Effects of shade and solar drying methods on physicochemical and sensory properties of Mentha piperita L

Mentha piperita L., known as mint or peppermint used extensively in the food, pharmaceutical, and cosmetics industries. Although different techniques have been studied for drying mint leaves, there is not enough information on solar drying of peppermint (especially the Persian variety) in the literature. In this study, thin layers of peppermint leaves were dehydrated evenly with three methods of shade (MI), sun (MII), and solar heat collector (MIII). The air temperature rise and drying time in I, II, and III were (1, 5, and 18ºC) and (880, 300, and 150 min), respectively. The particle size, porosity, and rehydration rate of peppermint dried in III were significantly higher than those dried with I and II. While the overall color (ΔE) of peppermint dried in I and III did not change, the greenish index and chlorophyll of peppermint dried in II were ~21% and ~15% less than those in III because it was exposed to direct sunlight radiation. The peppermint dried with III had lower bulk density, higher sensory attributes (minty aroma, flavor, cooling mouthfeel, and visual color), and overall acceptance scores than II and I. The solar dryer produced high quality dehydrated peppermint with renewable energy and without environmental contamination.