Determination of drying characteristics and kinetics of bitter kola (garcinia kola) using page’s model

Abstract

Single-layer drying characteristics and kinetics of garcinia kola was studied with slice thicknesses of 1mm, 3mm, 5mm and 7mm at temperatures 45^oC, 55^oC, 65^oC and 75^oC using natural convention laboratory oven . The results obtained revealed that garcinia kola slices dried in the falling rate period. Moisture ratio, characteristics drying rate constant, drying time, effective diffusivity and activation energy were significantly (p<0.05) affected by drying air temperature and slice thickness. The effect of moisture diffusivity of garcinia kola increased with increase in drying air temperature and slice thickness from 0.82x10^-8 to 5.24x10^-8m^-2s^-1. Activation energy (E_a) also increased from 3.53kJ/mol to 35.56kJ/mol as slice thickness increased from 1mm to 7mm. Moisture transfer from garcinia kola slices were described by applying page’s model. Non-linear regression analysis was used to predict the effect of temperature on page’s model indicators. Slice thickness of 5mm had the best goodness of fit of the indicators with lowest reduced chi-square (x² = 0.00015), root mean square error (RMSE = 0.00236), mean bias error (MBE = -0.0557) and high coefficient of determination (R² = 0.997). The mathematical model showing the relationship between pages model constant, characteristics drying constant and drying air temperature were also shown.