Relative contributions of charged species to conductivity changes in skim milk during electrochemical acidification

Abstract

Bipolar membrane electroacidification (BMEA) is an acidification technique that approximates chemical acidification. However, differences in the casein precipitation profile have been observed between these two procedures and correlated with differences in conductivity. In this work, ionic and protein contributions to conductivity during BMEA were mathematically modeled. Chloride, potassium, calcium and sodium made major contribution during electrochemical acidification. The evolution of protein contribution was the same as observed previously for chemical acidification, but with slightly higher values. During pH decrease, chloride contribution to conductivity was greater during chemical acidification while the decrease in potassium contribution was more marked during BMEA. Since the contribution of proteins during BMEA was greater, electrostatic repulsions between proteins would also be greater than during chemical acidification, explaining their precipitation at a higher pH value.