Thermal Conductivity

Knowledge of thermal conductivity of food substances is

essential to researchers and designers for predicting the

drying rate or temperature distribution within foods of

various compositions when subjected to different drying,

heating, and cooling conditions in the field of food

engineering. This information is also necessary for the

optimization design of heat transfer equipment, and dehy-

drating and sterilizing apparatus. With the increasing

amount of food preparation in industry and food institu-

tions the importance of such fundamental data also

increases. General mathematical models to predict the

thermal conductivity of food products based on tempera-

ture, composition, and structure of food would be valuable

for engineers and scientists. Previous investigators have

determined, to a limited extent, some of these values for

tomato products and fruit juices. Riedel[1] measured ther-

mal conductivity of fruit juices such as apple, grape, and

pear of various water contents at temperatures of 20C and 80C. Dickerson[2] reported the thermal properties such as thermal productivity, thermal diffusivity, density, and spe-

cific heat of some fruit juices. Sweet and Haugh,[3] using a

probe method, measured thermal conductivities of cherry

tomato and other fruits at room temperatures. Bhowmik

and Hayakawa[4] measured thermal diffusivity and density

of cherry tomato at 26C. Thermal property data have been collected by several

investigators. Qashou, Vachon, and Touloukian[5] pre-

sented a preliminary compilation of experimental thermal

conductivity data for foods and food products including

fruit juices. Polley, Snyder, and Kotnour[6] compiled the

thermal property data of various foods. Existing thermal

properties of tomato juice products are primarily for room

temperature, and very limited information is available on

the effect of concentration and temperature. The thermal

conductivity is affected by composition, density, and

temperature.