Regardless of the whole products, e.g. buttermilks or butter serums,
the skimming step was shown to be an efficient step for the removal of
particles with sizes larger than 1 μm. The whole buttermilks and butter
serums initially contained large milk fat particles (fat globules with a diameter larger than 1 μm; butter fines; aggregates of fat globules)
which were systematically removed by the skimming process as
shown by the structural analyses (microscopies and particle size
profile). Small lipid particles, such as MFGM fragments and vesicles
of polar lipids (only in butter serum) with sizes lower than 1 μm,
were however not removed by the skimming process (Figs. 3, 4, 5, 6).