Indicators for detecting the presence of metabolic byproducts from microorganisms

Abstract

Polymeric indicator films and pH indicating wraps are provided for visually monitoring, detecting, and/or determining the presence of metabolic byproducts from harmful or potentially harmful microorganisms. Also provided are methods of use and preparation of the polymeric indicator films.

1 . A polymeric indicator film comprising a transparent polymer layer or layers and a plurality of pH indicating moieties, wherein the pH indicating moieties are entrapped within the polymer layer or between two or more of the polymer layers and further wherein the pH indicating moieties retain the transparency of the polymer film at neutral pH but which impart color to at least a portion of the film when exposed to an acidic pH. 
     
     
         2 . A polymeric indicator film comprising a polymer and a plurality of pH indicating moieties selected from heptamethoxy red and hexamethoxy red or a combination thereof, wherein the pH indicating moieties are entrapped within the polymer. 
     
     
         3 . A polymeric indicator film comprising:
 a) a first layer comprising one or more hydrophilic, hydronium ion penetrating layers;   b) a second layer comprising one or more hydrophobic, water impermeable layers; and   c) a pH indicator layer placed between the first layer and the second layer.   
     
     
         4 . The polymeric indicator film of  claim 1  wherein the polymer is selected from the group consisting of polyethylene terephthalate, poly(vinylidene fluoride), poly(vinyl chloride), poly(vinylidene chloride), polypropylene, phenoxy resins, butadiene/styrene copolymers, butadiene/methylstyrene copolymers, poly(meth)acrylates, butadiene/acrylonitrile copolymers, ethylene/propylene copolymers, polybutadiene, polyisoprene, poly(oxy-2,6-dimethyl-1,4-phenylene), poly(oxycarbonyloxy-1,4-phenyleneisopropylidene-1,4-phenylene), acrylonitrile styrene copolymers, acrylonitrile/methyl acrylate/butadiene copolymers, acrylonitrile/styrene/butadiene copolymers, poly-1-vinylnaphthalene, polyvinylphenyl ketone, poly-p-xylenedodecanedioate, poly-tetramethylene octenediamide, poly-tetramethylene terephthalene, poly-trimethylene-3,3′-dibenzoate, poly-terephthallic anhydride, poly-4-methyl-diamine, polyvinylene carbonate, polyvinylene laurate, polyisopropenyl acetate, polyallylbenzene, polyvinylbutyl ether, polyvinyl formate, polyvinyl phenyl ether, polynorbornadine, polycarbonate, hydrophobic polyesters and polyurethanes, or a mixture thereof. 
     
     
         5 . The polymeric indicator film of  claim 1  wherein the polymer is polyethylene. 
     
     
         6 . The polymeric indicator film of  claim 1  that is transparent. 
     
     
         7 . The polymeric indicator film of  claim 1  that undergoes a detectable colorimetric change in the presence of an acid. 
     
     
         8 . The polymeric indicator film of  claim 7  wherein the acid is selected from the group consisting of carbonic acid, sulfuric acid, and hydrogen sulfide. 
     
     
         9 . The polymeric indicator film of  claim 7  wherein the acid is a microbial byproduct or is formed by reaction of a microbial byproduct with water, said microbial byproduct selected from the group consisting of carbon dioxide and sulfur dioxide. 
     
     
         10 . The polymeric indicator film of  claim 9  wherein the microbial byproduct is generated by a microbe selected from the group consisting of  Bacillus, Brucella, Campylobacter, Clostridium, Escherichia coli, Listeria monocytogenes, Salmonella, Streptococcus, Pseudomonas aeruginosa, Staphylococcus aureus, Shigella  spp.,  Vibri  spp.,  Yersini  spp. or a mixture of two or more such microbes. 
     
     
         11 . A food storage container containing the polymeric indicator film of  claim 1 . 
     
     
         12 . The food storage container of  claim 11  that is a sealable bag. 
     
     
         13 . The food storage container of  claim 11  that is a jug or bottle for storing liquids. 
     
     
         14 . A flexible pH indicating wrap comprising an outer hydrophobic barrier layer and an indicator layer, wherein the indicator layer is the polymeric indicator film of  claim 1 . 
     
     
         15 . A flexible pH indicating wrap comprising an outer hydrophobic barrier layer and an inner barrier layer permeable to microbial byproducts and acids thereof, wherein sandwiched between the outer and inner layers is a plurality of pH indicating moieties selected from heptamethoxy red and hexamethoxy red or a combination thereof, and wherein the pH indicating moieties are entrapped within a polymer or are adherent to an adhesive, said polymer or adhesive being situated between the outer and inner layers. 
     
