Crust freezing is a freezing phenomenon in which the outer surface of a food product solidifies rapidly while the core remains unfrozen, creating a temperature gradient that can cause uneven ice-crystal formation and internal moisture migration.
In trade practice
Industrial tunnel operators manage crust freezing by balancing air temperature, airflow velocity and belt loading so that surface and core temperatures converge within an acceptable time. Overloaded belts slow heat transfer from the core and increase the risk of a pronounced crust-to-core gradient. Quality teams reviewing freezing records should check that core temperature probes, not only surface sensors, confirm the product has reached the required temperature before leaving the tunnel.
In a specification
Freezing process specifications may require that the product core reaches a defined exit temperature, verified by periodic core-probe measurement, to confirm that crust freezing has not masked an inadequately frozen centre.