CA2012299A1 - Method and device for indicating deterioration of organoleptic properties of refrigerated food - Google Patents
Method and device for indicating deterioration of organoleptic properties of refrigerated foodInfo
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- CA2012299A1 CA2012299A1 CA 2012299 CA2012299A CA2012299A1 CA 2012299 A1 CA2012299 A1 CA 2012299A1 CA 2012299 CA2012299 CA 2012299 CA 2012299 A CA2012299 A CA 2012299A CA 2012299 A1 CA2012299 A1 CA 2012299A1
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Abstract
ABSTRACT OF THE INVENTION
A time-temperature indicator for indicating the exces-sive exposure of refrigerated food products to elevated tem-peratures, thereby indicating the deterioration of the organoleptic qualities of the food product comprising a bio-logical growth medium, an anaerobic indicator culture in the medium which modifies the medium at a rate directly propor-tional to temperature, and a means for indicating the extent of modification of the medium. Exposure to elevated temper-atures for excessive periods results in the color change in the medium warning of unacceptable food quality.
A time-temperature indicator for indicating the exces-sive exposure of refrigerated food products to elevated tem-peratures, thereby indicating the deterioration of the organoleptic qualities of the food product comprising a bio-logical growth medium, an anaerobic indicator culture in the medium which modifies the medium at a rate directly propor-tional to temperature, and a means for indicating the extent of modification of the medium. Exposure to elevated temper-atures for excessive periods results in the color change in the medium warning of unacceptable food quality.
Description
~99 METHOD AND DEVICE FOR INDICATING
DETERIORATION OF ORGANOLEPTIC PROPF.RTIES
OF REFRIGERATED FOOD
DISCLOSURE
The present invention relates to the art of packaging, stors~e and distribution of refrigera~ed food and more par~
ticularly to the method and device for indicating deteriora-tion of the organoleptic quality of refri~ersted food.
INCORPORATION BY REFERENCE
For the purpose of back~round information, the follow-in~ United States Patents are incorporated by reference herein: Clark 2,485,566; Brockmann 2,950,202; Golber 3,206,317; Khsttsb 3,966,414; Tornmarck 3,977,945; Patel 4,228,126. These patent6 relste to concepts for fsbrication and use of time-temperature indicatinK devices designed to .. ..
monitor the thermal exposure of food products and serve as indicators of food deterioration. These pstents constitute a portion of the patented prior art for background of the present invention 80 that details known in the art need not ~ p be repeated to understand the present invention and its nov-elty and sub6tantial contribution to the field of indicating the or~,anoleptic quality of refri~erated foods. ;~
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BACKGROUND
The present invention i6 particularly applicable for ~ ~ .
indicatin~ deteriora~lon of the organoleptic qualities of refrip,erated food as ~ result of extended stora~e or expo-sure to elevsted temperature6 conducive to such deteriora-tion. Food products almost universslly must work their way through a complex distribution chain to pass from producer to consumer. Ideally, the customer will always receive a "farm-fresh" product, but potentisl mi~adventures can cause deleterious effect~ to the quality of a food product. As a .. . ..
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Z0~2299 result, without expensive labor, intensive intervention and record r.laintenance, food quality may be co~promised, yet the problem reDlains undetected un~il the product is ultimately in the hands of the consu~ler. Not only does the consumer receive a ~ubstandard product, but also the expen~e and ef-forts of the producer to deliver a high quslity food item adds substantislly to the food cost. This problem is espe-cially acute with refrigerated foods which are especially susceptible to temperature fluctuation~ and the duration of storage. These susceptibilitie~ hsve become particularly significant in recent years with increa6ing cu6tomer demand for refrigerated, prepared foods. The growinR 60phi6tica-tion of the customer ha~ created an increasing emphasis on the appearsnce and quality of refrigerated foods cont~ining the like of ssuces, cheeses and meatfi, and such foods mu~t be delivered to the customer without noticeable loss of tsæte, texture or appearance. The traditional approach to in6uring the quality of refri~erated food has been to use preservatives which, although they may increa~e safety, do not necessarily maintain, or may even detract from the tex-ture, appearance and taste of the food. Also, the public has increaslngly demanded fresh and "natursl" food6 without preservative6. This i6 especially true of the rapidly ~row-in~ hi~h end of the market which caters to the more sophi6-ticated customer. This customer also require6 reassurancethat the refrigerated food purchased in the 6upermarket has had it~ quality and safety maintainèd throughout distribu-tion snd sales. The manufacturer of quality food products which require refrigeration therefore face6 a dilemma of how to deliver a quality product through a complex system over which~he may have little control as well as how to reassure the customer that the food quality has been maintained throughout that distribution and sales 6ystem. In these situations, it is not possible to merely apply a date beyond which the food product may be unacceptable since loss of ' lZ299 refrigeration for a time may chan~e the quality of the food product.
To alleviate this problem, a number of devices have been developed to monitor temperature expo~ure. Typically, such a dev;ce is packaged wit~" or attached to a food prod-uct after production. This device travels with the food product throu~h the distribution chain to the customer.
While in transit, the device monitors the thermal environ-ment to which it is exposed. Upon exposure to thermal con-ditions of a preselected magnitude, the device undergoes avisible change thereby indica~in~ the unacceptability of the associated food product. The more sophisticated of the de~
vices are time-temperature indicators which integrate tem~
perature exposure over time. The relationship between inte-grated temperature exposure and indicator response is depen-dent on the actual physical or chemical phenomenon being u~ed to measure time temperature exposure. These indicators have taken a variety o~ forms using variou~ principles for time and temperature integration. The phenomena which have bçen used include polymerization, enzyme hydroly6is, and chemicsl decomposition. These systems, although having some advantsges, suffer from the inability to trsck what i~ U6U-ally an organism-induced deterioration of the food product using a systeol with a different order of kinetics an~ tom-perature response. Also, chemical snd physical re~ponsesystems exhibit at best a linear indicator relation to time whereas the deterioration itself accelerates exponentially.
AB a result, these devices measure acceptability limits with le~s thsn desired accuracy and the length of the transition times for the indicator switching from an acceptable to a non-acceptable response becomes confusing to the con6umer.
rrior work has reco~,nized that an organism or indicator culture sctivated, integrsting indicator might be used to indicate food spoilage. The use of an indicator culture in a time-temperature indicator also satisfies the requirement , . :. : ~
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that the indicator ~witch from an acceptable to non-accept-able response rapidly. Organism growth increa6es expon~n-tially with ti~le, and an indicator based on the growth will have a shortened transition time reflecting thi~ accclera~-ing change.
Procedures for using indicator culture~ to trsck thespoilage in food have heretofore been proposed. These sys-tems have typically been based on a culture medium compris-ing an acid-producin~, indicator culture, a medium for growth and an acid base indicator. This culture medium is typical-ly enclosed in a transparent container and stored with the food product to be monitored. Subsequent growth of the or-ganism results in acid production causing the acid-base in-dicator to change color. A color change signifies that the product has been subjected to conditions which would induce spoilage.
The biological time-temperature indicator described in ~olber 3,206,317 employs multiple organisms obtained from a sample of the food product itself for the indicator culture medium. The results obtained from such a system can be very complex. Depending on the numbers snd types of orgsnisms present, the scidity of the system can either decroase or increase. Also, different organisms will flourish at dif~
erent temperatures, and variations in temperature csn cause complex relative population changes resulting in a system in which the final pH might be unrelated to organism growth or product deterioration. Single organism systems suggested by Clark 2,485,566 and Brockmann 2,950,202 do not prevent this problem. The time-temperature indicators described in these patents are designed to indicate food spoilage and utilize single types of bacteria which flourish within the desired temperature range. Although sn improvement over other sys-tems such a criterion would not necessarily provide a bacte-rium which would track the organism growth in the food prod-uct, and give sn accurate indication of food quality ,, ~, ' .
20~2299 deterioration. These time-temperature indicators also suf-fer froD~ numerous un301ved practical problems, which pre~
clude their commercial u6e. In a practical time-temperature indicator, the indicator culture must be encapsulated in a limitecl environment precluding its use or production of ga~-eou~ material6. Sufficient gases cannot be dissolved in the medium to sustain the growth of the indicator culture and appreciable production of gas by the indicator culture may either modify its sctivity or bur6t the container. In actu-al u6e, indicator cultures are subjected to unexpectedly lowtemperatures which cause injuries snd population changes which 6ub6tsntially alter the re6ponee and render the re~
sults unreliable. Containment systems are sub~ected to physical abuse snd breakage will re6ult in 1086 of customer confidence.
In summary, even wi~h various attempts to develop time-temperature indicator~, there has been no practical indica~
tor capable of tracking biologically induced deterioration in the organoleptic propertie~ of refrigerated food prod-uct6.
SUMMARY OF THE INVENTION
The disadvantage6 and deficiencie~ of prior attempts tomonitor the environmental conditions to which refrigerated food is exposed during storsge and di6tribution have been overcome by the present invention 80 that the consumer can readily determine whether a refrigerated food product has been 6ub6tantially mi6handled, exposing it to prolonged 6torage or elevated temperature6 re~ulting in a deteriora-tion of organoleptic propertie~ of the food item.
! In accordance with 8 general aspect of the present in-vention, there i~ provided a time-temperature indicator ~7herein the culture medium comprise6 a biological growth medium, an anaerobic indicator culture which modifies the growth medium at a rate directly proportional to the ,: . . , . - .
