Effect of drying methods on the quality characteristics of dill (Anethum graveolens) greens

Different drying methods hot air (HA), 50 degrees C, 58-63% relative humidity (RH); low humidity air (LHA), 50 degrees C and 28-30% RH; and radiofrequency (RF), 50 degrees C, 56-60% RH) were investigated for efficient dehydration of dill (Anethum graveolens) greens with optimal retention of color and constituents. The drying for HA and RF was marginally higher (similar to 22%) compared to HA. Lightness, greenness and yellowness of LHA dried sample were higher than those of the RF and hot-air dried dill greens. Aqueous methanolic extract of dill greens dehydrated by LHA method exhibited higher anti-oxidant activity. Forty-two compounds were identified representing similar to 85% of the volatile oil and the major volatile compounds for fresh and dried dill leaf oil were alpha-Phellandrene, alpha-cymene, alpha-pinene, Apiol, 1,6-Cyclodecodiene, and 1-methyl-5-methylene. Dehydrated dill greens with their constituent polyphenols, carotenoids, ascorbic acid and minerals have been shown good consumer acceptance as well as shelf life and could serve as a valuable food additive to enhance human nutrition. (C) 2015 Elsevier Ltd. All rights reserved.