TABLE OF CONTENTS The thermal properties of ice cream, such as the heat capacity and the thermal conductivity, are important for several reasons. Parameters of the production process, such as the length of time required to harden the ice cream, depend on the thermal properties, as does the rate at which ice cream warms up and melts. This is important in storage and distribution and also when the ice cream is consumed. It should not melt so rapidly that it falls off the stick before it can be eaten. The thermal properties also affect the sensory properties such as the perception of coldness in the mouth. Furthermore, the freezing point and glass transition lines on the phase diagram, and the ice curve, are obtained from measurements of the thermal properties. The main techniques for measuring the thermal properties are calorimetry, conductivity measurements, thermal mechanical analysis and meltdown.
The heat capacity, freezing point curve and the ice curve of ice cream can be determined by calorimetry. In adiabatic calorimetry, the sample is held in an insulated chamber. A controlled amount of heat is input and the resulting increase in temperature is measured, from which the heat capacity, freezing point and ice content are calculated. Figure 6.16a shows the heat capacity of a sample of ice cream as a function of temperature, and Figure 6.16b shows the ice curve. Below -15 C the heat capacity is nearly constant. Between -15 and -2 C the ice content decreases rapidly. This appears as a...