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temperature of the culture medium, and an acid base indica-tor. The culture medium is confined in a contsiner having a tranfiparent window whereby the color imparted by the acid-bafie indicator to the culture medium can be observed. In i~s operative form the time-temperature indicator is pack-aged with the food product at the conclusion of production, at which time the product and its package are chilled before being sent into the distribution system. While in the re-frigersted storage system, the indicator culture maintains a low level of activity, during which it continually excretes small amounts of acid. If the package is maintained in the refrigerated condition, the indicator culture will continu- ~ -ally deplete the nutrients provided in the medium ~hile at the same time causing the medium to con~inuslly increase in acidity. Once the mediu~ has reached a certain ~cidity, the acid base indicator will change color. Such A color chan~e indicates the product has been ~tored for an excessive peri-od of time and no longer meets the producers standards of quality. In the event that the food product and its includ-cd time-temperature indicator enter the distribution chsin and are exposed to unexpectedly high temperatures, the growth rate of the indicator culture increases, thus rapidly increasing the ~cidity of the medium. Paralleling thi~ in-cresse in acidity will be the increased rate of deteriora-tion of the organoleptic quslity of the food product. At ashortened interval the acid in the medium will build up to a level that will change the color of the acid base indicator.
Again, by inspecting the color of the time-temperature indi-cator, the consumer can determine that the food product does not meet the manufacturer's quality standards, which in this case, was caused by exposure to elevated temperatures as opposod to extended storflge. In either case the consumer can verify that he has purchased a high quality product and this as6urance leads to con6umer confidence in the product itself. Alfio, the retailer can be reassured of not having -6- `
2012; 99 ' '' received an old or mishandled product. This ability to check previous handlin~ along the distribution chain will insure improved handlinp, resul~inR in a hi~her quality food product being delivered to the customer. ~ ~-5In accordance wi~h another aspect of the invention, the indicator culture is a single type, naturally occurring, non-pathogenic bacterium capable of a low level of growth at 3-5 C, the temperature at which refrigerated food i6 stored. The indicator culture is obtained by isolation from l0naturally occurring organisms found in food products growing ;
at 3-5 C and thereby should track ~he organism induced de-terioration of the organoleptic qualities of the food.
In accordance with another sspect of the invention, the indicator culture is anaerobic showing the presence of ni-15trate reductaes whereby it can utilize a soluble nitrate as a terminal electron acceptor. Oxygen is therefore not re-quired by the indicator culture allowing it to be encapsu-lated as required for a practical time-temperature indica-tor.
~. . -In accordance with another feature of the invention, the medium contains a nutrient and a nitrate in such propor-tion~ that the indicator culture depletes both simultaneous~
ly and wherein the nutrient is preferably ~lucose and the nitrate is preferably potassium nitrate, they are included in the medium in a 4 to 3 ratio by weight, thereby minimiz- ~- -ing the formation of alkaline reversion products upon deple- :
tion.
In accordance with another aspect of the invention, the medium contains sucrose and Tween 80, materials which the 30organism cannot utilize as nutrients, but serve as ~ '' cryoprotectant~ to protect the indicator culture from injury ~ ;
upon its beinp, subjected to unexpectedly low temperatures.
In accordance with another aspect of the invention, the -~
indicator culture is deactivatcd ~y chillinp, the time-tem-35perature indicator from 5 C to -20 C at a rate of 14 per ;~t,~'''!'" ' .,.';, ', ."""~
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~ -hour. This chilling rate in~ures that the indicator culture will ~uffer minimsl injury during deac~ivation.
In accordance with another a~pect of the invention, the culture medium i~ contained in a pliable packet which is enclosed within a ri~,id container, the rigid container al60 enclosing an indicator culture deactivator externsl to the packet. In 6uch case that the indicator culture escape6 from the packet, it would be deactivated, thu6 in~piring con6umer confidence in the system.
The primary object of the prefient invention i~ to pro~
vide a time-temperature indicator which is packaged with a food product and indicates when exces~ive exposure has caused unacceptable deterioration in the or~anoleptic quali-ties of the food product.
Another object of the present invention i6 to provide a time-temperature indicator in which the indicator culture ncither produces nor consume~ ~aseous materials thereby be-in~, sble to thrive in an enclosed en~ironment.
Another object of the invention i~ to provide a time-tempcrature indicator, as defined above, in which the indi-cstor culture can be frozen without 6evere injury or modifi-cation to the indicator culture populatic,n.
Another object of the present invention i8 providing a time-temperature indicator as defined above which eliminates the po~sibility of spuriou~ re6ults caused by the formation of alkaline reversion product~.
Another object of the present invention i6 providing a method whereby a timc-temperature indicatc!r as defined abovc can be deactivated for extended periods uithout significant injury to or modifications of the indicator culture.
~ Another object of the present inYention i8 providing a timc-te~perature indicatc-r a6 deined above which can resist shock and mechanical abrafiion.
ZOlZ299 These and other objects and advantages will become 8p-parent from the following description taken together with the accompanying drawings described in the next section.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing objects and others will, in part, be ap-parent and, in part, pointed out more fully hereafter in conjunction with the description of the preferred embodiment of the invention illus~rated by the accompanying drawin~,~ in which:
FIGURE 1 is a perspective view of a food container in-corporating a time-temperature indicator.
FIGURE 2 is an enlarged cross-sectional view taken gen-erally along lines 2-2 of FIGURE 2.
FIGURE 3 is a cro~s-sectional view on an enlarged scale taken along lines 3-3 of FIGURE 2.
FIGURE 4 is an exploded per~pective view of the compo-nents of a time-temperature indicator.
FIGURE 5 is a perspective view of a modiication of the preferred embodiment illustrated in FIGURES 1 and 2 wherein the food product is contained in a shallow tray, the tray, ~ -time-temperature indicator and food product being wrapped together in a plastic wrap. -~
FIGURE 6 is 8 psrtial crosfi-sectional view tsken acro6s lines 6-6 of FIGURE 5. ~---~
FIGURE 7 is a cross-sectional view of a modification of the preferred embodiment illustrated in FIGURE 2 wherein the ; `~
food product and time-temperature indicator are packaged together in a paperboard container without separate contsin-ment of the food product.
FIGURE 8 is a cross-sectional view of a modiication of --.. .
the preferred embodiment illustrated in FIGURE 2 wherein the time-temperature indicstor and the food product are wrapped together in plastic wrap within a paperboard container.
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FIGURE 9 i~ a cross-sectional view of a modification of the preferred e~bocliment illustrated in FIGURE 3 in which the culture ~edium ifi contained ~olely within a ri~id plas-tic container.
FIGURE 10 ig ~ parti~l cros~-~ectionsl view of the pre-ferred embodi~ent illus~rsted in FIGURE 3 wherein the cul-ture medium is encased in a pliable plastic packet within a rigid outer 6keleton.
FIGURE 11 is a partisl cross-sectional view of a modi-fication of the preferred embodiment illustrated in FIGURE 3 wherein the culture medium is enca~ed in a pliable packet with 8 rigid back, FIGURE 12 is a partial cros6-sectional view of the cul-ture medium enca~ed in a pliable plastic packet 6ealed at the peripheries - -FIGURE 13 is a top view of alternate ~hapes of the time-temperature indicator FIGURE 14 i~ a time-pH graph illu6trating the increa~e in acidity of a stirred culture medium usin~, buffered and non-buffered media PREFERRED E~RODInENT
Referrin~ to the drawing~ wherein the 6howin~ are for the purpose of illustra~ing the preferred e~bodiment of the invention only snd not for the purpose of limiting 6ame, FIGURES 1 and 2 illu~trate a food package A for the ship-ping, di6tribution, and cli~play of a refrigerated food prod-uct B. The pack~ge compri~es two generally flat parallel panels, the bottom panel 10 for 6upporting the food product B and the top or upper panel 12 forming a cover or lid.
The~e two panels sre interconnected by a pair of parallel lateral support wall6 14, 16. The packa~,e i6 sealed at each end 18, 20 by a pair of overlapping flap6 22, 24. Flap 22 extend6 from the upper panel 12 and flap 24 extend6 from the lower panel 10 The container is con~tructed of rigid paperbosrd. Im-prints 26 of desi~,ns and label6 are located on the outer surface of the container. The top of the container includes an opening 28 through the paperboard. Surrounding the open-inp, 28 is the imprint or inclicia rinp, 30 containin~ a color representing the standard to which quality indicator C is compared to determine the continued quality of food product B. Within the container, the food article B i~ enclosed in an air impermeable plastic wrspper or bag 36 which can be evacuated or filled with an inert gas. The environmental integrity within the wrapper is maintained by seals 3R at either end.
Affixed to the interior surface 34 of the csrdboard container, in such a way that it completely covers the open~
in8 28, i6 a time-temperature indicator C. The dimensions of the time-temperature indicator C are larger thsn those of the openin~ providing overlappin~ portions of the cardboard container 32 which overlap portions 58 of the time-tempera-ture indicator C. These overlapping portions are joined by an adhesive 40 securing the time-tempera~ure indicator C
within container A. The time-temperature indicator is com-prised of a rigid outer container 50, which encases a pli-able plastic packet 70 which in turn contains the culture ~ledium lO0. The outer container 50 comprises an upper face or window 52, a bottom portion 54, and sides 56. Prefera~
bly, the bottom portion 54 and the sides 56 are a single unit, the sides terminatin8 in upper faces 60 which are flat. The window 52 overlaps and is secured to the upper faces 60 forming an internal cavity 68 within the container.
