DE3021582A1 - METHODS AND DEVICES FOR DISPLAYING AND SIGNALING WHEN DEFROSTING, OR PERIODICALLY DEFROSTING, OF FROZEN PRODUCTS - Google Patents

Description

The invention relates to a method and devices for signaling the thawing, including temporary thawing Products that must be kept at temperatures below 0 C.

Many products, e.g. B. in the fields of food, chemicals and pharmaceuticals, must at low temperatures, be stored. A possible thaw even if it happens accidentally and temporarily, it can spoil the products or change their properties without the loss of the product Consumers notice this because the appearance remains unchanged if the products subsequently freeze again.

When you consider the potential consequences of using spoiled products, you can see the need for a process and / or devices that signal thawing, even temporary, can, and indeed irreversibly and by signs that anyone can easily see and understand.

In the particular case of foods, such as frozen foods, this means that in addition to the dispensing of safe foods and immediately detectable displays, the method or the device must be extremely economical, so that they can also be applied to products with high sales without affecting product costs.

Means are available that can give signals when a frozen product is brought to temperatures that will be above the prescribed, but this Remedies are ineffective because they either work so quickly that they also indicate temperature changes, which occur for such a short time that they have no effect on the product, or they do not give clearly understandable ones Show by acting on a continuous relationship between exposure temperature and time duration based on this temperature without really giving effective signals that the product is changing suffers, relate.

With regard to the special case of frozen food, it should be noted that for perfect storage continuous continuity of the so-called cold chain is essential

In fact, new research has shown that an insufficient standard temperature or occasional or repeated temperature changes, the phenomenon of recrystallization of that present in the product cells Water, which causes larger and larger crystals to develop which break the cells open can, so that substrates and enzymes come into contact with each other and bring about such changes that through Cold were prevented. Because cold the enzyme activity does not stop, but only slows down, a Tompera-

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rise, even a partial one, especially if it occurs repeatedly, leads to an increase in conditions among which the quality of the product deteriorates, to lead.

On the other hand, the frozen product has a certain degree of thermal inertia resulting from the stored refrigeration units and mass, and is thus well protected against sudden changes in the ambient temperature.

This protection is provided by the insulation provided by the packaging, so that even if the product is kept at unsuitable temperatures for very short periods of time (vas ζ. Β · can occur during transport), the quality is not impaired.

The invention is therefore based on the object of providing a method for signaling when thawing frozen products and a device for carrying it out, by means of which the difficulties indicated above are overcome. The device should not immediately signal changes in the outside temperature, but should be sensitive to a certain extent to the life cycle of the frozen product in the packaging and should not register every slight increase in temperature. It is intended to indicate the total amount of repetitive temperature changes or the length of periods of unsuitable temperature.

The display device should therefore work with a delay time which, among other things, takes into account the possible occurrence of such sudden, slight temperature changes, even in the best cold chains cannot be avoided, must be selected.

The object is achieved by a method for displaying and signaling when, even temporarily, thawing frozen items Products, which is characterized in that an aqueous salt solution and a colorant by a mechanical means are separated from each other, which is caused by the change in volume of the solution at the moment of Freezing, in which the solution and the colorant are immiscible with one another due to their physical state are broken or cranked, so that any further increase in temperature is a visible and irreversible one Causes reaction between the solution and the colorant.

Further advantageous refinements of this method and devices for carrying it out are given in the foregoing Claims stated.

The invention provides a method and devices for its implementation that display and signal when products that need to be stored at a low temperature, possibly temporarily, at a unsuitable temperature are kept. An essential one

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The feature of the invention is the utilization of the physicochemical Properties of an aqueous salt solution, the eutectic point of which is based on the calibration temperature of the device of the invention provides. It wix-d applied the principle after which at a temperature below the eutectic point an aqueous solution is completely in its solid state present (e.g. ice plus solid salt)

Such a temperature, which is different for each of the selected solutions or mixtures of solutions, is called the calibration temperature the device used *

If you look at the freeze-thaw diagram (Fig. 8) one aqueous saline solution, one can determine: if the temperature of an aqueous solution is lowered with z. B. C. Percentage by weight of salt from temperature t to t, »so ge

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the solution does not freeze up to point E. If point B is reached once the outside temperature is below t. lies _{ some ice begins to separate from the solution. This process results in an increase in the concentration of the saline solution. Tits continues until the temperature of the entire solution has reached t j then almost all of the water has separated from the ice and all of the salt has crystallized.

