Elevated storage temperature induces bitterness: decoding the formation and taste mechanisms of bitter peptides in...

Flavor profile is a critical determinant for milk product development and consumer acceptance. Although extensive research has documented alterations in the peptide profiles of UHT milk under various storage conditions, the sources, molecular mechanisms, and sensory properties of bitter peptides at different storage temperatures remain unclear. This study employed an integrated analytical approach combining spectroscopic characterization with peptidomics to identify and validate bitter peptides generated during thermal storage. Results demonstrated that elevated temperature storage (37 °C for 30 days) significantly increased the levels of four bitter peptides in full-fat UHT milk and two in low-fat UHT milk approaching the best-before date. Molecular docking analyses revealed these peptides stably bind to the TAS2R14 receptor through hydrogen bonding. Sensory evaluation confirmed that six peptides exhibited bitterness, among which PVEGSSGRQV, DERFFSD, ITGGKDF, and PEVPVHFD demonstrated notably lower taste thresholds. These findings established a theoretical framework for understanding flavor defects in stored milk products.