Process optimization and thermodynamic analysis of ultrasonic-assisted extraction of peanut meal protein

Abstract This study optimized the ultrasonic-assisted extraction (UAE) of protein from peanut meal (PMP). The operational ranges for the key variables, pH (9–11), temperature (25–45 °C), time (10–30 min), and ultrasonic power density (100–300 W·L⁻¹), were established through single-factor experiments. A Box-Behnken design, centered on a four-factor-three-level, was subsequently employed to simultaneously maximize protein yield and solubility while minimizing energy consumption. The developed models demonstrated a significant fit to the experimental data ( p < 0.0001), as validated by a non-significant lack-of-fit ( p ≥ 0.055) and high coefficients of determination (R 2 ≥ 0.975 and adjusted R 2 ≥ 0.953). The optimized extraction conditions for all responses were pH 10, 39 °C, 19 min, and 172 W·L⁻¹. Under these conditions, the observed values for protein yield (35.81%), solubility (62.49%), and energy consumption (121.06 kJ) were in close agreement with the predicted data. Furthermore, thermodynamic analysis showed that UAE significantly lowered the energy barrier for PMP extraction, thereby augmenting process efficiency. Notably, ultrasonication substantially improved PMP yield and solubility by 44.21% and 25.08%, respectively, relative to the control ( p < 0.05), supported by particle size distribution and zeta potential outcomes. SEM and AFM analyses revealed that the sonicated isolate exhibited dissociated microstructures with smaller particles, irregular fragments, and disordered lamellar structures, indicating the disruption of crosslinking and molecular bonds. UV-Vis spectroscopy and DSC thermograms further indicated that sonicated PMP possessed higher peak absorption and greater thermostability than the control. This study highlights the potential of UAE to enhance the yield and solubility of PMP, providing an efficient and industrially scalable strategy for the food sector.