Characterisation of Bovine and Buffalo Milk Triacylglycerols at the C=C Double Bond Positional Level Using OAD

User Benefits

- Oxygen Attachment Dissociation (OAD) is a radical-induced dissociation technique which specifically fragments carbon-carbon double bonds and can be used to determine the positions of double bonds (C=C) in complex lipids. - Acquisition of CID-MS/MS and OAD-MS/MS fragments (OAciD) was applied to the analysis of triacylglycerols (TGs) in milk samples to annotate TGs to the fatty acid (FA) composition level and generate unique OAD fragment ions to determine C=C position. - Closely eluting TG isomers were differentiated by C=C showing species specific differences at the double bond positional level.

Introduction

Worldwide milk consumption is dominated by bovine milk, which accounts for approximately 85% of global milk production, followed by buffalo milk at around 11%. In recent years, consumer preferences have shifted towards higher protein milk products and whole milk, however, milk containing lower fat content is also considered desirable. With a better understanding of lipid composition in milk, alternative products may be developed through processing or animal breeding that favour more desirable characteristics. Buffalo milk typically contains 7-8% fat compared to 3-4% in bovine milk with >98% total fat estimated to be TGs. Separation of isomeric TGs identified not only relative abundance differences between buffalo and bovine but also different TG isomers were characteristic to a species. As one example TG 28:1 contained five main isomers in buffalo compared to four in bovine. CID-MS/MS successfully identified the fatty acid (FA) chain composition of these isomers, however the two main TG peaks produced identical MS/MS spectra meaning that the structural differences were most likely due to positional differences of the acyl chains or the C=C position. Recent advancements in alternative fragmentation methods such as oxygen attachment dissociation (OAD) have now provided an opportunity to gain greater understanding of C=C differences. OAD is a radical-induced dissociation technique which specifically fragments C=C double bonds and can be used to determine the positions of double bonds in complex lipids. OAD-MS/MS and conventional CID-MS/MS can be applied simultaneously in positive or negative ion mode data acquisition on a high-resolution LC/QTOF instrument to generate OAD- and CID-specific fragment ions. This approach was used to characterise C=C positional information in profiling TGs in bovine and buffalo milk.

October 19, 2026 GMT