The Preparation Method Of Milk Liposome And The Physio-chemical Propertites Of Milk Polar Lipids

Milk polar lipids, located on the milk fat globule membrane, have interestingnutritional and functional properties that could be further exploited. For example,liposomes could be used for encapsulation of bioactive molecules, such as vitamins,drugs and so on. Recently, it has been revealed that milk polar lipids areheterogeneously distributed in the milk fat globule membrane with the lateralsegregation of sphingomyelin (SM) and cholesterol (Chol) in domains called“lipid rafts”, the properties of which need to be elucidated.In this context, the first objective of the study was to evaluate the possibilitiesof producing liposomes with the milk polar lipids and to characterize theirphysicochemical properties and their physical stability during changing the pH andionic strength (NaCl and CaCl2). Spherical liposomes with100nm diameter havebeen produced using homogenization. The analysis of liposome’s size and zetapotential revealed that between pH1.9and4, and for high ionic strength (ICaCl2≥7.5mmol/L and INaCl≥50mmol/L) liposomes form aggregates.The second objective was to characterise the thermotropic phase behaviour ofmilk SM and its interactions with cholesterol (Chol) in order to better understand the“lipid raft” properties in the milk fat globule membrane. We have determined usingdifferential scanning calorimetry that the temperature (Tm) of gel L�'liquid-crystalline L phase transition of milk SM is Tm=34.4±0.1°C. The additionof Chol leads to changes in the SM bilayer with the formation of the liquid-orderedLo phase for concentration [Chol]≥40%mol. Moreover, we showed usingLangmuir method the condensing effect of Chol on the monolayer of milk SM,particularly for T <Tm.All these results increase the knowledge about milk polar lipid properties,particularly those of SM as a function of temperature and Chol concentration, andprovide new opportunities in the use of milk liposomes for food applications.