution containing 100 ppm of chlorine dioxide gas were desired, the required amount of the metal chlorite (specifically sodium chlorite) would be about 170 mg. In a particular embodiment of the present invention, a drip pan which may be located below the products in a storage or display area (e.g., a food product storage or display case typically found in retail grocery stores), may be provided with a treated pad or a mat containing an antimicrobially effective amount of one or more Antimicrobial Agent(s). The antimicrobially effective amount of the selected Antimicrobial Agent is within the skill of the art to determine. When a broad spectrum biostat compound such as INTERSEPT* is used as an Antimicrobial Agent, a microbially effective amount may be from about 0.5% to about 5.0%, by weight, (preferably from about 2.0% to 4.0%), based on the weight of the matting material. Alternatively, an antimicrobially effective amount of an Antimicrobial Agent such as ιNTERSEPTE, used in connection with a pad, may be from about 0.005 to about 5.0 gm/ft , more preferably from about 0.1 to about 1.0 grn/ft2. The Antimicrobial Agent may be provided in a dry, solid form, or it may be provided as a dry, water soluable agent that, when contacted with moisture, forms an antimicrobial solution that remains in the drip pan to reduce the presence and proliferation of microorganisms. The Antimicrobial Agent inhibits the proliferation of microorganisms in the drip pan and also helps to reduce the proliferation of microorganisms in the air recirculation system.
The matting material may be selected to provide one or more of the following functions: (1 ) to provide a physical barrier which prevents the deposition and accumulation of waste and food debris on the drip pan; (2) to provide a substrate for the incorporation of one or more adhering or chemically bonding Antimicrobial Agent(s) to prevent or reduce the growth of microorganisms, including bacteria and fungi, on the matting and the drip pad; and (3) to provide a water absorbant material that collects moisture from a humidification and/or misting system and assists in maintaining a high relative humidity in the product environment, generally a display or storage case for fresh food or floral products.
A suitable pad or matting material for use in the present invention may have varying degrees of liquid absorbency. For example, the matting material may be comprised of at least one absorbent sheet (i.e., a sheet capable of absorbing one or more Antimicrobial Agents) made of absorbing materials such as wood fiber, cotton fiber, synthetic fiber and the like, as well as mixtures thereof. The pad or matting material may be composed of multiple layers of individual sheet materials, including alternating layers of sheet materials having different absorption properties. The Antimicrobial Agent(s) may be uniformly distributed throughout the matting matenal, or may be confined to selected regions of the pad according to either a random or systematic arrangement (e g , as a checkerboard)
According to one embodiment, a suitable matting matenal compnses multiple layers of materials having different properties, including two outer layers having generally non-absorbent properties An Antimicrobial Agent, preferably a broad spectrum biostat agent having demonstrated efficacy against bacteria and fungi and having no toxicity, such as the LNTERSEPT® antimicrobial agent descnbed above, is preferably applied to one or both outer layers of the matting material by spraying, coating, soaking, impregnating, or any suitable means According to this embodiment, one or more intermediate matting layers is also provided The intermediate layer(s) preferably has greater liquid absorbency properties than the outer layers and may be treated with the same or a complementary Antimicrobial Agent
The matting treated with one or more Antimicrobial Agent(s) may be provided in any convenient form for placement in dnp pans or similar receptacles located in proximity to products such as meat, produce, dairy, and floral items The matting may be provided in selected standardized sizes for placement in dnp pans or other receptacles, or it may be piovided in one or more sizes and cut to fit to dnp pan or other receptacle dimensions Alternatively, the treated matting may be provided in a continuous roll form with perforations or markings or other indications marking standard or selected predetermined dimensions Perforations are preferred, so that mats having standard or selected predetermined sizes may simply be separated from a roll of matenal
As previously described, in accordance with the present invention, the "Combination" of chlorine dioxide gas and/or chloπne dioxide aqueous solution and one or more Antimicrobial Agents may be applied to the food products themselves, and/or to the environment in proximity to the food products, including the region above and/or below the food products and the drip pan As previously described, the components of the Combination may be applied together to the food products and/or the surrounding environment, or they may be applied separately For example, in one embodiment of the invention, chloπne dioxide gas is circulated through the air recirculation system of the food display case, while one or more Antimicrobial Agent(s) alone, or in combination with an aqueous solution of chloπne dioxide, is applied to the dnp pan Other applications of the Combination to storage and display cases are within the purview of the present invention.
