Triacylglycerol (TAGs) composition variation and crystallization behaviour on Milk Fat

Influence of the variations in Triacylglycerols (TAG) composition on crystallization behaviour and functional properties of Milk Fat.

Milk Fat (MF) is one of the most important components of milk quality, influencing the technological, sensorial, and nutritional properties of milk and dairy products (Cozma et al., 2013).  MF is composed of triacylglycerols (TAG) (> 95% of total lipids) with a wide range of fatty acids (FA) (about 400) with different chain length, sn-positional distribution and degrees of saturation (Jensen, 2002). TAGs determine the physical and functional properties of MF, therefore it is important to understand their composition and the positioning of the fatty acid (FA) within the glycerol backbone (Tzompa-Sosa et al. 2014). One property of interest in this study is crystallization of MF, where the formation of crystals are  directly influenced by TAG composition. Accordingly, being able to correlate the variations in TAG composition with crystallization behavior of MF will contribute to a better understanding for specific MF applications.

Several studies show that FA and TAG composition can be modified through the alteration of cows feed (Lock at al., 2004, Grummer R., 1990, Sutton J., 1988). Together the Animal Nutrition Group, the Breeding and Genetics Group and  the Food Quality and Design Group have been working on different feeding trials combined with selective breeding to analyze the impact of cows feed alteration and breeding selection on Milk composition and MF profiles.

The objectives of this project are, first to correlate the already studied fatty acid profiles obtained from selective breeding and feeding trials to the variations in TAG composition in MF, and second to analyze the effect of the variation in TAG composition on MF crystallization behavior.

The main aim of this project is to correlate the already studied fatty acid (FA)  profiles obtained from selective breeding and feeding trials to the variations in TAG composition and their effect on crystallization behavior. Once we are able to correlate variations in TAG composition to crystallization behavior, will be possible to apply this knowledge in fractionation of milk fat for target product applications.

The methodology chosen for this project  for FA and TAG composition analysis are Gas Chromatography (GC) and Matrix-Assisted Laser Desorption/Ionization– Time-of-Flight (MALDI-TOF) Mass spectrometry (MS). Gas Chromatography (GC) method is frequently used for FA and TAG composition analysis due to the range of the measurements and the repeatability of the results (Emerson, 2010). The MALDI-TOF MS method was proven to be advantageous for simultaneously detecting TAGs at various unsaturation degrees with different TAG classes (Cn) (Picariello et al., 2007).
The methodology chosen for MF crystallization analysis are X Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and  Rheological Analysis. XRD and DSC can be used to monitor crystalline phase transition, where XRD measures the amount of different polymorphic forms and DSC measures the polymorphic changes in MF (ten Groetenhuis et al, 1999, Wiking et al., 2009); and combining XRD and DSC with rheological analysis should be possible to obtain a more accurate understanding of the phase crystallization behavior of MF.

Cozma, A., Miere, D., Filip, L., Andrei, S., Banc, R., & Loghin, F. (2013). A Review of the Metabolic Origins of Milk Fatty Acids. Notulae Scientia Biologicae, 5(3), 270–274.
Emerson. (2010). Fundamentals of Gas Chromatography. 85th Annual Internasional School of Hydrocarbon Measurement, 43, 1–8.

Grummer, R. R. (1991). Effect of feed on the composition of milk fat. Journal of Dairy Science, 74(9), 3244–57.

Grotenhuis, E., Aken, G. a Van, Malssen, K. F. Van, Schenk, H., ten Grotenhuis, E., van Aken, G. A., … Schenk, H. (1999). Polymorphism of milk fat studied by differential scanning calorimetry and real-time X-ray powder diffraction. Journal of the American Oil Chemists’ Society, 76(9), 1031–1039.