Elucidation of lipid precursors and formation pathways for flavor changes during storage of UHT sterilized milk based on non-targeted lipidomics.

This study investigated the role of lipids in the flavor evolution of ultra-high temperature sterilized (UHT) milk. Volatile compounds (VOCs) in UHT whole milk (UWM) and skim milk (USM), together with lipid composition in UWM, were monitored over 45 days at room temperature. The results showed that 35 VOCs were detected, with ketones over 70%. 2,3-butanedione, 2-heptanone[M], pentanal[M], and acetic acid ethyl ester[M] were the key VOCs influenced by lipid content. Among them, the peak areas of three were significantly higher in UWM compared to USM (P < 0.05). Lipidomics analysis identified 1633 lipids in UWM, with 19 glycerides, 27 glycerophospholipids, and 25 sphingolipids as differential lipids which served as main precursors for VOC formation. Correlation analysis further revealed phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol with 16-, 18-, and 20‑carbon fatty acids, and ceramides were important precursors of key VOCs. These findings provide a theoretical basis for improving UHT milk flavor and storage stability.