Food product display cases of the type used in large grocery stores and supermarkets can extend to 50 foot lengths or more. In this embodiment of the invention, a single location of the components of the Combination may be insufficient to treat and/or prevent infestation of microorganisms throughout the full length of the display case. It is therefore desirable to provide a plurality of locations for the Combination. In a preferred form of the invention, units of the Combination are placed about 6 to 7 feet from each other along the length of the display case. An amount of the Combination sufficient to treat and/or prevent the proliferation of microorganisms is then generated for each 6 or 7 foot length of the display case. By way of example, if a sachet containing chlorine dioxide generating components is employed for each 6 to 7 foot length of the display case, then each sachet will typically contain about 50 grams of the chlorine dioxide generating components. Referring to the drawings and first to Figure 1 , there is shown a typical display case of the type used in retail grocery stores for displaying food products, such as produce, including fruits and vegetables. Display case 2 comprises housing 4 having a vertical wall 6, a horizontal wall 8 and a slanted display counter 10, as more fully described below, which is supported by the vertical and horizontal walls 6, 8. Slanted counter 10 has an outer slanted display surface 12 which can be tailored to provide appropriate storage and display areas for a variety of products 13, including produce, meat, dairy and floral items. Slanted counter 10 may have ridges, spaced apart boards, and the like, to provide support for storage and display of food products on slanted display surface 12 so that the food products 13 can be displayed in an attractive manner.
Slanted counter 10 contains openings 14 of sufficient size to enable broken and/or withered portions of the food products 9 to fall therethrough into the region 15 below the slanted counter 10. At the bottom of the region 15 and generally spaced above the horizontal wall 8 is a drip pan 16 for catching the droppings of food products as they fall through the region 15. The drip pan 16 is generally made of lightweight metal (e.g., aluminum) so that it can be readily removed from the display case 2 for cleaning and to remove the loose droppings 9 therein. As previously indicated, a drip pan containing droppings of food product becomes an ideal environment for the growth and proliferation of microorganisms. As the microorganisms grow, they contaminate the food product stored above on slanted counter 10.
As shown in Figure 1 , it is desirable to maintain a flow of air throughout the display case. This is provided typically by a fan assembly 18 including a fan 20 which draws air into the display case through an opening 22 and thereby maintains a circulation of air throughout the display case including the food products being displayed. The fan assembly 18 can be conveniently located to provide adequate air circulation.
If the region 15 or drip pan 16 is contaminated with microorganisms, these microorganisms enter the circulation system provided by the fan assembly 18 and thereby come into contact with the stored food product in the display case. This can result in infestation of the displayed food products and premature spoilage of the displayed food product.
The present invention provides methods and systems for reducing and/or inhibiting the infestation by and proliferation of microorganisms in the area of a display or storage case, thereby reducing infestation and spoilage of the displayed food products.
The methods and systems of the present invention also improve the shelf life of the displayed products and substantially eliminate unpleasant odors.
Referring to Figure 2, drip pan 16 is provided with a treated pad 30. The pad 30 may be provided with ingredients, in accordance with the present invention, that are necessary to generate chlorine dioxide in a gaseous or solution form. Treated pad 30 may, for example, comprise a metal chlorite and an acid component which, when they are brought together in the presence of water vapor (i.e., relative humidity), are capable of generating chlorine dioxide gas. Alternatively, the treated pad 30 may contain liquid water which causes the reactants to form an aqueous solution of chlorine dioxide, which remains in drip pan 16 to kill microorganisms. The components for generating chlorine dioxide gas may be provided in the pad, or in the drip pan directly, or contained within a sachet as previously described.
Pad 30 may be additionally treated with at least one Antimicrobial Agent, which may be in dry, solid or other suitable form, in an antimicrobially effective amount. Alternatively, treated pad 30 may contain a dry, water soluble Antimicrobial Agent.
