ABSTRACT

The energy requirements for drying of different sample geometries of some selected fruit vegetables was conducted at Bio Process and Food Engineering Laboratory, Michael Okpara University of Agriculture Urnudike using a laboratory convective dryer. The Box-Behnken design (BBD) approach was adopted to design the experiment and investigate the effects of varying drying conditions: drying air temperature (50, 60 and 70°C), drying air velocity (1.0, 1.5 and 2.0 mIs), and shapes: sliced (15mm), cylindrical (25mm) and rectangular (20mm) on the total energy consumption, specific energy consumption, drying efficiency of the system, product shrinkage, and drying time of cucumber, garden egg and white carrot samples. Results obtained show that the total energy requirements ranged between 190.34— 600.7 8kJ, specific energy requirements 2.99 —21 .76kJ/kg, the mean system drying efficiency ranged from 1.18 -28.22%, while the percentage shrinkage ranged between 87.14 Sh 94.73%, the drying time ranged from 490 i Td f 840 minutes for cucumber samples. Drying garden egg samples showed that the total energy requirements ranged between 287.0— 505.8kJ, specific energy requirements 12.33 — 32.96kJIkg, the mean system drying efficiency ranged from 9.5 - 24.6%, while the percentage shrinkage ranged between78.66 Sb 89.57%, the drying time ranged from 470 Td 690 minutes. Total energy requirements ranged between 270.23— 498.88kJ, specific energy requirements 13.18 —22.93kJIkg, the mean system drying efficiency ranged from 7.22 - 23.4%, while the percentage shrinkage ranged between 82.06 Sb 88.72%, the drying time, ranged from 480 Td 690 minutes for white carrot samples. The desirability of the control variables was obtained as 0.9999 because their goal for numerical optimization is set "in range". At optimum condition, the experimental factors had values: -0.679 159 (shape), 5 1.2448°C (drying air temperature), 1.1255m1s (drying air velocity), 0.347659 (crop), whereas the response variables: Total energy requirements = 241.272kJ, specific energy requirements = 9.08526(kJlkg), drying time = 668.615 Minutes, drying efficiency = 15.8186%, shrinkage = 91.3305% at overall desirability index of 99.99%.