Characterization and modeling of thin layer drying of cocoyam slices

Abstract

Convective hot air drying of cocoyam slices was investigated at different drying temperature (40 to 90) and slice thickness (2, 4, 6 mm) at an air velocity of. The effect of drying temperature and slice thickness on the drying characteristics and drying time were determined to study the effects of heat on processed cocoyam. Mathematical modeling of the thin layer drying process was performed using eight thin layer drying models. The models were tested for validity using coefficient of determination (), chi square () and root mean square error (RMSE). The effect of the drying temperature on the colour of dried cocoyam was also investigated. The colour was measured using CIE L* a* b* method. The results showed that, increasing the drying air temperature and decreasing slice thickness reduces the drying time of cocoyam. The effective moisture diffusivity increased with increase in drying temperature and the biot number () of cocoyam at temperature of 40 to 70 were less than 0.1 while that of 80 to 90 were in the range of 0.1 <  100. The activation energy obtained at 40 to 90 was 37.92 kJ. The Page model was found to be best fit for the drying kinetics of cocoyam. The largest colour difference was observed at 90 compared to the fresh sample. Increase in temperature reduced the brightness and yellowness of cocoyam.