Optimization of Convective Hot Air Drying of Okra Slices Using Response Surface Methodology

Abstract

In this study, response surface methodology was applied to optimize the drying conditions of okra during convective drying in a designed and fabricated cabinet dryer. The output variables of interest were the moisture content ( ), protein ( ), carbohydrate  and total plate count ( ) which were evaluated based on the effect of four independent variables, namely; air velocity ( ), humidity ( ), drying temperature ( ) and drying time ( ). Analysis of variance (ANOVA) showed that all individual factors (air velocity, drying temperature and drying time except relative humidity for moisture response were highly significant with p values 0.005.  Interactive effect of the process variables such as relative humidity and time, and air velocity and time were highly significant (p < 0.001). The response surface plots revealed the combined effect of air velocity, drying time, temperature and humidity on moisture content, protein, carbohydrate, total plate count, TPL and moisture. Optimal drying conditions were found to be 3.98 m³/s, 348 seconds, 52.2 ⁰C and 60.40% respectively while the output was 1.116% H₂O, 10.02 protein, 66.94% H and 2.88 x 10^-3 TPL.