Effects of infrared drying and air flow rate on qualitative parameters of Matricaria chamomilla L.

To evaluate the effect of infrared drying on color parameters, essential oil content and composition of German chamomile (Matricaria chamomilla L.), three different infrared intensities (125, 132, and 220 W) with three airflow velocities (0.5, 1.0, and 1.5 m.s-1) on a total of nine treatments were examined in a completely randomized design, and the shade-dried plants were considered as a control treatment. The results indicated that the treatments had significant effects on drying time, color parameters, and essential oil content. The control (shade drying) and the 220 W radiation intensity with 0.5 m.s-1 air velocity treatments had the highest (2367 min) and lowest (83 min) drying time, respectively. With increasing infrared intensity, the main color parameters such as L, a, b, ΔE (total color changes) and BI (browning index) changed significantly, compared to the control; however, increasing the airflow rate caused less variation of the mentioned parameters in all levels of infrared radiation intensity than the control. The highest essential oil content (0.23% w/w) was obtained at 125 W radiation intensity with 0.5 m.s-1 air velocity and the lowest (0.12% w/w) was observed at the 220 W radiation intensity with 0.5 and 1 m.s-1 air velocity treatments. Essential oil analysis showed that the highest amount of α-bisabolol-oxide A (60.6%), (Z)-spiroether (16.5%), and chamazulene (4.6%) belonged to 132 W radiation intensity with 0.5 m.s-1 air velocity, 220 W radiation intensity with 0.5 m.s-1 air velocity, and control treatments, respectively. In general, the results of this experiment showed that due to the decreased duration of drying time, color preservation and desired essential oil content and composition, the 125 W radiation intensity with 0.5 m.s-1 air velocity treatment could be a suitable method for chamomile flowers drying.