Polar lipids, sphingomyelin and long-chain unsaturated fatty acids from the milk fat globule membrane are increased in milks produced by cows fed fresh pasture based diet during spring
Résumé
Milk lipids are an interesting source of bioactive molecules with functional and nutritional properties. Although
the composition of milk lipids is of utmost importance for food processing and human consumption, it is far from
being fully known. The objective of this studywas to perform a comparative analysis of the chemical composition
of lipids frombovine milks produced in French Brittany during spring (fresh pasture based diet) and winter (corn
silage based diet). The polar lipid content and relative proportions of the glycerophospholipids and
sphingomyelin were determined using HPLC/ELSD. The fatty acid composition of total lipids and polar lipids
was determined using GC. The milks collected in spring contained i) a lower amount of total lipids: 39.7 ±
0.8 g/kg vs 41.7 ±0.5 g/kg inwinter, ii) a higher amount of polar lipids: 138 ±11 vs 112 ±8 mg/kgmilk; 3.5±
0.3 vs 2.7 ± 0.4 mg/g fat, which was related to a smaller size of fat globules, and iii) a higher amount of
sphingomyelin, 32 mg/kg milk vs 25 mg/kg milk in winter. Interestingly, the polar lipids from the milk fat globule
membrane contained a higher concentration of unsaturated fatty acids in spring (C18:1 n−9, C18:2 n−6,
C18:3 n−3 and long-chain n−3 fatty acids). Milk from cows fed a fresh pasture-based diet during spring is
an interesting source of dietary long chain polyunsaturated fatty acids for human consumption