COLLAPSE OF STRUCTURE DURING DRYING OF CELERY

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 (T(g)). It has been speculated that collapse 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 temperatures. 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 volumetric shrinkage, rehydration characteristics and porosity changes. significant shrinkage occurred at all drying conditions. At low water content 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 improved quality characteristics.