Effect of air-drying temperature on the quality and bioactive characteristics of dried galega kale (brassica oleraceaL. var. acephala)

The objective of this work was to evaluate the drying characteristics and the effect of drying temperature on the quality characteristics of Galega kale without any pretreatment. Drying times of 330, 162, 78 and 51min provided minimal moisture contents, using temperatures of 35, 50, 70 and 85C, respectively. The L* and a* values diminished and b* increased, resulting in increasing values of chroma, total color difference and browning index, as well as decreasing values of the hue angle. A pronounced effect on the retention of total phenolic compounds and vitamin C losses ranging from 4.8±9.7 to 55.5±7.4% were observed. Regarding antioxidant capacity, losses from 51.7±7.5 to 69.6±3.7% were obtained. Chlorophyll a content decreased with increasing drying temperatures, with losses between 8.9±6.7 and 35±5.6%, while degradation of chlorophyll b was negligible. In conclusion, the air drying of Galega kale without any pretreatment resulted in considerable deterioration of its quality characteristics and nutritional value.