CA2184677A1 - Spoilage indicating device for food containers - Google Patents
Spoilage indicating device for food containersInfo
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- CA2184677A1 CA2184677A1 CA 2184677 CA2184677A CA2184677A1 CA 2184677 A1 CA2184677 A1 CA 2184677A1 CA 2184677 CA2184677 CA 2184677 CA 2184677 A CA2184677 A CA 2184677A CA 2184677 A1 CA2184677 A1 CA 2184677A1
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- permeable membrane
- wall
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Abstract
A spoilage indicating device for food containers, wherein the device provides a visual indication of bacterial spoilage of a food product stored in the container, the device having a pH-responsive indicator in contact with the product through a semi-permeable membrane porous only to ion containing water molecules of the product.
Description
2 ~ ~ ~ 6 7 7 A SPOILAGE INDICATING DEVIOE FOR FOOD CONTAINERS
BACKGRO~D OF l~IE INVENTION
1. Field of the Invention.
The present invention relates to detection and warning systems for controlling the state of freshness of food-stuffs and biological preparations which are stored in food cnnt~inPrs during some time oefore consumption, which food cnnt~;nPrs are preferably to be purchased by final consumers who are warned by the visual indication of any harmful bacterial process inside the food package. Most preferably, the invention refers to a spoilage visual indication device for use in milk-based-product cnnt~inprs~
Although the present invention will be disclosed in relation to the diary industry, the same is applicable to any field of the food industry where the state of freshness of stored products must be constantly monitored 2. Description of the Prior Art.
One of the most important parameters to be monItored during conservation of products is the acidity 2 1 8~677 level of the products. The suitable acidity will depend on the kind of product, thus a high acid level must be kept for pickles to avoid bacterial and fungi multiplication, while a low level must be controlled for a diary product to avoid spoilage under a high level of acidity.
Diary products, such as milk, butter, cream, yogurt and the like are extremely susceptible to decomposition and, therefore, control must be kept on the pX which must be, in the fresh state of milk, for example, of 6.5 to 6.6.
The pH level is affected, in diary products, by the undue bacterial multiplication, such as the lactobacilli, which causes the pE level to decrease whereby the product is excessively acid and below the acceptable conditions for human consumption. Generally, the freshness of the milk is controlled only during the bulk processing so that the quality thereof is high at the time the bottled milk or milk-based packaged product is delivered through the distribution system to customers. However, under the distribution conditions the products may be exposed, during long periods of time, to undue high temperatures which cause the bacteria to undergo an excessive multiplication whereby the milk becomes unsafe and spoiled well before the date marked generally in the cr~nt;3;nF~r for indicating an estimated freshness time period within which the product must be consumed. This period of time, marked in the package, is estimated by the manufacturer on the basis of 2 1 ~4677 t 3 tests and tables, but the changing weather conditions, the different geographical areas and freezing interruptions may alter the e~pected freshness life of the product, and that period is generally shorter than expected.
In some cases the organoleptic characteristics of the product depends on the solubility and dispersion capability of the proteins and/or polymers in the packaged product. The physicochemical characteristics of the lacteous proteins, such as the solubility based on the pH o zero-electric-charge point, are sensitive to the solution conditions, the pH, salt concentration, other proteins and carbohydrates, etc. When orrllrr;nri changes in the product due to the bacterial activity, proteins may lose their emulsifying and/or stabilizing functions for the product emulsion or dispersion, as well as the proteins may undergo a coagulation or precipitation whereby the organoleptic features are lost, although the product may be in acceptable human consumption conditions.
Under the above conditions, neither the retailer nor t~Le f inal consumer have the means to be aware that the product is under a minimum riuality for human consumption.
This is why many attempts have been made ln order to have a reliable way and systems for the cfmsllmPrs to deterrnine whether a diary product is in conditions to human consumption and in a high rluality state.
2 ~
U.S. Patent N 2,485,566 refers to a method and device for indicating spoilage, and more particularly refers to an indicator system for indicating harmful bacterial processes inside a food package, the system consisting of a transparent cell associated with the package, in which a bacterial process analogous to that occurring inside the package is visually observable. A pX-change-responsive indicator reacts to bacterial or enzymatic change of the pX produced by a strain of bacteria, inside the cell, which is activated by the same temperatures which bring about the harmful process inside the f ood package . The property of bacteria to produce enzymes is well known, and such enzymatic action is visually indicated as a result of the change of the pH of the indicator.
The above ref erred indicator comprises a paper dyed or impregnated with a neutral or weakly ~1 ki~-, n.- solution of a suitable pH indicator such as brom cresol green The dyed paper is also coated or saturated with a nutrient culture medium and inoculated with an acid-forming bacteria such as one of the lactobacilli, and covered with a film of cellophane. The indicator is placed ~n a package, in a visible manner so that, when the temperature of the package becomes sufficiently high, the bacteria in the indicator will multiply sufficiently to produce enough lactic or acetic acid to transform the color of the indicator dye 2~ ~4~77 used from its blue i3lki~1 ;n~ color to its yellow acid color.
