DETERMINATION OF THIN-LAYER SOLAR DRYING KINETICS OF CASSAVA NOODLES (TAPIOCA)

Abstract

The aim of this study is to determine the thin-layer drying kinetics of cassava noodles (tapioca) using a solar dryer. To achieve this, an integral type forced convection solar dryer, equipped with rock storage, was developed. Drying kinetics of tapioca were determined using the solar dryer. The treatments in the experiment comprise of air flow velocities (V) of 1.5, 2.5, and 3.5 m/s; and drying layer thicknesses (B) of 0.48 and 0.72 cm. Tapioca samples were dried from an average initial moisture content of 297% (dry basis) to 9.8% (dry basis). Control experiments in the form of open air sun drying of similar quantity of tapioca were also set up and monitored. Graphical plots of moisture content versus drying time, exhibited the characteristic moisture desorption curve, characterized by initial high rate of moisture removal, followed by a slower rate of moisture removal. It was observed from drying rate curves plotted using the drying data, that the drying of the tapioca took place entirely in the falling rate period. The drying rate of the tapioca varied with the different combinations of velocity and drying layer thickness. The drying rate of the tapioca increased with increase in the air flow velocity until velocity of 2.5 m/s; beyond this velocity the drying rate reduced slightly. Also the drying rate of tapioca decreased with increase in drying layer thickness. A maximum drying rate of 39.2%/hr was obtained during the experiment. The maximum system drying efficiency of the dryer was determined as 47.14%, while the maximum dryer pick-up efficiency of 50% was determined during the drying test.