Engineering peptide-functionalized fermented milk with enhanced DNA-protective, antioxidant and anti-inflammatory...

The limited peptide yield and bioactivity in conventional fermented milk often restrict their physiological efficacy. To address this limitation and produce fermented milk rich in bioactive peptides, we developed an innovative strategy (ultrasound-assisted enzymolysis) to enhance the functional properties of Lactobacillus helveticus fermentation. Ultrasonication (28 kHz, 35 W/L, 40 min) at the 8th h of a co-culture system containing papain and L. helveticus to intensify proteolysis was used. Results indicated that the synergistic treatment increased peptide content to 21.07 mg/mL and the degree of hydrolysis to 9.22%, reference to the control (i.e. fermentation involving only enzymolysis). The approach further increased the oxygen radical absorbance capacity (ORAC) to 3.27 μM TE, COX-2 inhibition rate to 89.15%. Importantly, it also demonstrated a strong protective effect against oxidative DNA damage, an emerging area of interest in fermented milk research, with a supercoiled DNA retention rate of 73.19%. Rheologically, the treatment significantly enhanced the viscoelasticity, as evidenced by increased storage (G') and loss (G") moduli, and a left-shifted crossover point, indicating faster formation of a stronger gel network. The treatment also improved colloidal stability, reduced phase separation, and enriched the volatile flavor profile. This study demonstrates that ultrasound-assisted enzymolysis could be an effective strategy for the production of high-value/quality functional dairy (fermented) products.