Department of Food Science, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark; Instituto Federal de Educação, Ciência e Tecnologia de São Paulo, Campus Capivari. Avenida Doutor Ênio Pires de Camargo, 2971, São João Batista, CEP: 13360-000 Capivari, SP, Brazil.
IMFUFA, Department of Science and Environment, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark.
Food Res Int. 2020 Nov;137:109539. doi: 10.1016/j.foodres.2020.109539. Epub 2020 Jul 15.
Saturated solutions of calcium l-lactate in water or in deuterium oxide continuously dissolve calcium l-lactate by addition of solid sodium d-gluconate and become strongly supersaturated in calcium d-gluconate due to no or slow precipitation. The quantification of total dissolved calcium allied with the calcium complexes equilibrium constants allowed an ion speciation, which shows an initial non-thermal and spontaneous supersaturation of more than a factor of 50 at 25 °C only slowly decreasing after initiation of precipitation of calcium d-gluconate after a lag phase of several hours. A mathematical model is proposed, based on numerical solution of coupled differential equations of dynamics of l-lactate and d-gluconate exchange during the lag phase for precipitation and during precipitation. A slow exchange of l-lactate coordinated to calcium with d-gluconate is indicated with a time constant of 0.20 h in water and of 0.15 h in deuterium oxide and a kinetic deuterium/hydrogen isotope effect of 1.25. Such spontaneous non-thermal supersaturation and slow ligand exchange with a pseudo first order equilibration process with a half-life of 3.5 h in water for calcium hydroxycarboxylates can help to understand the higher calcium bioavailability from calcium hydroxycarboxylates compared to simple salts.
在水或重水溶剂中，饱和的 L-乳酸钙溶液通过添加固体 D-葡萄糖酸钠，不断溶解 L-乳酸钙，由于沉淀缓慢或几乎不沉淀，导致 D-葡萄糖酸钙强烈过饱和。总溶解钙与钙配合物平衡常数的定量分析允许进行离子形态分析，结果表明在 25°C 时，初始非热和自发过饱和度超过 50 倍，在沉淀开始后几小时的滞后阶段之后，沉淀 D-葡萄糖酸钙后，过饱和度缓慢降低。提出了一个数学模型，该模型基于沉淀滞后阶段和沉淀过程中 L-乳酸和 D-葡萄糖酸盐交换的耦合微分方程的数值解。结果表明，L-乳酸与钙配位缓慢交换 D-葡萄糖酸盐，在水中的时间常数为 0.20 h，在重水中的时间常数为 0.15 h，动力学氘/氢同位素效应为 1.25。这种自发的非热过饱和度和缓慢的配体交换，具有拟一级平衡过程，半衰期为 3.5 h，对于钙羟羧酸盐来说，可以帮助理解与简单盐相比，钙羟羧酸盐具有更高的钙生物利用度。
