Evaluating the bioaccessibility of yak milk lipids in infants: Dynamic gastrointestinal simulation reveals lipidomic alterations

Yak milk is considered an excellent dairy source for infant formula, owing to its lipid advantages including superior fatty acid composition, abundant short- and medium-chain fatty acids, and higher phospholipid content. This study compared the physical characteristics, lipidomic profiles, and fatty acid differences between human milk and yak milk digestion products through an in vitro simulation of infant digestion. The results revealed that human milk exhibited higher lipolysis rates and greater release of free fatty acids compared with yak milk. No significant differences were observed in the average particle size of fat globules or zeta potential between the 2 milk types at the same digestion stage. Distinctive differential metabolites identified during gastric digestion included TG (18:1_18:1_18:2), TG (18:0_18:2_18:3), TG (16:0_18:1_20:4), TG (O-11:0_14:0_3:0), and SM (d36:1). In the intestinal digestion phase, MG (P-21:6), MG (O-21:6), FA (22:6), FA (20:4), FA (16:0), and FA (18:0) served as characteristic differential metabolites. Palmitic acid (C16:0) and stearic acid (C18:0) served as critical discriminators of fatty acid profiles between yak milk and human milk digesta, predominantly via their enrichment in key metabolic pathways, including "Biosynthesis of unsaturated fatty acids" and "Fatty acid biosynthesis." This could provide data support for the design of yak milk-based infant formula.