Antihypertensive and antioxidant peptide identification and storage stability assessment of novel probiotic fermented sheep milk: A comparative study with bovine milk

This study investigated angiotensin-converting enzyme (ACE) inhibitory activity (ACE-IA), antioxidant activity (AnOxA), and bioactive peptides in novel probiotic fermented sheep and bovine milks, along with their storage stability and sensory properties over 28 days at 4 °C. Milks fermented by <i>Lactobacillus delbrueckii</i> MF55 exhibited strong ACE-IA and AnOxA, whereas <i>Lacticaseibacillus paracasei</i> MF48 produced only pronounced AnOxA. After ultrafiltration, QExactive identification, <i>in silico</i> analysis, and molecular docking simulations, four novel peptides with antihypertensive and antioxidant potential (ITVDDKHYQK, AMKPWTQPK, YPVEPFTER, KYNVPQLEIVPK) were screened from the <3 kDa fractions. Among them, AMKPWTQPK and KYNVPQLEIVPK were uniquely detected in fermented sheep milk. During cold storage, MF55 fermented sheep milk (MF55-FSM) maintained significantly higher ACE-IA and water-holding capacity than MF55 fermented bovine milk (<i>P</i> < 0.05), while the latter showed superior viable cell counts and sensory properties. Overall, MF55-FSM demonstrated potent functional performance, highlighting sheep milk as a promising matrix for functional dairy products.