High-pressure treatment of milk in industrial and pilot-scale equipments: effect of the treatment conditions on the protein distribution in different milk fractions

The effects of two different high-pressure (HP) equipments, operating at industrial- and pilot scales, and of the HP-release rate on the contents of non-sedimentable proteins and denatured whey proteins were investigated after treatments of skim milk-from 250 to 650 MPa. Non-sedimentable caseins and denatured whey proteins significantly increased with the pressure level. The industrial-scale equipment produced lower micellar disintegration than the pilot-scale equipment with similar degrees of whey protein denaturation. Ultracentrifugation supernatants obtained from skim milk at 100,000xg and 20 A degrees C for 1 h were also HP-treated for comparative purposes, showing that, in skim milk, the presence of casein promoted the denaturation of whey proteins, although the extent of whey protein denaturation did not influence the release of casein to the soluble phase. Furthermore, most denatured whey proteins remained soluble after treatment in both equipments. In the pilot-scale equipment, the pressure-release rate influenced casein solubilization and whey protein denaturation.