HPLC-APCI analysis of triacylglycerols in milk fat from different sources

Triacylglycerols (TAG) from milk-fat from different sources (cow, goat and human milks) were characterised using non-aqueous reversed phase high-performance liquid chromatography-atmospheric-pressure chemical ionisation, coupled to MS/MS (RP HPLC-APCI MS/MS). The fatty-acid content of all samples was also established by methyl transesterification and GC-MS analysis. Optimisation of the HPLC gradient, combined with APCI tandem MS, enables TAGs complex mixtures to be analysed without prior separation. More than 160 different glycerides were identified; between 50 and 70 compounds were identified in the chromatograms of each sample. This method also enabled the principal TAG regioisomers to be recognized. The study focused on the investigation of the structure of TAGs containing very-long-chain PUFA, namely all cis-4,7,10,13,16,19- DHA (DHA, C(22:6), (n-3)) and all cis-5,8,11,14,17-eicosapentaenoic acid (EPA, C(20:5), (n-3)), both in human and in n-3-enriched cow's milks. Ten TAGs containing DHA were identified in human milk and only one in milk from cows fed an n-3 enriched diet.