Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
  • G01K11/06—Measuring 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D29/00—Arrangement or mounting of control or safety devices
  • F25D29/008—Alarm devices

Definitions

• the present invention relates to a method for indicating whether an
• An object of the present invention is to provide a simple, low cost, and
• Another object of the invention is to provide an indicator for use in such method.
• microcapsule walls enclosed within microcapsule walls, and a second material normally separated
• the first material further including a liquid which, when frozen,
• the liquid which expands when frozen is water. Also,
• the indicator includes a rigid housing enclosing the first and second materials and
• the color change substance in the second material is an
• the first material provides a weak acid environment
• freeze-thaw indicator for application to articles, particularly food articles to provide
• Fig. 1 schematically illustrates one form of freeze-thaw indicator
• 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
• Figs. 3a, 3b and 3c illustrate three phases in the operation of the
• Fig. 4 schematically illustrates the indicator of Fig. 1 incorporated in a
• Fig. 4a is an enlarged sectional view along IVa. Va of Fig. 4.
• Fig. 4b illustrates a modification in the construction of Fig. 4a.
• Fig 1 there is illustrated a freeze-thaw sequence
• the first material 3 includes a liquid which,
• freeze-thaw sequence Housing 6 enclosing the two materials 3 and 5 is rigid to
• Fig 3b illustrates the microcapsule walls 4 enclosing the first material
• microcapsule walls 4 causes the first material to expand and therefore to
• FIG. 3c illustrates the condition wherein
• Fig 4 illustrates the freeze-thaw sequence indicator 2 applied to a
• packaged food article such as a fish or meat product
• two color- change materials 3, 5, are normally colorless or transparent so that the
• the rigid housing 11 containing the two materials 3, 5 the rigid housing 11 containing the two materials 3, 5
• FIG. 4a illustrates another example wherein the
• the color former substance of the second material 5 is a
• the substance of the first (encapsulated) material 3 provides a weak acid environment and includes water which expands when frozen to rupture
• Leucodyes is the name given to colorless chemical substances that
• the encapsulated material is the water plus weak acid
• a preferable weak acid environment for the encapsulated material is a water solution of citric acid or acetic acid
• microcapsule walls In the present invention, the microcapsule walls are ruptured
• the core liquid preferably water, which is expanded when frozen
• Microencapsulation is a well established technology used in a variety of materials.
• microcapsules are based on the polarity between the two immiscible phases, oil and water, which in turn enables the
• microcapsule walls are of polyurea, and its structural features include the ability to
• microcapsules flows into the surrounding continuous phase containing the
• the continuous phase can be, for example, a solution of leucodyes in
• organic solvents preferably an aromatic oil or ester containing benzene rings
• a color former such as ones made and
• the immiscible phase is composed of granules of citric acid
• a preferred leucodye is one made by Hilton-Davis Corporation of
• Water-loaded polyurea microcapsules were prepared by making use of
• citric acid instead of citric acid, there may be also used acetic acid, or other weak
• encapsulated microcapsules are prepared with cyclohexane in the water
• immiscible phase is edible, but also the process allows placing microcapsules of
• microcapsules with each batch containing microcapsules of the same size, but

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)
• Cold Air Circulating Systems And Constructional Details In Refrigerators (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=11069066

Family Applications (1)

Country Status (7)

Cited By (10)

Families Citing this family (1)

Citations (11)

• 1996
  • 1996-07-11 IL IL11884096A patent/IL118840A0/xx unknown
• 1997
  • 1997-07-08 WO PCT/IL1997/000229 patent/WO1998002722A1/en not_active Application Discontinuation
  • 1997-07-08 BR BR9711806A patent/BR9711806A/pt not_active IP Right Cessation
  • 1997-07-08 JP JP50580998A patent/JP2003519461A/ja active Pending
  • 1997-07-08 EP EP97928418A patent/EP0886768A4/en not_active Withdrawn
  • 1997-07-08 CA CA002260184A patent/CA2260184A1/en not_active Abandoned
  • 1997-07-08 AU AU32721/97A patent/AU757162B2/en not_active Ceased

Patent Citations (11)

Non-Patent Citations (1)

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