AU3272197A - Method and indicator for indicating thawing - Google Patents

Method and indicator for indicating thawing

Info

Publication number
AU3272197A
AU3272197A AU32721/97A AU3272197A AU3272197A AU 3272197 A AU3272197 A AU 3272197A AU 32721/97 A AU32721/97 A AU 32721/97A AU 3272197 A AU3272197 A AU 3272197A AU 3272197 A AU3272197 A AU 3272197A
Authority
AU
Australia
Prior art keywords
microcapsule walls
indicator
freeze
undergone
color change
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
AU32721/97A
Other versions
AU757162B2 (en
Inventor
Amiram Carmon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Merck Patent GmbH
CDW Sicherheitstechnik GmbH
Original Assignee
Merck Patent GmbH
CDW Sicherheitstechnik GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Merck Patent GmbH, CDW Sicherheitstechnik GmbH filed Critical Merck Patent GmbH
Publication of AU3272197A publication Critical patent/AU3272197A/en
Assigned to MERCK PATENT GMBH, CDW SICHERHEITSTECHNIK GMBH reassignment MERCK PATENT GMBH Alteration of Name(s) of Applicant(s) under S113 Assignors: CARMON, AMIRAM
Application granted granted Critical
Publication of AU757162B2 publication Critical patent/AU757162B2/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01KMEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/06Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using melting, freezing, or softening
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25DREFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D29/00Arrangement or mounting of control or safety devices
    • F25D29/008Alarm devices

