the effects of drying methods on drying time and some biochemical characteristics of mentha × piperita l.

in this research an experiment based on completely randomized design with three replications and 11 treatments was conducted of mentha piperita. treatments consisted of dryer drying, artificial shade drying, oven drying (50 and 70 °c), and microwave drying with different powers (100, 180, 300, 450, 600 and 900 w) and fresh sample as control. the end time of each treatment determined on the basis of moisture content equal to 0.10 on the basis of dried weight. after drying the samples, traits such as drying time, essential oil content, color parameters (l*, a*, b*, hue and chroma) and some biochemical parameters (total polyphenolic content, total flavonoids, flavone and flavonols, total carbohydrate and antioxidant activity) were studied. the results showed a significant effect of different drying methods on the studied traits. the minimum and maximum drying times (5.03 and 570 minutes) associated with microwave dried (900w) and drying method of dryer, respectively. the maximum essential oil content (2.6%) obtained from dryer dried samples. the highest amount of chroma and b* index related to fresh, artificial shade and dryer dried samples while the minimum content related to microwave dried samples (180 and 900 w). also, the maximum amount of polyphenol compound obtained in fresh sample and microwave (900 w) and artificial shade dried samples, respectively. while the minimum content obtained to oven dried samples (70 °c). the most antioxidant activity (percentage of radical scavenging activity) obtained to fresh, artificial shade dried and microwave dried (600 and 900 and 450w) samples and the minimum amount were observed on oven dried samples (70 and 50 °c).