MODELLING OF THIN-LAYER MICROWAVE DRYING OF BITTER LEAF SAMPLES (Vernonia Amygdalina) FOR PRESERVATION

• Samuel Olugbenga Oladele

  Dept. of Agricultural and Environmental Engineering Federal University of Technology, Akure

The thin-layer drying characteristics of bitter leaf (Vernonia amygdalina) was investigated over a microwave power settings range between 90 and 900 W. The effect of microwave power from the experiment affected the samples drying behaviours. The process of microwave drying of the samples occurred in the falling-rate period. The drying rate increased as the drying microwave power increased, and the drying process time decreased with the increase in the microwave power. The total drying time decreased from 3 minutes to 15 seconds with microwave power increase. Seven mathematical thin-layer drying models were applied to the experimental drying data The Midilli et al. model was adjudged the best as it adequately gave the best results and showed good consistency with the data obtained from the experiments over the microwave power range with result values of 0.9930< R²<1, 0.000 ×10^−2<RMSE<4.80×10^−2, 0.000 ×10^−2 <SSE <1.03×10^−2 and 0.000 ×10^−2 <NRMSE <2.57×10^−2. The moisture ratio of the samples during the drying processes decreased with microwave power increase and effective moisture diffusivity coefficients values of the samples across the microwave output power using Fick’s second law of diffusion varied from 2.30138× 10^−8 m²/s to 9.69307 × 10^−8 m²/s. The activation energy obtained from the Arrhenius type equation was found as 6.8545 kW/kg.

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