Milk fat globule membrane conditions the reactivity and enzymatic susceptibility ofmilk fat. The use of bovine membrane extracts to formulate infant formulas morebiomimetic of human milk has been suggested in the recent literature1,2. A comparisonof the physico-chemical behavior of human (HMM) and bovine (BMM) milk membraneextracts and their interaction with gastric lipase is lacking to assess whether theirinterfacial behavior is similar[br/]This comparison is undertaken in the present project using complementary biophysicaltools based on Langmuir film characterization as tensiometry, ellipsometry, Brewsterangle (BAM) and atomic force (AFM) microscopies in the presence or in absence ofgastric lipase. Milk membrane extracts were obtained from either a pool of maturehuman milk (n=5) or bovine butterserum and were analyzed using GC and HPLC.[br/]Compression isotherms indicated a higher compressibility of HMM than BMM.However, both extracts presented close collapse pressures (~45 mN/m). Despite thepresence of liquid condensed (LC) domains (AFM and BAM) from low to highest surfacepressure in the two extracts, their morphological aspect and growth differed strongly inrelation with their specific lipid composition (GC and HPLC). As reported for BMM3, thegastric lipase got adsorbed toward liquid expanded phase (LE) and at several heightlevels in HMM. However its insertion did not impact on LC domain morphology asobserved in BMM.Despite differences in their physico-chemical properties, both extracts present closeinterfacial reactivity in gastric conditions. Such biophysical Investigation of ‘lipasecomplexlipid’ interactions will be broaden to other milk membrane extracts (equidae)interesting for human milk substitution.