When contacted with liquid water, the dry Antimicrobial Agent forms an aqueous solution which remains in the drip pan 16 to inhibit the proliferation of microorganisms. An antimicrobial system of the present invention contemplates the use of the treated pads, described above, in combination with a system for dispersing an Antimicrobial Agent and/or chlorine dioxide in a liquid or gaseous form. According to one embodiment, capsules or sachets containing ingredients that generate chlorine dioxide in a liquid or gaseous form, are used in combination with a treated pad. In one exemplary embodiment, dry ingredients that, upon activation, generate chlorine dioxide gases, which are confined by a gas permeable membrane, such as TYVEK®, and placed in proximity to a treated pad. According to a preferred embodiment, the dry ingredients are activated by exposure to moisture, or aqueous solutions, to generate chlorine dioxide on a controlled, sustained release basis. The treated or untreated absorbent pad may be provided with markings indicating suitable locations for sachets containing the dry ingredients. The treated pads and sachets may furthermore be provided with attachment means, such as adhesives, hook and loop fasteners, or the like, the provide attachment of a sachet to a pad at selected locations. Packets or sachets containing such ingredients in a gas permeable membrane maybe placed, at selected intervals, on the treated pad. The size and composition of the packet or sachet, the ingredient, and the number of sachets used in a selected area may be chosen to deliver the desired sustained chlorine dioxide gas release and concentration.
Thus, systems of the present invention contemplate the combination of a pad or matting treated with an Antimicrobial Agent with a device containing a chlorine dioxide generating system, such as one or more sachets that, upon activation, provide sustained release of chlorine dioxide gas at an appropriate concentration. The treated pad or matting may be marked to indicate suitable locations for such chlorine dioxide devices. The treated pads and/or the chlorine dioxide devices may furthermore be provided with attachment means, such as adhesives, hook and loop fasteners, and the like, that provide attachment of the device(s) to a treated pad at a selected location.
In a further aspect of the present invention, the circulatory system is provided with at least one Antimicrobial Agent as a gas and/or solution from the storage vessel 40. The Antimicrobial Agent is passed into a conduit 42 having openings 44 which allow the Antimicrobial Agent to be passed into the region 14 as a fine mist or gas and thereby treat microorganisms both in the drip pan 16 and on food product resting on the slanted counter 10. In an additional or alternative aspect of the present invention, a circulatory system for chlorine dioxide gas may be provided, or a system in which a chlorine dioxide solution is provided from a storage vessel 40 and then passed into a conduit 42 having openings 44 which allow the chlorine dioxide solution to be passed into the region 15 as a fine mist, to kill microorganisms both in drip pan 16 and on product 13 resting on the slanted counter 10. Both of the systems discussed above in connection with Figure 2 can be employed to provide optimal coverage of the display case.
The following examples are illustrative of embodiments of the invention and are not intended to limit the invention as encompassed by the claims forming a part of the application.
Example 1
A display case in a retail grocery store of the type shown in Figure 1 was provided with a quantity of typical fruits and vegetables as shown in Table 1. The display had a fan which was operated on a constant basis to provide air circulation. After nine days, the amount of spoiled food product was measured and an estimate of the total revenue loss was calculated. The results are shown in Table 1.
Table
Commodity Spoiled Food Product Cost Revenue Loss in Pounds
Radish 48 2/99 23.76
Cucumber 32 2/99 15.84
Gr. Onion 25 2/99 12.37
Spinach 25 .99 ea. 24.75
Head Lettuce 95.5 .99 ea. 94.54
Green Leaf 115 .99 ea. 113.85
Red Leaf 43 .99 ea. 37.62
Butter Leaf 38 .99 ea. 37.62
Romaine 27 .99 ea. 26.73
Orange Pepper 14.0 4.99 lb 69.86
Green Pepper 53 2/99 26.23
Pears 39.2 1.99 1b 78.00
Sm. Pears 10.6 1.99 1b 31.69
Bartlett 5.9 1.49 1b 8.79
Organic Banana 35.8 .99 1b 35.44
Red Banana 10.1 1.99 1b 20.09
Plum 21.9 1.59 1b 34.82
Fuyu Tomato 8 1.99 ea. 15.92 Kiwi 13 .89 ea. 1 1.57
Palmagranite 8 2.99 ea. 23.92
Peaches 30.2 1.99 1b 60.09
Total revenue loss: $ 808.45
The same procedure referred to above was repeated on a very similar food display, except that sachets containing 50 grams each of metal chlorite and an acid component were placed in drip pans at a distance of every 8 feet.
