LUNAM Université du Maine , IMMM UMR-CNRS, Polymers, Colloids, Interfaces, 72085 Le Mans Cedex 9, France.
Biomacromolecules. 2013 Jun 10;14(6):1980-9. doi: 10.1021/bm400347d. Epub 2013 May 15.
The effect of the addition of NaCl or CaCl2 on the structure of protein particles and gels was investigated in detail for aqueous solutions of the globular milk protein β-lactoglobulin at 40g/L and pH 7.0. When heated in the presence of NaCl or at very low CaCl2 concentrations, the proteins form small strand-like particles, but if more than about two Ca(2+) ions per protein are present, larger spherical particles (microgels) are formed, which increase in size with increasing CaCl2 concentration. The effect of the heating temperature was investigated between 62 and 85 °C. At lower heating temperatures, more Ca(2+) ions per protein are needed to drive the formation of microgels. Particle size measurements done with dynamic light scattering suggest that the aggregation occurs via a nucleation and growth process. The nuclei grow either by fusion or by addition of denatured proteins. If more than three Ca(2+) ions per protein are added, particulate gels are formed by random association of the microgels. Similar particulate gels are also formed at high NaCl concentrations (>200 mM), but by a different mechanism. In this case, the randomly aggregated small strands formed at the early stage of the heating process formed dense spherical domains at a later stage of the heating process by microphase separation that randomly associated to form a particulate gel.
研究了在 40g/L 和 pH 7.0 的球状乳蛋白β-乳球蛋白水溶液中，NaCl 或 CaCl2 的添加对蛋白质颗粒和凝胶结构的影响。当在 NaCl 存在下或在非常低的 CaCl2 浓度下加热时，蛋白质形成小的链状颗粒，但如果存在超过约两个 Ca(2+)离子/蛋白质，则形成较大的球形颗粒（微凝胶），随着 CaCl2 浓度的增加而增大。研究了加热温度在 62 和 85°C 之间的影响。在较低的加热温度下，需要更多的 Ca(2+)离子/蛋白质来驱动微凝胶的形成。用动态光散射进行的颗粒尺寸测量表明，聚集通过成核和生长过程发生。核通过融合或添加变性蛋白质而生长。如果添加超过三个 Ca(2+)离子/蛋白质，则通过微凝胶的随机缔合形成颗粒状凝胶。在高 NaCl 浓度（>200 mM）下也形成类似的颗粒状凝胶，但通过不同的机制。在这种情况下，在加热过程的早期形成的随机聚集的小链通过微相分离在加热过程的后期形成密集的球形域，这些球形域随机缔合形成颗粒状凝胶。
