Estimating the Thermal Properties of Foods from Their Moisture Contents

Snapshot 1: thermal properties of a dry food (e.g., grain having 10% moisture)

Snapshot 2: thermal properties of a moist food (50% moisture)

Snapshot 3: thermal properties of a fruit juice (90% moisture)

Snapshot 4: thermal properties of pure water

This Demonstration calculates the thermal conductivity, , in , below and above the freezing point, the specific heat capacity, , in °, below and above the freezing point, and the latent heat, , in , of a food as a function of its moisture content, , as a percentage on a wet basis. The values obtained can be used as estimates only for foods that are not primarily salt or fat, or, in the case of thermal conductivity, foamy. The estimates are based on the assumption that the moisture and solid components' contributions to the properties are independent. This translates to the following formulas:

above the freezing point = ,

below the freezing point = ,

,

above the freezing point = ,

below the freezing point = ,

where the first term represents the properties of water or ice and the second those of the solid components such as carbohydrates or protein.

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