T~e strain of bacteria used and the quality of alkali or buffering salt employed in the uutrient must be carefully adjusted so that the time for the development of the acid color corresponds with the minimum time and temperature for undesirable development of any toxic bacteria in the packaged product. This indicator, therefore does not react upon the direct spoilage of the product but upon the room conditions where the product is stored. If, for any reasons, the temperature within the indicator containing cell differs from the temperature in the product mass the indicator reaction will not reflect the exact state of freshness of the product.
US Patent N3,067,015 discloses a spoilage indicator including a transparent window mounted in a wall of a cnnt~in~r, an indicator element positioned in said cnn~;~;n~or behind said window, a diffusion sheet being unidirectionally permeable to gases but impermeable to liquids and solias, said indicator element being sealed between said diffusion sheet and said window, said indicator element including a color changing chemical substance reactive to gases in said rr,n~linF~r, particularly C2 resulting from the spoilage of ~ood in the C--n~ilin~r, whereby said substance when spoilage occurs undergoes a color change observable through said window.
2~8~677 US Patent N4, 003, 709 discloses the detection of C2 gas in food r~ntA;nPrs by using a microporous plastic material to permit C02 gas to reach a C02 detector while preventing passage of liquids and solids. Thus, liquids and solids cannot penetrate the microporous plastic and the C02 detecting medium is not in cQntact with the food contents.
More particularly, such a detecting system provides a liquid impermeable pouch in which a liquid C02 detecting solution rr)ntA;n;ng calcium hydroxide is entrapped. The solution provides a visually observable change when the concentration of C02 rises substAnt;Al ly above a normal concentration. One side of the pouch is formed of a plastic material defining a window through which the ;n~ AtOr may be observed . Another portion of the pouch i8 f ormed of the gas permeable mi~LU~UULUUs plastic mAtPr;Al. The C,-ntA;nPr has an opening formed therein and the pouch is sealed into and over the opening so that the inert plastic material seals the opening and the microporous plastic portion is inside the ~-,,ntA;nPr in at least gaseous contact or communication with the food contents. Thus, as C02 gas is generated it will pass through the mi-:LU~ULUUS plastic and react with the calcium hydroxide to precipitate calcium carbonate. This causes the solution to change from clear to milky white, and this change is readily observable from outside the ,,ntA; nPr by looking through the window . When the gas is produced, the observer sees the color change 2 1 ~4~77 indicating that the food is probably spoiled and should not be consumed. Again, as far as the pouch material is -~hl e to liquids this indicator does not enter into direct contact with the packaged product and only reacts upon C02 generation.
The above indicating devices only react upon the presence of C02 gas generated upon undue bacterial multiplication but this is not an index of the acidity or alkalinity of the product. Since the acceptable pH level varies from product to product it would be very convenient to count on an indicator which may be adapted to indicate the prF~ t~rm;n~ pH level of a desired product to be monitored so as to keep a control thereon not only in connection wlth its quality to human conditions but also in connection to its organoleptic features and proteins quality .
The conv,~n~ n~l gas detecting devices, in addition, must be prevented from entering into contact with the liquid stored in the ~mt~;n~rs as far as the C02 detector may be affected by the solids or liquids. To this purpose the above disclosed C02 detectors are closed within a microporous membrane ; , e '~hl e to liquids but the C02 gas generated will pass through the membrane and react to the indicator to provide the visual indication. The membrane, however, must also be prevented from entering into contact with the stored liquid because af ter many 2 ~
times the liquid is in contact with the microporous membrane a covering film from the liquid may be deposited on the membrane and the microporous may be closed by the solidified or crystallized liquid particles and solids.
Wit~l the microporous membrane thus blocked no C02 gas will be able to pass through the membrane and enter the cell to react with the indicator. It would be therefore also convenient to have a spoilage detector which is not affected by the contact with the liquid contained in the package but the liquid is directly monitored in contact with the device.
BACKGRO~D OF l~IE INVENTION
1. Field of the Invention.
The present invention relates to detection and warning systems for controlling the state of freshness of food-stuffs and biological preparations which are stored in food cnnt~inPrs during some time oefore consumption, which food cnnt~;nPrs are preferably to be purchased by final consumers who are warned by the visual indication of any harmful bacterial process inside the food package. Most preferably, the invention refers to a spoilage visual indication device for use in milk-based-product cnnt~inprs~
Although the present invention will be disclosed in relation to the diary industry, the same is applicable to any field of the food industry where the state of freshness of stored products must be constantly monitored 2. Description of the Prior Art.
