GB1576766A

GB1576766A - Device using the degradation of a polymer for detecting and permanently indicating a transient reheating of a deep-frozen product

Info

Publication number: GB1576766A
Application number: GB3362677A
Authority: GB
Original assignee: Thomson CSF SA
Current assignee: Thales SA
Priority date: 1976-08-13
Filing date: 1977-08-10
Publication date: 1980-10-15
Also published as: FR2361635A1; CH620768A5; DE2736470A1; IT1079824B; FR2361635B1; ES461561A1

Abstract

In order to provide reliable information on whether or not a frozen product has been constantly maintained at a temperature situated below a particular safety threshold, for example -18 DEG C, the device comprises a covering (2) made of an organic polymer which can progressively degrade by cracking at a temperature below -18 DEG C, completely filled with a coloured solution which solidifies at -18 DEG C with an increase in volume. In the event of reheating, the liquid expands and colours a blotting paper (3) wrapping the covering. This device applies to the conservation of products of biological origin. <IMAGE>

Description

(54) A DEVICE USiNG THE DEGRADATION OF A POLYMER FOR DETECTING AND PERMANENTLY INDICATING TRANSIENT REHEATING OF A DEEP-FROZEN PRODUCT (71) We, THOMSON-CSF, a French Body Corporate, of 173, Boulevard Hauss mann-75()08 PARISFRANCE-do hereby declare the invention. for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by tthe following statement: This invention relates to a device using the degradation of a polymer for detecting and permanently indicating a transient reheating of a deep-frozen product. The products in question are, in particular, food products of biological origin which are to be kept at a temperature of - 18 0C, even during handling and transport.A food product which has exceeded this temperature, even for a relatively short time, may not be deep-frozen again without seriously endangering the health of the consumer. A sure information relating to the fact of this transient break in the deep freezing constitutes a guarantee of safety.

According to the present invenion, there is provided a device using the degradation of a polymer for detecting and permanently indicating a transient reheating of a deepfrozen product, comprising: -a liquid whose solidification point lies at the normal temperature of deep freezing; means for accommodating said liquid in a capsule made of an organic polymer which degrades and cracks at said normal temperature and below, enabling the liquid to flow if it thaws; and means for indicating the flow of said liquid, said means functioning in an irreversible manner.

The invention will be better understood and other features thereof will become apparent from the following description in conjunction with the accompanying drawings, wherein: FIGURE 1 illustrates an embodiment of the prior art; and FIGURE 2 illustrates one embodiment of the invention.

In the case of the device illustrated in Figure 1, a liquid 1 consisting of a mixture of an aqueous saline solution solidifying at --18"C with a substance of strong colouring power is enclosed in a fluid-tight capsule 2 of a fragile, inelastic material such as a glass.

The capsule is surrounded by a substance which absorbs the liquid and assumes a permanent coloured appearance.

This absorbent substance is, for example, blotting paper.

The device operates as follows.

-when the liquid reaches the normal temperature of the deep freezing, it solidifies undergoing almost as large an increase in volume as in the case of pure water in view of the proportions of salt used. The glass capsule is shattered although the liquid does not flow out as long as the temperature does not rise significantly above - 180C. By contrast, any reheating, even of short duration, above that temperature causes the liquid to thaw and flow out and the blotting paper to become coloured which enables any break in the cold chain to be visually detected.

In the embodiment of the invention shown in Figure 2, the material of the capsule 2 is made of an organic polymer which has the particular property of degrading by cracking at a temperature of about --18"C. The principle of operation is similar to that which has just been described.

Since the capsule is cracked directly by the cold and not indirectly by the increase in volume of the liquid, the safety of operation is greater, particularly in the case of defective filling of the capsule-for example presence of air bubbles. One example of a suitable polymer is poly methyl methacrylate.

Claims

WHAT WE CLAIM IS.

1. A device using the degradation of a polymer for detecting and permanently indicating a transient reheating of a deepfrozen product comprising: -a liquid whose solidification point lies at the normal temperature of deep freezing; means for accommodating said liquid in a capsule made of an organic poymer which degrades and cracks at said normal temperature and below, enabling the liquid to flow if it thaws; and means for indicating the flow of said liquid, said means functioning in an irreversible manner.

2. A device as claimed in claim 1, wherein said organic polymer is polymethyl methacrylate.

3. A device using the degradation of a polymer for detecting and permanently indicating a transient reheating of a deepfrozen product. substantially as hereinbefore described with reference to Figure 2 of the accompanying drawing.