TEMPERATURE-DEPENDENCE OF THE EFFECTIVE THERMAL-CONDUCTIVITY OF FOODS GELS IMPREGNATED WITH AIR BUBBLES

Air-impregnated alginate and ovalbumin gels were prepared as model systems for porous foods, and their effective thermal conductivity was measured at 30-70-degrees-C by a steady-state method. The effective thermal conductivity of the air-impregnated gels increased with temperature more greatly than that of gels containing no air bubbles. For effective thermal conductivity of air-impregnated gels, a theoretical model which included latent heat transport accompanied by water vapor diffusion in addition to heat conduction was presented and was compared with experimental data. The model gave a good approximation to the experimental data up to 50-degrees-C. At higher temperature, however, the model overestimated the effective thermal conductivity, especially for gels of high porosity.