Drying characteristics, specific energy consumption, qualitative properties, total phenol compounds and antioxidant activity during hybrid hot air-microwave- rotary drum drying of green pea

Abstract

This study is aimed to investigate the effect of a hybrid hot air-microwave- rotary drum (HMRD) dryer on the thermal properties, quality and nutritional characteristics of green pea under different operational conditions. The experiments were conducted under different air temperatures (40, 55 and 70 °C), microwave power (90, 270, 450 and 630 W), and drum rotation speeds (5, 10 and 15 rpm). The thermal properties (e.g. drying time, effective moisture diffusion coefficient, activation energy, and specific energy consumption), quality features (color, shrinkage, and rehydration ratio) and nutritional properties (antioxidant activity and total phenol content) were determined. The results indicated that by increasing the microwave power, air temperature and drum rotation speed, the drying time will decline. The highest diffusion coefficient and energy consumption were determined as 5.04×10-11 m2/s and 109.91 MJ/kg, respectively. The lowest changes in the color, shrinkage, and rehydration were calculated as 41.34, 24.08% and 1.57. The highest total phenol (14.02 mg GAE/g d.w) and antioxidant (85.86%) were obtained. Thus the newly designed dryer can be employed for drying the granular products and lead to satisfactory results.