Preparation of housefly (Musca domestica) larvae protein hydrolysates: Influence of dual-sweeping-frequency ultrasound-assisted enzymatic hydrolysis on yield, antioxidative activity, functional and structural attributes.

Dual-sweeping-frequency ultrasound (DSFU) was utilized in the preparation of polypeptides from housefly (Musca domestica) larvae protein (HLP). Results indicated that ultrasonication (20 ± 2/28 ± 2 kHz, 42 W/L, 25 min) significantly increased peptide yield and DPPH scavenging capacity by 8.25 % and 14.83 %, respectively. Solubility, foaming and emulsification properties of polypeptides were improved by 19.89 %, 33.33 % and 38.74 % over the control; along with notable reduction in particle size and increase in zeta potential. Tertiary structural changes of the sonicated hydrolysates were illustrated by UV and fluorescence spectra. FTIR showed that ultrasonication increased α-helix, β-turn, and random coil by 38.23 %, 46.35 % and 16.36 %, respectively, but decreased β-sheet by 48.03 %, indicating partial unfolding in HLP hydrolysate conformation and reduction in intermolecular interactions. The research results demonstrated that dual-sweeping-frequency ultrasonication has a great prospect in industry application for the purpose of improving enzymolysis efficiency and product quality for housefly larvae protein hydrolysates production.