Abstract
The present study aimed to estimate the effects of different drying methods on appropriate drying time, essential oil yield, total phenol content and antioxidant capacity of Anethum graveolens L. and Mentha piperita L. Factorial experiment was conducted in completely randomized design at research field and laboratory of agricultural campus of the University of Guilan during 2011-2012. Treatments were: two levels of plant type (peppermint and dill) and four levels of drying methods (oven drying at 60°C and 75°C, drying at natural shade and drying exposed to sunlight). Results indicated that different drying methods had significant effect on all observed characteristics. In this experiment increasing oven temperature lead to reduction of essential oil yield. Minimum and maximum essential oil were obtained when dill and peppermint were oven dried at 75°C (20.11 ml m-2) and dried in shading (28.44 ml m-2), respectively. Oven drying at 75°C reduced antioxidant capacity of dill while shade-drying increased antioxidant capacity of peppermint. However drying at 60°C may be an appropriate temperature for drying peppermint and dill plant material, due to a significant reduction of drying time with no adverse effects on the essential oil yields.
Highlights
Peppermint (Mentha piperita L.) belongs to Lamiaceae family and is a medicinal plant widely used in food, pharmaceutical and health care industries (Miliauskas et al 2004, Omidbeigi 2009)
Since there is limited information regarding essential oil, total phenol content and antioxidant capacity of dill and peppermint under different drying methods this experiment was conducted in order to select the most appropriate drying method with regard to the qualities of those medicinal plants
Drying time decreased in both plants when oven dried at 75°C
Summary
Peppermint (Mentha piperita L.) belongs to Lamiaceae family and is a medicinal plant widely used in food, pharmaceutical and health care industries (Miliauskas et al 2004, Omidbeigi 2009). Chemical compounds with strong antioxidative properties can be classified into two groups: natural and synthetic (Singh et al 2007) In many cases their primary antioxidant role in suppressing the negative effects of free radicals in the tissues of living organisms, as well as the prevention of some forms of cancer is confirmed (Namiki et al 1990, Kahl & Kappus 1993). For these reasons, scientists are attracted to the opportunity to study a broad population of medicinal herbs and utilize aromatic organic compounds isolated from these plants as a natural source of chemical compounds with strong antioxidant activity (Kulisic et al 2004). Since there is limited information regarding essential oil, total phenol content and antioxidant capacity of dill and peppermint under different drying methods this experiment was conducted in order to select the most appropriate drying method with regard to the qualities of those medicinal plants
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