DRYING KINETICS OF RED PEPPER

Abstract

Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. The desorption data were exploited to estimate equilibrium moisture contents of the peppers at drying temperatures other than 30C by using a semi-empirical method. Red pepper samples were dried in a tunnel-type drier with an air velocity of 2 m/s at 50C, 60C, 70C, and 80C. The blanched samples dried faster than the unblanched ones. The drying behavior of unblanched and blanched samples was characterized by falling rate period, and constant and falling rate drying periods, respectively. The interphase mass and heat transfer coefficients of the blanched sample during the constant rate period were not affected by temperature and estimated to be 1.94*10−3 kg mol/s. m2 and 57.3 W/m2. K, respectively. Effective moisture diffusivity was estimated between 6.83*10−10−17.4*10−10 m2/s for the unblanched sample and 11.4*10−10−31.0*10−10 m2/s for the blanched sample within the given temperature range. Effect of temperature on the diffusivity was described by an Arrhenius-type equation with an activation energy of 28.4 kJ/mol for the unblanched pepper and 33.3 kJ/mol for the blanched pepper.