The container is constructed of a high impact plastic, the bottom portion 54 and sides 56 being opaque, white or light in color, and the window 52 being transpsrent. The cavity 68 of the container contains a tough pliable plastic packet 70 having a flat ront portion 72 generally parallel to the back portions, 74 which are sealed together at the juncture . . .
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~ 2 0 ~ 299 of the front periphery 82 with the back periphery 84 formin~
a leak-proof container. The size of the packet is such that it does not fill the cavity 68 thereby leaving an intersti-tial space 76. The interstitial space 76 is filled with an indicator culture deactivator. Enclosed within the packet is the culture medium 100, comprisin~ sn indicator culture, the growth medium, and the acid-ba6e indicator. The indica-tor culture is a non-pathogenic, naturally occurring organ-ism, isolated from food product deterioration at 4_5V C, producing acid at these temperatures, the rate of acid pro-duction increa~ing with increasing temperature. The organ-ism flourishes in the 4-5 C temperature range thereby msin-taining a low level of acid production which is sufficient to increase the acidity of the medium by one pH unit in 30 hours. The indica~or culture shows the presence of nitrate reductaes so that nitrate can serve as the terminal electron acceptor snd thus the indicator culture can grow anaerobically with little gas production. The preferred indicator culture is from the pseudomonas fluorescens group, designated as the third pseudo~lonad, second fluorescent type isolated from refrigerated food products, thu~ assigned the designation P3f2 for simplicity. A subculture of this strain can be obtained from the permanent collection of the Northern Marketing and Nutrient Research Divi~ion, Agricul~
tural Service, U.S. nepartment of Agriculture, Peoria, Illi-nois.
Tbe acid-base indicator has specific characteristic~
which are compatible with the indicator culture. The acid-base indicator is not metnbolized by the indicator culture nor doe6 it affect the gro~th oP the indicator culture. The preferred indicator changes color near the midpoint of the working pH range of the indicator culture. Preferably, the acid base indicator change6 color at least one p~l unit below the initial pH of the sy6tem, and at least one pH unlt above a point where the indicator culture ic still visble and : ~ . - .
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relatively unaffected by the increased acid concentrstion in the medium. An~ther criterion in the preferred sy~tem i~
that the acid-base indicator under~,o a definite color chan~,e which is readily perceivable to the untrained ob~erver.
This color chan~,e should also take place in as short a tran-sition ran~e as possible in order to preclude the customer having to guess whether the indicator is sctually one color or the other. In the preferred embodiment, brom thymol blue is used as the acid base indicator.
The gro~th medium comprises a mixture of a nutrient, a nitrogen source, and an electron acceptor as well as addi-tives to enhance the growth and stability of the ~ndicator culture. In the preferred embodiment, glucose is used as the nutrient. Glucose is effectively utilized by the indi-cator culture and also minimizes the formation of gaseous product~ which are more probsble with more complex nutri-cnts. Potassium nitrate i6 used as 8 terminal electron ac-cep.or. Three percent nitrate in the pre~ence of unlimited glucose provides the best indicator culture growth. In the preferred embodiment, three percent nitrate is used with four percent glucose. With this ratio of components, the or~ani~m completely depletes both components at the same time. The indicator culture can produce alkaline products late in it~ growtll phu6e presumably due to 6econdary metabo-lism product~. The adjustment of the concentrations of glu~cose and nitrate to effect simultsneou6 depletion of those materials is designed to minimize the problem with alkaline rever~ion. Since ga6eous oxygen can compete wi~h nitrate a~
a terminal electron acceptor the culture medium mu6t be deoxy~,enated to prevent erratic re6ults. The nitro~,en 60urce can be any of a variety of compound~ well known to those versed in the art. The preferred embodiment use6 tryptone, a pancrestic digest of ca~ein, which i6 manufac-tured by Difco Laboratories, Inc. of Detroit, Michi~an.
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201;~299 In addition to the required components of the medium, various additivcs are included to enhance the repeatability of the syste~l and also to effect modifications in re6pon~e time. Additives incorporated in~o the medium include a vi-tamin and minersl source, a cryoprotectant and a surfactant.In the preferred embocliment, vitamin and mineral require-ments are supplied by yeast extract which is a wster ~oluble portion of autolyzed yeast snd is a product of Difco Labora-torie6, Detroit, Michigan. A cryoprotectant is included in the medium to prevent da~age to the indicator culture fro~
exposure the low temperatures. The cryoprotectant cannot injure or be metabolized by the indicator culture. In the preferred embodiment, sucrose is used as a cryoprotectant.
At the low temperature8 under which the time-temperature indicator is uæed, movement of chemicals through the cell walls of the indicator culture is impeded. A ~urfactant i~
added to the medium to allow easier movement of nutrient~
and by-products in and out of the cell. A surfactant which doe6 not inhibit indicator culture growtb must be u6ed. In the preferred embodiment, Tween 80 is used. In addition to allowing easier movement through the cell wall, the Tween 80 ~ -also contributes the cryoprotection of the indicator culture in a frozen state. Tween 80 also interacts with the bron thymol blue indicator by shiftin8 the absorption maximum toward longer wavelengths. At sn initial pH of 7.6 where brom thymol blue would exhibit a blue color, the presence of Tween 80 cau~es the indicator to be green. As a result, st low pH values the yellow color of brom thymol blue is more intense and the indicator exhibits a sharper transition point. Thi~ desirable artefact of the Tween 80 reduces the pro~pect of customer confusion as to whether there has been a significant change in the indicator color.
In order to modiy the re~ponse time of the lndicator, a buffer i6 included in the medium. As with other special 35 purpose additives, the buffer cannot affec~ or be affected ~ -,'' ' '.;, :. ,,. :' '.. ~.':' ,: ~ , , :
Z0~2299 by the indicator culture. The pKa of the buffer 6hould be about 1 pH unit above the pH required for color change of the indicator. In the preferred embodiment, (4-(2-hydroxyetltyl)-l-piperazine ethanesulfonic acid lHEPES]
is u~ed. - , In the preferred embodiment, a culture medium which ~ -will indicate a four day shelf life at 5 C i~ formulated a~
follows: In 900 ml distilled water i~ dis~olved 0.100 gram brom thymol blue, 1.0 ml Tween 80, 2.500 grams bacto yeast -extract, 30.000 grams potassium nitrste, 40.000 grams glu- ~ -cose, 120.000 grams sucrose. The ~olution i sterilized so as to avoid any volume loss. At room temperature, lO0 ml of a pre-~terilized 5% ~tock solution of bacto tryptone is add- ~ -ed to 900 ml of base medium snd the two mixed. Solid HEPES s buffer is added to the desired concentration; preferred to be 1.500 grams for 4 day self lift inclication. The pH i~
adjusted to 7.60. The mixture i~ heated just to boilin~ to drive off all oxygen and thcn cooled to 5 C under snaerobic condition~. The medium i 6 then inoculated with 1% stock -~culture (3 day, 5 C growth in the same medium without llEPES
buffer).
The resulting culture medium is enclo6ed in a container using standard technique~ and the completed time-temperature indicator is chilled 80 as to temporarily deactivate the culture D)edium. Deactivation mu~t be accomplished BO a~ to -~
minimize damage to the indicator culture. Deactivation is effected by chillin~> from a tempera~ure of +5 C to -20 C
at a rate of 14 per hour. The time~tcmperature indicator can then be ~ored until ready for u~e.
Activation of tl-e time-temperature indicator i8 effect-ed by warming to the temperature at which it will be used. -~
The preferred method of activation is to remove the time-temperature indicator from frozen storage and immedistely packaging it with the food product as it is being produced. ~ -- ~ --15- ~
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An alternate cul~ure medium i8 formulated ai6i followe:
In 800 ml distilled wster i5'i dissolved 30.0 grams l)otassium nitrate, 2.5 grams yeast extract, 1~0 ml Tween 80, and 0.1 gram of brom thymol ~lue. The solution iEi boiled 1-2 min-utes to achieve disEiolution. In one liter of di6tilled ua-ter, 400 gr~ms of gluco~ is di6~01ved. In one liter of diitilled water, 50 grams of tryptone ic di~solved. The three solutions are sterilized, cooled to 20 C and asceptically combined usin~ on a volume basis 80% of solu-tion 1, 10% of ~olution 2 and 10% of solution 3. To the combined solutic~ns, 0.4Z agar is sdded and the acidity ad-justed to a p~i~i of 7.60. The resulting solution is heated to boiling to dissolve the agar and drive off dissolved oxygen, after which it is cooled to 40 C and inoculated with a 3-4 day old 1% stock culture of P3f2 grown under anaerobic con-ditions at 4-5 C. The inoculated medium is cooled to 4-5 C and overlaid with sterile mineral oil to prevent sbsorp-tion of oxygen. Stock cultures are prepared using the same media and conditions as above without the u6e of agflr.
FIGURE 14 shows the pH time changes in a two culture media. Curve A reE~resents the pHltime curve of a typical unbuffered culture medium. After incubation of the culture medium for 30 hours at 5 C, the tran6ition range of the indicator is reachcd in which the color changes from green to yellow over a 5.5 hour period. ~ifter the color change, the acidity continued to increase to a pH of 4.80. Curve B
represents the pH/time chan&e under similar conditions wherein 0.5% HEPES buffer was added. The pHi drop is less rapid and the transition range of the indicator i6 reached after 58 hours. The color change froDI green to yellow takes place over 71 5 hour~i, after which the acidity of the isystem continued to increase. The experiments providing the data for FIGURE 14 utilized a sanitized pH probe which was sub~
merged into hot media overlaid with oil and cooled to 5 C
and inoculated with 1% P3f2, 3 day, 5 C, anserobic culture.
