Towards the Discovery of
the Lipid Composition of Milk Fat
N.J.L.C. Das, Author 2, Author 3, Author 4, Teacher
Stratingh Institute for Chemistry, University of Groningen, Department of Bio-Organic Chemistry, Nijenborgh 7,
9747 AG Groningen, The Netherlands
Introduction
Table 1: Average lipid composition in milk fat 1
The identification and quantification of a single compound in a Lipid class Average
complex mixture can be a daunting task. In the field of lipid composition,
% (w/w)
analysis, this is a regularly encountered challenge. Within a
Triacylglycerols 97 - 98
particular class of lipids, for example Tri-acyl glycerols (TAG), Di-
acyl glycerols (DAG), or phospholipids, the members differ Diacylglycerols 0.28 – 0.59
often little in their physical properties. This makes separation,
in order to allow identification, even with advanced techniques Monoacylglycerols 0.16 – 0.38
often very difficult or impossible. Milk fat is the most complex
species of a very complex mixture of lipids. Bovine milk fat Free fatty acids 0.10 – 0.44
predominantly consists of TAG (>98%). 1 The analysis of the
Tri-acylglycerols are synthesized in a one pot reaction
quantity and identity of the constituting, individual fatty acids Phospholipids 0.20 – 1.00
starting from their corresponding glycidyl ester.
(FA) of the fat is very well possible upon hydrolysis. However,
the identification of the individual Tri-acyl glycerols is extremely Cholesterol 0.42
difficult. Mono-unsaturated fatty acid used is C18:1 (ω-9), oleic acid (abb. ~C16H31)
Cholesterol esters traces Poly-unsaturated fatty acid used is C18:2 (ω -6), linoleic acid (abb. ~ C16H29)
Knowledge about the lipid composition of bovine milk fat is of particular importance in the dairy
industry. On the one hand, molecular-level lipid structures relate to their crystallization kinetics and by Separation of Tri-acylglycerols by NP-HPLC
that the functionality of dairy lipids in dairy products. On the other hand, the arrangement of FA on the
glycerol backbone of lipids is responsible for specific nutritional and metabolic effects which may not
be explained by the constituting FA alone. Finally, the TAG composition may vary with the cow’s feed
en breed. A single identification of TAG composition in a particular sample is therefore not sufficient
but the analysis is a necessary tool to control lipid functionality in dairy products.2
Synthesis of Tri-acylglycerols
Graph 1: Mixture of PBM (20) and POP (25) Graph 2: Mixture of PBM (20), POP (25) and PMS (15)
Optimised NP-HPLC Conditions:
- Eluens: 100% n-heptane
- Flow: 0,5 ml/min
- Inj. Vol.: 5 µl
- Column: Chiracal OD-H
Graph 3: Mixture of MPS (19) and PMS (15)
Tri-acylglycerols with different total carbon numbers (>8) can be separated with NP-HPLC,
1) Synthesis of Glycidyl Ester with Steglich Esterfication with chiral based OD-H column.
2) Asymmetric Ring Opening of Epoxide (1,3-DAG) 3,4 Regio-isomers from TAG’s come off at same retention time. (Several experiments have been done)
3) Steglich Esterfication to synthesize TAG One Pot Reaction3
Outlook
[R,R]-Co(salen) catalyst is now being synthesized for parallel synthesis.
Building blocks have been synthesized .
Resin supported synthesis of Tri-acylglycerols with
[R,R]-Co(salen) cat. and resin supported dehydrating agent (DCC)
Parallel synthesis of Tri-acylglycerols with resin supported compounds with LISSY (robot)
Separation of regio-isomers of Tri-acylglycerols with Supercritical Fluid Chromatography (SFC)
Library of Tri-acylglycerols
Conclusions
Stereospecific synthesis of Tri-acylglycerols is achieved by the in-house developed synthetic route
in high overall yields over three steps ( 70 – 85 %).
Mixtures of Tri-acylglycerols with great different total carbon number can be separated with NP-
HPLC, with as eluens 100% n-heptane and the best screened chiral based column (OD-H column).
Mixtures of regio-isomers of Tri-acylglycerols can not be separated on NP-HPLC (chiral based
columns)
References
[1] Jensen, R. G. (2002). The composition of bovine milk lipids. Journal of Dairy Science, 85, 295-350.
[2] Kontkanen, H., Rokka, S., Kemppinen, A., Miettinen, H., Hellström, J., Kruus, K., Marnila, P.,
Alatossava, T., Korhonen, H. (2010). Enzymatic and physical modification of milk fat: a review.
International Dairy Journal.
[3] Fodran, P., Minnaard, A.J. (2013). Fast and efficient synthesis of protected mixed diacylglycerols –
Total synthesis of a major M. Tuberculosis phospholipid. To be published.
[4] Jacobsen, E.N. (2000). Asymmetric Catalysis of Epoxide Ring-Opening Reactions. Acc. Chem. Res.
33, 421-431.
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