Heat Balance in Freezing and Thawing Food

Snapshot 1: freezing pure water

Snapshot 2: thawing a meat-like product

Snapshot 3: thawing pure water ice

The net heat, , in kJ kg^-1, is calculated using the formula

​, where is the food's heat capacity above freezing in , is the temperature drop or rise above the freezing point in °C, is the latent heat in , is the heat capacity below freezing in , and is the temperature rise or drop below the freezing point in °C. The initial, final, and freezing point values as well as the food's thermal properties are entered with the sliders. The schematic graphical display below the calculated value depicts the process on an arbitrary time scale in which the heating or cooling stages are shown as straight lines and the freezing or thawing stage as a horizontal line. Note that the temperature versus time relationships during heating or cooling are not actually linear. The Demonstration lets you enter combinations of thermal properties that might not be found in real foods.

Reference: R. L. Earle and M. D. Earle, Unit Operations in Food Processing, NZIFST, Inc., 1983.