de Zawadzki Andressa, Skibsted Leif H
Department of Food Science, University of Copenhagen, Rolighedsvej 26, DK-1958 Frederiksberg C, Denmark.
Department of Food Science, University of Copenhagen, Rolighedsvej 26, DK-1958 Frederiksberg C, Denmark.
Food Res Int. 2020 Nov;137:109372. doi: 10.1016/j.foodres.2020.109372. Epub 2020 Jun 4.
Insoluble mineral residues from whey processing dominated by hydroxyapatite and calcium hydrogen phosphate were found to dissolve isothermally in aqueous sodium hydrogen citrate. Dissolution occurred spontaneously and the resultant homogeneous solutions were found to be supersaturated solutions in both calcium citrate and calcium hydrogen phosphate. Supersaturation was investigated by visual inspection combined with turbidity measurements and analyses of calcium and phosphorous by ICP. The maximal supersaturation was found to be proportional to total hydrogen citrate concentration. For 0.2 M hydrogen citrate, maximum calcium concentration was achieved in the first hours of dissolution resulting in the supersaturation of calcium hydrogen phosphate with a factor of 10. Calcium citrate rather than calcium hydrogen phosphate precipitated from the supersaturated solutions and the time elapsing before precipitation began, increased with increasing concentrations of excess of hydrogen citrate. This lag phase for precipitation ranged from several hours for 0.2 M hydrogen citrate to more than a day for higher hydrogen citrate concentrations, for which the solutions were saturated in calcium hydrogen phosphate and became supersaturated only in calcium citrate due to the strong binding of calcium by citrate. The appearance and decay of supersaturation was kinetically studied in order to provide the background for future exploration of whey minerals in functional foods for improved calcium nutrition.
研究发现，以羟基磷灰石和磷酸氢钙为主的乳清加工过程中产生的不溶性矿物残渣能在柠檬酸氢钠水溶液中发生等温溶解。溶解过程自发进行，所得均匀溶液在柠檬酸钙和磷酸氢钙中均为过饱和溶液。通过目视检查、浊度测量以及电感耦合等离子体（ICP）对钙和磷的分析来研究过饱和度。结果发现，最大过饱和度与柠檬酸氢根总浓度成正比。对于0.2 M的柠檬酸氢根，在溶解的最初几个小时内达到了最大钙浓度，导致磷酸氢钙的过饱和度达到10倍。过饱和溶液中沉淀出的是柠檬酸钙而非磷酸氢钙，并且开始沉淀前经过的时间随着过量柠檬酸氢根浓度的增加而延长。这种沉淀的延迟阶段从0.2 M柠檬酸氢根时的几个小时到较高柠檬酸氢根浓度时的一天多不等，在较高柠檬酸氢根浓度下，溶液在磷酸氢钙中饱和，仅在柠檬酸钙中过饱和，这是由于柠檬酸对钙的强结合作用。对过饱和度的出现和衰减进行了动力学研究，以便为未来探索功能性食品中的乳清矿物质以改善钙营养提供背景。