One of the most important parameters to be monItored during conservation of products is the acidity 2 1 8~677 level of the products. The suitable acidity will depend on the kind of product, thus a high acid level must be kept for pickles to avoid bacterial and fungi multiplication, while a low level must be controlled for a diary product to avoid spoilage under a high level of acidity.
Diary products, such as milk, butter, cream, yogurt and the like are extremely susceptible to decomposition and, therefore, control must be kept on the pX which must be, in the fresh state of milk, for example, of 6.5 to 6.6.
The pH level is affected, in diary products, by the undue bacterial multiplication, such as the lactobacilli, which causes the pE level to decrease whereby the product is excessively acid and below the acceptable conditions for human consumption. Generally, the freshness of the milk is controlled only during the bulk processing so that the quality thereof is high at the time the bottled milk or milk-based packaged product is delivered through the distribution system to customers. However, under the distribution conditions the products may be exposed, during long periods of time, to undue high temperatures which cause the bacteria to undergo an excessive multiplication whereby the milk becomes unsafe and spoiled well before the date marked generally in the cr~nt;3;nF~r for indicating an estimated freshness time period within which the product must be consumed. This period of time, marked in the package, is estimated by the manufacturer on the basis of 2 1 ~4677 t 3 tests and tables, but the changing weather conditions, the different geographical areas and freezing interruptions may alter the e~pected freshness life of the product, and that period is generally shorter than expected.
In some cases the organoleptic characteristics of the product depends on the solubility and dispersion capability of the proteins and/or polymers in the packaged product. The physicochemical characteristics of the lacteous proteins, such as the solubility based on the pH o zero-electric-charge point, are sensitive to the solution conditions, the pH, salt concentration, other proteins and carbohydrates, etc. When orrllrr;nri changes in the product due to the bacterial activity, proteins may lose their emulsifying and/or stabilizing functions for the product emulsion or dispersion, as well as the proteins may undergo a coagulation or precipitation whereby the organoleptic features are lost, although the product may be in acceptable human consumption conditions.
Under the above conditions, neither the retailer nor t~Le f inal consumer have the means to be aware that the product is under a minimum riuality for human consumption.
This is why many attempts have been made ln order to have a reliable way and systems for the cfmsllmPrs to deterrnine whether a diary product is in conditions to human consumption and in a high rluality state.
2 ~
U.S. Patent N 2,485,566 refers to a method and device for indicating spoilage, and more particularly refers to an indicator system for indicating harmful bacterial processes inside a food package, the system consisting of a transparent cell associated with the package, in which a bacterial process analogous to that occurring inside the package is visually observable. A pX-change-responsive indicator reacts to bacterial or enzymatic change of the pX produced by a strain of bacteria, inside the cell, which is activated by the same temperatures which bring about the harmful process inside the f ood package . The property of bacteria to produce enzymes is well known, and such enzymatic action is visually indicated as a result of the change of the pH of the indicator.
The above ref erred indicator comprises a paper dyed or impregnated with a neutral or weakly ~1 ki~-, n.- solution of a suitable pH indicator such as brom cresol green The dyed paper is also coated or saturated with a nutrient culture medium and inoculated with an acid-forming bacteria such as one of the lactobacilli, and covered with a film of cellophane. The indicator is placed ~n a package, in a visible manner so that, when the temperature of the package becomes sufficiently high, the bacteria in the indicator will multiply sufficiently to produce enough lactic or acetic acid to transform the color of the indicator dye 2~ ~4~77 used from its blue i3lki~1 ;n~ color to its yellow acid color.
T~e strain of bacteria used and the quality of alkali or buffering salt employed in the uutrient must be carefully adjusted so that the time for the development of the acid color corresponds with the minimum time and temperature for undesirable development of any toxic bacteria in the packaged product. This indicator, therefore does not react upon the direct spoilage of the product but upon the room conditions where the product is stored. If, for any reasons, the temperature within the indicator containing cell differs from the temperature in the product mass the indicator reaction will not reflect the exact state of freshness of the product.
US Patent N3,067,015 discloses a spoilage indicator including a transparent window mounted in a wall of a cnnt~in~r, an indicator element positioned in said cnn~;~;n~or behind said window, a diffusion sheet being unidirectionally permeable to gases but impermeable to liquids and solias, said indicator element being sealed between said diffusion sheet and said window, said indicator element including a color changing chemical substance reactive to gases in said rr,n~linF~r, particularly C2 resulting from the spoilage of ~ood in the C--n~ilin~r, whereby said substance when spoilage occurs undergoes a color change observable through said window.
2~8~677 US Patent N4, 003, 709 discloses the detection of C2 gas in food r~ntA;nPrs by using a microporous plastic material to permit C02 gas to reach a C02 detector while preventing passage of liquids and solids. Thus, liquids and solids cannot penetrate the microporous plastic and the C02 detecting medium is not in cQntact with the food contents.
