Résumé
Milk polar lipids have attracted attention over the last decade due to their interesting nutritional properties and high content in sphingolipids which are implicated in cell metabolism. Milk polar lipids are currently available under the form of commercial powders derived from buttermilk of variable purity. The composition of these powders could be tailored using lipases or phospholipases to modulate their polar lipids profile, increase their purity in sphingolipids and possibly enhance their bioactivity. The objective of this work was thus to assess the potential of various lipolytic enzymes in modifying the composition of a milk polar lipid concentrate. In this work, 8 microbial lipases of variable specificity and of variable level of annex phospholipase activity and 2 phospholipases (PLA1 and PLA2) have been used to catalyze the hydrolysis of a milk polar lipid concentrate. The initial lipid composition of the milk polar lipid concentrate was: 7 % triacylglycerides (TAG), 23 % phosphatidylethanolamine (PE), 11 % phosphatidylinositol (PI) , 4 % phosphatidylserine (PS), 41 % sphingomyelin (SM). After 4 hours hydrolysis, lipid classes were quantified by high performance liquid chromatography. The highest hydrolysis levels were obtained using: PLA1 > PLA2 > M. miehei lipase. Lipases generally triggered a specific enrichment in polar lipids through a preferential hydrolysis of apolar lipids whithout modifying the polar lipids profile. Except for M. Miehei lipase which presented a high annex phospholipase activity and decreased both TAG content and PE content. PLA2 and PLA1 led respectively to a final composition dominated by PI, PC and SM on one hand and SM only on the other hand. Phospholipases allowed the obtention of an ingredient highly concentrated in sphingomyelin which could be an interesting precursor of ceramides. The potential of these biocatalyzers to modulate milk polar lipids composition was thus underlined