Experimental study on drying of mint by solar, tray and freeze dryers

ABSTRACT EXPERIMENTAL STUDY ON DRYING OF MINT BY SOLAR, TRAY, AND FREEZE DRYERS PEKMEZ, Hatice M.Sc. in Food Engineering Supervisor: AssistProf.Dr. A.Coşkun Dalgıç November 2004, 65 Pages Mint leaves were dried by three different types of dryer, namely; tray dryer, freeze dryer and distributed (indirect)-type solar dryer. Drying curves of solar dried and tray dried mint samples processed both at 65°C with 1.0 m/s air velocity and at 60°C with 2.0 m/s air velocity were obtained, respectively. It was found that there was no significant effect of drying methods (solar and tray drying methods) on the moisture content of mint samples during drying period (P>0.05). Total drying time, color values and total ash content of dried mint samples were evaluated. Sorption isotherms of fresh, solar dried, tray dried and freeze dried mint were determined at temperatures of 15°C, 25°C and 35°C within the range of 10-90 % relative air humidity by using saturated salt solutions method. Oswin, Halsey, BET, BET linear, GAB and Peleg models were employed for describing the sorption isotherms. It was determined that Peleg' s model has shown a good fit for describing all of the desorption and adsorption isotherm curves of mint. The effect of drying methods on the sorption isotherms of dried mint samples was not observed (P>0.05). Key words: mint, tray drying, solar drying, freeze drying, sorption isotherm. m