More particularly, such a detecting system provides a liquid impermeable pouch in which a liquid C02 detecting solution rr)ntA;n;ng calcium hydroxide is entrapped. The solution provides a visually observable change when the concentration of C02 rises substAnt;Al ly above a normal concentration. One side of the pouch is formed of a plastic material defining a window through which the ;n~ AtOr may be observed . Another portion of the pouch i8 f ormed of the gas permeable mi~LU~UULUUs plastic mAtPr;Al. The C,-ntA;nPr has an opening formed therein and the pouch is sealed into and over the opening so that the inert plastic material seals the opening and the microporous plastic portion is inside the ~-,,ntA;nPr in at least gaseous contact or communication with the food contents. Thus, as C02 gas is generated it will pass through the mi-:LU~ULUUS plastic and react with the calcium hydroxide to precipitate calcium carbonate. This causes the solution to change from clear to milky white, and this change is readily observable from outside the ,,ntA; nPr by looking through the window . When the gas is produced, the observer sees the color change 2 1 ~4~77 indicating that the food is probably spoiled and should not be consumed. Again, as far as the pouch material is -~hl e to liquids this indicator does not enter into direct contact with the packaged product and only reacts upon C02 generation.
The above indicating devices only react upon the presence of C02 gas generated upon undue bacterial multiplication but this is not an index of the acidity or alkalinity of the product. Since the acceptable pH level varies from product to product it would be very convenient to count on an indicator which may be adapted to indicate the prF~ t~rm;n~ pH level of a desired product to be monitored so as to keep a control thereon not only in connection wlth its quality to human conditions but also in connection to its organoleptic features and proteins quality .
The conv,~n~ n~l gas detecting devices, in addition, must be prevented from entering into contact with the liquid stored in the ~mt~;n~rs as far as the C02 detector may be affected by the solids or liquids. To this purpose the above disclosed C02 detectors are closed within a microporous membrane ; , e '~hl e to liquids but the C02 gas generated will pass through the membrane and react to the indicator to provide the visual indication. The membrane, however, must also be prevented from entering into contact with the stored liquid because af ter many 2 ~
times the liquid is in contact with the microporous membrane a covering film from the liquid may be deposited on the membrane and the microporous may be closed by the solidified or crystallized liquid particles and solids.
Wit~l the microporous membrane thus blocked no C02 gas will be able to pass through the membrane and enter the cell to react with the indicator. It would be therefore also convenient to have a spoilage detector which is not affected by the contact with the liquid contained in the package but the liquid is directly monitored in contact with the device.
3. Summary o~ the Invention.
It is therefore one object of the present invention to provide a spoilage indicating device to be added to a f ood container in a way to provide a visual indication of bacterial spoilage of a food product stored in the ~nnt~inc~r, the device having a pH indicator in contact with the product through a semi-permeable membrane porous only to selected ion -nnt~inins r~ ,lnnF~nt~ of the product.
It is still another object of the present invention to provide a spoilage indicating device for a food nnnt~;nl~r for providing a visual ;nf9;~t;on of bacterial spoilage of a product comprising perishable food-stuffs and biological preparations stored in the cnnt~;n~r, the indicating device comprising a close cell in a wall of the g c~-nt~in--r, the cell comprising a transparent wall impermeable to liquids and peripherally sealed to a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a p~-responsive indicator being housed in the cell, between the transparent wall and the semi-permeable membrane, the membrane being in contact with the product, the indicator being visible ~rom outside the rr,nt~inPr through the transparent wall and being selectively separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator f rom being hidden by the product .
It is a further object of the invention to provide a combination of a food cr,nt~in~r and a spoilage indicating device, the r~nt~in~r comprising a transparent impermeable wall and the spoilage indicating device comprising a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a p~-responsive indicator housed between a portion of the transparent impermeable wall of the rrnti~inPr and the semi-permeable membrane, the semi-permeable membrane being poriph,orally sealed to said portion of the rnnt~inPr wall and in contact with the product, the indicator being visible from outside the crnt~in~r through the crlnt~in,-r transparent wall and being separated from the product by the semi-permeable membrane lo2~ 77 which allows the ions of the product to enter into contact with the indicator f or causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
It is still a further object of the invention to provide a combination of a food cnnt~1nPr and a spoilage indicating device for providing a visual indication of bacterial spoilage of a product, the cnnt~;nPr comprising an impermeable wall including an opening formed therein, the spoilage indicating device comprising a, close cell ~ormed by a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, and a transparent impermeable wall sealed over the opening so that the transparent impermeable wall of the cell seals the opening and is outside the cnn~ nl~rl and the semi-permeable membrane remains in contact with the product through the opening, a pH-responsive indicator within the cell, housed between the transparent impermeable wall and the semi-permeable membrane of the cell, the indicator being visible ~rom outside the cnn~;npr through the cell transparent wall and being separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact wlth the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
2 i 8~77 The above and other objects, features and advantages of this invention will be better understood when taken in connection with the acr~ ~nying drawings and description .