The display was maintained for nine days under continuous operation of the fan. The results are shown in Table 2.
Table 2
Commodity Spoiled Food Product Cost Revenue Loss in Pounds
Cucumber 16 2/99 7.92
Radish 54 2/99 26.73
Gr. onion 15 2/99 7.42
Spinach 46 .99 ea. 45.54
Head Lettuce 21 .99 ea. 20.79
Green Leaf 21 .99 ea. 20.79
Red Leaf 19 .99 ea. 18.81
Butter Leaf 31 .99 ea. 30.69
Romaine 15 .99 ea. 14.85
Orange Pepper 7 4.99 lb 34.93
Green Pepper 39 2/99 19.30
Pears 4.12 1.99 1b 8.19
Sm. Pears 8.12 2.99 lb 24.27
Bartlett Pears 5 1.49 1b 7.45
Organic Banana 5.1 .99 1b 5.04
Red Banana 0 1.99 1b 0.00
Plum 1.6 1.59 1b 2.54
Fuyu Tomato 1 1.99 ea. 1.99
Kiwi 0 .89 ea. 0.00
Palmagranite 0 2.99 ea. 0.00
Peaches 27.8 1.99 1b 55.32
Total loss in revenue: $ 352.57 As shown by a comparison of Tables 1 and 2, the presence of the chlorine dioxide gas, in accordance with the present invention, significantly reduces loss of food product which is generally attributable to the presence of microorganisms and may also result from exposure to ethylene gas during the ripening process. Example 2
A display of the type descπbed m Example 1 is treated in accordance with the present invention by placing in the drip pan, an absorbent pad which was treated with about 2% by weight of a quaternary ammonium compound produced by Interface Research of Atlanta, Georgia and sold under the trademark LNTERSEPT® Thereafter, the display case was sprayed with an aqueous solution of chlorine dioxide in a concentration sufficient to provide 5 ppm of chlorine dioxide The combination of chlorine dioxide and the quaternary ammonium compound was sufficient to reduce the proliferation of microorganisms in the dnp pad and the environment proximate to the displayed food products
Example 3
A quantity of sodium hypochlonte was added to a quantity of water sufficient to provide a concentration of 1,000 ppm The solution was sprayed over a display case of the type show n in Figure 1 containing fruits and vegetables, sufficient to cover but not drench the same The fruits and vegetables were tested for the presence of microorganisms Few, if any, microorganisms were detected
Example 4 A quantity of a solid quaternary ammonium compound, namely methyl dimethylammonium chloride, was added to the dnp pad of a display case of the type shown in Figure 1 The amount of the antimicrobial agent was about 1-2% by weight, based on the weight of the drip pad The drip pad containing discarded leaves of vegetables was tested for the presence of microorganisms Few, if any, microorganisms were detected
While the present invention has been has been described with reference to certain preferred embodiments, and certain preferred manufacturing techniques have been described, it will be understood that alternative embodiments and manufacturing techniques may be developed and adapted without departing from the pπncφles of the invention

Claims

Claims:
1 A method for extending the shelf life of food and floral products stored and displayed in a case and reducing infestation by microorganisms, compπsmg exposing the food products, or the environment in proximity to the food products, to an antimicrobially effective amount of at least one agent
2 The method of claim 1 wherein the products are contained within a storage and/or display case, the method comprising treating the products, the storage and/or display case, or both, with an Antimicrobial Agent
3 The method of claim 2 compnsmg forming a liquid solution of the Antimicrobial Agent and a suitable solvent
4 The method of claim 3 wherem the solution is applied directly to the food products
5 The method of claim 3 wherein the solution is applied to at least a portion of the food storage and/or display case
6 The method of claim 5 wherem the food storage and/or display case comprises a dnp pan for receiving waste pieces of product and water, the method comprising introducing the solution containing the Antimicrobial Agent to the dnp pan
7 The method of claim 6 wherein the drip pan compnses an absorbent pad comprising at least one sheet of an absorbent material, the method comprising adding the solution to the adsorbent pad
8 The method of claim 1 wherem the products are contained within a storage and/or display case, the method compnsmg exposing the storage and/or display case to chlorine dioxide in a gaseous or solution form
9 The method of claim 8 comprising a) forming a mixture of at least one metal chlorite and at least one material capable of reacting with the metal chlorite to produce chlorine dioxide gas in the presence of water but not in the substantial absence of water; b) exposing said mixture to an atmosphere comprising water vapor to produce chlorine dioxide gas in a sustained concentration of from about 0.001 to 1,000 ppm; and c) contacting the products or droppings thereof with chlorine dioxide gas.
