Modelling and kinetic study of microwave assisted drying of ginger and onion with simultaneous extraction of bioactive compounds.

Onion and ginger are rich sources of bioactive compounds which are lost during conventional drying process. The present study was designed to optimize the novel Microwave Assisted Drying and Extraction technique (MADE) for simultaneous drying and extraction/recovery of bioactive compounds from model food products. The time required for drying of samples was 11 (onion) and 16 (ginger) minutes with recovery yield of 87% (onion) and 85% (ginger). The drying time was reduced to 100 times compared to hot air drying and moisture ratio of dried samples was best described by Midilli model. The diffusivities of onion and ginger slices were 1.27 e-11 and 1.43 e-11 m2/s, respectively. Moreover, microwave-based extraction was compared with conventional one. The results of antioxidant activity and total phenolic contents of condensates obtained through MADE were higher compared to conventional method. In short, MADE exhibited better yield of extraction and drying properties compared to conventional methods.