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention i8 illustrated by way of example in the following drawings wherein:
FIG. 1 is a cross-sectional view of a spoilage indicating device of the invention;
FIG. 2 is a cross-sectional view of another embodiment of the spoilage indicating device as mounted in a yogurt cup;
FIG. 3 is a- cross-sectional view of the spoilage indicating device o~ Figure 1, as mounted in a milk carton;
DESCRIPTION OF THE ~Kk~;~J EMBODI~6ENTS
Now ref erring in detail to the drawings, the spo~lage indicating device of the invention, shown in cross-section in Figure 1, is generally indicated by the reference number 1 in all the applications. The novel device includes an impermeable transparent wall 2 and a semi-permeable porous wall 4, both walls being peripherally sealed to each other so as to form a close cell. A pX-responsive ;n~ ;3tor is placed inside the cell, between the impermeable wall and the semi-permeable wall of the cell.
21 8~677 Wall 2 can be made from any kind of suitable impermeable transparent material, hard or flexible, depending on the package or rnn~;l; nt~r to which the device is to be added, but preferably the material is selected from polyethylene, polypropylene, polyester or glass. Nall 4 is made of a miUlu~uoLuus semi-permeable film which defines a selective passage to some elements of the product to be monitored. In the case of a diary product, such as milk, the semi-permeable film is porous only to water molecules of the milk and the hydrogen ions carried by the water molecules passing through the wall 4 as indicated by the arrows in Figure 1. Wall 4 has an outer side 40 in contact with the product under monitoring and an inner side 4i inside the cell. Membrane 4 can be made of a composite material, cellulose, polypropylene, polyester, polyamide, polysulphon, polytetrafluoroethylene, or ylass, all well known in the food industry, pharmaceutical industry, agrochemistry, chemistry, etc.
The pH-responsive indicator ~nnt~in~fl inside the cell formed by walls 2, 4 may comprise any suitable chemical compound or substance available in the art, such as an indicator dye, which can be applied onto inner face 4i of wall 4 or impregnated in a support strip 3, such as a paper or plastic strip. The indicator type and the quantity thereof will be selected on the basis of the pH levels to be indicated. The pH level at which the indicator will ~ 1 846~7 react will depend on the kind of product to be monitored, milk for example, has a pH level of 6.5 to 6.6 in fresh state. The pH level will reflect the state of the product in connection with its consumption conditions, acidity, physicochemical conditions, organoleptic characteristics, etc. The indicator will be retained either on the strip or on the semi-permeable wall in the way the chemicals are not transferred from the cell outside into the packaged product .
Any matter, liquid, solid or gas is prevented to pass into device 1 through wall 2, but indicator 3 is easily visible from outside the device so as its color change is visually observable by the consumer before purchasing a product or by the retailer so as the product under a low level of ~[uality is removed from the store. As explained above, only water molecules and hydrogen ions of the product to be monitored can pass through membrane 4 into co~tact with indicator 3, but other components of the product, such as polymers, colloids, proteins, starch, oil, fat particles, which can hide the color change of the indicator, are prevented from entering into the device and covering the; nt~; Catnr from visibility . Spoilage indicating device 1 may be inserted into a food cnnti:lin'~r in any way that the device is visible from outside the nnnt;~in~r and is preferably fixed to a wall of the cnnt~in~r as in the arrangements shown in Figures 2, 3.
2 i ~77 Figure 2 is a cross sectional view of a food container 5, a cup ~ntAi~ yogurt 7 for example, wherein the spoilage ;n~ Atin~ device is formed by an impermeable wall, consisting of a transparent impermeable wall 6 of the container, to which semi-permeable membrane 4 is sealed at peripheral edges 4e thereof to form a close cell. Indicator 3 is housed within the indicating device so as to be isolated from the envirorment and in selected contact with monitored product 7 through membrane 4. The color reaction of indicator 3 can be easily observed from outside the cup through transparent wall 6 of the cup. Indicator 3 is not to be hidden by product 7 as f ar as only water molecules and hydrogen ions can reach the same through the selected pass in the semi-permeable membrane.
Figure 3 shows an alternative application of the spoilage indicating device of the invention, in a C~-ntAin~r having non transparent walls 8. In this case the device of the invention could not be arranged like in the embodiment of Figure 2 as far as the indicator would not visible through non transparent walls 8. Under these circumstances a window 9 is provided in wall 8 of the container over which the spoilage indicating device of the invention is located .