10. The method of claim 8 comprising: a) having liquid water in a first zone and at least one metal chlorite and at least one acid forming component in a second zone, said first and second zones being separated by a membrane; b) contacting said membrane with water from said first zone such that liquid water or water vapor passes through said membrane to said second zone, thereby facilitating the reaction between said at least one acid forming component and said at least one metal chlorite to produce chlorine dioxide; c) allowing the chlorine dioxide produced in the second zone to pass out through said membrane to the first zone into the liquid water to form said aqueous solution; and d) applying the aqueous solution to an area of the display case containing the loose droppings of the food product.
1 1. The method of claim 10 comprising adding the metal chlorite and the acid forming component to a pad positionable in a drip pan located in proximity to the products and the case, and exposing the pad to liquid water.
12. The method of claim 1 1 comprising adding the metal chlorite and the acid forming component to the pad positionable in a drip pan, and adding liquid water to the
13. The method of claim 8 wherein the chlorine dioxide is in a gaseous form and the sustained concentration of chlorine dioxide gas is from 0.01 to 500 ppm.
14. The method of claim 8 wherein the chlorine dioxide is in a gaseous form and the sustained concentration of chlorine dioxide gas is from 0.01 to 100 ppm.
15. The method of claim 8 wherein the chlorine dioxide is in a gaseous form and the sustained concentration of chlorine dioxide gas is from 0.01 to 10.0 ppm.
16. The method of claim 8 wherein the chlorine dioxide is in a solution form and the concentration of chlorine dioxide in solution is from 0.01 to 200 ppm.
17. The method of claim 8 wherein the chlorine dioxide is in a solution form and the concentration of chlorine dioxide in solution is from 0.1 to 20 ppm.
18. The method of claim 9 comprising placing the metal chlorite and that at least one material capable of reacting with the metal chlorite in a satchet and placing the satchet in the display case.
19. The method of claim 8 comprising treating the case with said aqueous solution of chlorine dioxide in the form of a fine mist.
20. The method of claim 8 additionally comprising treating the storage and/or display case with a solution containing at least one non-chorine dioxide containing antimicrobial agent in the form of a fine mist.
21. The method of claim 8 comprising employing an amount of chlorine dioxide sufficient to reduce overripening of the food product in the display case.
22. A method for extending the shelf life of food and floral products and inhibiting the infestation of microorganisms in said products comprising providing the products, or the environment in proximity to the products, or both, with an antimicrobially effective amount of the combination of chlorine dioxide in a gaseous or liquid form, and at least one Antimicrobial Agent.
23. The method of claim 22 wherein the products are contained within a storage or display case, said method comprising treating the products, the storage or display case, or both, with said combination.
24. The method of claim 23 wherein the combination is applied directly to the products.
25. The method of claim 23 wherein the storage or display case comprises a drip pan that accumulates waste pieces of product and water, said method comprising placing reactants that react in the presence of moisture to form chlorine dioxide in the drip pan.
26. The method of claim 25 wherein the drip pan is provided with a disposable pad, said method comprising introducing reactants for generating chlorine dioxide to the pad.
27. The method of claim 23 comprising providing the combination at spaced apart locations in the storage or display case.
28. The method of claim 27 wherein the reactants for generating chlorine dioxide are contained within a device that enables moisture to enter therein to induce the production of said chlorine dioxide.
29. The method of claim 28 wherein the device is in the form of a sachet.
30. The method of claim 28 wherein the device is positioned in the drip pan.
31. The method of claim 22 comprising forming a solution of the Antimicrobial Agent and a suitable solvent.
32. The method of claim 31 wherein the solution is applied directly to the products.
33. The method of claim 22 wherein the Antimicrobial Agent is selected from the group consisting of: sodium hypochlorite; sodium chlorite -(p-nonylphenyl)- hydroxypoly (oxyethylene)-iodine complex; hydrogen peroxide; glutaraldehyde/phenol; acid glutaraldehyde; quaternary ammonium chlorides; phenol derivatives; and combinations thereof.
