Assembly of artificial casein micelles with sodium hexametaphosphate

Abstract

This study explored the potential of hexametaphosphate (HMP) to assemble caseins into artificial casein micelles (ACM) as an alternative to calcium phosphate nanoclusters. HMP cross-linked caseins through their phosphoserine residues in the presence of calcium ions. At high calcium-to-HMP ratios, insoluble calcium-HMP complexes formed, cross-linking the calcium-sensitive caseins and resulting in stable ACM that were smaller, more hydrated, and formed weaker curds upon chymosin coagulation than conventional ACM with calcium phosphate nanoclusters. As the HMP concentration increased, micelle formation reached an optimum at a molar calcium-to-HMP ratio of 10:1. However, at lower ratios, HMP chelated calcium ions, leading to the formation of soluble calcium-HMP complexes that impeded micelle formation. These findings highlight the dual functionality of HMP as both a micelle-forming agent at high calcium-to-HMP ratios and a calcium-chelating agent at lower ratios, providing new insights into alternative mechanisms for casein micelle assembly.