Process for monitoring the history of temperature versus time of deep-frozen product, indicator for applying said process and utilization of said process

Claim 1

A time temperature integrating indicator for monitoring the history of a deep-frozen product by the diffusion of water along a diffusion path wherein the water front advancement along the diffusion path is a function of elapsed time and of the temperature of the product, the indicator comprising a wick of a material which defines a diffusion path along which water will diffuse; the wick being provided along its diffusion path with citric acid or a mixture of sodium chloride/citric acid or of sodium chloride/sugar, as an absorbing and hydrate forming substance; the formation of the hydrate at least partially providing a visible indication of the water front location; a moisture tight covering enclosing the wick; an opening in the covering for permitting intimate contact between the wick and water on the frozen product, located at the opening in the covering; and additional indicating means for indicating the location of the water front along the diffusion path from the opening in the covering.