Collapse of structure of foodstuffs during air drying affects quality. In many materials the soluble components, mainly sugars, are an important part of the tissue in which case collapse may be related to their glass transition temperature (Tg). It has been speculated that collapse occurs at a temperature (Tc) related to, but greater than, Tg. Plant tissues with high moisture contents, such as celery, have low TgS. Therefore considerable collapse is expected at drying temperatures.