Résumé
The hydrolysis of native milk fat globules by three microbial lipase preparations, two sn-1,3 specific and onenon-specific, exhibiting variable level of an annex phospholipase activity was investigated. The reactionkinetics, the evolution of supramolecular structure and the interfacial properties of hydrolyzed fat globuleswere monitored. The hydrolytic efficiency of the three enzymes preparations was lower for the natural emulsionthan for a model emulsion based on homogenized milk fat. Therefore, it indicated a limited accessibilityof the enzymes to the natural emulsion. The hydrolysis was preceded by a lag time, the duration of which wasnegatively correlated to the annex phospholipase activity. Pre-hydrolysis of membrane components withprotease or phospholipase modulated the observed lag times. The sn-1,3 specific lipases triggered an accumulationof sn-2 monoglycerides with a limited destabilization of the natural emulsion structure while thenon specific lipase, which generated fatty acids as major hydrolytic products, induced a significant destabilizationof the emulsion. Our results suggest that the specificity of lipase contributes to diversify the structureand interfacial reactivity of natural milk fat-based emulsions, and consequently their functional and nutritionalvalues.