Effect of ambient parameters change on mint leaves solar drying
Abdul Wasim Noori * a, Mohammad Jafar Royen b, Juma Haydary †
Institute of Chemical and Environmental Engineering, Slovak University of Technology in Bratislava,
Radlinského 9, 81237 Bratislava, Slovakia
a Faculty of Chemical Technology, Kabul Polytechnic University, Kart-e Mamoorin, Kabul, Afghanistan
b Faculty of Chemical Technology, Kabul Polytechnic University, Kart-e Mamoorin, Kabul, Afghanistan
E-mail: * awnoori@kpu.edu.af, † juma.haydary@stuba.sk
Abstract: This study investigates the effect of ambient conditions change on mint leaves solar drying performance and product water activity. Two drying methods, active indirect solar drying (AISD) and open sun drying (OSD) were compared while the experiments were carried out at specific dry climate conditions. During the experimental days, temperature varied from 20 to 30 °C, air relative humidity from 14 to 28.8 % and ambient pressure was around 82 kPa. The effect of air relative humidity change during the day on the rehydration of the product during the drying process was observed. After 7 h of drying, moisture content of mint leaves decreased from 85.29 % to 5.38 % in the AISD and 7.42 % in the OSD system. The 0.97 initial water activity decreased to 0.195 in AISD and 0.79 in OSD. Rehydration during the evening hours caused an increase in product water activity from 0.2 to 0.51. Changes of ambient conditions such as temperature and air relative humidity during the day can significantly affect water activity of dried product due to its rehydration and thus increase the risk of product spoilage.
Keywords: drying, mint, rehydration, solar dryers, sun drying
Acta Chimica Slovaca, Vol. 14, No. 1, 2021, pp. 14—24, DOI: 10.2478/acs-2021-0003