Calcium ion binding to native and heat treated β-lactoglobulin genetic variants

Calcium ion binding to native and heat denatured β-lactoglobulin A, B and C genetic variants at pH 7.0 and 0.08 m NaCl was investigated. Native β-lactoglobulin bound calcium ions and the binding increased after denaturation. Small variations in calcium ion binding were observed for the three genetic variants. Analysis of the binding by the Scatchard model suggested about 10 binding sites in the unheated β-lactoglobulin and this decreased to about 5 in the heated samples. The association constants were low in the unheated samples and increased in the heated samples. Analysis of the binding by the Langmuir adsorption model indicated the maximum binding was about 10–13 calcium ions per β-lactoglobulin monomer in the unheated samples and this was about half in the heated samples, possibly due to aggregation making binding sites less available. The affinity constants were low for the unheated samples and increased substantially for the heated samples.