Effects of heat treatment on fat digestion and DHA bioaccessibility in naturally DHA-enriched milk

Naturally DHA-enriched milk represents a crucial functional food, yet the impact of thermal processing on DHA bioaccessibility has not been fully elucidated. This research systematically compared raw, pasteurized, infusion (INF), and ultra-high temperature (UHT) milk through in vitro digestion and lipidomic analysis. The INF and UHT treatments substantially altered milk fat globule membranes and lipid compositions. Throughout the digestion process, INF and UHT milk maintained reduced particle sizes and elevated absolute zeta potentials, thereby enhancing lipase accessibility. As a result, INF and UHT milk demonstrated accelerated lipolytic rates and significantly greater DHA bioaccessibility (66.08% and 59.88%, respectively) than raw and pasteurized counterparts. Lipidomic analysis confirmed that intensive thermal treatments facilitated DHA release in bioavailable forms, including free fatty acids, monoglycerides, and lysophosphatidylcholine, without increasing digestive losses. Collectively, these findings establish that INF and UHT processing augment endogenous DHA bioaccessibility by restructuring lipid interfacial characteristics and improving digestive efficiency.