Response Surface Methodology (RSM) Optimization on Extraction and Antioxidant Activity Evaluation of Peptide From Enzymatic Hydrolysates of Housefly ( Musca domestica ) Larvae

Response surface methodology (RSM) was applied to determine the optimal enzymatic hydrolysis conditions for obtaining antioxidant peptides from Musca domestica (MDPs). The results indicated that neutral protease was the most effective enzyme for producing MDPs. Under the optimized conditions (time: 3.2 h, temperature: 43.0°C, enzyme dosage: 5300.0 U/g, pH: 6.4), the DPPH radical scavenging rate of MDPs reached 70.9% ± 0.2%. The model demonstrated high reliability, as evidenced by the close agreement between experimental and predicted values, with R ² _adjusted and R ² _predicted both exceeding 0.9036. Subsequently, the particle size, zeta potentials, and structural features of MDPs were characterized using ultraviolet-visible (UV) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The analyses revealed statistically significant differences in the physicochemical properties among MDPs, MDPs_{> 10 kDa}, and MDPs_{< 10 kDa}. Furthermore, both MDPs_{> 10 kDa} and MDPs_{< 10 kDa} were rich in amino acids associated with antioxidant activity. Compared to MDPs_{> 10 kDa}, the MDPs_{< 10 kDa} exhibited superior antioxidant activities, including DPPH radical scavenging, hydroxyl radical scavenging, and reducing power. This study highlights the potential of M. domestica-derived peptides as natural antioxidants, supporting their future application in supplements, functional foods, and pharmaceuticals, and promoting the sustainable utilization of this resource.