Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology & Business University, Beijing 100048, China.
R&D Center of China Tobacco Yunnan Industrial Co. Ltd., Kunming 650202, Yunnan Province, China.
Food Chem. 2020 Aug 30;322:126709. doi: 10.1016/j.foodchem.2020.126709. Epub 2020 Apr 3.
This study elucidated the formation mechanism of calcium-indigo carmine (IC) complex. Parameters of the complex, such as Turbiscan stability index (TSI), yield and stoichiometric ratio (Ca to IC) were investigated. Isothermal titration calorimetry (ITC), UV/Visible spectrophotometry, infrared spectroscopy and Raman spectroscopy were used to explore the interaction between IC and Ca(II) during formation reaction and in the powdered lake. The TSI analysis and yield test suggested pH 7.0 as the most suitable pH to produce this complex. The conjugation between IC and Ca(II) was an exothermal reaction with increase of entropy (ΔH = -0.728 ± 0.11 kJ·mol and ΔS = 66.55 ± 1.89 kJ·mol·K at 25 °C). Both ITC and stoichiometric ratio test suggested one Ca atom tended to conjugate five IC molecules at ambient temperature when an adequate amount of Ca(II) appeared. Spectrometry techniques suggested that the sulfonic acid groups in IC formed coordination bonds with the Ca to construct the complex.
本研究阐明了靛胭脂钙（IC）配合物的形成机制。考察了配合物的参数，如 Turbiscan 稳定性指数（TSI）、产率和化学计量比（Ca 与 IC）。采用等温滴定量热法（ITC）、紫外/可见分光光度法、红外光谱和拉曼光谱研究了 IC 与 Ca(II)在形成反应过程中和在粉状色淀中的相互作用。TSI 分析和产率测试表明，pH 7.0 是生成该配合物的最适 pH。IC 与 Ca(II)的结合是一个放热反应，熵增加（ΔH=-0.728±0.11 kJ·mol，ΔS=66.55±1.89 kJ·mol·K，在 25°C）。ITC 和化学计量比测试均表明，在环境温度下，当出现足够量的 Ca(II)时，一个 Ca 原子倾向于与五个 IC 分子结合。光谱技术表明，IC 中的磺酸基与 Ca 形成配位键，构建配合物。