DETERIORATION OF ORGANOLEPTIC PROPF.RTIES
OF REFRIGERATED FOOD
DISCLOSURE
The present invention relates to the art of packaging, stors~e and distribution of refrigera~ed food and more par~
ticularly to the method and device for indicating deteriora-tion of the organoleptic quality of refri~ersted food.
INCORPORATION BY REFERENCE
For the purpose of back~round information, the follow-in~ United States Patents are incorporated by reference herein: Clark 2,485,566; Brockmann 2,950,202; Golber 3,206,317; Khsttsb 3,966,414; Tornmarck 3,977,945; Patel 4,228,126. These patent6 relste to concepts for fsbrication and use of time-temperature indicatinK devices designed to .. ..
monitor the thermal exposure of food products and serve as indicators of food deterioration. These pstents constitute a portion of the patented prior art for background of the present invention 80 that details known in the art need not ~ p be repeated to understand the present invention and its nov-elty and sub6tantial contribution to the field of indicating the or~,anoleptic quality of refri~erated foods. ;~
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BACKGROUND
The present invention i6 particularly applicable for ~ ~ .
indicatin~ deteriora~lon of the organoleptic qualities of refrip,erated food as ~ result of extended stora~e or expo-sure to elevsted temperature6 conducive to such deteriora-tion. Food products almost universslly must work their way through a complex distribution chain to pass from producer to consumer. Ideally, the customer will always receive a "farm-fresh" product, but potentisl mi~adventures can cause deleterious effect~ to the quality of a food product. As a .. . ..
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Z0~2299 result, without expensive labor, intensive intervention and record r.laintenance, food quality may be co~promised, yet the problem reDlains undetected un~il the product is ultimately in the hands of the consu~ler. Not only does the consumer receive a ~ubstandard product, but also the expen~e and ef-forts of the producer to deliver a high quslity food item adds substantislly to the food cost. This problem is espe-cially acute with refrigerated foods which are especially susceptible to temperature fluctuation~ and the duration of storage. These susceptibilitie~ hsve become particularly significant in recent years with increa6ing cu6tomer demand for refrigerated, prepared foods. The growinR 60phi6tica-tion of the customer ha~ created an increasing emphasis on the appearsnce and quality of refrigerated foods cont~ining the like of ssuces, cheeses and meatfi, and such foods mu~t be delivered to the customer without noticeable loss of tsæte, texture or appearance. The traditional approach to in6uring the quality of refri~erated food has been to use preservatives which, although they may increa~e safety, do not necessarily maintain, or may even detract from the tex-ture, appearance and taste of the food. Also, the public has increaslngly demanded fresh and "natursl" food6 without preservative6. This i6 especially true of the rapidly ~row-in~ hi~h end of the market which caters to the more sophi6-ticated customer. This customer also require6 reassurancethat the refrigerated food purchased in the 6upermarket has had it~ quality and safety maintainèd throughout distribu-tion snd sales. The manufacturer of quality food products which require refrigeration therefore face6 a dilemma of how to deliver a quality product through a complex system over which~he may have little control as well as how to reassure the customer that the food quality has been maintained throughout that distribution and sales 6ystem. In these situations, it is not possible to merely apply a date beyond which the food product may be unacceptable since loss of ' lZ299 refrigeration for a time may chan~e the quality of the food product.
To alleviate this problem, a number of devices have been developed to monitor temperature expo~ure. Typically, such a dev;ce is packaged wit~" or attached to a food prod-uct after production. This device travels with the food product throu~h the distribution chain to the customer.
While in transit, the device monitors the thermal environ-ment to which it is exposed. Upon exposure to thermal con-ditions of a preselected magnitude, the device undergoes avisible change thereby indica~in~ the unacceptability of the associated food product. The more sophisticated of the de~
vices are time-temperature indicators which integrate tem~
perature exposure over time. The relationship between inte-grated temperature exposure and indicator response is depen-dent on the actual physical or chemical phenomenon being u~ed to measure time temperature exposure. These indicators have taken a variety o~ forms using variou~ principles for time and temperature integration. The phenomena which have bçen used include polymerization, enzyme hydroly6is, and chemicsl decomposition. These systems, although having some advantsges, suffer from the inability to trsck what i~ U6U-ally an organism-induced deterioration of the food product using a systeol with a different order of kinetics an~ tom-perature response. Also, chemical snd physical re~ponsesystems exhibit at best a linear indicator relation to time whereas the deterioration itself accelerates exponentially.
AB a result, these devices measure acceptability limits with le~s thsn desired accuracy and the length of the transition times for the indicator switching from an acceptable to a non-acceptable response becomes confusing to the con6umer.
rrior work has reco~,nized that an organism or indicator culture sctivated, integrsting indicator might be used to indicate food spoilage. The use of an indicator culture in a time-temperature indicator also satisfies the requirement , . :. : ~
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that the indicator ~witch from an acceptable to non-accept-able response rapidly. Organism growth increa6es expon~n-tially with ti~le, and an indicator based on the growth will have a shortened transition time reflecting thi~ accclera~-ing change.
Procedures for using indicator culture~ to trsck thespoilage in food have heretofore been proposed. These sys-tems have typically been based on a culture medium compris-ing an acid-producin~, indicator culture, a medium for growth and an acid base indicator. This culture medium is typical-ly enclosed in a transparent container and stored with the food product to be monitored. Subsequent growth of the or-ganism results in acid production causing the acid-base in-dicator to change color. A color change signifies that the product has been subjected to conditions which would induce spoilage.
The biological time-temperature indicator described in ~olber 3,206,317 employs multiple organisms obtained from a sample of the food product itself for the indicator culture medium. The results obtained from such a system can be very complex. Depending on the numbers snd types of orgsnisms present, the scidity of the system can either decroase or increase. Also, different organisms will flourish at dif~
erent temperatures, and variations in temperature csn cause complex relative population changes resulting in a system in which the final pH might be unrelated to organism growth or product deterioration. Single organism systems suggested by Clark 2,485,566 and Brockmann 2,950,202 do not prevent this problem. The time-temperature indicators described in these patents are designed to indicate food spoilage and utilize single types of bacteria which flourish within the desired temperature range. Although sn improvement over other sys-tems such a criterion would not necessarily provide a bacte-rium which would track the organism growth in the food prod-uct, and give sn accurate indication of food quality ,, ~, ' .
20~2299 deterioration. These time-temperature indicators also suf-fer froD~ numerous un301ved practical problems, which pre~
clude their commercial u6e. In a practical time-temperature indicator, the indicator culture must be encapsulated in a limitecl environment precluding its use or production of ga~-eou~ material6. Sufficient gases cannot be dissolved in the medium to sustain the growth of the indicator culture and appreciable production of gas by the indicator culture may either modify its sctivity or bur6t the container. In actu-al u6e, indicator cultures are subjected to unexpectedly lowtemperatures which cause injuries snd population changes which 6ub6tsntially alter the re6ponee and render the re~
sults unreliable. Containment systems are sub~ected to physical abuse snd breakage will re6ult in 1086 of customer confidence.
In summary, even wi~h various attempts to develop time-temperature indicator~, there has been no practical indica~
tor capable of tracking biologically induced deterioration in the organoleptic propertie~ of refrigerated food prod-uct6.
SUMMARY OF THE INVENTION
The disadvantage6 and deficiencie~ of prior attempts tomonitor the environmental conditions to which refrigerated food is exposed during storsge and di6tribution have been overcome by the present invention 80 that the consumer can readily determine whether a refrigerated food product has been 6ub6tantially mi6handled, exposing it to prolonged 6torage or elevated temperature6 re~ulting in a deteriora-tion of organoleptic propertie~ of the food item.
! In accordance with 8 general aspect of the present in-vention, there i~ provided a time-temperature indicator ~7herein the culture medium comprise6 a biological growth medium, an anaerobic indicator culture which modifies the growth medium at a rate directly proportional to the ,: . . , . - .
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temperature of the culture medium, and an acid base indica-tor. The culture medium is confined in a contsiner having a tranfiparent window whereby the color imparted by the acid-bafie indicator to the culture medium can be observed. In i~s operative form the time-temperature indicator is pack-aged with the food product at the conclusion of production, at which time the product and its package are chilled before being sent into the distribution system. While in the re-frigersted storage system, the indicator culture maintains a low level of activity, during which it continually excretes small amounts of acid. If the package is maintained in the refrigerated condition, the indicator culture will continu- ~ -ally deplete the nutrients provided in the medium ~hile at the same time causing the medium to con~inuslly increase in acidity. Once the mediu~ has reached a certain ~cidity, the acid base indicator will change color. Such A color chan~e indicates the product has been ~tored for an excessive peri-od of time and no longer meets the producers standards of quality. In the event that the food product and its includ-cd time-temperature indicator enter the distribution chsin and are exposed to unexpectedly high temperatures, the growth rate of the indicator culture increases, thus rapidly increasing the ~cidity of the medium. Paralleling thi~ in-cresse in acidity will be the increased rate of deteriora-tion of the organoleptic quslity of the food product. At ashortened interval the acid in the medium will build up to a level that will change the color of the acid base indicator.
