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

• Published in: Journal of dairy science 2021-03, Vol.104 (3), p.2834-2842
• Main Authors: Bogahawaththa, Dimuthu, Trajkovska, Biljana, Markoska, Tatijana, Vasiljevic, Todor
• Format: Article
• Language: English
• Subjects: Animals; casein micelle; Caseins; Cattle; heat; Hot Temperature; Micelles; Milk - chemistry; Milk Proteins - analysis; pressure; Protein Denaturation; shear; Whey Proteins
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2020-19542

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 αS1- 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 αS1- 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.