Effects of high pressure on some constituents and properties of buffalo milk

In this study, effects of high pressure (HP) on some constituents and properties of buffalo milk were examined. HP treatment at 100-600 MPa for 30 min affected casein micelle size only slightly, whereas treatment at 800 MPa increased it by ∼35%. Levels of non-micellar α_s1-and β-caseins were increased by treatment ≥250 MPa, and were highest after treatment at 400-800 MPa. The level of non-micellar calcium increased with increasing pressure up to 600 MPa. The L*-value of the milk decreased gradually with increasing pressure, from ∼82 for untreated milk to ∼65 for milk treated at 800 MPa. Milk pH was increased by ∼0.07 units after treatment at 100-800 MPa, with no significant difference between treatment pressures. Denaturation of α-lactalbumin occurred at pressures ≥400 MPa, and reached >90% after treatment at 800 MPa, whereas β-lactoglobulin (β-lg) was denatured >100 MPa, reaching ∼100% after treatment at 400 MPa; after treatment ≥400 MPa, all β-lg was associated with the casein micelles. The rennet coagulation time of buffalo milk increased with increasing pressure, whereas the strength of the coagulum formed decreased after treatment at 250-800 MPa. Overall, HP treatment affected many constituents and properties of buffalo milk; some of these effects have also been observed in the milk from other species, but the extent of the effects, and the pressure at which they occurred, differed considerably.