process for the preparation of a device and for enacting terms act at the detection of changes in the conditions of conservation in dependence of time and unfavorable conditionsand temperature

摘要

1323833 Temperature indicating FOOD CONTROL AB 12 July 1971 [13 July 1970] 32564/71 Heading G1D A device for indicating whether or not a food package has been subjected to too high a temperature for too long comprises a permeable membrane through which one substance is able to permeate to react with another substance and to produce a visual change in the other substance. As shown, an impermeable envelope 3 which may be of plastics material encloses silica gel 4 and water 6 (which may contain glycerine) which interact to change colour with time and temperature, due to the migration of the water through a permeable diaphragm 5, a support 7 of aluminium foil coated with polyethylene being provided to secure the device to a food package 2. In other embodiments, a PVC or glass ampoule completely encloses the two substances, Fig. 2 (not shown); and a rupturable metal foil partition (10) Fig. 3, (not shown) is arranged to maintain the two interacting substances apart at least until the partition is broken. Apart from silica gel and water the inter-acting substances may alternatively comprise iodine and starch or ammonia and cupric ions to provide a change in colour when the substances interact.