At point E of the curve (the eutectic point), coexist equal amounts of water, ice and solid salt. Under point E

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only ice and solid salt (solid eutectic) coexist. The hatched part in Fig. 8 shows the area in which solution and ice form at the same time.

The dotted part shows the area in which ice and solid Eutectic coexist. The part between the diaphragm and the ordinate t shows the area in which solution and

Salt are present at the same time.

Some possible salt solutions with their respective eutectic points are given in Table A at the end of the description listed.

Using the properties given above Aqueous salt solutions will be the combination of an aqueous salt solution of a known eutectic point and an indicator colorant, the latter being suitably treated so that it is not in the liquid Solution resolves before a predetermined time has passed. Before freezing, a diaphragm is placed between the Solution and the stain placed in position to prevent their mutual contact.

When the temperature drops below 0 ^° C., the diaphragm is broken or removed by the action of increasing the volume of the water separating from the salt in the solution; but because of the fixed state in which the

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The solution itself is located as soon as the temperature, which corresponds to the eutectic point, is reached and undershot no mixing occurs between the solution and the colorant.

If the temperature is above the eutectic point for a short time, the solution dissolves and touches it Coloring agent so that after a predetermined time by the treatment to which the coloring agent has been subjected colored the solution and retained the assumed color egg even if a subsequent re-freezing process takes place.

It should be noted that with the queues "partition" and "Diaphragm" in this description and the claims is to be understood as any means which is under the effect The increase in the volume of the aqueous saline solution can break or tear, get a hole in or out of position can be pushed.

The invention and in particular the devices for practicing the method according to the invention is now described in detail on preferred embodiments, reference being made to the accompanying figures.

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ORIGINAL

Show it:

Pig. 1 shows a cross section through a device for Implementation of the method according to the invention, in which the solution and the colorant are in a solid container and are kept separated from each other by a breakable partition.

2 shows a cross section through a device for carrying out the method according to the invention, in which the dye is in a breakable container, infiltrated in the solution

3 shows a cross section through a device for carrying out the method according to the invention, in which the solution and the stain are kept separated from each other by a removable septum

Fig. H a cross section through an apparatus for carrying out the Verfäirens invention, in which a durchlöcherbares partition member is used.

5 shows a cross section of more than one for carrying out the method according to the invention, which are connected to one another and calibrated for different thawing temperatures

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ORIGINAL INSPECTED

6 shows a plan view of a particularly preferred embodiment of a device for carrying out the invention Procedure

Pig. 7 shows a vertical section through the device shown in FIG. 6 in the open state

Figure 8 is a freeze-thaw diagram of an aqueous saline solution.

Reference is now made to FIG. The aqueous salt solution 4 of suitable concentration is in one solid (rigid) container 1 made of non-deformable, non-toxic material that is resistant to low temperatures is e.g. B. made of polystyrene.

The container 1 is covered by a cover 2 made of transparent solid material, e.g. B. crystalline polystyrene, thermally locked.

The aqueous solution h is separated from the coloring agent 5 through a wall 3 of fragile material, e.g. B. a glass film sheet (fragile septum) separated.

While the saline solution takes up all of the available space, the dye (e.g. a suitable one) does so packaged food coloring). This causes the aqueous solution (which is produced during the freezing or cooling process has increased its volume)

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exert pressure on the diaphragm until it breaks.

The coloring or indicating agent is preferably pretreated by means of techniques derived from microencapsulation or the like so that it takes on a grainy appearance. Each granule is covered with a membrane, the chemical nature and thickness of which enables contact between the colorant and selected aqueous salt solution in the liquid state, but only after a predetermined time has elapsed. This period of time is directly proportional to the membrane thickness and the granule size and inversely proportional to the temperature at which the contact between the liquid aqueous solution and the granular display medium takes place} it is referred to as "delay time ¹ *".

Therefore, during the freezing cycle, after the diaphragm is broken, the solution will come in with the colorant Contact, but either because it solidifies quickly or because of the presence of the protective membrane no color on.

