Ghorbani Gorji Sara, Ghorbani Gorji Elham, Mohammadifar Mohammad Amin
Department of Food Science and Technology, Faculty of Nutrition and Food Science, Shahid Beheshti University of Medical Sciences, P.O.Box 19395-4741, Tehran, Iran.
Department of Food Science and Technology, University of Natural Resources and Life Sciences, Vienna (BOKU), Muthgasse18, Vienna, A-1190 Austria.
J Food Sci Technol. 2015 Mar;52(3):1820-4. doi: 10.1007/s13197-013-1144-2. Epub 2013 Aug 23.
The characterization of sodium caseinate solutions as a function of pH was determined using titration with HCL through turbidimetry in different concentrations (0.03 wt.%, 0.045 wt.%, 0.06 wt.%, 0.09 wt.%, 0.2 wt.%, and 0.3 wt.%). Additionally, the coupling of slow in situ acidification of the solution and rheometry was utilized to gain deeper insights into pH-induced structural transitions during the self assembly process and particle size distribution analysis have been used to determine the behavior of sodium caseinate solutions in different pHs. The formation of aggregates during the acidification process was clearly visualized using microscopy. Surprisingly the viscosity of sodium caseinate solution at pH 4.64 was maximum and decreased by lowering pH. Particle size analysis confirmed the onset of big aggregates on decreasing pH but further acidification led to formation of smaller aggregates. A small concentration effect on pI was seen where at sodium caseinate levels of 0.03 wt.% the pI occurred at 4.29, where at sodium caseinate levels of 0.30 wt.% pI value was 4.64.
通过在不同浓度（0.03 wt.%、0.045 wt.%、0.06 wt.%、0.09 wt.%、0.2 wt.%和0.3 wt.%）下用盐酸滴定并采用比浊法测定了酪蛋白酸钠溶液随pH值的特性。此外，利用溶液的缓慢原位酸化与流变学的结合，以更深入地了解自组装过程中pH值诱导的结构转变，并通过粒度分布分析来确定酪蛋白酸钠溶液在不同pH值下的行为。使用显微镜清晰地观察到了酸化过程中聚集体的形成。令人惊讶的是，酪蛋白酸钠溶液在pH 4.64时粘度最大，且随着pH值降低而降低。粒度分析证实，随着pH值降低会开始形成大的聚集体，但进一步酸化会导致形成较小的聚集体。观察到酪蛋白酸钠浓度对pI有较小影响，在酪蛋白酸钠水平为0.03 wt.%时，pI出现在4.29，而在酪蛋白酸钠水平为0.30 wt.%时，pI值为4.64。
