![]() The aim of this study was to determine effects of high-pressure homogenization (HPH) treatment to milk concentrates on powder flow properties of skim milk powders (SMP). The added phospholipids could participate in the recombination of MFGM during homogenization, promoted the stability of the newly generated MFGs and protected native membrane proteins, which would provide guidance for the optimization of dairy products functionality. The digestibility of MFG was also studied in vitro with a simulated intestine digestion system. Moreover, SDS-PAGE patterns showed that adding phospholipids reduced serum proteins absorption onto the MFG membrane (MFGM) and preserved more native MFGM proteins including XDH, BTN and MFGE8. More surface area of the MFGs in PLM was observed to be covered by phospholipids using a laser confocal microscope, which was similar to the state of MFGs in the raw milk sample (RM). As a result, the storage stability increased according to a Turbiscan analysis. Compared with normally homogenized milk (HM), the particle size of MFGs in PLM decreased from 1.35 μm to 1.15 μm, and the ζ-potential decreased from −11.97 mV to −13.77 mV. In order to protect the structure and membrane protein of milk fat globules (MFGs), a milk sample rich in phospholipid (PLM) was prepared by adding soybean lecithin before homogenization. ![]() The structural changes of the CN micelles observed in this study throughout the combination of alkalinization and UHPH could be of interest for developing new dairy ingredients with improved functionality. Although UHPH did not influence the average CN micelle size at pH 6.7 and 8.5, a pressure-dependent decrease was observed at pH 10.5 for both skim milks. The amount of CN found in the serum phase at pH 8.5 also increased with the UHPH pressure. ![]() At alkaline pH, more proteins were recovered in the serum phase, which suggested that the CN underwent major rearrangements into nonsedimentable CN forms of various sizes, as confirmed by transmission electron microscopy. Alkalinization of both skim milks induced a significant reduction in turbidity, whereas an increase of the average particle size was observed, the effect being more severe in pSM than rSM. Finally, ultracentrifugation (70,000 × g for 1 h at 20☌) was carried out to evaluate the protein's distribution between the supernatant (serum phase) and the pellet (colloidal phase) by gel electrophoresis and protein concentration measurement. The structural changes of the CN micelles during the treatments were assessed using laser diffraction, transmission electron microscopy, and turbidity measurements. The pH of both skim milks (approximately 6.7) was adjusted to 8.5 and 10.5 before UHPH at 100, 200, and 300 MPa. Here, we studied the effect of alkalinization and ultra-high-pressure homogenization (UHPH) on CN micelles in raw skim milk (rSM) and pasteurized skim milk (pSM). Mechanical and physicochemical treatments of milk induce structural modifications of the casein (CN) micelles, affecting their techno-functional properties in dairy processing. Furthermore, UHPH treatments performed at 300 MPa with Ti = 75 and 85☌ produced sterile milk after sample incubation (30 and 45☌), obtaining similar or better characteristics than UHT milk in color, particle size, viscosity, buffer capacity, ethanol stability, propensity to protein hydrolysis, and lower scores in sensory evaluation for cooked flavor. The UHPH-treated milks presented a high level of microbial reduction, under the detection limit, for treatments at 300 MPa with Ti of 55, 65, 75, and 85☌, and at 200 MPa with Ti = 85☌, and few survivors in milks treated at 200 MPa with Ti of 55, 65, and 75☌. Ultra-high-pressure homogenization treatments of 200 and 300 MPa at inlet temperatures (Ti) of 55, 65, 75, and 85☌ were compared with a UHT treatment (138☌ for 4 s) in terms of microbial inactivation, particle size and microstructure, viscosity, color, buffering capacity, ethanol stability, propensity to proteolysis, and sensory evaluation. The effect of ultra-high-pressure homogenization (UHPH) on raw whole milk (3.5% fat) was evaluated to obtain processing conditions for the sterilization of milk.
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