CONTRIBUTION OF THE ELEMENT SPECIATION TO THE QUESTION OF THE BIOAVAILABILITY OF CALCIUM FROM SEVERAL KINDS OF BREAD

In NaCl and NaCl/HCI extracts from 11 kinds of bread and flour the calcium ion concentrations in comparison to the total calcium contents were determined by a calcium-selective electrode. Crisp-breads showed the slowest values of extractable calcium and calcium ion concentrations in the extracts. Differentiated investigations on calcium binding in the neutralized extracts were carried out with a view to studying calcium resorption in the duodenum. Correlations with the phytic acid contents have shown that other degradation products also take part in the re-binding of calcium. By these investigations the contribution of element speciation to the evaluation of calcium bioavailability has been shown by the analytical methodology and the results of application.