Low temperature vacuum frying of edamame assisted by ultrasound and microwave: Effects on the kinetics of oil and product storage properties

Ultrasonic microwave-assisted vacuum frying (USMVF) process was investigated to achieve better process efficiency and shorten the frying time and improve the quality of fried edamame at lower frying temperature. Kinetics of oil uptake in vacuum frying (VF), microwave-assisted vacuum frying (MVF) and USMVF samples was investigated. It was studied applying an empirical kinetic model in order to fit the oil content during frying. The first order model fitted properly the values of oil uptake during VF, MVF, and USMVF. For all the studied conditions of the model, the specific rate increased with the application of microwave and ultrasound and frying temperature, however the equilibrium oil content decreased with the application of microwave and ultrasound and frying temperature. The USMVF samples are the least temperature sensitive with an activation energy of 15.92 kJ/mol, while for MVF and VF it was 18.80 kJ/mol and 20.76 kJ/mol. The changes in moisture content, oil content, water activity, and vitamin C and chlorophyll retention of USMVF edamame at selected storage temperatures (0, 10, and 25 °C) were studied during a storage period of 6-months. Vitamin C and chlorophyll content retention was 72% and 80%, at the storage temperature of 10 °C and, 54% and 73% at 25 °C respectively.