Sequential Microwave – Ultrasound assisted extraction of soymilk and optimization of extraction process

In the present study, a combination of microwave and thermosonication treatment was introduced in the soymilk extraction process, and the process was optimized to minimize the enzymatic activity of Soybean Trypsin Inhibitor (STI) and Lipoxygenase (LOX) enzymes. Protein content, fat content, TSS (Total Soluble Solids), and viscosity of soymilk increased upon thermosonication process and was most affected by microwave time followed by ultrasonification time. The inactivation rate constant for STI and LOX was 0.2034 min−1 and 0.3232 min−1, respectively, indicating LOX was more susceptible to inactivation under microwave treatment as compared to STI. The activation energy of STI and LOX decreased from 48.44 to 10.24 kJ/mol and 53.47 to 3.07 kJ/mol after 5 min of microwave pasteurization. FTIR analysis confirmed the conformational deformation of proteins and enhanced molecular interactions in the optimized soymilk. The optimized condition was obtained as 3 min of microwave pasteurization followed by 30 min of ultrasonication at 60 °C in an ultrasonic bath of 28 ± 2 kHz frequency. The optimized treatment produced the soymilk with enhanced nutritional quality and low enzymatic activities. [Display omitted] •Effect of microwave and ultrasound on soymilk quality attributes was analyzed.•Thermosonication increased TSS, fat, and viscosity of extracted soymilk.•LOX enzyme was more sensitive to microwave and ultrasound than STI enzyme.•The activation energy of LOX and STI enzymes decreased after microwave treatment.•Soymilk extraction process was optimized for minimum STI and LOX activities.