Thermophysical properties of plain yogurt as functions of moisture content

Plain yogurt was prepared, concentrated and then microwave vacuum dried to obtain samples of different moisture content (0.04-0.85 kg water/kg sample). The yogurt samples were used to determine the thermophysical properties. Bulk density was determined with the water displacement method, shrinkage by measuring the thickness, specific heat according to the calorimetric method, and thermal conductivity with the line-source probes. Both specific heat and shrinkage were linear with moisture content, but bulk density changed nonlinearly with moisture content. Thermal conductivity was linear with temperature (25-55 degrees C) but changed logarithmically with moisture content. (C) 1997 Elsevier Science.