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-The aim of this research was to determine the calcium-binding capacity of inorganic and organic ortho-and polyphosphates. This calcium-binding capacity can be used to influence the stability of, for example, casein micelles in dairy systems. Four phosphates were selected: disodium uridine monophosphate (Na 2 UMP, organic orthophosphate), disodium hydrogen phosphate (Na 2 HPO 4 , inorganic orthophosphate), sodium phytate (SP, organic polyphosphate), and sodium hexametaphosphate (SHMP, inorganic polyphosphate). Concentrations of up to 100 mmol·L −1 phosphate were added to a 50 mmol·L −1 CaCl 2 solution. The samples were prepared at pH 8.0 and were analyzed before and after sterilization for calcium-ion activity, conductivity, pH, sediment, and turbidity. Both SHMP and SP are strong chelators, as calcium ions bind to these phosphates in the ratio of 3:1 and 6:1, respectively. Calcium ions also strongly bind to Na 2 HPO 4 , but in a ratio of 3:2 with insoluble Ca 3 (PO 4 ) 2 complexes as result. The equilibrium position of Na 2 UMP is not strong towards the chelated complex, and significant levels of free calcium and free phosphate can exist. An equilibrium constant of 0.29 ± 0.08 L·mol −1 was determined for calcium uridine monophosphate (CaUMP) complexes. Both calculation of the equilibrium constant and analysis on the CaUMP precipitate confirmed a reactivity of 1:1 between calcium and Na 2 UMP. The CaUMP complexes are well soluble at ambient temperature, and insoluble complexes appear after sterilization, because the solubility of CaUMP decreases during heating. Finally, we concluded that the structure of phosphate molecules determines their calcium-binding capacity rather than organic or inorganic origin of phosphates.orthophosphate / polyphosphate / organic phosphate / inorganic phosphate / calcium 摘要 -有机和无机正磷酸盐和多磷酸盐对钙的结合能力○ 本文测定了无机和有机正磷酸 和多磷酸盐对钙的结合能力○ 这种结合能力影响到乳体系中酪蛋白酪胶束的稳定○ 四种 磷酸盐分别为 :尿苷磷酸二钠 (Na 2 UMP，有机正磷酸盐)，磷酸氢二钠 (Na 2 HPO 4 ，无 机正磷酸盐)，肌醇六磷酸钠 (SP，有机多磷酸盐)和六偏磷酸钠 (SHMP，无机多磷酸盐)○ 100 mmol·L −1 的磷酸盐添加到 50 mmol·L −1 的 CaCl 2 溶液中○ 分析了杀菌前后样品在 pH 8.0 的钙离子活度、电导率、pH 值、沉淀值和浊度○ SHMP 和 SP 都是强螯合剂，钙离 子与这些磷酸盐螯合的比分别为 3:1 和 6:1○ 同时，钙离子与 Na 2 HPO 4 结合能力较强，产 生了 3:2 的不溶性 Ca 3 (PO 4 ) 2 混合物○ 平衡状态下的 Na 2 UMP 不能与钙形成稳定的螯合物，存