The fatty acid composition of bovine milk and its role in human health has been a topic of much research. Ongoing research is investigating the affiliations of these fatty acids with human disease through the addition of unsaturated supplemental oils to the dairy cow’s diet; thus reducing potentially harmful saturated fatty acids and increasing the proportion of mono- and poly-unsaturated fatty acids. However, incomplete biohydrogenation of unsaturated feed in the rumen produces a highly diverse bovine milk fatty acid composition – containing a multitude of trans and branch chain isomers. Highly sensitive analytical techniques are required to accurately identify the presence of these fatty acids due to their very low concentrations. Scientists at MTT Agrifood Research have developed methods of sample preparation and analysis that enable accurate identification and quantification of trans mono-unsaturated and poly-unsaturated fatty acids. In particular, the use of silver-ion High Performance Liquid Chromatography (HPLC) to identify conjugated linoleic acid (CLA) isomers and Gas Chromatography-Mass Spectroscopy (GC-MS) analysis of DMOX (Dimethyloxazolines) derivatives of polyenoic trans fatty acids are used routinely.
Purpose of the visit
The purpose of my visit was to achieve two key objectives, both of which will contribute substantially to my PhD:
- To obtain training in the use of silver-ion HPLC to identify CLA isomers and GC-MS analysis of DMOX derivatives of polyenoic trans fatty acids.
- Create opportunities for future collaborations with MTT as well as the publication of joint papers.
Work carried out and main results In preparation for the visit the lipid content from 20 milk samples (IDF method, with methylation modifications by Christie (1988) and Grenarie (1998)) was extracted and fatty acid methyl esters (FAME) were prepared. Four of these samples were run on the GC-FID (Gas Chromatograph- Flame Ionization Detector), followed by the GC-MS in order to focus on identification of trans fatty acids, while the remaining sixteen samples were run on the HPLC for identification of CLA isomers. A primary aim of my visit was to obtain training in the use of silver-ion HPLC. The primary use for this technique would be the identification of CLA isomers in milk; however the application of this technique could allow identification of a multitude of fatty acids in milk and, in effect, in many other materials, including human plasma. A further aim of our visit to the MTT laboratories was to gain proficiency in the use of GC-MS. While GC-FID allows identification of a substantial number of fatty acids based on retention times, it remains reliant on standards. In contrast, GC-MS has the potential for identification of novel fatty acids based on spectra analysis. For details about work carried and the results click here
Future collaboration with host institution
The visit to MTT was considered a success and future collaborations are likely in two areas: Collaborative paper on the identification and quantification of trans fatty acids in retail milk Potential future visit to MTT for use of novel tandem GC-MS, which has been proposed to infer double bond geometry