Effects of pressurized thermal processing on native proteins of raw skim milk and its concentrate

Abstract

Heating, pressurization, and shearing can modify native milk proteins. The effects of pressurized heating (0.5 vs. 10 MPa at 75 or 95°C) with shearing (1,000 s −1 ) on proteins of raw bovine skim milk (SM, ~9% total solids) and concentrated raw skim milk (CSM, ~22% total solids) was investigated. The effects of evaporative concentration at 55°C and pressurized shearing (10 MPa, 1,000 s −1 ) at 20°C were also examined. Evaporative concentration of SM resulted in destabilization of casein micelles and dissociation of α S1 -and β-casein, rendering CSM prone to further reactions. Treatment at 10 MPa and 1,000 s −1 at 20°C caused substantial dissociation of α S1 -and β-casein in SM and CSM, with some dissociated caseins forming shear-induced soluble aggregates in CSM. The pressure applied at 10 MPa induced compression of the micelles and their dissociation in SM and CSM at 75 or 95°C, resulting in reduction of the micelle size. However, 10 MPa did not alter the mineral balance or whey proteins denaturation largely, except by reduction of some β-sheets and α-helices, due to heat-induced conformational changes at 75 and 95°C.

Health-Related Outcomes and Molecular Methods for the Characterization of A1 and A2 Cow’s Milk: Review and Update

“…It is responsible for the formation of the disulfide bond that causes a heat-induced aggregation of WPs and between WPs and CN micelles in milk [16]. Whey proteins, especially β-Lg, can denature or aggregate and possibly associate with CN micelles via κ-CN bonds or form κ-CN/β-Lg complexes in the serum phase depending on pH as well as heat [17].…”