Microwave drying effects on drying kinetics, bioactive compounds and antioxidant activity of green peas (Pisum sativum L.)

Microwave power effects (100, 300 and 450 W) on drying kinetics of green peas at an initial 3.06 kg water/kg DM (76.2% wb) was investigated. The density level of microwave power (W/g DM) affected the drying kinetics, bioactive substances and green peas color. The parabolic model was found to be the best in matching the experimental data of green pea drying kinetics. It is well known that microwave drying is mainly due to Darcy's law with the gradient of total pressure as the driving force. Thus, this parameter was used to identify the drying operation as being controlled by effective moisture diffusivity. The values obtained ranged between 1.69 and 5.36 x 10(-9) m(2)/s. The activation energy was determined as 1.38 kW/kg, using the modified Arrhenius equation. Application of high microwave power resulted in decreased L* and b* values, and an increase of a* values. The LC-ESI-MS analysis of peas extracts led to the identification of 7 phenolic acids and 8 flavonoids. Interestingly, peas dried at 100 W had the highest phenolic content as well as the highest DPPH center dot radical-scavenging activity.