In the case of thawing, the solution dissolves after a suitable one predetermined period of time the membrane with which the granules are coated and irreversibly takes a Coloring. This fact can be ascertained even in the case of the subsequent refreezing because the previously colorless solution has taken on the color "

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Fig. 2 shows a modification of the device according to the invention. It comprises a solid container 6, which the Contains aqueous salt solution 8 and is hermetically sealed by the transparent cover 7. That suitable treated colorant 10 is in a delicate capsule 9, which from the solution 8, while it freezes, is broken. In this case, the fragile septum mentioned above is composed of the delicate one Capsule 9,

Fig. 3 shows a further modification of the device according to the invention. With her, the container consists of a capsule 11 made of solid (rigid) material »filled by of the aqueous saline solution 12 and provided with a wall 13 which has a hole which passes through a pressure diaphragm 14 is completed. While the solution is freezing 12, the diaphragm 14 is moved and out of position removed what the contact with the dye 15 »that is located in the recess, makes possible during a subsequent evacuation.

According to a further modification (FIG. K) , the partition 16 (fragile partition) can be made of deformable, suitably stretched material which is in contact with pointed or cutting elements 17. You can divide the container 18 into two chambers.

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When the aqueous saline solution located in the upper chamber freezes, the increase in volume causes the wall 16 to rupture because it hits the pointed elements 17. After that, in case of thawing (if it
is in the liquid state) come into contact with the dye in the lower chamber.

As can be seen from the above, the devices for carrying out the method according to the invention can be calibrated to a predetermined temperature (e.g. near the limit temperature of a certain product) by employing an aqueous salt solution whose eutectic
Point corresponds to this temperature.

Ee , however, is also possible to combine two or more devices, the particular devices different from one another
Solutions and stains contain and on various
Temperatures are calibrated. In addition, two or
more devices "showing the same saline solution, but
contain different coloring agents treated in different ways, so that the coloring occurs after different lax periods at temperatures above the calibration temperature.

Such an embodiment (FIG. 5) has an outer shell 19, which is divided into several independent chambers.

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Each of them contains its own dye 20, the through a fragile partition 21 from the solution 20, which can also be different in each chamber, is separated. Such is the device according to the invention capable of varying degrees of defrosting or maintaining higher temperatures for different periods of time to signal.

A simplified embodiment of the multiple device just described, suitable for displaying different times of maintaining a temperature higher than the calibration temperature, may comprise a rigid envelope or container, such as that shown in FIG. 1, which is provided with a a fragile septum separating the aqueous saline solution from the indicating colorant. The latter contains a mixture of two or more different colorants, each of which is treated so that the color is delivered to the liquid solution with which it comes into contact after mutually different periods of time.

The different colorants can also be made up of successive layers in one or more elements be wrapped up so that they can be resolved one after the other, but with increasingly different delays.

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It should be noted that one of the main features of the invention is that the granules of the colorant are coated with a membrane which delays their melting in an aqueous solution.

The benefits to which this feature leads are twofold: First, it eliminates the inconveniences avoid that occur as a result of the fact that, according to the concentration, in the interval between the freezing point and the eutectic point of a saline solution a liquid solution remains, which after it has come into contact with the coloring agent, can cause a color change of the display agent

Second, because every period of even short duration in which the device is at a higher temperature than expected, with a decrease in the delay time agrees, it follows that the devices according to the invention the possible sudden Changes in temperature save what more and more the margin of delay on which the device was calibrated until the irreversible staining takes place, reduced. This phenomenon occurs because the solution in the liquid state contains the granules that contain the colorant every time it is in with them Contact is, attacks and stops when it is in his

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previous solid state returned vlrd.

After these more or less long attacks, a Reached the point where the colorant begins to diffuse and the indicator begins to change color.

This phenomenon takes place at the same time which the delay time ends and this is very important, because during short one-off temperature increases not act on the product and damage it, this can be the case if they occur repeatedly «

To make it possible to keep the product at a temperature above the usual storage temperature for such a to expose a short period of time so that the product is not attacked (for example the time that is required, take frozen food out of the freezer so that the consumer can judge whether he or she has it wants to buy \ can introduce a delay time during which the liquid saline solution and the dye do not react with each other, be provided.

For a better understanding, a non-limiting example of the application of the method according to the invention will now be given brought. The device used in this example is specifically designed for frozen food.

