Fatty acid composition of human milk triglyceride species. Possible consequences for optimal structures of infant formula triglycerides

Abstract

Human milk triglycerides (TGs) were separated into 14 fractions by silver ion high-performance liquid chromatography (HPLC) with light-scattering detection (LSD). Subsequent fractionation by reversed-phase HPLC-LSD resulted in 75 subfractions. The major 48 were analysed by gas chromatography for their intact TG and fatty acid (FA) compositions. Using a constrained non-linear optimization computer program, the FA compositions and abundances of 170 different TG combinations were calculated. The major two, 16:0/18:1/18:1 (11.8 mol%) and 16:0/18:1/18:2 (10.0 mol%), were almost twice as abundant as expected from random FA distribution. The apolarities of 16:0 and 18:0 seem to be modulated by unsaturated FAs (18:1, 18:2) or medium-chain FAs (MCFAs; 8:0-12:0). MCFAs were present in 19 mol%. Of these, 7.2 mol% are likely to harbour stereospecific structures with an MCFA at sn-3, 16:0 or 14:0 at sn-2, and 18:1 or 18:2 at sn-1. These structures are excellent substrates for lingual and gastric lipases, producing products that assist in duodenal TG lipolysis.