The synergistic effect of ultrasound and microwave on the physical, chemical, textural, and microstructural properties of vacuum fried Chinese yam ( Dioscorea polystachya )

Both the ultrasound and microwave are emerging technology, used for enhancement of heat and mass transfer, due to their cheap, simple, and energy saving characteristics. The combined effect of ultrasound and microwave on vacuum frying of Chinese yam at various power levels were investigated. The trends of moisture removal and oil uptake were analyzed at different power combinations of ultrasound (300 and 600 W) and microwave (1,800, 2,400, and 3,000 W). The frying time was reduced from 18 to 12 m and oil uptake was decreased by 40.29%, when ultrasound and microwave powers were increased to 600 and 3,000 W, respectively. The texture, and color were found to be improved by the proper combination of ultrasound and microwave and was better at higher power levels. Lastly, the scanning electron microscopy (SEM) analysis revealed the more disrupted and porous structure when the ultrasound and microwave powers were at higher end. Practical applications The results showed that the fried chips at higher ultrasound and microwave powers gave the best result with regard to frying process and fried product qualities, owing to the consumers demand of low-fat fried chips with better texture and color.