~ ike in the other disclosed embodiments, device comprises an impermeable transparent wall 2, a semi-permeable microporous membrane 4 peri~hPrAlly sealed to 15 2 1 8~677 wall 2 and a pH-responsive indicator 3 retained between wall 2 and membrane 4. In order to keep the rrn~inf~r impermeable to liquids, particularly impermeable to liquid 7 stored in the cnnti~;n~rl impermeable film 2 is sealed over window 9, against wall 8 of the rr,n~;n,~r, In order to keep the indicator selectively exposed to contact with the liquid to be monitored, microporous membrane 4 is sealed and f ixed to wall 8, over window 9, so that only water molecules and ions of product 7 can pass through membrane 4 and enter into contact with indicator 3. Like in the other disclosed embodiments, product 7 may be any perishable product, preferably a diary product such as milk, yogurt, cream, etc.
Although only one indicator strip has been disclosed and illustrated it will be obvious for any skilled in the art that other forms may be applied ~or example, more than one strip may be arranged, each strip being impregnated o~ a p3~[ indicating chemical responsive to different pX levels. In this way different and progressive pH levels may be indicated to have a better parameter of the state o~ freshness of a stored product.
It is therefore one object of the present invention to provide a spoilage indicating device to be added to a f ood container in a way to provide a visual indication of bacterial spoilage of a food product stored in the ~nnt~inc~r, the device having a pH indicator in contact with the product through a semi-permeable membrane porous only to selected ion -nnt~inins r~ ,lnnF~nt~ of the product.
It is still another object of the present invention to provide a spoilage indicating device for a food nnnt~;nl~r for providing a visual ;nf9;~t;on of bacterial spoilage of a product comprising perishable food-stuffs and biological preparations stored in the cnnt~;n~r, the indicating device comprising a close cell in a wall of the g c~-nt~in--r, the cell comprising a transparent wall impermeable to liquids and peripherally sealed to a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a p~-responsive indicator being housed in the cell, between the transparent wall and the semi-permeable membrane, the membrane being in contact with the product, the indicator being visible ~rom outside the rr,nt~inPr through the transparent wall and being selectively separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator f rom being hidden by the product .
It is a further object of the invention to provide a combination of a food cr,nt~in~r and a spoilage indicating device, the r~nt~in~r comprising a transparent impermeable wall and the spoilage indicating device comprising a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a p~-responsive indicator housed between a portion of the transparent impermeable wall of the rrnti~inPr and the semi-permeable membrane, the semi-permeable membrane being poriph,orally sealed to said portion of the rnnt~inPr wall and in contact with the product, the indicator being visible from outside the crnt~in~r through the crlnt~in,-r transparent wall and being separated from the product by the semi-permeable membrane lo2~ 77 which allows the ions of the product to enter into contact with the indicator f or causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
It is still a further object of the invention to provide a combination of a food cnnt~1nPr and a spoilage indicating device for providing a visual indication of bacterial spoilage of a product, the cnnt~;nPr comprising an impermeable wall including an opening formed therein, the spoilage indicating device comprising a, close cell ~ormed by a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, and a transparent impermeable wall sealed over the opening so that the transparent impermeable wall of the cell seals the opening and is outside the cnn~ nl~rl and the semi-permeable membrane remains in contact with the product through the opening, a pH-responsive indicator within the cell, housed between the transparent impermeable wall and the semi-permeable membrane of the cell, the indicator being visible ~rom outside the cnn~;npr through the cell transparent wall and being separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact wlth the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
2 i 8~77 The above and other objects, features and advantages of this invention will be better understood when taken in connection with the acr~ ~nying drawings and description .
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention i8 illustrated by way of example in the following drawings wherein:
FIG. 1 is a cross-sectional view of a spoilage indicating device of the invention;
FIG. 2 is a cross-sectional view of another embodiment of the spoilage indicating device as mounted in a yogurt cup;
FIG. 3 is a- cross-sectional view of the spoilage indicating device o~ Figure 1, as mounted in a milk carton;
DESCRIPTION OF THE ~Kk~;~J EMBODI~6ENTS
Now ref erring in detail to the drawings, the spo~lage indicating device of the invention, shown in cross-section in Figure 1, is generally indicated by the reference number 1 in all the applications. The novel device includes an impermeable transparent wall 2 and a semi-permeable porous wall 4, both walls being peripherally sealed to each other so as to form a close cell. A pX-responsive ;n~ ;3tor is placed inside the cell, between the impermeable wall and the semi-permeable wall of the cell.
21 8~677 Wall 2 can be made from any kind of suitable impermeable transparent material, hard or flexible, depending on the package or rnn~;l; nt~r to which the device is to be added, but preferably the material is selected from polyethylene, polypropylene, polyester or glass. Nall 4 is made of a miUlu~uoLuus semi-permeable film which defines a selective passage to some elements of the product to be monitored. In the case of a diary product, such as milk, the semi-permeable film is porous only to water molecules of the milk and the hydrogen ions carried by the water molecules passing through the wall 4 as indicated by the arrows in Figure 1. Wall 4 has an outer side 40 in contact with the product under monitoring and an inner side 4i inside the cell. Membrane 4 can be made of a composite material, cellulose, polypropylene, polyester, polyamide, polysulphon, polytetrafluoroethylene, or ylass, all well known in the food industry, pharmaceutical industry, agrochemistry, chemistry, etc.
