Structural collapse of plant materials during freeze-drying

Structural collapse of plant materials, which affects quality of foods, was studied. Fresh and osmotically dehydrated plant materials were freeze-dried at several chamber pressures, to achieve initial sample temperatures that were below (?55?C), near (?45?C), or above (?28?C) their glass transition temperature (T _g=?45?C). Freeze-drying at ?55?C resulted in products retaining their original volume. When the initial sample temperature was increased aboveT _g, the resulting freeze-dried samples collapsed. When the initial sample temperature was increased above the temperature of ice melting (T′_m), the samples collapsed further.