Influence of humidity on thermophysical properties of starch sheets

The photopyroelectric method was used for measuring the thermal parameters of starch sheets as a function of water content and temperature. The thermal conductivity, thermal effusivity and volume specific heat are increasing with water content while the thermal diffusivity remains almost constant. The temperature behaviour of the thermal parameters in the -15+70 degrees C temperature range was measured for samples with different water contents. No phase transition was observed at 0 degrees C, which proves either that water is bound in the starch matrix, or the fact that water has dissolved other particles that shifted the melting point to a lower temperature.