A novel vacuum frying technology of apple slices combined with ultrasound and microwave

The aim of this work was to apply the ultrasound-assisted or ultrasound combined microwave vacuum frying (UMVF) technology in frying of foods to reduce frying time and improve color and crispness. Apple slices were used as model material for frying. Two microwave power levels (800 W and 1000 W) were used at fixed ultrasound power and frequency of 600 W and 28 kHz, respectively. Frying was carried out for 16 min. The effect of UMVF on residual moisture content, oil uptake, textural crispness and color parameters was measured and analyzed. The odor profile of the fried slices was measured and analyzed using electronic nose (E-nose). The application of UMVF technology significantly increased the moisture evaporation rate, shortened the frying time, increased the textural crispiness and produced more desirable yellow color compared to microwave vacuum frying (MVF) technology. The ultimate oil uptake in UMVF products was similar to that in MVF products. The UMVF produced less Maillard reaction products compared to MVF. Therefore, the UMVF technology is more effective than MVF and can be preferably used in frying foods.