Collapse of structure of foodstuffs during air drying affects quality.
In many materials the soluble components, mainly sugars, are an impor
tant part of the tissue in which case collapse may be related to their
glass transition temperature (T(g)). It has been speculated that coll
apse occurs at a temperature (T(c)) related to, but greater than, T(g)
. Plant tissues with high moisture contents, such as celery, have low
T(g)s. Therefore considerable collapse is expected at drying temperatu
res. The aim of this study was to determine how air drying temperature
affected the quality characteristics of the tissue. Celery, air dried
at temperatures between 5 and 80-degrees-C, was examined for volumetr
ic shrinkage, rehydration characteristics and porosity changes. signif
icant shrinkage occurred at all drying conditions. At low water conten
t collapse was limited, probably due to a higher collapse temperature.
Porosity development was insignificant during drying until the sample
was very dry. Lower air-drying temperatures gave a product with impro
ved quality characteristics.