Description

METHOD AND INDICATOR FOR INDICATTNG THAWING
FIELD OF THE INVENTION
The present invention relates to a method for indicating whether an
article, particularly a perishable food article, has undergone a freeze-thaw
sequence, and also to indicators for use in such method.
BACKGROUND OF THE INVENTION
Various kinds of food substances are kept in a frozen condition in order
to inhibit spoilage by bacterial or other microbial growth. Certain frozen foods,
particularly sea and meat products, are very susceptible to spoilage when the
temperature increases above the freezing point even for short periods. Thus, a
temporary power failure in a freezer may cause thawing, and thereby spoilage of
the food article, which may not be noticed when the article is refrozen by the
resumption of the power. This may occur in the consumer's freezer, but may also
occur anywhere along the distribution channel until the food article reaches the
consumer.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a simple, low cost, and
effective method for indicating whether an article has undergone a freeze-thaw
sequence so as to alert a consumer of the possible spoilage of the food article.
Another object of the invention is to provide an indicator for use in such method.
According to one aspect of the present invention, there is provided a
method of indicating whether an article has undergone a freeze-thaw sequence, comprising: applying to the food article an indicator including: a first material
enclosed within microcapsule walls, and a second material normally separated
from the first material by the microcapsule walls; the first and second materials
including substances which produce a color change when brought into contact with each other, but which are normally separated from each other by the
microcapsule walls; the first material further including a liquid which, when frozen,
expands sufficiently to rupture the microcapsule walls such that when the first
material has been frozen and is subsequently thawed, it passes through the
ruptured microcapsule walls and comes into contact with the second material to
produce a color change indicating that the food article has undergone a
freeze-thaw sequence.
According to further features in the preferred embodiments of the
invention described below, the liquid which expands when frozen is water. Also,
the indicator includes a rigid housing enclosing the first and second materials and
preventing manual rupture of the microcapsule walls. According to still further features in the described preferred
embodiments, the color change substance in the second material is an
acid-sensitive leucodye, and the first material provides a weak acid environment
Embodiments of the invention are described below wherein the leucodye (color
former) is dissolved in an organic solvent which is water immiscible, the weak acid
environment is a water solution of citric acid, and the capusule walls are polyurea
According to another aspect of the present invention, there is provided a
freeze-thaw indicator for application to articles, particularly food articles to provide
an indication in accordance with the above method of whether the article has
undergone a freeze-thaw sequence
As will be described more particularly below, the foregoing method and
indicator provide a simple, low-cost and effective means to indicate whether an
article, particularly a perishable food article, has undergone a freeze-thaw
sequence, and thereby to alert the consumer that the article may have become
spoiled
Further features and advantages of the invention will be apparent from
the description below
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is herein described, by way of example only, with
reference to a number of examples set forth below and also with reference to the accompanying drawings, wherein:
Fig. 1 schematically illustrates one form of freeze-thaw indicator
constructed in accordance with the present invention;
Fig. 2a illustrates one of the microcapsules in the indicator of Fig. 1 in the normal condition of the capsules;
Fig. 2b illustrates the microcapsule of Fig. 2a, but in its ruptured
condition resulting from the expansion of the water within the encapsulated
material caused by freezing;
Figs. 3a, 3b and 3c illustrate three phases in the operation of the
indicator of Fig. 1 ;
Fig. 4 schematically illustrates the indicator of Fig. 1 incorporated in a
housing applied to a perishable food article to prominently display the word
"SPOILED" when the indicator has undergone a freeze-thaw sequence;
Fig. 4a is an enlarged sectional view along IVa. Va of Fig. 4; and
Fig. 4b illustrates a modification in the construction of Fig. 4a.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
With reference first to Fig 1 , there is illustrated a freeze-thaw sequence
indicator, generally designated 2, including a plurality of microcapsules of a first
material 3 enclosed within microcapsule walls 4 dispersed within a second
material 5, and all enclosed within a transparent rigid housing 6 The first material
3 and the second material 5 both include substances which produce a color
change when brought into contact with each other, but which substances are
normally separated from each other by the walls 4 of the microcapsules in which
the first material is encapsulated The first material 3 includes a liquid which,
when frozen, expands sufficient to rupture the microcapsule walls 4, such that
when the first material 3 is thawed, it comes into contact with the second material
5 producing a color change indicating that the indicator has undergone a
freeze-thaw sequence Housing 6 enclosing the two materials 3 and 5 is rigid to
prevent manual rupture of the capusle walls 4, and is transparent to permit
viewing the color change when it occurs
The foregoing is schematically illustrated in Figs 3a-3c Thus, Fig 3a
illustrates the normal condition of the indicator, wherein microcapsules of the first
material 3 are dispersed in the second material 5 but are separated therefrom by
the microcapsule walls 4 enclosing the first material 3, Fig 3b illustrates the
condition wherein freezing of the indicator, particularly the first material 3 within
the microcapsule walls 4, causes the first material to expand and therefore to
rupture the microcapsule walls, whereas Figs 3c illustrates the condition wherein
subsequent thawing of the indicatorn causes the first material 3 to come into direct contact with the second material 5 and thereby to produce the color change
indicating that the indicator, and thereby the article to which the indicator has
been attached, has undergone a freeze-thaw sequence This indicator remains
even if the indicator, and the food articles including the indicator, are subsequently
re-frozen
Fig 4 illustrates the freeze-thaw sequence indicator 2 applied to a
packaged food article, generally designated 10, such as a fish or meat product
normally sold in a frozen condition and to be retained in a frozen condition until
ready for consumption or cooking In the case illustrated in Fig 4, the housing 11
for the indicator is shaped to spell the word "SPOILED", so that when the
color-change is produced by the freeze-thaw sequence, the food article will be
irreversibly marked "SPOILED", and thereby alert the consumer Preferably, the
two color- change materials 3, 5, are normally colorless or transparent so that the
word "SPOILED" is not prominently noticeable until a color change has been
produced by the food article undergoing the freeze-thaw sequence
As one example, the rigid housing 11 containing the two materials 3, 5,
may be made of two transparent plastic sheets 11a, 11b, sealed along their
peripheries, as shown in Fig 4a Fig 4b illustrates another example wherein the
transparent rigid housing, therein designated 11', containing the two color-change
materials 3, 5, is in the form of a transparent glass or plastic tube which is sealed
at its opposite ends
