Some notes about Fats and Oils in Food and about FAME and FAMEWAX
In Europe, the last transition periods named in REGULATION (EU) No 1169/2011 on the provision of food information to consumers are running out on Dec. 13th, 2016. Since then, a nutrition declaration is mandatory for nearly all packed food in Europe, wherein the amounts of fat, saturates, carbohydrate, sugars, protein and salt have to be included. The content of the mandatory nutrition declaration may be supplemented with an indication of the amounts of one or more of the following:
(b) polyunsaturates; …
This was my starting point to investigate some of the Restek solutions in measuring Fat content in Food. The nutrient fat is one of the main energy providers from Food. Fortunately the civilized world is not suffering from a lack of nutrient energy, but from the opposite, which, unluckily, leads to some of the so called lifestyle diseases. This underlines the importance of such nutrition declarations, but also the importance of scientific investigations about different fat classes.
Different fats are all built in the same simple way. The trivalent alcohol Glycerine is esterified by fatty acids. Though simple in its basic structure, fats are varying by hundreds of different fatty acid combinations, some of them identified as healthy, others as unhealthy. For example, mono- and polyunsaturated fatty acids (MUFA and PUFA) are known as more healthy than saturated fatty acids (SFA). Unfortunately we also have to divide between cis- and trans-unsaturated fatty acids, whereas cis-fatty acids are recognized as more healthy than trans-fatty acids. A special role is given to polyunsaturated fatty acids (PUFAs) depending upon the position of the double bond closest to the ester group: n-3 (also notated as ω -3) systems and n-6 (ω -6) systems, wherein the ω -3 systems seem to have a special healthy role in human metabolism.
Sounds confusing? It is, especially for the analyst, who is asked to classify fats in food and other matrices. The huge amount of different, structurally nearly identical compounds, which cannot be easily resolved in an MS, makes it impossible to use an LC approach for this task. Fats itself cannot be transferred into the gas phase to use an easy GC approach. So a lot of techniques are standardized from organizations like AOAS, ISO or DGF to cut the fats into glycerine and its fatty acids, followed by derivatization of the fatty acids into their Fatty Acid Methyl Esters (FAME) for further GC measurement.
The next question is, which GC column would be best to analyze the remaining complex mixture of Fatty Acid Methyl Esters? Restek has developed a wax column, specially designed for such a challenging approach, the FAMEWAX column. So what, if I would recommend this column? I am sure that you are sure that I believe in the quality of Restek products. I am a Restek employee and in the end you would have to trust in my or Restek’s reliability. Or you have to check different columns by your own.
But what, if others would have done this before? Think about the most demanding ones? Instrument suppliers. If they have to proof their complex systems in front of a customer, they do well to know everything about the performance of a strategic compound like a GC column. And so they do. I recently found an application note from Shimadzu Europe, comparing different types of GC columns for this approach, including Restek’s FAMEWAX column, which I mentioned before.
The finding of the Shimadzu scientists was that under six different types of columns the FAMEWAX column with a 30m length performed as good or better as five others with 60 m length. The complete application note can be found here:
Another interesting publication using our FAMEWAX column was published by young scientist Annika Ostermann from the research group of PD Dr. Schebb at the University of Veterinary Medicine in Hannover, Germany.
This research group investigates the role of ω -3 fatty acids in human and veterinary metabolisms. For this work, Annika Ostermann compared different derivatization and extraction procedures suitable for the determination of the fatty acid composition in plasma and tissues as fatty acid methyl esters using gas chromatography. Sample preparation and derivatization methods for the analysis of small amounts of tissue and low plasma volumes is more challenging than determining FAME in food, where sample amounts may not play such a big role.
Annika Ostermann provided the following chromatogram, showing this nice separation for the interesting compounds in her work. The complete work was published in PLEFA (Prostaglandins, Leukotrienes and Essential Fatty Acids) and can be found here.