*2.1. Microfiltration*

Raw ovine and bovine milk obtained from the farm of Agricultural University of Athens were defatted to fat content 0.30% and 0.40%, respectively, using a laboratory milk fat separator, and were subsequently heated at 50 ◦C. Crossflow MF processing (Figure 1) took place on a pilot microfiltration module (PALL Italia s.r.l, MILANO, Italy) under a constant transmembrane pressure (TMP) of 1.5 bar at 50 ◦C using ceramic membrane P19–40 (Membralox®) of 1.4 μm pore size, with length 1020 mm and area 0.24 m2. Filtration duration was 15 min with constant flux at 105 <sup>±</sup> 32 L·m−2·h−<sup>1</sup> for ovine milk and 314 <sup>±</sup> 32 L·m−2·h−<sup>1</sup> for bovine milk. Retention flow rates were 363.23 <sup>±</sup> 86.32 L·m−2·h−<sup>1</sup> and 795.83 <sup>±</sup> 18.37 L·m−2·h−<sup>1</sup> for bovine and ovine milk retentates, respectively. After processing, the microfiltration unit was cleaned by rinsing in series with water, NaOH 1% solution, water, HNO3 1% solution and water to reach pH 7.0 [17]. Five and three experimental trials were carried out for ovine milk and bovine milk, respectively. Samples codes were as follows: feed ovine milk (O), permeate ovine milk (OP), retentate ovine milk (OR), feed bovine milk (B), permeate bovine milk (BP) and retentate bovine milk (BR).

**Figure 1.** Simplified diagram showing the crossflow microfiltration process.

#### *2.2. Physicochemical Analyses*

The pH was measured on a pH meter and acidity was determined by the titration method using 0.11 N NaOH solution. Fat, protein, lactose and total solids contents were determined by means of infrared spectroscopy (Milkoscan FT6000, Foss, Hillerod, Denmark). Ash content was determined by the AOAC method [18]. Total nitrogen (TN) as well as water soluble nitrogen (WSN) were determined by the Kjeldahl method. Phosphorus content was determined by molecular absorption spectrometry [19]. Moreover, calcium content of ovine milk was measured by Atomic Absorption Spectrometry [20] on a Shimadzu AA-6800 Atomic Absorption Spectrophotometer (Shimadzu, Kyoto, Japan) equipped with the autosampler Shimadzu ASC-6100 and the software WizAArd v. 2.30.

Somatic cell counts (SCC) were determined on Fossomatic (Foss, Hillerod, Denmark). All analyses were performed in duplicate.
