Calcium d-Saccharate: Aqueous Solubility, Complex Formation, and Stabilization of Supersaturation

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• 作者：André C. Garcia ; Martina Vavrusova ; Leif H. Skibsted
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2016
• 出版时间：March 23, 2016
• 年：2016
• 卷：64
• 期：11
• 页码：2352-2360
• 全文大小：365K
• ISSN：1520-5118

文摘

Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, K_assoc = 1032 ± 80, ΔH_assoc^° = −34 ± 6 kJ mol^–1, and ΔS_assoc^° = −55 ± 9 J mol^–1 K^–1, were determined electrochemically. Calcium d-saccharate is sparingly soluble, with a solubility product, K_sp, of (6.17 ± 0.32) × 10^–7 at 25 °C, only moderately increasing with the temperature: ΔH_sol^° = 48 ± 2 kJ mol^–1, and ΔS_assoc^° = 42 ± 7 J mol^–1 K^–1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d-saccharate becomes spontaneously supersaturated with both d-gluconate and d-saccharate calcium salts, from which only calcium d-saccharate slowly precipitates. Calcium d-saccharate is suggested to act as a stabilizer of supersaturated solutions of other calcium hydroxycarboxylates with endothermic complex formation through a heat-induced shift in calcium complex distribution with slow equilibration upon cooling.