The pH-responsive indicator ~nnt~in~fl inside the cell formed by walls 2, 4 may comprise any suitable chemical compound or substance available in the art, such as an indicator dye, which can be applied onto inner face 4i of wall 4 or impregnated in a support strip 3, such as a paper or plastic strip. The indicator type and the quantity thereof will be selected on the basis of the pH levels to be indicated. The pH level at which the indicator will ~ 1 846~7 react will depend on the kind of product to be monitored, milk for example, has a pH level of 6.5 to 6.6 in fresh state. The pH level will reflect the state of the product in connection with its consumption conditions, acidity, physicochemical conditions, organoleptic characteristics, etc. The indicator will be retained either on the strip or on the semi-permeable wall in the way the chemicals are not transferred from the cell outside into the packaged product .
Any matter, liquid, solid or gas is prevented to pass into device 1 through wall 2, but indicator 3 is easily visible from outside the device so as its color change is visually observable by the consumer before purchasing a product or by the retailer so as the product under a low level of ~[uality is removed from the store. As explained above, only water molecules and hydrogen ions of the product to be monitored can pass through membrane 4 into co~tact with indicator 3, but other components of the product, such as polymers, colloids, proteins, starch, oil, fat particles, which can hide the color change of the indicator, are prevented from entering into the device and covering the; nt~; Catnr from visibility . Spoilage indicating device 1 may be inserted into a food cnnti:lin'~r in any way that the device is visible from outside the nnnt;~in~r and is preferably fixed to a wall of the cnnt~in~r as in the arrangements shown in Figures 2, 3.
2 i ~77 Figure 2 is a cross sectional view of a food container 5, a cup ~ntAi~ yogurt 7 for example, wherein the spoilage ;n~ Atin~ device is formed by an impermeable wall, consisting of a transparent impermeable wall 6 of the container, to which semi-permeable membrane 4 is sealed at peripheral edges 4e thereof to form a close cell. Indicator 3 is housed within the indicating device so as to be isolated from the envirorment and in selected contact with monitored product 7 through membrane 4. The color reaction of indicator 3 can be easily observed from outside the cup through transparent wall 6 of the cup. Indicator 3 is not to be hidden by product 7 as f ar as only water molecules and hydrogen ions can reach the same through the selected pass in the semi-permeable membrane.
Figure 3 shows an alternative application of the spoilage indicating device of the invention, in a C~-ntAin~r having non transparent walls 8. In this case the device of the invention could not be arranged like in the embodiment of Figure 2 as far as the indicator would not visible through non transparent walls 8. Under these circumstances a window 9 is provided in wall 8 of the container over which the spoilage indicating device of the invention is located .
~ ike in the other disclosed embodiments, device comprises an impermeable transparent wall 2, a semi-permeable microporous membrane 4 peri~hPrAlly sealed to 15 2 1 8~677 wall 2 and a pH-responsive indicator 3 retained between wall 2 and membrane 4. In order to keep the rrn~inf~r impermeable to liquids, particularly impermeable to liquid 7 stored in the cnnti~;n~rl impermeable film 2 is sealed over window 9, against wall 8 of the rr,n~;n,~r, In order to keep the indicator selectively exposed to contact with the liquid to be monitored, microporous membrane 4 is sealed and f ixed to wall 8, over window 9, so that only water molecules and ions of product 7 can pass through membrane 4 and enter into contact with indicator 3. Like in the other disclosed embodiments, product 7 may be any perishable product, preferably a diary product such as milk, yogurt, cream, etc.
Although only one indicator strip has been disclosed and illustrated it will be obvious for any skilled in the art that other forms may be applied ~or example, more than one strip may be arranged, each strip being impregnated o~ a p3~[ indicating chemical responsive to different pX levels. In this way different and progressive pH levels may be indicated to have a better parameter of the state o~ freshness of a stored product.
Claims (10)
1. A spoilage indicating device for a food container for providing a visual indication of bacterial spoilage of a product comprising perishable food-stuffs and biological preparations stored in the container, the indicating device comprising a close cell in a wall of the container, the cell comprising a transparent wall impermeable to liquids and peripherally sealed to a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a pH-responsive indicator being housed in the cell, between the transparent wall and the semi-permeable membrane, the membrane being in contact with the product, the indicator being visible from outside the container through the transparent wall and being selectively separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
2. A spoilage indicating device according to claim 1, wherein the pH-responsive indicator comprises a pH-responsive indicator dye placed in a paper strip, capable of changing its color upon contacting the ion-containing water of the product passing through the semi-permeable membrane.
