Document Type : Original Article


1 Department of Food Science and Technology, Roudhen Branch, Islamic Azad University, Roudhen, Iran

2 Department of Food Science and Technology, Faculty of Agricultural Technology and Engineering, University of Tehran, Karaj, Iran

3 Department of Food Safety and Hygiene, Science and Research Branch, Islamic Azad University, Tehran, Iran


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 (∆E) 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.


  1. Tomlinson TR, Akerele O. Medicinal plants: their role in health and biodiversity: University of Pennsylvania press; 2015.
  2. Singh R, Shushni MA, Belkheir A. Antibacterial and antioxidant activities of Mentha piperita L. Arabian Journal of Chemistry. 2015;8(3):322-8.
  3. Schmidt E, Bail S, Buchbauer G, Stoilova I, Atanasova T, Stoyanova A, et al. Chemical composition, olfactory evaluation and antioxidant effects of essential oil from Mentha x piperita. Natural Product Communications. 2009;4(8):1107-12.
  4. Alankar S. A review on peppermint oil. Asian Journal of Pharmaceutical and Clinical Research. 2009;2(2):27-33.
  5. Khanna R, MacDonald JK, Levesque BG. Peppermint oil for the treatment of irritable bowel syndrome: a systematic review and meta-analysis. Journal of Clinical Gastroenterology. 2014;48(6):505-12.
  6. Riachi LG, De Maria CA. Peppermint antioxidants revisited. Food Chemistry. 2015;176:72-81.
  7. Berezina E, Brilkina A, Veselov A. Content of phenolic compounds, ascorbic acid, and photosynthetic pigments in Vaccinium macrocarpon Ait. dependent on seasonal plant development stages and age (the example of introduction in Russia). Scientia Horticulturae. 2017;218:139-46.
  8. Orphanides A, Goulas V, Gekas V. Drying technologies: vehicle to high-quality herbs. Food Engineering Reviews. 2016;8(2):164-80.
  9. Mokhtarian M, Tavakolipour H, Ashtari AK. Effects of solar drying along with air recycling system on physicochemical and sensory properties of dehydrated pistachio nuts. LWT-Food Science and Technology. 2017;75:202-9.
  10. Sahin S, Sumnu G, Tunaboyu F. Usage of solar-assisted spouted bed drier in drying of pea. Food and Bioproducts Processing. 2013;91(3):271-8.
  11. Morad M, El-Shazly M, Wasfy K, El-Maghawry HA. Thermal analysis and performance evaluation of a solar tunnel greenhouse dryer for drying peppermint plants. Renewable Energy. 2017;101:992-1004.
  12. Sallam Y, Aly M, Nassar A, Mohamed E. Solar drying of whole mint plant under natural and forced convection. Journal of Advanced Research. 2015;6(2):171-8.
  13. El-Sebaii A, Shalaby S. Experimental investigation of an indirect-mode forced convection solar dryer for drying thymus and mint. Energy Conversion and Management. 2013;74:109-16.
  14. Akpinar EK. Drying of mint leaves in a solar dryer and under open sun: modelling, performance analyses. Energy Conversion and Management. 2010;51(12):2407-18.
  15. Doymaz İ. Thin-layer drying behaviour of mint leaves. Journal of Food Engineering. 2006;74(3):370-5.
  16. Müller J, Reisinger G, Kisgeci J, Kotta E, Tesic M, Mühlbauer W. Development of a greenhouse-type solar dryer for medicinal plants and herbs. Solar & Wind Technology. 1989;6(5):523-30.
  17. AOAC. Moisture in Dried Fruits. Official methods of analysis, 17th Ed, Association of Official Analytical Chemists, Washington, D C. 1990.
  18. Duffie JA, Beckman WA. Solar engineering of thermal processes: John Wiley & Sons; 2013.
  19. Uribe E, Marín D, Vega-Gálvez A, Quispe-Fuentes I, Rodríguez A. Assessment of vacuum-dried peppermint (Mentha piperita L.) as a source of natural antioxidants. Food Chemistry. 2016;190:559-65.
  20. Therdthai N, Zhou W. Characterization of microwave vacuum drying and hot air drying of mint leaves (Mentha cordifolia Opiz ex Fresen). Journal of Food Engineering. 2009;91(3):482-9.
  21. Sárosi S, Sipos L, Kókai Z, Pluhár Z, Szilvássy B, Novák I. Effect of different drying techniques on the aroma profile of Thymus vulgaris analyzed by GC–MS and sensory profile methods. Industrial Crops and Products. 2013;46:210-6.
  22. Mokhtarian M, Tavakolipour H, Kalbasi-Ashtari A. Energy and exergy analysis in solar drying of pistachio with air recycling system. Drying Technology. 2016;34(12):1484-500.
  23. Montero I, Blanco J, Miranda T, Rojas S, Celma A. Design, construction and performance testing of a solar dryer for agroindustrial by-products. Energy Conversion and Management. 2010;51(7):1510-21.
  24. Zogzas N, Maroulis Z, Marinos-Kouris D. Densities, shrinkage and porosity of some vegetables during air drying. Drying Technology. 1994;12(7):1653-66.
  25. Caparino O, Tang J, Nindo C, Sablani S, Powers J, Fellman J. Effect of drying methods on the physical properties and microstructures of mango (Philippine ‘Carabao’var.) powder. Journal of Food Engineering. 2012;111(1):135-48.
  26. Antal T, Figiel A, Kerekes B, Sikolya L. Effect of drying methods on the quality of the essential oil of spearmint leaves (Mentha spicata L.). Drying Technology. 2011;29(15):1836-44.
  27. Negi P, Roy S. Effect of blanching and drying methods on β-carotene, ascorbic acid and chlorophyll retention of leafy vegetables. LWT-Food Science and Technology. 2000;33(4):295-8.
  28. Rudra SG, Singh H, Basu S, Shivhare U. Enthalpy entropy compensation during thermal degradation of chlorophyll in mint and coriander puree. Journal of Food Engineering. 2008;86(3):379-87.
  29. Weemaes CA, Ooms V, Van Loey AM, Hendrickx ME. Kinetics of chlorophyll degradation and color loss in heated broccoli juice. Journal of Agricultural and Food Chemistry. 1999;47(6):2404-9.
  30. Krokida M, Maroulis Z. Effect of microwave drying on some quality properties of dehydrated products. Drying Technology. 1999;17(3):449-66.