Again, by inspecting the color of the time-temperature indi-cator, the consumer can determine that the food product does not meet the manufacturer's quality standards, which in this case, was caused by exposure to elevated temperatures as opposod to extended storflge. In either case the consumer can verify that he has purchased a high quality product and this as6urance leads to con6umer confidence in the product itself. Alfio, the retailer can be reassured of not having -6- `
2012; 99 ' '' received an old or mishandled product. This ability to check previous handlin~ along the distribution chain will insure improved handlinp, resul~inR in a hi~her quality food product being delivered to the customer. ~ ~-5In accordance wi~h another aspect of the invention, the indicator culture is a single type, naturally occurring, non-pathogenic bacterium capable of a low level of growth at 3-5 C, the temperature at which refrigerated food i6 stored. The indicator culture is obtained by isolation from l0naturally occurring organisms found in food products growing ;
at 3-5 C and thereby should track ~he organism induced de-terioration of the organoleptic qualities of the food.
In accordance with another sspect of the invention, the indicator culture is anaerobic showing the presence of ni-15trate reductaes whereby it can utilize a soluble nitrate as a terminal electron acceptor. Oxygen is therefore not re-quired by the indicator culture allowing it to be encapsu-lated as required for a practical time-temperature indica-tor.
~. . -In accordance with another feature of the invention, the medium contains a nutrient and a nitrate in such propor-tion~ that the indicator culture depletes both simultaneous~
ly and wherein the nutrient is preferably ~lucose and the nitrate is preferably potassium nitrate, they are included in the medium in a 4 to 3 ratio by weight, thereby minimiz- ~- -ing the formation of alkaline reversion products upon deple- :
tion.
In accordance with another aspect of the invention, the medium contains sucrose and Tween 80, materials which the 30organism cannot utilize as nutrients, but serve as ~ '' cryoprotectant~ to protect the indicator culture from injury ~ ;
upon its beinp, subjected to unexpectedly low temperatures.
In accordance with another aspect of the invention, the -~
indicator culture is deactivatcd ~y chillinp, the time-tem-35perature indicator from 5 C to -20 C at a rate of 14 per ;~t,~'''!'" ' .,.';, ', ."""~
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~ -hour. This chilling rate in~ures that the indicator culture will ~uffer minimsl injury during deac~ivation.
In accordance with another a~pect of the invention, the culture medium i~ contained in a pliable packet which is enclosed within a ri~,id container, the rigid container al60 enclosing an indicator culture deactivator externsl to the packet. In 6uch case that the indicator culture escape6 from the packet, it would be deactivated, thu6 in~piring con6umer confidence in the system.
The primary object of the prefient invention i~ to pro~
vide a time-temperature indicator which is packaged with a food product and indicates when exces~ive exposure has caused unacceptable deterioration in the or~anoleptic quali-ties of the food product.
Another object of the present invention i6 to provide a time-temperature indicator in which the indicator culture ncither produces nor consume~ ~aseous materials thereby be-in~, sble to thrive in an enclosed en~ironment.
Another object of the invention i~ to provide a time-tempcrature indicator, as defined above, in which the indi-cstor culture can be frozen without 6evere injury or modifi-cation to the indicator culture populatic,n.
Another object of the present invention i8 providing a time-temperature indicator as defined above which eliminates the po~sibility of spuriou~ re6ults caused by the formation of alkaline reversion product~.
Another object of the present invention i6 providing a method whereby a timc-temperature indicatc!r as defined abovc can be deactivated for extended periods uithout significant injury to or modifications of the indicator culture.
~ Another object of the present inYention i8 providing a timc-te~perature indicatc-r a6 deined above which can resist shock and mechanical abrafiion.
ZOlZ299 These and other objects and advantages will become 8p-parent from the following description taken together with the accompanying drawings described in the next section.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing objects and others will, in part, be ap-parent and, in part, pointed out more fully hereafter in conjunction with the description of the preferred embodiment of the invention illus~rated by the accompanying drawin~,~ in which:
FIGURE 1 is a perspective view of a food container in-corporating a time-temperature indicator.
FIGURE 2 is an enlarged cross-sectional view taken gen-erally along lines 2-2 of FIGURE 2.
FIGURE 3 is a cro~s-sectional view on an enlarged scale taken along lines 3-3 of FIGURE 2.
FIGURE 4 is an exploded per~pective view of the compo-nents of a time-temperature indicator.
FIGURE 5 is a perspective view of a modiication of the preferred embodiment illustrated in FIGURES 1 and 2 wherein the food product is contained in a shallow tray, the tray, ~ -time-temperature indicator and food product being wrapped together in a plastic wrap. -~
FIGURE 6 is 8 psrtial crosfi-sectional view tsken acro6s lines 6-6 of FIGURE 5. ~---~
FIGURE 7 is a cross-sectional view of a modification of the preferred embodiment illustrated in FIGURE 2 wherein the ; `~
food product and time-temperature indicator are packaged together in a paperboard container without separate contsin-ment of the food product.
FIGURE 8 is a cross-sectional view of a modiication of --.. .
the preferred embodiment illustrated in FIGURE 2 wherein the time-temperature indicstor and the food product are wrapped together in plastic wrap within a paperboard container.
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FIGURE 9 i~ a cross-sectional view of a modification of the preferred e~bocliment illustrated in FIGURE 3 in which the culture ~edium ifi contained ~olely within a ri~id plas-tic container.
FIGURE 10 ig ~ parti~l cros~-~ectionsl view of the pre-ferred embodi~ent illus~rsted in FIGURE 3 wherein the cul-ture medium is encased in a pliable plastic packet within a rigid outer 6keleton.
FIGURE 11 is a partisl cross-sectional view of a modi-fication of the preferred embodiment illustrated in FIGURE 3 wherein the culture medium is enca~ed in a pliable packet with 8 rigid back, FIGURE 12 is a partial cros6-sectional view of the cul-ture medium enca~ed in a pliable plastic packet 6ealed at the peripheries - -FIGURE 13 is a top view of alternate ~hapes of the time-temperature indicator FIGURE 14 i~ a time-pH graph illu6trating the increa~e in acidity of a stirred culture medium usin~, buffered and non-buffered media PREFERRED E~RODInENT
Referrin~ to the drawing~ wherein the 6howin~ are for the purpose of illustra~ing the preferred e~bodiment of the invention only snd not for the purpose of limiting 6ame, FIGURES 1 and 2 illu~trate a food package A for the ship-ping, di6tribution, and cli~play of a refrigerated food prod-uct B. The pack~ge compri~es two generally flat parallel panels, the bottom panel 10 for 6upporting the food product B and the top or upper panel 12 forming a cover or lid.
The~e two panels sre interconnected by a pair of parallel lateral support wall6 14, 16. The packa~,e i6 sealed at each end 18, 20 by a pair of overlapping flap6 22, 24. Flap 22 extend6 from the upper panel 12 and flap 24 extend6 from the lower panel 10 The container is con~tructed of rigid paperbosrd. Im-prints 26 of desi~,ns and label6 are located on the outer surface of the container. The top of the container includes an opening 28 through the paperboard. Surrounding the open-inp, 28 is the imprint or inclicia rinp, 30 containin~ a color representing the standard to which quality indicator C is compared to determine the continued quality of food product B. Within the container, the food article B i~ enclosed in an air impermeable plastic wrspper or bag 36 which can be evacuated or filled with an inert gas. The environmental integrity within the wrapper is maintained by seals 3R at either end.
Affixed to the interior surface 34 of the csrdboard container, in such a way that it completely covers the open~
in8 28, i6 a time-temperature indicator C. The dimensions of the time-temperature indicator C are larger thsn those of the openin~ providing overlappin~ portions of the cardboard container 32 which overlap portions 58 of the time-tempera-ture indicator C. These overlapping portions are joined by an adhesive 40 securing the time-tempera~ure indicator C
within container A. The time-temperature indicator is com-prised of a rigid outer container 50, which encases a pli-able plastic packet 70 which in turn contains the culture ~ledium lO0. The outer container 50 comprises an upper face or window 52, a bottom portion 54, and sides 56. Prefera~
bly, the bottom portion 54 and the sides 56 are a single unit, the sides terminatin8 in upper faces 60 which are flat. The window 52 overlaps and is secured to the upper faces 60 forming an internal cavity 68 within the container.
The container is constructed of a high impact plastic, the bottom portion 54 and sides 56 being opaque, white or light in color, and the window 52 being transpsrent. The cavity 68 of the container contains a tough pliable plastic packet 70 having a flat ront portion 72 generally parallel to the back portions, 74 which are sealed together at the juncture . . .
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~ 2 0 ~ 299 of the front periphery 82 with the back periphery 84 formin~
a leak-proof container. The size of the packet is such that it does not fill the cavity 68 thereby leaving an intersti-tial space 76. The interstitial space 76 is filled with an indicator culture deactivator. Enclosed within the packet is the culture medium 100, comprisin~ sn indicator culture, the growth medium, and the acid-ba6e indicator. The indica-tor culture is a non-pathogenic, naturally occurring organ-ism, isolated from food product deterioration at 4_5V C, producing acid at these temperatures, the rate of acid pro-duction increa~ing with increasing temperature. The organ-ism flourishes in the 4-5 C temperature range thereby msin-taining a low level of acid production which is sufficient to increase the acidity of the medium by one pH unit in 30 hours. The indica~or culture shows the presence of nitrate reductaes so that nitrate can serve as the terminal electron acceptor snd thus the indicator culture can grow anaerobically with little gas production. The preferred indicator culture is from the pseudomonas fluorescens group, designated as the third pseudo~lonad, second fluorescent type isolated from refrigerated food products, thu~ assigned the designation P3f2 for simplicity. A subculture of this strain can be obtained from the permanent collection of the Northern Marketing and Nutrient Research Divi~ion, Agricul~
tural Service, U.S. nepartment of Agriculture, Peoria, Illi-nois.