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example

The device shown in Fig. 6 and used in this example consists of a container 23 in the form of a rectangular parallelepidedon with a base of 22 mm and a height of 8.8 mm. This container 23 consists of a lower part 24 which is closed by a cover 25 , which can be inserted by pressure (FIG. 7). The edges of the base 2k and the cover 25 are shaped so that they fit into one another. At the bottom of the lower part 2k is a rectangular recess 28 of a side wall of 5 now and a depth of 2 mm; it is an upper stage 31 provided with a side wall of 1 51 ^ O

The walls of the recess are equidistant from the inner walls 27 of the cover 25 in order to favor a well-timed diffusion of the colorant over the entire solution *

The cover 2 $ is provided with a round, inwardly projecting middle part 29 with flat sloping sides 30. The thickness of part 29 has been researched in such a way that the gas bubble that forms when the liquid solution enters the indicator well spreads as evenly as possible around the base of the cover and that the beveled sides the

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individual characteristics (particular characteristics) keep inside the device (during use and after dissolving the solution)

The inner edges of the cover are round, so that a better expansion of the gas bubble is promoted.

The fragile septum (not shown in the figure) consists of a rectangular sheet of glass film, a Side wall of 20 mm and a thickness of 0.130 to 0.145 mm. The pike-corner shape, especially the square shape, was chosen for the glass because it is considered the most economical of All was found «The fragile septum is attached to the lower edge 26 of the cover 25 by means of a layer glued on by silicone rubber (Silastic RTV 73 * 0.

So a triple result was obtained:

a) The pressure connection between the cover and the lower part makes it possible to adjust the diaphragm in the desired Position and penetrate some of the adhesive along the touching edges of the cover and base to leave, which contributes to the tightness of the device.

b) Since the glue is applied to the upper part of the diaphragm, it "dampens" the expansion pressure of the freezing one Solution does not and tends to break the glass.

c) The diaphragm is in addition to the gluing between

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Bottom and cover pinched, which makes breaking even more effective

The length of the step 31 "which, together with the lower edge 26 of the cover 25, holds the fragile septum, is such that the diaphragm can bend so much under the action of the pressure of the freezing solution that the breaking limit is exceeded"

The device is made of materials such as opaque white polystyrene for the base Zk and transparent crystalline polystyrene for the cover 25. The reasons for choosing these materials are their non-toxicity at low temperatures and their low cost «

An aqueous 19.7 # strength ammonium chloride solution was chosen as the solution and the food coloring E 12k (red), microencapsulated as the display means, so that a delay time of one hour can be provided.

This colorant was chosen because it is a food type (although not strictly necessary is because the substance is isolated within the indicating means), and because it was examined under more than fifty Colorants of various types, which is the one that dissolves most quickly in ammonium chloride, is not sensitive to light and its color is bright red.

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As a variant, yellow E 102 was used, which led to practically the same results.

The choice of the solution of ammonium chloride, a solution that works at the concentration and in the amount in which it is used becomes, is non-toxic, was due to the fact that the eutectic point is 15 »8 ° C and in the most countries frozen products are kept at a maximum temperature of 18 ° C. At this temperature held, ammonium chloride is in a solid state and snow-white.

At the chosen high concentration ($ 19.7 is the same the eutectic concentration) the freezing point is close the eutectic point, so that the period of time during the cooling phase in which the liquid salt solution with the colored indicator means is in contact is minimal.

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TABLE A Some saline solutions and their eutectic points

Dinatxium maleate 0.4 C

Sodium Sulphate Monosodium Citrate Potassium Nitrate Magnesium Sulphate Trisodium Citrate Potassium Chloride Disodium Citrate Potassium bromide ammonium cliloride dipotassium citrate Sodium nitrate sodium chloride sodium bromide magnesium chloride Potassium carbonate tripotassium citrate

1.1 ° c 2.1 ° c 2.9 ° c 4.0 ° c 6.9 ° c 10.7 ° c 12.0 ° c 13.0 ° c 15.4 ⁰ C 15.6 ⁰ C 18.5 ⁰ C 21.8 ° c 28.0 ° c 33.6 ⁰ C 36.5 ⁰ C 4o, o ° c

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COPY

Claims (11)

