The food polymer science (FPS) approach has been effectively used to investigate the physical stability
of amorphous food materials. The glass transition, a key FPS parameter, has traditionally been determined using thermal techniques that scan temperature while holding the plasticizer (moisture)
content constant. Moisture sorption isotherms provide information about the physical properties of
food as the plasticizer level is adjusted and temperature is held constant. New automatic isotherm
generators can be used to produce high resolution, dynamic isotherms much faster than traditional
static methods. Dynamic isotherms for a small selection of amorphous materials have been investigated and shown to experience distinct inflection points in the water activity region where the glass
transition temperature is close to the experimental temperature. Several studies on amorphous spray
dried milk powder and amorphous polydextrose indicate very good agreement between glass transitions determined using thermal techniques and dynamic isotherm methods. This agreement suggests
that dynamic isotherms are a viable alternative to traditional thermal methods for investigating glass
transitions of amorphous foods.