Preferably, the color former substance of the second material 5 is a
leucodye, and the substance of the first (encapsulated) material 3 provides a weak acid environment and includes water which expands when frozen to rupture
the microcapsule walls.
Leucodyes is the name given to colorless chemical substances that
produce a color change when reacting with a specific chemical agent. For
example, certain substances containing e.g., lactones, will color when reacting
with weak acids. Such leucodyes are well known from their use in carbonless
paper, in color copiers based on the Cycolor process developed by Mead
Corporation of Dayton, Ohio, and in radiation-sensitive indicators such as
described in US Patent 5,206, 118, incorporated herein by reference. In the
Cycolor process the leucodyes are dissolved in in dispersed acrylic monomers
that are then encapsulated with a wall made of another polymer and dispersed in
a phenolic resin containing zinc salicylate which forms an acidic environment.
Once the microcapsules are crushed by mechanical force, their colourless dye
content spills out and interacts with the weak acidic environment to form a colored
dye.
In the carbonless paper technique, the leucodye in an oily phase is
encapsulated, while the continuous phase in which the microcapsules are dispersed is the weak-acid watery phase. In the present invention the two phases
are reversed; that is, the encapsulated material is the water plus weak acid, and
the continuous water immiscible phase in which the capsules are dispersed
contains the leucodye.
In addition, both color former materials used for producing the color
change are selected to be edible, or at least non-toxic if ingested in the quantity
included in the indicator so as to be useable with food products. Thus, a preferable weak acid environment for the encapsulated material is a water solution of citric acid or acetic acid
Further, in carbonless paper, the two color former substances are
brought into contact by the application of external force to rupture the
microcapsule walls In the present invention, the microcapsule walls are ruptured
by the freezing of the core liquid, preferably water, which is expanded when frozen
Microencapsulation is a well established technology used in a variety of
applications In general, creation of microcapsules is based on the polarity between the two immiscible phases, oil and water, which in turn enables the
dispersion of one phase in the form of tiny droplets in the other phase
A preferred example of a process that can achieve the desired
microcapsular structure is called "Interfacial Polymerization", which can be used to
encapsulate aqueous solutions dispersed in oil or polymers The resultant
microcapsule walls are of polyurea, and its structural features include the ability to
create a non-permeable continuous wall that can be very thin Such a process of
producing water containing microcapsules enclosed by polyurea walls is
described in detail by Yamane, Ohshima and Kondo in the Journal of
Microencapsulation Volume 9, pp 279-286, 1992, incorporated herein by
reference
When the watery content of these microcapsules is frozen, the inside
volume is increased due to the state change of the water from liquid into ice The
increase of volume of the microcapsule content causes the microcapsules walls to
rupture If a weak aqueous acid solution, or a dispersion of acidic salt in water, is the content of such microcapsules, this content will not start to flow into the
surrounding phase while in the freezing state, but once the temperature increases
above the melting point, the solution or dispersion from the inside of the ruptured
microcapsules flows into the surrounding continuous phase containing the
leucodye to produce the color change, which is irreversible
The continuous phase can be, for example, a solution of leucodyes in
organic solvents preferably an aromatic oil or ester containing benzene rings
For example, there could be used one of the organic solvents described in the
above cited US Patent 5,206,118 which is edible and which is used in food
products
In one preferred embodiment, a color former such as ones made and
sold commercially by Hilton-Davis of Ohio, USA or Mitsubishi of Japan, is
dissolved in an organic solvent, such as an ester which constitute the water
immiscible phase The aqueous phase is composed of granules of citric acid
dissolved in water in a concentration of up to 30% The aqueous phase is then
added to an oily medium, and by controlled fast stirring, is dispersed into tiny
droplets These watery droplets are then encapsulated by a reaction between, for
example, amines and isocyanate, the first present in the water phase and the
other present in an oily phase These two substances will interact on the surface
of the droplets to form a thin polyurea shell, which will constitute the microcapsular
wall normally preventing contact between the weak acid inside the microcapsules
and the leucodye in the continuous oil phase
A preferred leucodye is one made by Hilton-Davis Corporation of
Dayton, Ohio and sold under the trademark "Copikem" This material is available in the form of white powder and is soluble in various organic solvents. A 0.3%
solution of "Copikem" (Reg.TM) in an ester is preferred for the continuous-phase
material 5; whereas a solution of citric acid (0.5% in alcohol, or 33% in water) is
preferred for the encapsulated material 3.
EXAMPLES
Water-loaded polyurea microcapsules were prepared by making use of
the interfacial polymerization reaction between tetraethylenepentamine (TEP) in
an aqueous phase and toluylenediisocyanate (TDI) in an organic solvent as
described in the above-cited 1992 publication by Yamane, Ohshima and Kondo,
except that (a) the oil phase included a leucodye, namely that supplied under the
trademark "Copikem" (Reg.TM) by Hilton-Davis Corporation of Dayton, Ohio,
dissolved in an aromatic solvent or ester, and (b) the aqueous phase including a
weak acid, namemly, a 30% water solution of citric acid.
The two phases were thoroughly mixed to produce the water-loaded
polyurea microcapsules, with the leucodye within the continuous oil phase, and
the weak acid within the dispersed water phase. Upon freezing, the microcapsule
walls were ruptured, such that upon thawing, the water phase came into contact
with the leucodye oil phase, to produce the color change indicating the
freeze-thaw sequence.
Instead of citric acid, there may be also used acetic acid, or other weak
acids.
Another way to achieve the structure described above and to permit the
use of ethanol, an edible material, instead of the water immiscible organic solvent, follows more closely the method of Yamane, Ohshima and Kondo. The polyurea
encapsulated microcapsules are prepared with cyclohexane in the water
immiscible phase, and the diluted citric or acetic solution in the aqueous phase.
The chemical substances which form the microcapsule walls after dispersion are
tetraethylenepentamine included in the aqueous phase, and toluyediisocyanate
included in the cyclohexane of the water immiscible phase. Following the
formation of the microcapsules they are separated from the liquid by
centrifugation, and placed in 95% ethanol in which 0.3% of the leucodye
(Copikem, Reg TM) was previously dissolved. In this way, not only the water
immiscible phase is edible, but also the process allows placing microcapsules of
predetermined size in the indicator
Yamane et al. have shown that the temperature of freezing decreases
with decrease of the microcapsular size. Centrifugation allows cropping of batches
of microcapsules with each batch containing microcapsules of the same size, but
different batches containing different sizes Those familiar with the art will
appreciate that using this method permits creating a variety of indicators with a
range of freezing temperatures.
It will be appreciated that the foregoing represent merely preferred
examples of the invention, that many other variations and modifications may be
made