760-21 ".. PATENT LAWYERS D.- ;. mo. Π. XEa2ND AK K asrs) O Π Ο "j COO DirL.-ing. K. HAXTCK-eit ^ -p ^ ys. W. 3CJOiTTZ dipl.-ing. E-GRAALFS Dipl..ing. W. WEHNERT Dipl.-Phys. W. CARSTENS dk.-ing. V /. DOERING HAMBI) IiG-MUNICH -! DÜSSELDORF * PATBNTANWiLTE · NEUEH WALL 41 · 2O0O HAMItUSG 30 * ^ SCHMITZ-GRAALFS NEW WALL 41 2OOO HAMBURG 3ft TBLEFON + TELECOPIER (04O) 3Θ 67 89 TELEX 02 Xi 769 INPAT I> Franco SaIa cable negbdapatenthamburq Via Mil aiii 6 / A 'HAUCK ■ WEHJJERT · CARSTENS MOZARTSTRASSE 2380OO MUNICH I-Milano phone + telecopier (wm 33 02 se TELEX 03 216 OSC PAMlT D CABLE NSGEDAPATENT MUNICH DOERING K.-WILH.-RING41-4000 DÜSSELDORF TELEPHONE (0211) 37 BO 27 . CABLi: NEGEDAPATBNT DUSSELDOHP DELIVERY ADDRESS PLEASE REPLYTO: HAMBURG, 6 June 1980 Methods and devices for displaying and signaling during thawing, including temporary thawing, of frozen products A_n_s_p_r_ü_c_h e_ £ Procedure for displaying and signaling during thawing, also temporary thawing of frozen products, characterized in that an aqueous salt solution and a colorant can be separated from each other by a mechanical means, which is caused by the change in volume of the solution at the moment of its freezing, in which the solution and the colorant are due to their physical properties State are immiscible, broken or displaced, so that any further increase in 030051/0831 APPROVED REPRESENTATIVES AT THE EUROPEAN PATENT OFFICE ··· / « PROFESSIONAL · KKPItESIiXTATlVKN HEKORK THE EL ¹ KOfEAX ΡΛΤΚΧΤ OFFICE OKOT »CB» JlANK ία. IUUBUIKl (sort code 200 700 00) KB. OO / 2S4S7 -DBMDKrB BAKK AQ. HAKDUJia (BtZ 200 8OO OOl NS. BUS «Η» 83 · ΡΟ.Τ «ΓΚ _Γ 0Κ Π« ». 28« -208 Temperature causes a visible and irreversible reaction between the solution and the dye. 2. The method according to claim 1, characterized in that the temperature of the eutectic point of the salt solution is chosen as the calibration temperature for effecting the process will. 3 · The method according to claim 1, characterized in that a colorant is used, which consists of parts which are provided with a restrained coating, the causes a delay in the visible and irreversible reaction. 4. The method according to claim 3, characterized in that the delay time of the specific properties of the coating layer with respect to the properties the saline solution as well as the thickness of the coating with respect to the size of the particles. 5, method according to claim 4, characterized in that the coating layer is applied in the manner of micro-encapsulation. 6 '. Device for carrying out the method according to claims 1 to 5r characterized by a solid container (1, 6, 11, 18, 1 9, 23) which has an aqueous, 03 0 051/0831 saline solution (4, 8, 12, 22) selected according to the calibration temperature of the performance, a dye (5 _t 10, 15, 20) and a separator (3i 9 »14, 16) arranged between the saline solution and the dye is breakable by increasing the volume of the saline solution during freezing. 7. Device for performing the Verfahreais according to claims 1 to 5, characterized in that the aqueous saline solution (4, 8, 12, 22) due to its eutectic Temperature is selected and the colorant (5, 10, .15, 20) has the form of particles which with one a delay time of the visible irreversible Are provided with a reaction-generating coating 8 · Device for carrying out the method according to Claims 1 to 5, characterized in that the with Coated particles are granules that are coated in the manner of microencapsulation. 9 · Device for carrying out the method according to the Claims 1 to 5, characterized by a £ ombi ~ . nation of several containers (i <?), the saline solutions (22) with different eutectic points and display bodies (20) of different colors, which are treated in this way are that they have the same delay time, contain" 030051/0831 10 · Device for carrying out the method according to the claims 1 to 5, characterized by a combination of multiple containers (19) | all the same watery Saline solution (22), but different indicator bodies (20), are treated so that they are predetermined from one another There are various delays in releasing the paint to the liquid saline solution. 11. Device for performing the method according to the claims 1 to 5, characterized in that the colored display bodies (5, 10, 15 »20) are a combination of two or contain more than one different colorant, each of which is treated so as to interfere with one another in color release various delay times to the liquid saline solution.