Optimization of microwave-assisted hot air drying conditions of okra using response surface methodology.
Okra (Abelmoschus esculentus) was dried to a moisture level of 0.1 g water/g dry matter using a microwave-assisted hot air dryer. Response surface methodology was used to optimize the drying conditions based on specific energy consumption and quality of dried okra. The drying experiments were performed using a central composite rotatable design for three variables: air temperature (40-70 °C), air velocity (1-2 m/s) and microwave power level (0.5-2.5 W/g). The quality of dried okra was determined in terms of color change, rehydration ratio and hardness of texture. A second-order polynomial model was well fitted to all responses and high R(2) values (>0.8) were observed in all cases. The color change of dried okra was found higher at high microwave power and air temperatures. Rehydration properties were better for okra samples dried at higher microwave power levels. Specific energy consumption decreased with increase in microwave power due to decrease in drying time. The drying conditions of 1.51 m/s air velocity, 52.09 °C air temperature and 2.41 W/g microwave power were found optimum for product quality and minimum energy consumption for microwave-convective drying of okra.
Department of Agricultural and Food Engineering, Indian Institute of Technology, Kharagpur, India ; Biological and Ecological Engineering, Oregon State University, Corvallis, USA.
Deepak
D
Kumar
Department of Agricultural and Food Engineering, Indian Institute of Technology, Kharagpur, India.
Suresh
S
Prasad
Biological and Ecological Engineering, Oregon State University, Corvallis, USA.
Ganti S
GS
Murthy
Microwave-convective drying; Okra; Rehydration ratio; Response surface; Specific energy