Moslem Namjoo

In this study, the convective drying of caraway seed was boosted by two nonthermal and physical field technologies: cold plasma (CP), and ultrasonic wave (US). For convective temperatures of 35, 45, and 55 ˚C, CP pretreatment with exposure times (CPt) of 25 and 50 s were considered before the drying process. In some cases, the convective drying was accompanied by US with 60, 120, and 180 W power (USp) levels. Experimentally, the most effective contribution was found by using both CP pretreatment (25 s) and US (180 W), in which the maximum decrease of 31 and 39 %, was estimated for the drying period and specific energy consumption, respectively. The total color change, the rupture force, TPC, TFC and antioxidant capacity were also estimated for evaluating the quality of dried products. In a CP-US-assisted drying program (25 s, 180 W), the minimum change in color and the rupture force were found to be 6.08 and 18.94 N, respectively. Compared to the conventional drying program, the combined application of CP-US resulted in 53.2 % increase in TPC, 43.6% increase in TFC, and 45.8 % improvement in antioxidant capacity of achieved extracts. Based on the Response Surface Methodology (RSM) approach and obtained experimental data, accurate mathematical predicting models were developed for finding the optimal drying condition. The optimization process revealed that 39˚C, 180 W, and 23 s provide the desirability of 0.78 for drying of caraway seeds.