Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
J Dairy Sci. 2012 Oct;95(10):5569-79. doi: 10.3168/jds.2012-5501. Epub 2012 Aug 15.
The use of casein preparations obtained by membrane separation is receiving increasing interest from the dairy and food industry. The objective of this work was to generate information about the steady shear rheological properties of micellar casein concentrates (MCC) and the effect of composition, temperature, and shear rate on these properties. Micellar casein concentrate preparations with 2 levels of serum proteins (SP; 65 and 95% SP reduced, respectively), were obtained from skim milk by microfiltration followed by spray drying. Micellar casein concentrate preparations with casein concentrations ranging from 2.5 to 12.5% were obtained by dispersing the MCC powders in ultrapure water. Steady shear rheological analyses at temperatures ranging from 0 to 80°C were performed using a strain-controlled rheometer. Viscosity versus shear rate curves were used to evaluate the effect of shear on viscosity, and the apparent viscosity at a shear rate of 100 s(-1) was used to make direct comparisons between various concentration and temperature conditions. The 65% SP-reduced MCC had lower viscosity than the 95% SP-reduced MCC at the same casein concentration and temperature. Protein preparations at casein concentrations above 7.5% displayed shear-thinning behavior, which was more pronounced as concentration increased. The viscosity of MCC increased exponentially with casein concentration and decreased with temperature. The dependency of viscosity on temperature followed an Arrhenius relationship. A modified Arrhenius model able to accurately predict rheological properties under desired shear, temperature, and concentration conditions was developed and validated. This study provides critical rheological data necessary for developing practical applications of micellar casein preparations.
膜分离法获得的酪蛋白制剂在乳品和食品工业中越来越受到关注。本工作的目的是提供关于胶束酪蛋白浓缩物（MCC）的稳态剪切流变特性的信息，以及组成、温度和剪切速率对这些特性的影响。通过微滤和喷雾干燥，从脱脂乳中获得了 2 种血清蛋白（SP）水平（分别降低 65%和 95%SP）的胶束酪蛋白浓缩物制剂。通过将 MCC 粉末分散在超纯水中，获得了酪蛋白浓度范围为 2.5%至 12.5%的胶束酪蛋白浓缩物制剂。在 0 至 80°C 的温度范围内使用应变控制流变仪进行稳态剪切流变分析。使用剪切率与粘度曲线来评估剪切对粘度的影响，并且使用在 100 s-1的剪切率下的表观粘度来直接比较各种浓度和温度条件下的结果。在相同的酪蛋白浓度和温度下，65%SP 降低的 MCC 的粘度低于 95%SP 降低的 MCC。在酪蛋白浓度高于 7.5%的蛋白制剂中，表现出剪切稀化行为，随着浓度的增加，这种行为变得更加明显。MCC 的粘度随酪蛋白浓度呈指数增加，随温度降低。粘度对温度的依赖性遵循阿累尼乌斯关系。开发并验证了一个能够准确预测所需剪切、温度和浓度条件下流变性能的改进的阿累尼乌斯模型。本研究提供了开发胶束酪蛋白制剂实际应用所需的关键流变数据。