Tbe acid-base indicator has specific characteristic~
which are compatible with the indicator culture. The acid-base indicator is not metnbolized by the indicator culture nor doe6 it affect the gro~th oP the indicator culture. The preferred indicator changes color near the midpoint of the working pH range of the indicator culture. Preferably, the acid base indicator change6 color at least one p~l unit below the initial pH of the sy6tem, and at least one pH unlt above a point where the indicator culture ic still visble and : ~ . - .
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relatively unaffected by the increased acid concentrstion in the medium. An~ther criterion in the preferred sy~tem i~
that the acid-base indicator under~,o a definite color chan~,e which is readily perceivable to the untrained ob~erver.
This color chan~,e should also take place in as short a tran-sition ran~e as possible in order to preclude the customer having to guess whether the indicator is sctually one color or the other. In the preferred embodiment, brom thymol blue is used as the acid base indicator.
The gro~th medium comprises a mixture of a nutrient, a nitrogen source, and an electron acceptor as well as addi-tives to enhance the growth and stability of the ~ndicator culture. In the preferred embodiment, glucose is used as the nutrient. Glucose is effectively utilized by the indi-cator culture and also minimizes the formation of gaseous product~ which are more probsble with more complex nutri-cnts. Potassium nitrate i6 used as 8 terminal electron ac-cep.or. Three percent nitrate in the pre~ence of unlimited glucose provides the best indicator culture growth. In the preferred embodiment, three percent nitrate is used with four percent glucose. With this ratio of components, the or~ani~m completely depletes both components at the same time. The indicator culture can produce alkaline products late in it~ growtll phu6e presumably due to 6econdary metabo-lism product~. The adjustment of the concentrations of glu~cose and nitrate to effect simultsneou6 depletion of those materials is designed to minimize the problem with alkaline rever~ion. Since ga6eous oxygen can compete wi~h nitrate a~
a terminal electron acceptor the culture medium mu6t be deoxy~,enated to prevent erratic re6ults. The nitro~,en 60urce can be any of a variety of compound~ well known to those versed in the art. The preferred embodiment use6 tryptone, a pancrestic digest of ca~ein, which i6 manufac-tured by Difco Laboratories, Inc. of Detroit, Michi~an.
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201;~299 In addition to the required components of the medium, various additivcs are included to enhance the repeatability of the syste~l and also to effect modifications in re6pon~e time. Additives incorporated in~o the medium include a vi-tamin and minersl source, a cryoprotectant and a surfactant.In the preferred embocliment, vitamin and mineral require-ments are supplied by yeast extract which is a wster ~oluble portion of autolyzed yeast snd is a product of Difco Labora-torie6, Detroit, Michigan. A cryoprotectant is included in the medium to prevent da~age to the indicator culture fro~
exposure the low temperatures. The cryoprotectant cannot injure or be metabolized by the indicator culture. In the preferred embodiment, sucrose is used as a cryoprotectant.
At the low temperature8 under which the time-temperature indicator is uæed, movement of chemicals through the cell walls of the indicator culture is impeded. A ~urfactant i~
added to the medium to allow easier movement of nutrient~
and by-products in and out of the cell. A surfactant which doe6 not inhibit indicator culture growtb must be u6ed. In the preferred embodiment, Tween 80 is used. In addition to allowing easier movement through the cell wall, the Tween 80 ~ -also contributes the cryoprotection of the indicator culture in a frozen state. Tween 80 also interacts with the bron thymol blue indicator by shiftin8 the absorption maximum toward longer wavelengths. At sn initial pH of 7.6 where brom thymol blue would exhibit a blue color, the presence of Tween 80 cau~es the indicator to be green. As a result, st low pH values the yellow color of brom thymol blue is more intense and the indicator exhibits a sharper transition point. Thi~ desirable artefact of the Tween 80 reduces the pro~pect of customer confusion as to whether there has been a significant change in the indicator color.
In order to modiy the re~ponse time of the lndicator, a buffer i6 included in the medium. As with other special 35 purpose additives, the buffer cannot affec~ or be affected ~ -,'' ' '.;, :. ,,. :' '.. ~.':' ,: ~ , , :
Z0~2299 by the indicator culture. The pKa of the buffer 6hould be about 1 pH unit above the pH required for color change of the indicator. In the preferred embodiment, (4-(2-hydroxyetltyl)-l-piperazine ethanesulfonic acid lHEPES]
is u~ed. - , In the preferred embodiment, a culture medium which ~ -will indicate a four day shelf life at 5 C i~ formulated a~
follows: In 900 ml distilled water i~ dis~olved 0.100 gram brom thymol blue, 1.0 ml Tween 80, 2.500 grams bacto yeast -extract, 30.000 grams potassium nitrste, 40.000 grams glu- ~ -cose, 120.000 grams sucrose. The ~olution i sterilized so as to avoid any volume loss. At room temperature, lO0 ml of a pre-~terilized 5% ~tock solution of bacto tryptone is add- ~ -ed to 900 ml of base medium snd the two mixed. Solid HEPES s buffer is added to the desired concentration; preferred to be 1.500 grams for 4 day self lift inclication. The pH i~
adjusted to 7.60. The mixture i~ heated just to boilin~ to drive off all oxygen and thcn cooled to 5 C under snaerobic condition~. The medium i 6 then inoculated with 1% stock -~culture (3 day, 5 C growth in the same medium without llEPES
buffer).
The resulting culture medium is enclo6ed in a container using standard technique~ and the completed time-temperature indicator is chilled 80 as to temporarily deactivate the culture D)edium. Deactivation mu~t be accomplished BO a~ to -~
minimize damage to the indicator culture. Deactivation is effected by chillin~> from a tempera~ure of +5 C to -20 C
at a rate of 14 per hour. The time~tcmperature indicator can then be ~ored until ready for u~e.
Activation of tl-e time-temperature indicator i8 effect-ed by warming to the temperature at which it will be used. -~
The preferred method of activation is to remove the time-temperature indicator from frozen storage and immedistely packaging it with the food product as it is being produced. ~ -- ~ --15- ~
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An alternate cul~ure medium i8 formulated ai6i followe:
In 800 ml distilled wster i5'i dissolved 30.0 grams l)otassium nitrate, 2.5 grams yeast extract, 1~0 ml Tween 80, and 0.1 gram of brom thymol ~lue. The solution iEi boiled 1-2 min-utes to achieve disEiolution. In one liter of di6tilled ua-ter, 400 gr~ms of gluco~ is di6~01ved. In one liter of diitilled water, 50 grams of tryptone ic di~solved. The three solutions are sterilized, cooled to 20 C and asceptically combined usin~ on a volume basis 80% of solu-tion 1, 10% of ~olution 2 and 10% of solution 3. To the combined solutic~ns, 0.4Z agar is sdded and the acidity ad-justed to a p~i~i of 7.60. The resulting solution is heated to boiling to dissolve the agar and drive off dissolved oxygen, after which it is cooled to 40 C and inoculated with a 3-4 day old 1% stock culture of P3f2 grown under anaerobic con-ditions at 4-5 C. The inoculated medium is cooled to 4-5 C and overlaid with sterile mineral oil to prevent sbsorp-tion of oxygen. Stock cultures are prepared using the same media and conditions as above without the u6e of agflr.
FIGURE 14 shows the pH time changes in a two culture media. Curve A reE~resents the pHltime curve of a typical unbuffered culture medium. After incubation of the culture medium for 30 hours at 5 C, the tran6ition range of the indicator is reachcd in which the color changes from green to yellow over a 5.5 hour period. ~ifter the color change, the acidity continued to increase to a pH of 4.80. Curve B
represents the pH/time chan&e under similar conditions wherein 0.5% HEPES buffer was added. The pHi drop is less rapid and the transition range of the indicator i6 reached after 58 hours. The color change froDI green to yellow takes place over 71 5 hour~i, after which the acidity of the isystem continued to increase. The experiments providing the data for FIGURE 14 utilized a sanitized pH probe which was sub~
merged into hot media overlaid with oil and cooled to 5 C
and inoculated with 1% P3f2, 3 day, 5 C, anserobic culture.
2()1~X99 The cultures were stirred slowly with a ssnitized stir bar on a magnetic stir plate using a pad to insulate any heat transfer from the stir plate. As can be seen in FIGURE 14, the color transition occurs between 6.75 pH and 5.75 p~ ir-respective of the addition of a buffer. The unbuffered me-dia of curve A ha6 a short transition ~ime (a) because the media decreases in pll rapidly. After the 5.5 hours to pa~s throu~h the transition zone, the indicator resches the yel-low zone at time ta. This time is sub6tantially less than the corresponding time tb of the buffered media depicted by curve B. Due to the more gradual slope of curve B, the transition zone is lar~er, i.e. 7.5 hours. FIGURE 14 show6 the effect of bufferin~ the delay the total time to change color (tb) without a si~nificant increase in the transition time.
A modification of the preferred packaging embodiment i~
illustrated in FIGURES 5 and 6 wherein the time-temperature indicator C is incorporated into an alternate packaging ~ys~
tem. The psckaging system compri6es an open tray D having a bottom 110 supporting the food product B, the peripheries of the bottom bending upward forming two parflllel outwardly sloping lateral sides 112, 114 perpendicular to and adjoin-inE two parallel outwardly ~lopin~, ends 116, 188, the outer edges of the sides 112, 114 and ends 116, 118 bendin~ out~
ward forming a continuous horizontal flange 120 encircling the container D. The bottom 110 support~ the food item B
which extends above the flange 120 and which in turn ~up-ports a time-temperature indicator C which lies in direct contact with the food item B. Plastic wrap 126 envelop~ the food item B and time-temperature indicator C securin~ them in position and extends over the outer cdge 122 of the flanEe 120, the bottoDI ed~es 124 snd covers the bottom 110 of the tray.
