Critical temperature indicator

A critical temperature indicator which provides an irreversible visual indication that the indicator has been exposed to a predetermined critical temperature, which includes:

• a transparent housing;
• a temperature sensitive transformable material operably contained within said transparent housing which includes mixture of water, latex, and ice nucleating active (INA) microorganism which is translucent prior to exposure of a predetermined temperature and is transformed upon being subjected to said predetermined temperature to render a substantially consistent opaque material thus precluding visibility therethrough and thereby providing a sure visual sign that said indicator has been subjected to said predetermined temperature;
• and
• a colored substrate operably disposed with respect to said housing such that said colored substrate can be seen through said housing while said material is in said transparent state and is substantially invisible when said material is opaque.