A hybrid vacuum frying process assisted by ultrasound and microwave to enhance the kinetics of moisture loss and quality of fried edamame

The characteristics of fried edamame were investigated in a newly designed vacuum frying assisted by ultrasound and microwave (USMVF) equipment to get better frying efficiency, shorten the frying time and improve the quality of fried edamame at low frying temperature in this work. Three frying temperatures (80, 90 and 100 °C) were comparatively analyzed in USMVF, microwave-assisted vacuum frying (MVF) and vacuum frying (VF). The USMVF remarkably enhanced the moisture diffusivity and moisture loss than MVF and VF at each frying temperature (80, 90 and 100 °C). The values of moisture diffusivity and activation energy were in between 2.014–3.823 × 10−9 m2/s and 22.57–20.07 kJ/mol, respectively. Ten distinct mathematical models were applied to explain the dehydration kinetics of fried edamame and the most suitable model found was Midilli model. The drying data (moisture ratio versus time) were successfully fitted to the Midilli model. The energy consumption in USMVF decreased, diminishing by 28–39% depending on the frying temperature used in this work. The oil content and water activity of fried edamame was also reduced in the USMVF compared to the samples treated with MVF and VF. The color and texture (crispness), chlorophyll and vitamin C of fried edamame were also significantly improved in the USMVF.