Elucidating the storage destabilization behavior of casein micelle models under direct-steam-infusion UHT processing: insights from plasmin hydrolysis patterns revealed by peptidomics.

Milk is complex system, in which multiple components interact, making it difficult to clearly elucidate micellar destabilization and plasmin hydrolysis patterns. In this study, a casein micelle-dominant model (CM model) was established to eliminate interference from other components. The model was subjected to direct UHT (dUHT) treatments and stored for 60 days to evaluate micellar destabilization by physical characterization, compositional measurements, and sediment analysis. Results showed that z-average diameter, turbidity, and viscosity decreased during storage. Plasmin activity increased progressively, leading to hydrolysis of αS-casein and β-casein and rise in soluble calcium and phosphorus. Sediments formed in CM model during storage. Their size decreased with increasing dUHT temperature and increased with prolonged storage. The sediments mainly contained peptides <10 kDa.Totally, 76 casein-derived peptides generated by plasmin were identified, and six characteristic peptides were shared across all groups. Overall, dUHT treatment altered plasmin hydrolysis patterns and dUHT-plasmin interplay governed micellar destabilization.