Evaluation of convective drying with cold and hot air of mint (Mentha spicata) leaves

Abstract

Mentha spicata, commonly known as peppermint, is a medicinal herb that is used for its pharmacological properties, obtained from its extracts and essential oils that have different health benefits, such as antioxidants, anticancer, antiparasitic, antimicrobial, and antidiabetic effects. In Mexico, it is estimated that around 130 tons of this perishable product are wasted per year, mainly due to various marketing problems. To minimize this loss, it is proposed to dehydrate it and thus prolong its shelf life. Two methods were used: first, hot air at 50 °C and 1 m/s velocity; the second one, with air at room temperature and the same velocity for 90 min and then, raise of temperature to 50 °C and the same velocity of air. In the first case 220 min and a total energy of 1800 W were needed, and with the combination of ambient temperature and later with hot air, 1700 W were required, but 290 min were used in total. In this later case the energy saving was marginal, so it is necessary to make a valorization between both methods. With respect to the numerical model that best simulates the behavior, the Henderson-Pabis model was suitable in both cases. Also, the color variation was very small, so both drying methods render similar results in the quality of the dried product.