Characterization of sodium caseinate derived from various sources: Unraveling the relationship between structure and functional properties

In this study, the structural and functional properties of laboratory-prepared sodium caseinate (L-SC) from yak Qula with three different sources of commercial products: yak milk, Qula, and milk sodium caseinate products (YM-SC, YQ-SC, M-SC) were compared. The physicochemical properties of different samples were analyzed, indicating significant fat content and color differences. The SDS-PAGE showed predominant protein subunits in the 25 kDa–35 kDa range, with M-SC having the highest κ-casein content and the least aggregation. M-SC exhibited the smallest particle size, lowest surface hydrophobicity (H0) and surface tension at the oil-water interface, with excellent functional properties, whereas YQ-SC exhibited contrast. FTIR suggested that the effect may be attributed to the decreased α-helix and β-sheet structure, and reduction in H0 and protein aggregation, resulting in a notable enhancement in protein solubility and surface activity. After optimizing the alkali extraction conditions and drying method, L-SC showed a reduced particle size of 135.0 nm, significantly improved foaming properties while the prepared emulsion had good stability and smaller d4,3. In addition, the relationship among the indicators was verified by the correlation analysis. These results could provide more information for the manufacturing of sodium caseinate in the food industry.