Claims (19)

  1. A method of indicating whether an article has undergone a freeze-thaw
    sequence, comprising, applying to the article an indicator including:
    a first material enclosed within microcapsule walls, and a second
    material normally separated from said first material by said microcapsule
    walls,
    said first and second materials including substances which produce
    a color change when brought into contact with each other, but which are
    normally separated from each other by said microcapsule walls;
    said first material further including a liquid which, when frozen,
    expands sufficiently to rupture said microcapsule walls such that when said
    first material has been frozen and is subsequently thawed, it passes through
    said ruptured microcapsule walls and comes into contact with said second
    material to produce a color change indicating that the food article has
    undergone a freeze-thaw sequence.
  2. The method according to Claim 1 , wherein said liquid which expands when
    frozen is water
  3. The method according to either of Claims 1 or 2, wherein said indicator
    includes a rigid housing enclosing said first and second materials and
    preventing manual rupture of said microcapsule walls.
  4. The method according to Claim 3, wherein said rigid housing spells out the
    word "SPOILED", which word becomes prominently displayed by said color
    change when the food article has undergone a freeze-thaw sequence
  5. The method according to any one of Claims 1 -4, wherein said color change
    substance in said second material is an acid-sensitive leucodye, and said
    first material provides a weak acid environment
  6. The method according to Claim 5 wherein said weak acid environment is a
    water solution of citric acid
  7. The method according to any one of Claims 1 -9 wherein said microcapsule
    walls are of polyurea
  8. A freeze-thaw indicator for application to an article to provide an indication of
    whether the article has undergone a freeze-thaw sequence, comprising
    a first material enclosed within microcapsule walls, and a second
    material normally separated from said first material by said microcapsule
    walls,
    said first and second materials including substances which produce
    a color change when brought into contact with each other, but which are
    normally separated from each other by said microcapsule walls,
    said first material further including a liquid which, when frozen,
    expands sufficiently to rupture said microcapsule walls such that when said
    first material has been frozen and is subsequently thawed, it passes through
    said ruptured microcapsule walls and comes into contact with said second material to produce a color change indicating that the food article has undergone a freeze-thaw sequence
  9. The indicator according to Claim 8, wherein said liquid which expands when
    frozen is water
  10. The indicator according to either of Claims 8 or 9, wherein said indicator
    includes a rigid housing enclosing said first and second materials and
    preventing manual rupture of said microcapsule walls
  11. The indicator according to Claim 10, wherein said housing is of rigid plastic
    sheet material sealed around its periphery
  12. The indicator according to Claim 11 , wherein said housing is a glass tube
    sealed at both ends
  13. The indicator according to any one of Claims 8-12, wherein said rigid
    housing spells out the word "SPOILED", which word becomes prominently
    displayed by said color change when the food article has undergone a
    freeze- thaw sequence
  14. The indicator according to any one of Claims 8-13, wherein said color
    change substance in said second material is an acid-sensitive leucodye, and
    said first material provides a weak acid environment
  15. The indicator according to Claim 14, wherein said weak acid environment is
    citric acid
  16. The indicator according to any one of Claims 8-15, wherein said
    microcapsule walls are of polyurea
  17. 17. The indicator according to Claim 16, wherein said microcapsule walls are the
    reaction product of an amine included in said first material, and an
    isocyanate included in said second material which reacts with said amine
    when the two materials are mixed to produce said polyurea microcapsule
    walls enclosing said first material and normally separating it from said
    second material.
  18. 18. The method of indicating whether a food article has undergone a
    freeze-thaw sequence substantially as described with reference to any of the
    disclosed examples.
  19. 19. An indicator for indicating whether a food article has undergone a freeze-thaw sequence substantially as described with reference to any of the
    disclosed examples.
AU32721/97A 1996-07-11 1997-07-08 Method and indicator for indicating thawing Ceased AU757162B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
IL11884096A IL118840A0 (en) 1996-07-11 1996-07-11 A colored indication for possible spoilage of frozen foods
IL118840 1996-07-11
PCT/IL1997/000229 WO1998002722A1 (en) 1996-07-11 1997-07-08 Method and indicator for indicating thawing

