The impact of ultrasound duration on the structure of β-lactoglobulin

This study aimed to investigate how ultrasound treatment for different durations (0, 10, 20, 30, 60, and 90 min) impacts the hydrolysis and structural characteristics of p-lactoglobulin (beta-LG). Ultrasound conditions were set at ultrasound frequency (40 +/- 2) kHz, power 600 W, power density 111.1 W/L, pulse on/off time 10 s/3 s, scanning period 500 ms, and temperature 25 degrees C. beta-LG was pretreated with ultrasound and hydrolyzed by alcalase. Ultrasound treatment for 20 and 30 min significantly improved the degree of hydrolysis and peptide yield; longer treatment durations (60 and 90 min) had little effect on these parameters. Ultrasound treatment caused dynamic changes in protein structure. After a 30-min ultrasound treatment, the particle size, free sulfhydryl groups, intrinsic fluorescence, surface roughness, alpha-helix, and beta-turns increased, whereas absolute zeta potential, disulfide bonds, and beta-sheets decreased. When the duration of treatment increased from 30 min to 90 min, the opposite trend was observed. Short-duration ultrasound treatment induced partial unfolding of beta-LG, while long-duration treatment induced protein aggregation. Therefore, physicochemical and structural changes in beta-LG are largely dependent on ultrasound treatment duration.

Automated summary

The study found that ultrasound treatment for 20 and 30 minutes significantly improved the degree of hydrolysis and peptide yield of beta-LG, while longer treatment durations had little effect. Ultrasound treatment caused dynamic changes in protein structure, with short-duration treatment inducing partial unfolding and long-duration treatment inducing protein aggregation.