Stevia leaves are usually used in dried state and
undergo the inevitable effect of drying process that changes
the quality characteristics of the final product. The aim of this
study was to assess temperature effect on Stevia leaves
through analysis of relevant bioactive components, antioxidant
capacity and content of natural sweeteners and minerals.
The drying process was performed in a convective dryer at
constant temperatures ranging from 30 to 80 °C. Vitamin C
was determined in the leaves and as expected showed a decrease
during drying proportional to temperature. Phenolics
and flavonoids were also determined and were found to increase
during drying below 50 °C. Antioxidant activity was
determined by DPPH and ORAC assays, and the latter
showed the highest value at 40 °C, with a better correlation
with the phenolics and flavonoids content. The content of
eight natural sweeteners found in Stevia leaves was also determined
and an increase in the content of seven of the sweeteners,
excluding steviol bioside, was found at drying temperature
up to 50 °C. At temperatures between 60 and 80 °C the
increase in sweeteners content was not significant. Stevia
leaves proved to be an excellent source of antioxidants and
natural sweeteners.