CLSM and TEM images of whole butter serum showed the presence
of species with sizes ranging from 0.1 to 10 μm. From the images, one
could identify casein micelles, vesicles of milk polar lipids with diameters
between 0.1 and 1 μm that might be formed with polar lipids issued
from membrane components after MFGM rupture during the churning
process (Fig. 6C) and fragments of MFGM with diameters between 0.1
to 2 μm (Fig. 6C) as already reported (Lopez et al., 2015). Moreover,
milk fat globules with diameters between 1 and 10 μm have been characterized
in the whole butter serums (Fig. 5C). These milk fat globules
contained a core rich in TAG enveloped by milk polar lipids (Fig. 5C).
The presence of these milk fat globuleswas not surprising since residual
milk fat globules have been characterized within the microstructure of
butter (Lopez et al., 2015).
Fragments of MFGM observed in butter serum were smaller than
fragments observed in buttermilk.