3. A spoilage indicating device according to claim 1, wherein the semi-permeable membrane comprises a microporous film.
4. A spoilage indicating device according to claim 3, wherein the semi-permeable membrane is selected from cellulose composite, polytetrafluoroethylene, glass fibers, polypropylene, polyamide, polyester and polysulfon.
5. A spoilage indicating device according to claim 1, wherein said transparent impermeable wall comprises a material selected from polyethylene, polypropylene, polyester and glass.
6. A spoilage indicating device according to claim 1, wherein the transparent impermeable wall is a portion of said wall of the container.
7. A spoilage indicating device according to claim 5, wherein said wall of the container has an opening formed therein and the cell is sealed over the opening so that the transparent impermeable wall of the cell seals the opening and the semi-permeable membrane is in contact with the product.
8. A spoilage indicating device according to claim 1, wherein the pH-responsive indicator is a pH-responsive indicator dye placed in an inner side of the semi-permeable membrane.
9. A combination of a food container and a spoilage indicating device, the container comprising a transparent impermeable wall and the spoilage indicating device comprising:
a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a pH-responsive indicator housed between a portion of the transparent impermeable wall of the container and the semi-permeable membrane, the semi-permeable membrane being peripherally sealed to said portion of the container wall and in contact with the product, the indicator being visible from outside the container through the container transparent wall and being separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, a pH-responsive indicator housed between a portion of the transparent impermeable wall of the container and the semi-permeable membrane, the semi-permeable membrane being peripherally sealed to said portion of the container wall and in contact with the product, the indicator being visible from outside the container through the container transparent wall and being separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
10. A combination of a food container and a spoilage indicating device for providing a visual indication of bacterial spoilage of a product, the container comprising an impermeable wall including an opening formed therein, the spoilage indicating device comprising:
a close cell formed by a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, and a transparent impermeable wall sealed over the opening so that the transparent impermeable wall of the cell seals the opening and is placed outside the container, and the semi-permeable membrane remains in contact with the product through the opening, a pH-responsive indicator within the cell, housed between the transparent impermeable wall and the semi-permeable membrane of the cell, the indicator being visible from outside the container through the cell transparent wall and being separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
a close cell formed by a semi-permeable membrane porous only to water molecules and hydrogen ions of the product, and a transparent impermeable wall sealed over the opening so that the transparent impermeable wall of the cell seals the opening and is placed outside the container, and the semi-permeable membrane remains in contact with the product through the opening, a pH-responsive indicator within the cell, housed between the transparent impermeable wall and the semi-permeable membrane of the cell, the indicator being visible from outside the container through the cell transparent wall and being separated from the product by the semi-permeable membrane which allows the ions of the product to enter into contact with the indicator for causing the indicator to undergo a visible reaction but preventing the indicator from being hidden by the product.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AR333394 | 1995-09-04 | ||
| AR33339495 | 1995-09-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2184677A1 true CA2184677A1 (en) | 1997-03-05 |
Family
ID=3478966
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2184677 Abandoned CA2184677A1 (en) | 1995-09-04 | 1996-09-03 | Spoilage indicating device for food containers |
Country Status (2)
| Country | Link |
|---|---|
| BR (1) | BR9604209A (en) |
| CA (1) | CA2184677A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0951644A1 (en) * | 1996-11-05 | 1999-10-27 | Biodetect Corporation | Methods and devices for detecting spoilage in food products |
| US6428748B1 (en) | 2001-01-31 | 2002-08-06 | Grouptek, Inc. | Apparatus and method of monitoring an analyte |
| EP1552288A1 (en) * | 2002-06-15 | 2005-07-13 | Sang-Kyu Park | A freshness indicator of foodstuffs |
-
1996
- 1996-09-03 CA CA 2184677 patent/CA2184677A1/en not_active Abandoned
- 1996-09-04 BR BR9604209A patent/BR9604209A/en not_active Application Discontinuation
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0951644A1 (en) * | 1996-11-05 | 1999-10-27 | Biodetect Corporation | Methods and devices for detecting spoilage in food products |
| EP0951644A4 (en) * | 1996-11-05 | 2002-08-21 | Group Tek Inc | Methods and devices for detecting spoilage in food products |
| US6428748B1 (en) | 2001-01-31 | 2002-08-06 | Grouptek, Inc. | Apparatus and method of monitoring an analyte |
| US6576474B2 (en) | 2001-01-31 | 2003-06-10 | Grouptek, Inc. | Apparatus and method of monitoring an analyte |
| EP1552288A1 (en) * | 2002-06-15 | 2005-07-13 | Sang-Kyu Park | A freshness indicator of foodstuffs |
| EP1552288A4 (en) * | 2002-06-15 | 2006-09-27 | Sang-Kyu Park | A freshness indicator of foodstuffs |
Also Published As
| Publication number | Publication date |
|---|---|
| BR9604209A (en) | 1998-05-26 |
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |
Effective date: 20000905 |