Influence of drying methods on the drying kinetics, bioactive compounds and flavor of solid-state fermented okara

Solid-state fermented Omar's was dried using microwave vacuum drying (MVD) and infrared freeze-drying (IFD). Hot air drying (AD) and traditional vacuum freeze-drying (FD) were used as controls. The effects of different drying methods on the drying kinetics, physicochemical properties (such as water retention capacity, oil retention capacity, swelling capacity, solubility, color), bioactive compounds (total phenols, soybean isoflavones, antioxidant activity) and flavor of solid-state fermented okara were studied. The results show that compared with AD, MVD required 86.2% less drying time and 62.2% lower energy while the fermented okara powder produced by MVD had better physicochemical properties and higher content of bioactive compounds. In terms of physicochemical and functional properties, IFD was close to FD, but it reduced drying time by 13.9% and energy consumption by 29.4%. As for flavor, MVD and IFD products were closer to fresh solid-state fermented okara.