While evaporating the moisture, the
product becomes porous in nature and the solid network
should be able to hold this porous structure. If the
temperature of the dehydrating porous product is above
Tg, the viscosity of the solid material may not be enough
to support the structure and ``collapse'' or shrinkage
occurs (To & Flink, 1978; Tsourou¯is, Flink & Karel,
1976).