*2.3. Spray Drying*

Spraying was carried out on the UF retentate sample (UF\_Ret20) provided by dairy company. The spray drier used was a Mobile MinorTM (GEA Process Engineering, Danimarca). Samples were loaded into the specific chamber by means of a peristaltic pump with a flow rate of 2–2.5 Kg/h, the internal temperature of the chamber (in which the sample remained in contact with the gas for drying for about 10 s) was of about 160–170 ◦C, the outlet temperature 80–85 ◦C; compressed air was used as the drying gas. One g of spraydried sample indicated as UF\_Ret20Pow was dissolved in 100 mL of sterile bi-distilled water and characterized to determine the protein, sugars, lactic acid and insoluble solid content. Water content was determined by drying 100 mg of powder on a thermobalance (Mettler Toledo HR 83 Halogen). The sample was heated at 105 ◦C and temperature was maintained for 6 h until a constant weight was recorded.

For ashes determination, 10 g of sample were placed in a tared crucible. The crucible was placed in a muffle furnace for 18 h at about 550 ◦C. When the temperature dropped below 250 ◦C the sample was quickly transferred to a desiccator until cooled before weighing. Calculation for dry ash content [20]:

% ash (dry basis) = (wt after ashing − tare wt of crucible)/(original sample wt × dry matter coefficient) × 100.
