Determination of calcium-binding constants of caseins, phosphoserine, citrate and pyrophosphate: A modelling approach using free calcium measurement

► Caseins and other chelatants differently bind calcium. ► We measured ionic calcium during titration of the molecules. ► We fitted the calcium-binding isotherms using a modelling approach. ► We determined the calcium-binding parameters of the different molecules. Dairy products contain large amount...

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Veröffentlicht in:Food chemistry 2011-07, Vol.127 (2), p.676-682
Hauptverfasser: Mekmene, Omar, Gaucheron, Frédéric
Format: Artikel
Sprache:eng
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Zusammenfassung:► Caseins and other chelatants differently bind calcium. ► We measured ionic calcium during titration of the molecules. ► We fitted the calcium-binding isotherms using a modelling approach. ► We determined the calcium-binding parameters of the different molecules. Dairy products contain large amount of calcium which is bound to caseins and different chelating agents like citrate and polyphosphates. The present study aimed to determine the calcium-binding capacities of phosphoserine (SerP), caseinophosphopeptide (CPP), β-casein, caseinate, citrate and pyrophosphate in the same conditions of temperature, pH and ionic strength. The free calcium (Ca2+) was measured using a calcium ion-selective electrode and plotted as a function of total calcium concentration. The association constants and the number of calcium-binding sites were determined by fitting the experimental data to a theoretical model. The phosphate groups of caseins were the main binding sites with evidence for participation of carboxylate groups. The intrinsic association constants determined by the best fit of the data were in the order: pyrophosphate (557×103M−1)>citrate (20×103M−1)>β-casein (5×103M−1)>caseinate, CPP and SerP (∼103M−1). These findings may be of interest for the development of calcium-enriched products to overcome calcium deficiency in specific populations.
ISSN:0308-8146
1873-7072
DOI:10.1016/j.foodchem.2010.12.121