Publications (2)

Publication Number Publication Date
AU3272197A true AU3272197A (en) 1998-02-09
AU757162B2 AU757162B2 (en) 2003-02-06

Family

ID=11069066

Family Applications (1)

Application Number Title Priority Date Filing Date
AU32721/97A Ceased AU757162B2 (en) 1996-07-11 1997-07-08 Method and indicator for indicating thawing

Country Status (7)

Country Link
EP (1) EP0886768A4 (en)
JP (1) JP2003519461A (en)
AU (1) AU757162B2 (en)
BR (1) BR9711806A (en)
CA (1) CA2260184A1 (en)
IL (1) IL118840A0 (en)
WO (1) WO1998002722A1 (en)

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Publication number Priority date Publication date Assignee Title
DE20000317U1 (en) * 2000-01-08 2001-06-07 Trender Lutz Device for permanent, permanent detection and display of an overshoot / undershoot of a predetermined temperature
US6679070B1 (en) * 2002-08-29 2004-01-20 Winterlab Method for identifying thawed and refrozen products
DE102006045821A1 (en) * 2006-09-28 2008-04-03 Wötzer, Philipp Display device and frozen food packaging
US8430053B2 (en) * 2010-09-30 2013-04-30 Temptime Corporation Color-changing emulsions for freeze indicators
RU2538450C1 (en) * 2013-10-16 2015-01-10 Игорь Николаевич Кочергин Cold indicator
JP2015159803A (en) * 2014-02-28 2015-09-07 三菱レイヨン株式会社 Nucleic acid for determining number of times of thawing frozen good, and method to determine number of times of thawing frozen good using the same
DE102016005070A1 (en) 2016-04-27 2017-11-02 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Apparatus and method for monitoring the temperature of a cryopreserved biological sample
DE102016005075A1 (en) 2016-04-27 2017-11-02 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Method and device for monitoring the temperature of a cryopreserved biological sample
DE102016005078A1 (en) 2016-04-27 2017-11-02 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Apparatus and method for monitoring the temperature of a cryopreserved biological sample
DE102016005133A1 (en) 2016-04-27 2017-11-02 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Method and device for monitoring the temperature of a cryopreserved biological sample
CN112396949A (en) * 2019-08-13 2021-02-23 余丽 Activation method of environment-friendly low-temperature protection failure prompt label

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US3177843A (en) * 1964-02-13 1965-04-13 Robert S Geocaris Frozen food indicator
US3786777A (en) * 1970-12-31 1974-01-22 Artech Corp Irreversible warm-up indicator
US3888631A (en) * 1972-04-11 1975-06-10 Oskar Edwin Sturzinger Temperature indicator
US3844718A (en) * 1972-05-01 1974-10-29 H Cohen Frozen food defrosting indicator
US3967579A (en) * 1975-10-29 1976-07-06 Stanton H. Kaye Telltale device
US4022149A (en) * 1976-02-06 1977-05-10 Lee Berger Thaw indicator
US4145918A (en) * 1976-09-07 1979-03-27 Akzona Incorporated Freeze-thaw indicator
US4163427A (en) * 1977-12-05 1979-08-07 Isadore Cooperman Freeze-thaw indicator apparatus
US4327117A (en) * 1980-03-18 1982-04-27 Lenack Roger D Thaw indicator for frozen foods
GB8410548D0 (en) * 1984-04-25 1984-05-31 Ciba Geigy Ag Colourable assembly
US5325721A (en) * 1993-02-17 1994-07-05 Minnesota Mining And Manufacturing Company System for indicating exposure to preselected temperatures or tampering

Also Published As

Publication number Publication date
WO1998002722A1 (en) 1998-01-22
IL118840A0 (en) 1996-10-31
EP0886768A4 (en) 1999-09-15
JP2003519461A (en) 2003-06-17
AU757162B2 (en) 2003-02-06
BR9711806A (en) 1999-08-24
EP0886768A1 (en) 1998-12-30
CA2260184A1 (en) 1998-01-22

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