Microfiltration of raw whole milk to select fractions with different fat globule size distributions: process optimization and analysis.

We present an extensive description and analysis of a microfiltration process patented in our laboratory to separate different fractions of the initial milk fat globule population according to the size of the native milk fat globules (MFG). We used nominal membrane pore sizes of 2 to 12 microm and a specially designed pilot rig. Using this process with whole milk [whose MFG have a volume mean diameter (d43) = 4.2 +/- 0.2 microm] and appropriate membrane pore size and hydrodynamic conditions, we collected 2 extremes of the initial milk fat globule distribution consisting of 1) a retentate containing large MFG of d43 = 5 to 7.5 microm (with up to 250 g/kg of fat, up to 35% of initial milk fat, and up to 10% of initial milk volume), and 2) a permeate containing small MFG of d43 = 0.9 to 3.3 microm (with up to 16 g/kg of fat, up to 30% of initial milk fat, and up to 83% of initial milk volume and devoid of somatic cells). We checked that the process did not mechanically damage the MFG by measuring their zeta-potential. This new microfiltration process, avoiding milk aging, appears to be more efficient than gravity separation in selecting native MFG of different sizes. As we summarize from previous and new results showing that the physico-chemical and technological properties of native milk fat globules vary according to their size, the use of different fat globule fractions appears to be advantageous regarding the quality of cheeses and can lead to new dairy products with adapted properties (sensory, functional, and perhaps nutritional).