Department of Food Science, University of Wisconsin-Madison, Madison, Wisconsin 53705-1565, USA.
J Dairy Sci. 2011 Sep;94(9):4255-63. doi: 10.3168/jds.2010-3343.
Calcium-chelating salts (CCS), such as phosphates and citrates, are often added to milk systems to modify physical properties like heat stability. The objective of this study was to investigate the effect of binary CCS mixtures on the properties of casein (CN) micelles including the distribution of Ca between the soluble and CN-bound states. Six binary CCS mixtures were prepared from 4 different types of CCS [i.e., trisodium citrate (TSC), disodium phosphate (DSP), tetrasodium pyrophosphate (TSPP), and sodium hexameta phosphate (SHMP)] by combining 2 CCS at a time in 5 different proportions (8.3:91.7, 29.2:70.8, 50:50, 70.8:29.2, and 91.7:8.3). Different concentrations of these mixtures (0, 0.1, 0.3, 0.5, and 0.7% wt/wt) were added to milk protein concentrate solutions (5% wt/wt) at pH 5.8. The ability of CCS to disperse CN particles and its interaction with Ca were assessed from turbidity measurements, acid-base titration behavior, and the quantity of CN-bound Ca and inorganic phosphate (Pi). Turbidity and the buffering peak at pH ∼5.0 during acid titration decreased with an increasing concentration of CCS. This was due to the chelation of Ca and the dispersion of CN micelles. The presence of TSC in mixtures decreased the amount of CN-bound Ca and Pi; however, the presence of TSPP in mixtures increased CN-bound Ca and Pi. When DSP was present at high proportions in mixtures of CCS, the CN-bound Ca and Pi slightly increased. When SHMP was used in mixtures of CCS, CN-bound Ca and Pi increased with the use of a low proportion of SHMP but decreased when SHMP was used at high proportions in the mixture. Combinations of DSP-TSPP used in the proportions 29.2:70.8, 50:50, and 70.8:29.2 resulted in the gelation of milk protein concentrates when the total CCS concentration was ≥0.3%. These results indicated that the type of CCS present in a mixture modified CN properties by various mechanisms, including chelation of Ca, dispersion of CN micelles, and formation of new types of Ca-CCS complexes. The type of interaction between the newly formed Ca-CCS complexes and the dispersed CN depended on the proportion, concentration, and type of CCS present in the mixtures. This information is useful in understanding how mixtures of CCS affect CN properties.
钙螯合盐（CCS），如磷酸盐和柠檬酸盐，常被添加到牛奶体系中以改变热稳定性等物理性质。本研究的目的是研究二元 CCS 混合物对酪蛋白（CN）胶束性质的影响，包括钙在可溶性和 CN 结合态之间的分布。通过将两种 CCS 以 2:1 的比例组合，共制备了 6 种二元 CCS 混合物，由 4 种不同类型的 CCS [即，柠檬酸三钠（TSC）、磷酸二氢钠（DSP）、焦磷酸四钠（TSPP）和六偏磷酸钠（SHMP）]组成，共制备了 6 种二元 CCS 混合物。通过以 5 种不同的比例（8.3:91.7、29.2:70.8、50:50、70.8:29.2 和 91.7:8.3）组合两种 CCS 一次。将不同浓度的这些混合物（0、0.1、0.3、0.5 和 0.7%wt/wt）添加到 pH5.8 的乳蛋白浓缩物溶液（5%wt/wt）中。通过浊度测量、酸碱滴定行为以及 CN 结合钙和无机磷（Pi）的量来评估 CCS 分散 CN 颗粒的能力及其与钙的相互作用。随着 CCS 浓度的增加，浊度和 pH~5.0 时的缓冲峰在酸滴定过程中降低。这是由于 Ca 的螯合和 CN 胶束的分散。混合物中 TSC 的存在减少了 CN 结合钙和 Pi 的量；然而，混合物中 TSPP 的存在增加了 CN 结合钙和 Pi。当 DSP 以高比例存在于 CCS 混合物中时，CN 结合钙和 Pi 略有增加。当 SHMP 用于 CCS 混合物时，CN 结合钙和 Pi 的量随着 SHMP 低比例的使用而增加，但当 SHMP 在混合物中高比例使用时则减少。当 DSP-TSPP 以 29.2:70.8、50:50 和 70.8:29.2 的比例组合使用时，当总 CCS 浓度≥0.3%时，乳蛋白浓缩物会凝胶化。这些结果表明，混合物中存在的 CCS 类型通过各种机制（包括 Ca 的螯合、CN 胶束的分散和新型 Ca-CCS 络合物的形成）改变了 CN 性质。新形成的 Ca-CCS 络合物与分散的 CN 之间的相互作用类型取决于混合物中存在的 CCS 的比例、浓度和类型。这些信息有助于理解 CCS 混合物如何影响 CN 性质。
