Abstract
This study investigated the effect of ultrasound pretreatment (5-15 min, 37 kHz, 300 W) on the fermentation performance and functional properties of buttermilk inoculated with Limosilactobacillus fermentum and Lacticaseibacillus rhamnosus. Buttermilk was sonicated prior to 24 h fermentation to assess microbial proliferation, acidification kinetics, total phenolic content (TPC), antioxidant capacity, and inhibitory activities against α-amylase, α-glucosidase, and lipase. Ultrasonication significantly (P ≤ 0.05) enhanced bacterial growth, with the B+10 treatment achieving 9.3 log CFU/mL, the highest viable count among treatments. Sonicated samples exhibited accelerated acidification (pH 3.4 in B+15) and a marked increase in TPC (9.2 mg/mL in B+10). Antioxidant properties improved substantially, as reflected by a 78.9% increase in reducing power and 82.1% superoxide radical scavenging activity. Enzyme inhibitory activities were also enhanced, with α-glucosidase and lipase inhibition reaching 29.2% and 19.3%, respectively. Notably, L. rhamnosus-fermented samples consistently demonstrated superior phenolic release and bioactivity compared with L. fermentum. Overall, ultrasonic pre-treatment effectively enhanced fermentation performance and biofunctional attributes of buttermilk, highlighting its potential as an innovative approach for developing value-added functional dairy products.