FIGURE 7 illustrates a further modification of the pre-ferred embodiment shown in FIGURE 1 and as therein the food , ' ~ ~ , .
product i~ contained in 8 paperboard container having an opening 28 in the upper panel 12, the ~ime-temperature indi-cator C adhering to the interior surfsce 34 o the container overlapping and covering the opening 28. In this alternate embodiment, the time-temperature indicator C iB not sepArst-cd from the food product by an intervening wrapper or ba~"
but rather lies in direct contact with the food product B.
FIGURE 8 illustrates a further modification of the em-bodiment in FIGURE 7 wherein the food product B is enclosed in a paperbosrd container A, having an opening 28 in the upper panel 12, covered on the interior by the time-tempers-ture indicator C. In this embodiment, the time-temperature indicator C lies on top of and in direct contact with the food product B being secured in place by a plastic wrap 126 which envelops both the ~ime-temperature indicator C and ~he food product B. The opcning 28 in the top panel 12 i8 closed by the time-temperature indicator C, the pressure e~erted against its bottom portion 54 forcing the window 52 up against the overlapping portions 32 of the paperboard container A around the opening 28.
Modifications in the preferred embodiment of the cul-ture medium container are shown in FIGURES 9 through 12.
Referrin~ now to FIGU~E 9, the container has a unitary structure comprising a flat bottom portion 54 and perpendic-ular sides 56 of rigid opaque plastic. Overlsying and af-fixed to the upper trsnsverse faces of the sides 60 is a trsnsparent window 52, forming a cavity 68 which contains the culture medium 100.
As can be seen with this modification, the thermal en-crgy is required to pa6s through only the single wall orbarrier thus increasing the response of the culture medium to surround the temperature changes.
A further modiication of the preerred embodiment is shown in FIGUR~ 10 wherein the culture med~um container com-3S prises a pliable plastic packct 70 surrounded by a rigid : '~ ~:'' '"
-- Z ~ ~Zz99 plastic frame 98. The pliable plastic packet has a flat back 78, a frontal portion 70 being flat around the periph-cries 84 and afixe~l to the peripheries of the back 82, the interior of the frontal portion bending away from the back forDling a side wall 86, then bending back essentially paral-lel to the back forming a cavity 88 bet~leen the front 70 and back 78 The back 78 is affixed to a second rigid pl8stic protective back 94 Overlaying and affixed to the peripher-ies of the fron~al portion 84 is a rigid pla~tic mask 92 In this construction, thermal energy can readily pas6 from the environment E through the pliable plastic to be seneed by the culture medium 100 while the ri~id plastic skeleton sa provides protection against severe mechanical abuse A further ~odification of the preferred embodiment is shown in FIGUP~E 11 wherein the culture medium packet hss a pliable front~l portion 72 attached to a flat rigid plastic back 94, the frontal portion 72 being flat around the pe~
ripheries 84, lies on and i6 affixed to the periphery of the bsck 96, the interiur of the frontal portion bending awsy from the bsck forming a si~e wall 86, then bending bsck es-sentially psrsllel to the bsck forming a cavity 68 between the frontal portion 72 snd the bsck 94 A further modification of this concept is shown in FIG-URE 12 wherein the culture medium container comprises a pli~
nble plastic packet wherein the peripheries 84 of the fron-tal portion 72 sre flst, lying in a plane, the interior bending away from the plane of the peripheries 84 forming a side wall 86 then bending back essentially parallel to the plane of the peripheries, the back 74 beinR a mirror ima~,e of the frontal portion, the peripheries 98 of the back and the frontsl portions lying against and being affixed to one snother, forming a csvity 68 in between.
Modificstions in the shape of the culture medium con-tainer are shown in FIGURE 13 in which the container is fihown to assume sn ellipfie in FIGURF. 13A, a square in FIGURF
20122~
13B, a rectangle in FIGUR~ 13C, and a triangle in FIGURE
13D.
- .
.`"'.,`' ~
., .' ' '.~,.' ,.," '';'' " ,~......
A modification of the preferred packaging embodiment i~
illustrated in FIGURES 5 and 6 wherein the time-temperature indicator C is incorporated into an alternate packaging ~ys~
tem. The psckaging system compri6es an open tray D having a bottom 110 supporting the food product B, the peripheries of the bottom bending upward forming two parflllel outwardly sloping lateral sides 112, 114 perpendicular to and adjoin-inE two parallel outwardly ~lopin~, ends 116, 188, the outer edges of the sides 112, 114 and ends 116, 118 bendin~ out~
ward forming a continuous horizontal flange 120 encircling the container D. The bottom 110 support~ the food item B
which extends above the flange 120 and which in turn ~up-ports a time-temperature indicator C which lies in direct contact with the food item B. Plastic wrap 126 envelop~ the food item B and time-temperature indicator C securin~ them in position and extends over the outer cdge 122 of the flanEe 120, the bottoDI ed~es 124 snd covers the bottom 110 of the tray.
FIGURE 7 illustrates a further modification of the pre-ferred embodiment shown in FIGURE 1 and as therein the food , ' ~ ~ , .
product i~ contained in 8 paperboard container having an opening 28 in the upper panel 12, the ~ime-temperature indi-cator C adhering to the interior surfsce 34 o the container overlapping and covering the opening 28. In this alternate embodiment, the time-temperature indicator C iB not sepArst-cd from the food product by an intervening wrapper or ba~"
but rather lies in direct contact with the food product B.
FIGURE 8 illustrates a further modification of the em-bodiment in FIGURE 7 wherein the food product B is enclosed in a paperbosrd container A, having an opening 28 in the upper panel 12, covered on the interior by the time-tempers-ture indicator C. In this embodiment, the time-temperature indicator C lies on top of and in direct contact with the food product B being secured in place by a plastic wrap 126 which envelops both the ~ime-temperature indicator C and ~he food product B. The opcning 28 in the top panel 12 i8 closed by the time-temperature indicator C, the pressure e~erted against its bottom portion 54 forcing the window 52 up against the overlapping portions 32 of the paperboard container A around the opening 28.
Modifications in the preferred embodiment of the cul-ture medium container are shown in FIGURES 9 through 12.
Referrin~ now to FIGU~E 9, the container has a unitary structure comprising a flat bottom portion 54 and perpendic-ular sides 56 of rigid opaque plastic. Overlsying and af-fixed to the upper trsnsverse faces of the sides 60 is a trsnsparent window 52, forming a cavity 68 which contains the culture medium 100.
As can be seen with this modification, the thermal en-crgy is required to pa6s through only the single wall orbarrier thus increasing the response of the culture medium to surround the temperature changes.
A further modiication of the preerred embodiment is shown in FIGUR~ 10 wherein the culture med~um container com-3S prises a pliable plastic packct 70 surrounded by a rigid : '~ ~:'' '"
-- Z ~ ~Zz99 plastic frame 98. The pliable plastic packet has a flat back 78, a frontal portion 70 being flat around the periph-cries 84 and afixe~l to the peripheries of the back 82, the interior of the frontal portion bending away from the back forDling a side wall 86, then bending back essentially paral-lel to the back forming a cavity 88 bet~leen the front 70 and back 78 The back 78 is affixed to a second rigid pl8stic protective back 94 Overlaying and affixed to the peripher-ies of the fron~al portion 84 is a rigid pla~tic mask 92 In this construction, thermal energy can readily pas6 from the environment E through the pliable plastic to be seneed by the culture medium 100 while the ri~id plastic skeleton sa provides protection against severe mechanical abuse A further ~odification of the preferred embodiment is shown in FIGUP~E 11 wherein the culture medium packet hss a pliable front~l portion 72 attached to a flat rigid plastic back 94, the frontal portion 72 being flat around the pe~
ripheries 84, lies on and i6 affixed to the periphery of the bsck 96, the interiur of the frontal portion bending awsy from the bsck forming a si~e wall 86, then bending bsck es-sentially psrsllel to the bsck forming a cavity 68 between the frontal portion 72 snd the bsck 94 A further modification of this concept is shown in FIG-URE 12 wherein the culture medium container comprises a pli~
nble plastic packet wherein the peripheries 84 of the fron-tal portion 72 sre flst, lying in a plane, the interior bending away from the plane of the peripheries 84 forming a side wall 86 then bending back essentially parallel to the plane of the peripheries, the back 74 beinR a mirror ima~,e of the frontal portion, the peripheries 98 of the back and the frontsl portions lying against and being affixed to one snother, forming a csvity 68 in between.
Modificstions in the shape of the culture medium con-tainer are shown in FIGURE 13 in which the container is fihown to assume sn ellipfie in FIGURF. 13A, a square in FIGURF
20122~
13B, a rectangle in FIGUR~ 13C, and a triangle in FIGURE
13D.
- .
.`"'.,`' ~
., .' ' '.~,.' ,.," '';'' " ,~......
Claims (54)
1. A device for indicating the deterioration of the organoleptic quality of refrigerated food products compris-ing:
a biological growth medium;
an anaerobic indicator culture means in said growth medium for modifying said medium at a rate directly propor-tional to the temperature of said medium; an acid-base indi-cator; and a container means for containing said growth medium, said indicator culture means, and said acid-base indicator.
a biological growth medium;
an anaerobic indicator culture means in said growth medium for modifying said medium at a rate directly propor-tional to the temperature of said medium; an acid-base indi-cator; and a container means for containing said growth medium, said indicator culture means, and said acid-base indicator.
