Glass Transition Temperature
Temperature stability of ice cream has focused on carbohydrate
glass formation as a function of temperature. A glass is characterized
as a metastable solid with a high viscosity. At the glass
transition temperature, polymeric materials change from a
viscoelastic liquid to an amorphous solid (glass) with an associated
increase in viscosity. For ice creams, this temperature is
defined as the glass transition temperature of a maximally
freeze-concentrated solution. The interest in glassy state in ice
creams has increased steadily since the last 15 years. It is now
well established that the glassy-state temperature influences the
storage stability as above these temperatures, the solutions are
unstable and reactive. Ice crystallization can also occur in this
phase. Below the glass transient temperature, the materials
become glossy and no molecular motion or chemical reaction
occurs. The ice crystallization is prevented and the shelf life of
the product is prolonged. Glass transition temperature for ice
cream is 32 C. Storage of ice cream at this low temperature
to maintain the glassy state for enhanced stability is not
practical.