     
         16 . The flexible pH indicating wrap of  claim 15  wherein the outer and inner layers are independently selected from the group consisting of polyethylene, polyethylene terephthalate, poly(vinylidene fluoride), poly(vinylidene chloride), phenoxy resins, butadiene/styrene copolymers, butadiene/methylstyrene copolymers, poly(meth)acrylates, butadiene/acrylonitrile copolymers, ethylene/propylene copolymers, polybutadiene, polyisoprene, poly(oxy-2,6-dimethyl-1,4-phenylene), poly(oxycarbonyloxy-1,4-phenyleneisopropylidene-1,4-phenylene), acrylonitrile styrene copolymers, acrylonitrile/methyl acrylate/butadiene copolymers, acrylonitrile/styrene/butadiene copolymers, poly-1-vinylnaphthalene, polyvinylphenyl ketone, poly-p-xylenedodecanedioate, poly-tetramethylene octenediamide, poly-tetramethylene terephthalene, poly-trimethylene-3,3′-dibenzoate, poly-terephthallic anhydride, poly-4-methyl-diamine, polyvinylene carbonate, polyvinylene laurate, polyisopropenyl acetate, polyallylbenzene, polyvinylbutyl ether, polyvinyl formate, polyvinyl phenyl ether, polynorbornadine, polycarbonate, hydrophobic polyesters and polyurethanes, or a mixture thereof. 
     
     
         17 . The flexible pH indicating wrap of  claim 14  having attached thereto or printed thereon a machine recognizable code. 
     
     
         18 . The flexible pH indicating wrap of  claim 17  wherein the code is a barcode. 
     
     
         19 . The flexible pH indicating wrap of  claim 18  wherein the code is in a RFID (radio frequency identification) tag. 
     
     
         20 . A method for detecting whether food is spoiled or contaminated with microbes such that said food is not edible, said method comprising:
 a) placing a portion of said food proximal to the polymeric indicator film of  claim 1 ;   b) detecting the presence or absence of a colorimetric change in the polymeric indicator film or pH indicating wrap; and   c) correlating the presence or absence of a colorimetric change in the polymeric indicator film or pH indicating wrap to whether the food is non-edible or edible.   
     
     
         21 - 38 . (canceled) 
     
     
         39 . A process for preparing a polymeric indicator film comprising an inner hydrophilic, hydronium ion penetrating transparent layer and an outer hydrophobic, water impermeable transparent layer which process comprises:
 a) selecting one or more hydrophilic, hydronium ion penetrating layers as the inner layer of the polymeric film wherein the inner layer has a first and second surface;   b) selecting one or more hydrophobic, water impermeable layers as the outer layer of the polymeric film wherein the outer layer has a first and second surface;   c) applying a pH indicator layer to at least a portion of one surface of the outer layer; and   d) bonding the inner and outer surfaces together such that the pH indicator layer is placed between the inner and outer layers.   
     
     
         40 . A process for preparing a polymeric indicator film comprising an inner hydrophilic, hydronium ion penetrating transparent layer and an outer hydrophobic, water impermeable transparent layer which process comprises:
 a) selecting one or more hydrophilic, hydronium ion penetrating layers as the inner layer of the polymeric film wherein the inner layer has a first and second surface;   b) selecting one or more hydrophobic, water impermeable layers as the outer layer of the polymeric film wherein the outer layer has a first and second surface;   c) applying an adhesive layer to one surface of the outer layer;   d) applying a coating of pH indicator to at least a portion of the adhesive layer; and   e) bonding the inner and outer surfaces together such that the adhesive layer coated with the pH indicator is placed between the inner and outer layers.   
     
     
         41 . The process of  claim 40 , wherein the adhesive is partially dried before the coating of pH indicator is applied. 
     
     
         42 . The process of  claim 40 , wherein the outer layer with the indicator applied thereto is dried before binding of the outer layer with the inner layer. 
     
     
         43 . The process of  claim 39 , wherein the pH indicator is selected from the group consisting of xylenol blue (p-xylenolsulfonephthalein), bromocresol purple (5′,5″-dibromo-o-cresolsulfonephthalein), bromocresol green (tetrabromo-m-cresolsulfonephthalein), cresol red (o-cresolsulfonephthalein), phenolphthalein, bromothymol blue (3′,3″-dibromothymolsulfonephthalein), p-naphtholbenzein (4-[alpha-(4-hydroxy-1-naphthyl)benzylidene]-1(4H)-naphthalenone), neutral red (3-amino-7-dimethylamino-2-methylphenazine chloride), hexamethoxy red and heptamethoxy red, and combinations thereof. 
     
     
         44 . The process of  claim 39 , wherein the pH indicator comprises hexamethoxy red. 
     
     
         45 . The process of  claim 39 , wherein the pH indicator comprises heptamethoxy red. 
     
     
         46 . The process of  claim 39 , wherein the polymeric indicator film is used as a food wrap. 
     
     
         47 . The process of  claim 39 , wherein the polymeric indicator film is used in a medical setting.