Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
Research Division, Minami Nippon Dairy Co-op Co., Ltd., 5282, Takagi, Miyakonojyo, Miyazaki 885-0003, Japan.
Food Chem. 2024 Jun 15;443:138606. doi: 10.1016/j.foodchem.2024.138606. Epub 2024 Jan 28.
Changes in milk pH significantly influence the behavior and physical properties of casein micelles; however, the effects of these changes on casein micelle structures are still unclear. The aim of this study was to elucidate the effect of changes in pH range from 5.9 to 7.1 on the structure of casein micelles in milk using small-angle X-ray scattering (SAXS) and ultra small-angle X-ray scattering (USAXS). The casein micelles formed one-dimensional aggregates. The micelle radius decreased with decreasing pH, whereas the size of the water domain increased. The distance between colloidal calcium phosphates (CCP) remained unchanged, whereas the CCP radius decreased with decreasing pH. Voluminosity, which was calculated from scattering intensities, increased at increased pH. In conclusion, the micelle structure changed significantly in response to changes in pH. Our findings help to understand the changes in the physical properties of milk at various pH levels in terms of the microscopic structure.
牛奶 pH 值的变化会显著影响酪蛋白胶束的行为和物理性质；然而，这些变化对酪蛋白胶束结构的影响仍不清楚。本研究旨在使用小角 X 射线散射（SAXS）和超小角 X 射线散射（USAXS）阐明 pH 值范围从 5.9 到 7.1 变化对乳中酪蛋白胶束结构的影响。酪蛋白胶束形成一维聚集体。胶束半径随 pH 值降低而减小，而水域的尺寸增大。胶态磷酸钙（CCP）之间的距离保持不变，而 CCP 半径随 pH 值降低而减小。根据散射强度计算出的体积，在 pH 值增加时增加。总之，胶束结构随 pH 值的变化而显著变化。我们的研究结果有助于从微观结构的角度理解不同 pH 值下牛奶物理性质的变化。
