PhD Candidate Wageningen University & Research, Netherlands
Seasonal variation in TAG composition occurs due to changes in feed according to the season, mainly driven by availability of fresh pasture. Variations in feeding regimes affect FA composition leading to changes in MF TAG composition, further influencing MF physicochemical and functional properties. The present study assessed the effect of seasonal variation in FA and TAG composition in bovine MF throughout a year and its effect on MF physical properties. Weekly pooled milk samples were collected from fourteen dairy factories in the Netherlands (May 2017 to April 2018). The samples were combined according to their respective month and analysed to characterize their physical properties. FA and TAG composition were analysed using GC-FID, SFC was determined with pNMR, and crystal network development was followed using oscillatory rheology (small deformation). Compared to winter in summer, when cows fresh grass intake increased, were found minimum concentrations of saturated low and medium Mw-TAGs as well as maximum concentration of unsaturated high Mw-TAGs. In winter the SFC and network strength increased measured against summer MF. These changes in SFC and network strength were correlated with changes in TAG composition and profile during the year. Saturated low and medium Mw-TAGs Cn30-36 and Cn42-46 increased the SFC and network strength and unsaturated high Mw-TAGs Cn50-54 decreased the SFC and network strength. This study shows the seasonal variation in FA and TAG composition and its effect on SFC and network strength in bovine MF, one of the first reports on a non-seasonal milking system.