2. A device as defined in claim 1 wherein said indica-tor culture flourishes at temperatures between 3° C and 5°
C.
C.
3. A device as defined in claim 1 wherein said indica-tor culture shows the presence of nitrate reductaes.
4. A device as defined in claim 1 wherein said indica-tor culture means utilizes nitrate as a terminal electron acceptor.
5. A device as defined in claim 4 wherein said nitrate is potassium nitrate.
6. A device as defined in claim 1 wherein said indica-tor culture means includes a substance which neither re-quires nor produces gaseous materials.
7. A device as defined in claim 1 wherein said indica-tor culture means is a non-pathogenic, single type bacterium occurring naturally in said food product.
8. A device as defined in claim 1 wherein said indica-tor culture is a psychotrophic pseudomonad bacterium.
9. A device as defined in claim 8 wherein said psychotrophic pseudomonad bacterium is in the pseudomonas fluorenscens group.
10. A device as defined in claim 9 wherein said bacte-rium is of the third pseudomonad, second fluorescent type.
11. A device as defined in claim 1 wherein said bio-logical growth medium contains a nutrient.
12. A device as defined in claim 11 wherein said nu-trient is a carbon/energy nutrient source.
13. A device as defined in claim 11 wherein said nu-trient is glucose.
14. A device as defined in claim 13 wherein said medi-um contains said glucose and said nitrate in a weight ratio of 4:3.
15. A device as defined in claim 1 wherein indicator culture is an organism capable of fully depleting said nu-trient and said nitrate simultaneously.
16. A device as defined in claim 1 wherein said acid-base indicator is inert to said indicator culture.
17. A device as defined in claim 1 wherein said organ-ic acid-base indicator exhibits color change between pH 5.1 and pH 7.4.
18. A device as defined in claim 16 wherein said acid-base indicator is brom thymol blue.
19. A device as defined in claim 1 wherein said acid-base indicator is brom thymol blue.
20. A device as defined in claim 1 wherein said medium contains a buffer.
21. A device as defined in claim 19 wherein said buff-er having a pKa between 6.8 and 7.8.
22. A device as defined in claim 20 wherein said buff-er is HEPES.
23. A device as defined in claim 19 wherein said buff-er is HEPES
24. A device as defined in claim 1 wherein said medium contain a cryoprotectant.
25. A device as defined in claim 23 wherein said cryoprotectant is sucrose.
26. A device as defined in claim 1 wherein said medium contains a surfactant.
27. A device as defined in claim 25 wherein said surfactant is Tween 80.
28. A device as defined in claim 1 wherein said medium is deoxygenated.
29. A device as defined in claim 1 wherein said con-tainer means is in a single compartment pliable packet.
30. A device as defined in claim 28 wherein said pack-et comprises a hard plastic container having at least one wall formed from a transparent material.
31. A device as defined in claim 29 wherein said hard container includes a deactivator for said indicator culture, said deactivator being external to said packet.
32. A device as defined in claim 28 wherein said hard container includes a deactivator for said indicator culture, said deactivator being external to said packet.
33. A device as defined in claim 29 wherein said con-tainer means is an opaque box, with an opening and including means for locating said transparent wall over said opening.
34. A method for producing a time-temperature indica-tor comprising the steps of:
a) providing a solution of an acid-base indicator, an electron acceptor, and a nutrient;
b) providing a solution of a nitrogen source;
c) individually sterilizing said solutions;
d) asceptically combining said sterilized solutions thereby obtaining a medium comprising said solutions;
e) deoxygenating said medium;
f) providing an indicator culture capable of modifying the acidity of said medium; and g) inoculating said medium with said indicator cul-ture, thereby obtaining a culture medium.
a) providing a solution of an acid-base indicator, an electron acceptor, and a nutrient;
b) providing a solution of a nitrogen source;
c) individually sterilizing said solutions;
d) asceptically combining said sterilized solutions thereby obtaining a medium comprising said solutions;
e) deoxygenating said medium;
f) providing an indicator culture capable of modifying the acidity of said medium; and g) inoculating said medium with said indicator cul-ture, thereby obtaining a culture medium.
35. The method as defined in claim 34 including the additional step of adjusting the pH of the solution to ap-proximately 7.60.
36. The method as defined in claim 34 including the further step of adding a buffer to a proper concentration to provide the desired delay in color change.
37. The method as defined in claim 36 wherein said buffer is HEPES.
38. The method as defined in claim 34 including the further step of adding a buffer to a proper concentration to provide the desired delay in color change.
39. The method a defined in claim 38 wherein said buffer is HEPES.
40. The method as defined in claim 34 including adding carbon/energy nutrient.
41. The method as defined in claim 34 including adding a vitamin and mineral course nutrient.
42. The method as defined in claim 34 including adding a cryoprotectant.
43. The method as defined in claim 34 including adding a surfactant.
44. A method as defined in claim 29 wherein said medi-um is deoxygenated by boiling said medium.
45. The method as defined in claim 29 wherein steps following deoxygenating step are conducted under anaerobic conditions.
46. The method as defined in claim 29 including the further step of:
h) sealing said inoculated medium in a transparent, oxygen impermeable packet.
h) sealing said inoculated medium in a transparent, oxygen impermeable packet.
47. The method as defined in claim 32 including the further step of:
i) freezing said packet.
i) freezing said packet.
48. The method as defined in claim 37 wherein said packet is frozen rapidly.
49. The method as defined in claim 34 wherein the tem-perature of said packet is decreased at a rate of 14° C/hour from 5° C to -20° C.
50. The method as defined in claim 36 wherein the tem-perature of said packet is decreased at a rate of 14 C/hour from 5° C to -20° C.
51. The method as defined in claim 33 wherein said nutrient solution contains cryoprotectants.
52. The method as defined in claim 41 wherein said cryoprotectants are Tween 80 and sucrose.
53. The method as defined in claim 33 wherein after said deoxygenating step, all subsequent steps are performed at temperatures below 5° C.
54. A method for monitoring the time-temperature expo-sure of a refrigerated perishable food item comprising:
a) providing a deactivated frozen time-temperature indicator having a biological growth medium; an anaerobic indicator culture means in said medium for modifying said medium at a rate directly proportional to the temperature of said medium; an acid-base indicator; and a means for con-taining said growth medium, said indicator culture means, and said acid-base indicator;
b) mounting said time-temperature indicator in the immediate proximity of said food item;
c) allowing said frozen deactivated time-temperature indicator to thaw while mounted in immediate proximity of said food item;
d) providing a color standard, said color standard having the same color as said time-temperature indicator after a predetermined extent of modification of said medium;
and e) comparing the color of said time-temperature indi-cator with that of said color standard whereby a color change of the time-temperature indicator is recognized.
a) providing a deactivated frozen time-temperature indicator having a biological growth medium; an anaerobic indicator culture means in said medium for modifying said medium at a rate directly proportional to the temperature of said medium; an acid-base indicator; and a means for con-taining said growth medium, said indicator culture means, and said acid-base indicator;
b) mounting said time-temperature indicator in the immediate proximity of said food item;
c) allowing said frozen deactivated time-temperature indicator to thaw while mounted in immediate proximity of said food item;
d) providing a color standard, said color standard having the same color as said time-temperature indicator after a predetermined extent of modification of said medium;
and e) comparing the color of said time-temperature indi-cator with that of said color standard whereby a color change of the time-temperature indicator is recognized.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US34372189A | 1989-04-27 | 1989-04-27 | |
| US343,721 | 1989-04-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2012299A1 true CA2012299A1 (en) | 1990-10-27 |
Family
ID=23347345
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2012299 Abandoned CA2012299A1 (en) | 1989-04-27 | 1990-03-15 | Method and device for indicating deterioration of organoleptic properties of refrigerated food |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2012299A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU200951U1 (en) * | 2020-06-26 | 2020-11-20 | Федеральное государственное казенное военное образовательное учреждение высшего образования "Военная академия материально-технического обеспечения имени генерала армии А.В. Хрулёва" Министерства обороны Российской Федерации | DEVICE FOR DETERMINING THE QUALITY OF MILK, VEGETABLE OIL AND OLIVE OIL |
| RU200950U1 (en) * | 2020-06-26 | 2020-11-20 | Федеральное государственное казенное военное образовательное учреждение высшего образования "Военная академия материально-технического обеспечения имени генерала армии А.В. Хрулёва" Министерства обороны Российской Федерации | DEVICE FOR DETERMINING THE QUALITY OF MILK, VEGETABLE OIL AND OLIVE OIL |
-
1990
- 1990-03-15 CA CA 2012299 patent/CA2012299A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU200951U1 (en) * | 2020-06-26 | 2020-11-20 | Федеральное государственное казенное военное образовательное учреждение высшего образования "Военная академия материально-технического обеспечения имени генерала армии А.В. Хрулёва" Министерства обороны Российской Федерации | DEVICE FOR DETERMINING THE QUALITY OF MILK, VEGETABLE OIL AND OLIVE OIL |
| RU200950U1 (en) * | 2020-06-26 | 2020-11-20 | Федеральное государственное казенное военное образовательное учреждение высшего образования "Военная академия материально-технического обеспечения имени генерала армии А.В. Хрулёва" Министерства обороны Российской Федерации | DEVICE FOR DETERMINING THE QUALITY OF MILK, VEGETABLE OIL AND OLIVE OIL |
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