34. The method of claim 31 comprising applying the solution to at least a portion of the product storage or display case.
35. A treated pad for reducing the population and proliferation of microorganisms in the environment of storage and display cases, the treated pad comprising at least one sheet having at least an antimicrobially effective amount of at least one agent applied thereto.
36. The treated pad of claim 35 wherein the treated pad comprises multiple layers of sheet materials, and at least one of the layers of sheet materials has liquid absorbency properties.
37. The treated pad of claim 36 wherein the multiple layers of treated sheet materials include layers having different liquid absorbency properties.
38. The treated pad of claim 35 comprising at least one Antimicrobial Agent.
39. The treated pad of claim 38 wherein the Antimicrobial Agent is uniformly distributed throughout the treated pad.
40. The treated pad of claim 38 wherein the Antimicrobial Agent is distributed over at least one selected region of the treated pad.
41. The treated pad of claim 40 wherein the Antimicrobial Agent is distributed over multiple selected regions of the treated pad and the multiple selected regions form a systematic pattern.
42. The treated pad of claim 35 wherein the treated pad comprises multiple layers of sheet materials, and at least one of the layers has low liquid absorbency properties and has an Antimicrobial Agent applied to its surface.
43. The treated pad of claim 42 wherein the treated pad comprises two exterior layers having low liquid absorbency properties, and each of the two exterior layers additionally has an Antimicrobial Agent applied to its surface.
44. The treated pad of claim 43 additionally comprising an intermediate layer having greater liquid absorbency properties than the exterior layers.
45. The treated pad of claim 44 wherein the intermediate layer is treated with an Antimicrobial Agent.
46. The treated pad of claim 35, comprising at least one perforation for facilitating separation of the treated pad to form multiple treated pads having predetermined dimensions.
47. The treated pad of claim 46, wherein multiple perforations are provided at selected locations of the treated pad and the treated pad is provided as a continuous pad in a roll form.
48. The treated pad of claim 35 comprising reactants that, under predetermined conditions, react to form chlorine dioxide in a gaseous or liquid form.
49. The treated pad of claim 48 wherein the pad contains reactants that, in the presence of moisture, react to form chlorine dioxide gas.
50. The treated pad of claim 49 in which the reactants are capable of releasing chlorine dioxide gas on a sustained basis.
51. The treated pad of claim 48 in which the reactants, in the presence of water, react to form chlorine dioxide in solution.
52 A treated pad for reducing the population and proliferation of microorganisms in the environment of storage and display cases, the treated pad comprising at least one sheet containing a combination of reactants capable of generating chlorine dioxide in a gaseous or solution form, and an Antimicrobial Agent
53 The treated pad of claim 52 wherein the pad compnses multiple layers of sheet materials
54 The treated pad of claim 53 wherein the multiple layers of sheet mateπals comprise layers having different liquid absorbence properties
55 The treated pad of claim 52 wherein the Antimicrobial Agent is uniformly distributed throughout the treated pad
56 The treated pad of claim 52 wherein the Antimicrobial Agent is distnbuted over one or more selected regions of the pad
57 The treated pad of claim 56 wherein the selected regions are randomly located or in the form of a systematic pattern
58 A kit comprising (l) a treated pad for reducing the population and proliferation of microorganisms in the environment of storage and display cases, the treated pad comprising at least one layer containing an Antimicrobial Agent, and (2) a device containing reactants that, under predetermined conditions, react to form chloπne dioxide in a gaseous or liquid form
59 The kit of claim 58 in which the device contains reactants that, in the presence of moisture, react to form chlorine dioxide gas
60 The kit of claim 59 in which the device is capable of releasing chloπne dioxide gas on a sustained basis
61. The kit of claim 58 in which the device contains reactants that, in the presence of water, react to form chlorine dioxide in solution.
62. The kit of claim 58 in which the treated pad is marked to indicate the location or placement of devices.
63. The kit of claim 58 in which at least one of the treated pads and the device is provided with attachment means for mounting the device on the pad.
PCT/US1999/028084 1998-11-25 1999-11-24 Methods and systems for reducing microbial populations WO2000032052A1 (en)

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