Insights into lipid oxidation during pasteurized milk storage based on chemical and non-targeted lipidomics analysis

This study investigated the lipid oxidation characteristics of pasteurized milk stored at 4 °C for 15 days by chemical analysis and lipidomics. After six days, oxidation entered an advanced stage, with glycerides (GLs) and glycerophospholipids (GPs) identified as key differential lipids. Notably, triglycerides, diacylglycerols, and phosphatidylcholines were highlighted as critical components in them. Lipidomics demonstrated that saturated GLs underwent continuous oxidation and hydrolysis, while 88 % unsaturated GLs showed re-esterification following oxidation. The re-esterified unsaturated GLs further oxidized to form conjugated structures and saturated aldehydes. In milk fat globules, GPs was located on the fat globule membrane (MFGM) and GLs was located inside, and they were oxidized simultaneously. GPs in the inner monolayer of MFGM more easily re-esterified than those in the outer bilayer. Given that the number of GLs involved in oxidation significantly exceeded that of GPs, GLs were considered the most crucial oxidized substrates in pasteurized milk during storage.