Temperature effects on calcium partition kinetics in pasteurised skim milk during storage

Abstract

Calcium (Ca) dynamics between casein micelles (CM) and serum phase (SP) in pasteurised skim milk were characterised by temperature dependence (4–35 °C) of Ca partition between phases and rate of formation of ionic calcium (Ca2+) in SP. Increase in Ca2+ during storage was characterised by two kinetic models: (1) 4–20 °C, with two parallel first order reactions, a fast dominating for first 3 h and a slower between 3 and 8 h, negative energies of activation (−22 kJ mol−1 and −48 kJ mol−1, respectively) explained by endothermic binding of Ca2+ to CM for the slow reaction and by endothermic Ca2+ binding to ligands in SP; (2) 4–35 °C, decrease in rate of Ca2+ formation with increasing temperature assigned to reversible endothermic association of serum Ca2+ to phosphate and β-casein. β-Casein release from CM decreased like Ca2+, suggesting interaction between β-casein and Ca2+ during transfer from CM to SP.