Optimization of Ultrasound-Assisted Extraction Process for Silkworm (Antheraea pernyi) Pupae Protein and Its Impact on Functional and Structural Characteristics of Protein

In this study, the ultrasonic-assisted extraction of silkworm pupae protein (SPP) was optimized using response surface methodology. Subsequently, the effects of ultrasonic treatment on the structural and functional characteristics of SPP were systematically analyzed and verified through Pearson correlation analysis. The results showed that the optimal extraction parameters were an ultrasonic treatment time of 120 min, a power of 115 W, a temperature of 54 °C, pH of 10.5, and the average extraction yield was 68.087%. Compared to the control, ultrasonic treatment significantly improved the functional properties of SPP, including solubility (13.13 g/L), water holding capacity (0.18%), oil holding capacity (0.28%), foaming capacity (55.35%), foam stability (12.71%), emulsification activity (2.15 m²/g), emulsification stability (21.95%), gel water holding capacity (11.5%), gel hardness (1.02 N), and gel elasticity (0.49 mm). In addition, the adsorption ability of SPP for 2-octanone and aldehyde was enhanced after ultrasonic treatment. Furthermore, the absorption intensity and maximum wavelength of the SPP fluorescence spectrum extracted via ultrasonic treatment were enhanced, along with the increased surface hydrophobicity and more stable secondary structure which contributed to promoting the functional properties of SPP, proven by Pearson correlation analysis. This study provides a theoretical basis for the further utilization of SPP in the food industry.